View Full Version : Is a TriangleTube Prestige Trimax Excellence PTE 110 the right one of the job?

08-07-2013, 06:23 PM

1800Sf, 1920 2 story Colonial house located in Westchester NY,
insulated attic (R20), new windows.
3 heating zones, the largest zone uses cast iron radiators,
the two smaller zones are using the fine tube baseboards.

Current heating: 25 year old oil burner.

I am interested to convert over to gas.

A contractor friend recommended the TiangleTube Prestige Trimax Excellence PTE 110.
This is a high efficiency combi condensing boiler with a 14 gallons build in water thank for domestic
hot water.

So far, we received several estimates but none of the contractors
performed an actual load analysis.

At best, an estimate for the output of the radiators was done and it
came in at 80K BTU's.


- If we need a heat load analysis, where do we find a good contractor to do
that? None of the 7 heating companies or plumbers that came out so far
even mentioned a heat load analysis.

- Do we need to be concerned about the temperature of the return water
given that two of the heating zones are using fine tube baseboards.

- How do we figure out if the TriangleTube Prestige Trimax Excellence PTE 110
(which has output of 86K BTU's) is properly sized for this application?

- Given that part of the radiator are the thin fin baseboard type, Is installing a high efficiency
condensing boiler a waste of money?



08-07-2013, 06:41 PM
Read some of the other threads. If you have your oil usage figures with the 'K' factor, you'd then download the heating degree day info for your zipcode. This will give you a reasonable upper bound on heating requirements. It's almost certainly much less than the output of the 110K unit.

Tom Sawyer
08-08-2013, 09:29 AM
At 86,000 out its probably a bit oversized but not grossly so. A heat loss would be a good idea but I don't think you would run into anything serious with that unit.

08-08-2013, 11:51 AM
At 86,000 out its probably a bit oversized but not grossly so. A heat loss would be a good idea but I don't think you would run into anything serious with that unit.

It may not be grossly oversized for the whole-house load, but it's minimum modulation of 30,000 BTU/hr is likely to be grossly oversized for the low mass fin-tube zones, and that could be an issue.

If the house has been air sealed & insulated, 30K could even be the whole-house load at 10F or 15F or whatever the 99% outdoor design temp (http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf) is at the particular zip code. (The 99% design temp for White Plains is +12F, NYC's is +15F.) I too have a 1920s house with 2400' of conditioned space (+ ~1500' of insulated basement), and my heat load is less than 30KBTU/hr @ +15F, and I DON'T have new windows (double-hungs + 1980s vintage clear storms).

But whether the minimum modulation output of concern can be sorted out using back-of-napkin math. How many feet of fin-tube is there on the smallest/shortest zone?

There are mod-cons with minimum modulation less than half that of the -110 combi that are probably better suited to the application, and if you had to add some thermal mass to keep the fin-tube zones from short cycling, that's possible too. If the 80K number they cooked up for the radiation presumed 160-180F water and your true heat load is under 30K, that's IDEAL for running a condensing boiler, since it will always run in condensing mode.

With a K-factor from a mid-winter or late-winter oil bill it's pretty easy to put an upper bound on the whole-house heat load. With that plus the size of the fin-tube zones we can narrow down on what actually makes sense. A true Manual-J or I=B=R type load calc on the fin-tube zones might be useful too, since it's likely that those zones will have the highest water temp requirements.

Tom Sawyer
08-08-2013, 02:53 PM
Yep, it probably is but I have no idea what the split between base and radiators is nor how the system is piped and zoned. If I had too I'd bet that the contractors bidding it are figuring around 35 thousand of that output for domestic hot water. A mistake to be sure but a common one.

08-08-2013, 04:51 PM
Thanks for the answers so far.

The home is located pretty close to White Plains, NY, so the suggested outdoor design temperature
will be close to the one suggested by Dana.

Regarding the 3 different heating zones, this is what we have:

zone 1: 34 feet fine tube baseboard.
zone 2: 30 feet fine tube baseboard.
zone 3 20 feet cast iron radiators.

Given the amount of fine tube baseboard, should we be concerned about the water return temperature?
In other words, will a condensing boiler be condesing and be worth the investment?



Tom Sawyer
08-08-2013, 05:09 PM
Typical 3/4" copper fin tube baseboard is rated at 580 btu/ft @ 180 degree input temperature so those two zones are capable of 37,120 btu/hr. the cast iron radiators depend on the size and number of tubes. There are charts that come pretty close so I'm gonna assume by your post that you have the equivalent of another 60' of baseboard and that rounds up to another 34,800 btu/hr and a grand total of 71,920 btu/hr possible @ 180 degree input water temperature. The heat loss of the envelope is unknown at this time but even if we go a little high, it's probably not more than 50k btu/hr. this isn't too bad because since you have more radiation than you need, return temperatures and inlet temperatures can be reduced although single zone operation may create a issue, however there are ways around that problem too. Anyhoo, if it were me I'd drop down to the prestige solo trimax 60.

08-08-2013, 05:19 PM
Two more pieces of information that might be relevant:

1. One big reason that I am attracted to the TriangleTube Prestige Trimax Excellence PTE 110 is the fact that this
is a combi unit, supplying both heat and domestic hot water.
The direct venting option on the boiler means that we no longer need the chimney (nor have to put in an expensive
chimney liner).

2. Hot water to the heating units (both radiators and baseboard units) is distributed by rather inefficient uninsulated 2.2 inch diameter network of cast iron pipes.


08-08-2013, 05:31 PM
O Yeah, getting the TriangleTube Prestige Trimax Excellence PTE 110 installed around here costs about 10.5K.


08-08-2013, 06:27 PM
FWIW, you may find that using an indirect WH is more efficient in the long run, connect it as a priority zone, and if sized properly, you should never run out of hot water, or let the house cool off. It doesn't make sense to me to have the boiler running to keep the water hot 24/7 when a good indirect may only call for heat once a day after a big use and the boiler can idle at essentially off for 23-hours in the summer.

08-09-2013, 08:00 AM
It only makes sense to buy a modulating condensing boiler if it can run in condensing mode with out short cycling itself into low-efficiency & early failur, and actually modulate much of the time. The size/mass of the fin-tube zones will prevent that with a boiler as big as the -110 unless you add more radiation or add more thermal mass, but the -60 can modulate low enough at minimum fire to get you there, with some adjustments to the zoning.

With only 30' of fin tube on the smallest zone the -110 will short-cycle like crazy running it at condensing temperatures. While it's output @ 180F AWT is on the order of 18,000 BTU/hr, when you drop the AWT to 135F (where it has to be to get any condensing efficiency) the output is half that, and the -110 boiler would be dumping 3x the amount of heat into the fin tube than the fin tube can deliver to the room at those water temps. If you tied the two fin-tube zones together (presuming the room-to-room temps would still be reasonably balanced, which isn't a given, though that could be tweaked slightly with ball-valves) it would limit the short cycling a bit, but it would still be doing 10 cycles/hour or more, and adding some thermal mass (or better yet, more radiation) might be necessary to really tame the beast.

The -60 (http://www.triangletube.com/documents/1/Prestige%20TriMax%20Literature_011713.pdf)would do fine with the fin-tube zones combined into one even at 120F AWT, temps where efficiency would hit the mid to high 90s, but would still do a bit of cycling with the fin tube zones were left separated. There is some figurin' & plumbin' to do here.

The radiator zone will do fine no matter what, because it undoubtedly has enough thermal mass to inhibit short cycling.

A 50-60K mod-con plus an indirect is probably the right solution. If the heat loads of the fin-tube zones are under 10KBTU/hr each (which they might be), you may do just fine using a condensing hot water heater with a heat exchanger isolating the potable from the heating loop. Doing a careful Manual-J or even a simple I=B=R using a spreadsheet would tell you if that's a possiblity.

No matter what you do, it's worth insulating as much of that 2" pipe as you can get to easily, since that represents a rather significant parasitic radiator. The crappy half-inch wall fiberglass R1.5-R2 stuff sold at box stores is nearly worthless, but the 1" wall thickness stuff sold for steam (http://www.statesupply.com/maintenance-supplies/steam-pipe-insulation/if1035x) distribution piping is OK at about R3.5-R4.

The only way your heat load would be anywhere near as high as 50K would be if the place leaks air like a sieve at both the attic-floor plane and at the foundation, and the foundation has no insulation. The air leakage is fixable on the cheap, but the foundation insulation costs will vary depending on how you go about it (but still worth it as a DIY.) If your basement isn't insulated, that's likely to be at least 10-15,000BTU/hr @ +15F, and a combination of air-sealing & insulating the band joist and insulating at least down to 2' below grade with R10-R15 would be a big uptick in first-floor comfort as well as an efficiency gain. With a big oil boiler and bare 2" pipes it's likely that the basement is the warmest place in the house when it's +15F outside, even uninsulated, but when you go to a more efficient boiler running minimal temps the basement (and first floor floor temp) will run much cooler during cold weather. But if you air seal & insulate, the basement will run in the mid to high 60s, (even with insulated pipes), but without the high heat loss out of the foundation. There are many ways to screw up foundation insulation- don't just slap up a studwall and stuff batts into it or you'll have re-invented the mold-farm. If/when you're going there research it a bit- Building Science Corp has quite a bit of info online on how to do it without creating more problems. (If pressed I can explain how & why some methods fail, others succeed, and how to do it on the cheap too.)

08-10-2013, 07:08 AM
I can heat your home with half the output of an Triangle Tube Excellence combi. We have had one operation in St.Paul, MN for about 5 seasons now without a problem, but the retrofit application was unique.

We install high efficiency condensing boilers here in Minneapolis on 9 of 10 renovations and 100% of new homes and addions. (OK we install an occasional condensing water heater for low-load combi systems). It is nearly impossible to find the right fit for a combi water heater or combi boiler for the reasons Dana so astutely asserts.

Every proper hydronic system, new and replacement must start with an ACCA Manual 'J' heat load and system load evaluation. We would never size a space heating boiler base on DHW loads. That is what and indirect-fired water heater is for. A combi-unit is a 'do-all' compromise seldom warranted, that most can ill afford.

08-10-2013, 03:22 PM
Thanks a lot for all the replies and suggestions. I've gotten much better advice here on this forum then from 95% of the
contractors that have put in an estimate for a new system. Just yesterday we had a plumber over would claimed that
we should install a 150K BTU gas boiler simply because that's is what the old oil burner delivers.

At this point, I am seriously looking at the suggested prestige solo trimax 60 plus an indirect.

Unfortunately, The two heating zones with the fin tube baseboard are installed on tow different floors. The original house
was extended with a two story addition. Each story received it's own baseboard heating zone.
Given the two different floors, I am not sure if it makes sense to combine the two zones. It would
means that at night, I have to heat the unused downstairs addition because I am heating the upstrairs addition.

Going with the 60, I assume we can set the outgoing water temperature low enough such that the boiler runs in
condensing mode?

Regarding the suggestion for an indirect water thank for domestic hot water, would the indirect basically be an additional zone
on the new boiler?



08-10-2013, 03:53 PM
If your boiler (many do) comes with or can have an outdoor reset control, it will, if properly adjusted, adjust the supply temperature based on the outside temp and the returning water temps - IOW, it will try to have the boiler output just be enough to operate at peak efficiency and comfort. Most of the time, this should be a condensing mode (again, if it is setup properly!).

Usually, an indirect is setup as a priority zone. When it calls for reheating the tank, it requests the boiler go to high fire, and then only supply that zone until it is satisfied. This normally doesn't take all that long, and it's rare to notice the other zones are not getting any heat (they don't immediately turn into icecubes and still supply some residual heat in the interim).

08-12-2013, 11:15 AM
At an average water temp of 130F (140F out, 120F back) you'd be getting pretty good condensing efficiency. At 130F AWT most fin tube is delivering ~250 BTU/foot, so your 30' zone is good for only ~7500 BTU/hr, which only about half the output of the -60 boiler at minimum modulation, which means it will cycle on/off/on/off fairly often during a call for heat from only that zone. At 110F AWT (120F out, 100F back, about the lowest you'd ever run fin-tube) you're only getting ~150BTU/ft out of it, with a 10,000BTU/hr difference between the boiler output and the fin-tube output.

There are a few ways do deal with this. The best way would be to add sufficient radiation to those zones to make it balance with the ~15K min output of the boiler when it's in condensing mode. Panel radiators would be the most comfortable, but aren't super-cheap. If there's more wall perimeter that could be used for more baseboard that would be the cheapest.

Another method is to at thermal mass to the system in the form of an insulated storage tank referred to as a "buffer". But to know whether the distribution plumbing already has enough thermal mass to save you take's a bit of napking math:

With 2" distribution plumbing you may already have enough buffering thermal mass to make a difference.The fin-tube has about 0.2lbs of water per foot, or 2lbs for ever 10'. The 2" iron is good for about 1.5lbs water-equivalent per foot, or 15lbs for every 10' (when you include the thermal mass oft the iron.) A typical mod-con will run a 7-10F ramp around the outdoor reset's setpoint. If you have say, 30' of 2" pipe in the loop between the boiler and the 30' of fin tube, and say 10' of copper too, that's about 40' of 3/4" copper for 8lbs of water, 30' of 2" iron for 45lbs, you're at 50lbs of thermal mass. The 2.5 gallons inside the boiler is good for another 20lbs, call it 70lbs total.

With an excess of 7500 BTU/hr (/60 = 125 BTU/minute) going into that water, the temp of the loop rises at a rate of 125BTU/70lb= 1.8F per minute, so with a 7F minimum hysteresis on the boiler's output setpoint you'd have a minimum burn time 7F/1.8= 3.8 minutes.

That's long enough to get you under 10 burns/hour, and not exactly terrible. If you have even more 2" iron between the boiler & fin-tube zones, so much the better, if it's less, measure it up and do the math. (Both supply & return plumbing counts.)

But if it's all 3/4" copper or PEX, the thermal mass is dramatically lower, and it'll short cycle. A cheap electric HW heater (not wired up) can often be impressed in to service as a buffer tank, or as a buffering hydraulic separator, but you really need to design the system (or pay somebody to design it, even if somebody else installes it), not just throw hardware at it and hope.

08-18-2013, 05:25 PM
O Yeah, getting the TriangleTube Prestige Trimax Excellence PTE 110 installed around here costs about 10.5K.


The quoted price explains ignorance of people giving quote. You will see a good installer when he will quote you at least double of that.

08-18-2013, 05:53 PM
Looking at the TT prestige trimax series, there is the 60 with input modulation of 16 to 60K MBH. The next size up is the trimax solo 110, with input modulation of 30 to 100k MBH
I understand that the 110 unit does not modulate low enough given the size/mass of the fine/tube zones, leading to short cycling, which led to the advice to take a look at the trimax 60.

What impact does air-sealing and insulation of the house have in all of this? The rooms with the baseboads units are both facing the north side of the house and they are pretty cold
in the winter. The addition was build about 15 years ago and insulation was part of the building code back then but I am not sure that they really followed it.

At this point I am looking into a energy home performance audit to get a better understanding of how leaky the house really is.


08-18-2013, 08:22 PM
To keep a place warm, you need to match the heat loss with heat from your heating system (basic, but some seem to forget it!). Insulation slows the heat loss, keeping the place warmer longer. The better the insulation, the less heat you need to put in to make up for what is lost. Air leaks are the worst, and sometimes the easiest to fix...they do several (bad) things: they cool the place down, and they can make the insulation less effective. So, if you tighten the house up and add insulation where possible, your heating load becomes smaller since the heat leaks out slower and you need less to maintain the internal temp.

FWIW, there is no such thing as cold...you can't make cold, you CAN remove heat, which ends up being what we call cold. The heat is ALWAYS trying to distribute itself (i.e., going from a warmer to a colder surface/area). Insulation just slows down that process, it does NOT prevent it!

If a room is cold, it may be that it needs more heat to make up for that lost (a good room-by-room Manual-J analysis would tell you what you need room-by-room), OR, it could be that there's either a lack of insulation, poorly installed insulation, OR lots of air leaks. Cold air blowing into the wall can make you feel really cold, and may be easy to fix.

08-19-2013, 01:11 PM
In addition to Jim's comments regarding air sealing...

Low density fiberglass insulation is highly air-permeable, and a leaky exterior sheathing will undercut the performance of an R19 batt substantially during cold weather. In the 1990s (and even today) many or even most builders will install low-density R19 batts to meet code min, but even when perfectly installed in air-tight wall cavities performance is R18 at-best. As-installed with leaky sheathing, batts compressed behind wiring/plumbing rather than split to accommodate while maintaining full loft, balling it up behind electrical boxes, cut an inch too short but installed anyway, etc, a "typical" installation is often under R15 in average performance. Which is still way better than nothing, but if the radiation was sized with the expectation of perfect installation, there will be issues.

Air sealing a house is about the cheapest performance upgrade you can buy, and it IS cheap. Spot-insulating a house to fill in gaps or mis-installed insulation is also pretty cost effective. An energy audit that measures & identifies big leakage points is a start, and infra-red imaging to show up the insulation gaps & compressions is also useful.

If the "cold" rooms have a lot of window area, that' could easily be the "the problem". Clear-glass U-0.60 double panes still met code 15 years, and are pretty marginal performance-wise, often underperforming a decent single-pane antique with a tight clear-glass storm window. Rather than replacing windows with higher performance versions at huge expense, it's often both better and cheaper to improve window performance with low-E storm windows over clear-glass double-panes. (Both of the big box store chains carry low-E Larsons (http://www.larsondoors.com/storm_windows/), which are pretty good. The "Silver" version is considerably more air tight than the Bronze, and usually worth the upcharge, and the Gold series is even tighter still. A low-E storm over a U-0.5 clear double pane improves the net performance to about U0.3-0.32, which is signficant.

Say you have a 400' addition with with 60' of 9' tall 2x6 exterior wall, and six ten square foot windows. The U-factor of less well insulated (but still insulated) 2x6 wall is about 0.075-0.08 BTU/degree-foot, and you have about (9 x 60=) 540' of gross wall area, less 60' of window area for about 480' of wall. When it's 15F outside and 70F inside (55F delta) the heat loss from the walls is at least:

U0.075 x 480' x 55F= 1980 BTU/hr.

But the heat loss through 60' of U0.50 window is:

U0.50 x 60' x 55F= 1650 BTU/hr

...which is very comparable number. But if you added low-E storms, dropping the U-factor to U0.32 or lower, the window losses would be:

U0.32 x 60' x 55F= 1056 BTU/hr, making the window losses more like half the wall losses rather than a near-equal.

And the window improvement is about a 600 BTU/hr, the heating-equivalent of a small 180 W electric space heater (that uses no power), or another 3' of baseboard running at condensing temperatures.

If you air-sealed the walls and blow cellulose into any thin spots you'd improve the wall U-factor to about U0.7 or less, and the wall losses would be:

U0.07 x 480' x 55F= 1848 BTU/hr.

That's better than a 130 BTU/hr on conducted losses alone, but the reduced air leakage losses are likely to be another 100-200 BTU/hr improvement. (It just depends.)

If you do it all it's like adding another 4-6' of baseboard or more, but because it's more air tight and the interior window temps are higher, it feels less drafty to boot.

Whenever possible & reasonably economical it's better to attack the load rather than add more radiation to meet the higher load. Comfort is about more than air-temperature- the exterior window & wall surface temps affect the "radiant emperature", which is more important for human comfort than the air temp. Standing outside in full sun on a calm autumn day can be quite comfortable even at 35F air temperature, due to the improved radiant temperature (full sun), whereas standing in 55F shade can feel pretty cold.

08-22-2013, 06:54 AM
Reason that I brought up air-sealing and insulation is that several heating contractors are concerned that the
TT prestige trimax series 60 (input modulation of 16 to 60K MBH) would not be able to supply enough heat for the whole house.

08-22-2013, 08:10 AM
Reason that I brought up air-sealing and insulation is that several heating contractors are concerned that the
TT prestige trimax series 60 (input modulation of 16 to 60K MBH) would not be able to supply enough heat for the whole house.

And unless they did a careful fuel-use analysis on the previous system and an honest Manual-J or even an I=B=R spreadsheet calc, their opinions aren't worth the toilet-paper they wrote it on. Fear of undersizing is rampant amongst hacks, but rarely justifiable. The more reasonable fear should be of oversizing.

Air sealing is almost always cost-effective, as is fixing any gaps in the insulation, and those measures DO lower the heat load. But the notion that an 1800' house in Westchester needs more than 55,000BTU/hr of boiler output (that's 30 BTU/ft-hr!) is just nuts, unless there is literally no insulation in the walls, and all of the windows are single-pane, all of which would be necessary & cost-effective things to rectify on comfort grounds alone. Ratio rules of thumb are pretty lousy gauges of reality, but most 1920s homes won't run more than ~20 BTU/ft-hr , and will often be in the 15BTU/ft-hr range with a bit of air sealing and (usually absent) foundation insulation. At the more likely 20 BTU/ft-hr an 1800' house would only need 36,000 BTU/hr which is barely over the MINIMUM output of the -110.

As-zoned the -110 is guaranteed to short-cycle at condensing temps- you'd literally be better off with ~100KBTU/hr mid-efficiency cast iron boiler with smarter controls if you're hell-bent on installing a boiler that oversized. You only get the benefits of mod-con efficiency if it's actually modulating and condensing, which is why you HAVE to install the smallest one that actually meets the load, and have small zones of low-mass-low-emittance radiation like fin-tube.

Run a crude I=B=R spreadsheet on your house on a room-by-room basis. Assume an interior temp of 70F, exterior 12F for a 58F delta. For any double pane windows of unknown U-factor or any single-pane + storm, and exterior doors use 0.5 BTU/degree-ft. For all 2x4 framed wall area with at least some type of insulation use 0.1 BTU/degree-ft, for any 2x6 use 0.08. For an attic with anything better than sloppily installed R19s use 0.07. For uninsulated above-grade foundation down to a foot below grade, use 1BTU/degree-foot.

A typical 1800' house will have about 270' of window, and assuming a couple of exterior doors, call it 40' of door for 310 square feet of window + door:

U0.5 x 310' x 58F= 8990 BTU/hr

A typical 1800' 2-story will have 900' of attic floor:

U0.07 x 900' x 58F= 3654 BTU/hr

Assuming a perimeter of say 180' and 2' of above/near grade foundation for 360' of U 1.0), and a basement 15F colder than the upstairs when it's +12 F outside you're looking at.

U 1 x 360 x 43F= 15,480 BTU/hr

Assuming 10' per story and 180' of perimeter you have 1800' of gross wall area, less 310' of window & door leaves 1490' of U0.1:

U0.1 x 1490 x 58F= 8642 BTU/hr.

For 900' of U 0.07 attic you get:

U0.07 x 900' x 58F= 3654 BTU/hr.

Add it all up and you're at 40,420 BTU/hr. Add 30% 'cuz you live in the absolute DRAFTIEST house in Westchester (or always sleep with the windows open, even when it's +12 F outside) and you're still only at 52,546 BTU/hr, a load still covered by the -60 running with 160F output.

And those U-factors presume some pretty crummy & poorly installed insulation- reality is almost always better than that (or could be made better than that at very low cost). You'll note the biggest single number is usually an uninsulated unheated basement, which is an upgrade needed by more than half the homes in Westchester county NY. It's not super-cheap to retrofit foundation insulation, but there are lower cost and higher cost ways to get there. Using even intermediate-cost methods (say, 2" of closed cell spray foam + intumescent paint, at ~$3 per square foot) it's worth it, even at buck-a-therm gas.

Seriously- take the time to measure up your house on a room by room basis and use a spreadsheet tool to come up with the numbers- they're a lot lower than your bidding contractors think. Buy some low-E storms to retrofit on those colder rooms, or install more radiation in those rooms, and buy some air-sealing & insulation if you think it's still too drafty.

08-22-2013, 10:51 AM
The last thing a contractor wants is to put in a new system and then you tell them it can't keep the house warm. So, the easy thing is to put on one bigger than needed. It also gets them more money, since the bigger it is, the more it costs. But, if you want it done right, you have to be smarter, especially if you want to maximize your investment. Contractors don't like to argue with people when they are taking out a 150K BTU unit, and replacing it with a 60K unit, people just assume they need the same size as what was there originally. Well, energy costs are way higher now, and the technology is better...you really NEED to match your load with the properly sized supply.

What people here have been trying to tell you is that those contractors are taking the easy way out, and it will NOT end up in saving you money. WHen it comes to things like heating appliances, they work much more efficiently when they run long burns. That can ONLY happen when it is sized properly. On/off cycles kill efficiency and can hurt longevity...things work better, longer, when they don't turn on/off a lot. A boiler that is too big will need to turn on/off LOTS!

If you take a weird situation where you have the coldest week in 100-years and your system was typically just able to keep up normally, the house might cool off a degree or two - it won't immediately (or ever!) turn into a refrigerator! It might take longer to reheat if you turned the heat way down while on vacation, but then, again, only on that really cold day...you're somewhat limited by the radiators in the house, they can only output so much heat, regardless of what type of supply you have.

08-22-2013, 03:35 PM
Thing is, his real heat load probably IS no more than about 36-40K, even as-is, with no building improvements, which means even with the -60 he would be good down well into negative double digit temps from a boiler output point of view. The hacks recommending the bigger boilers are just that, hacks.

Anybody who has bothered to work through more than a couple of real heat load calcs would be able to tell you that at a 99% outside design temp 30BTU/foot is an insane number for an 1800' house that has glass in the windows, and doors that shut. Move the same house to Fairbanks and sure, it could be 30BTU/ft. But that is STILL a heat load that could be delivered by the -60(!).

So why would anybody even consider installing a -110 in that house?

Ignorance & apathy would be my best guess, but there could be other reasons I s'pose.

But if they're not even willing to do a heat load calc it leaves me wondering what other critical system design aspects they're missing? They clearly missed the boat on the short fin-tube zone short-cycling problem, and that's dead obvious even on the napkin-math model. (Any real mod-con system designer/installer would have flagged that as a high-potential problem for the -110 without even breaking out the crayons.)

08-22-2013, 04:01 PM
Before we install buffer tanks (generally expensive, if properly sized, installed and controlled) we try to specify more radiation in the form of sub-floor radiation, radiant ceilings or real wall-hung panel radiators sized for low temperature. This is a long-term investment in comfort and economy.

Sizing a micro-zone may be as simple as tying it to another (not letting it call the boiler) or knowing from your room-by-room heat load analysis, that the micro-zone will never, or rarely, call by itself.

All residential high efficiency condensing boilers modulate flame and feature on-board outdoor reset.

Buffer tanks must be sized by an experienced designer, no WAGS will work.

08-23-2013, 07:51 AM
As previously discussed, even if he tied his 30' & 34' sticks of fin tube together operating in condensing mode would be a serious problem for the -110, but you might be able to deal with it on the -60. As separate zones they'll still be problematic even with the -60.

CLEARLY this system needs a real designer, not a hack-installer to run it on a mod-con. If he's leaving the zones alone and there's a dearth of design talent available, a tiniest in class 2-3 plate mid-efficiency cast iron boiler with heat-purge controls would come pretty close to hitting it's AFUE numbers, leaving some cash on the table to spend on the building envelope to reduce the load in his colder zones. If this place has no foundation insulation and leaks a lot of air, fixing those issues + tiny cast iron are probably more cost effective than adding sufficient radiation (or mass) to deal with a mod-con.

I wonder what fraction of already-installed mod-con boilers are as ridiculously oversized for their loads as the -110 would be for this one? (I'm guessing it's more than 30%, maybe even 50%, based solely on how common threads like this are.)

08-26-2013, 11:54 AM
What companies are selling 2-3 plate mid-efficiency cast iron boilers?



08-26-2013, 01:27 PM
Lots of 'em.

The smallest Burnham ES2 (http://cdn.usboiler.net/products/boilers/es2/assets/literature.pdf) might be a good prospect, only ~1.5-2x oversized for the likely load, plenty of smart-control options for both comfort & efficiency. Less than $2K for the hardware (http://www.pexsupply.com/Burnham-ES2-3-ES2-3-51000-BTU-Output-High-Efficiency-Cast-Iron-Boiler) @ internet pricing. It tolerates 110F return water without exterior plumbing, and has hooks for quickly integrating outdoor reset with an add-on card. Even a hack of an installer should be able to handle it, and would have to get creative to really screw it up.

The smallest Buderus GC124 (http://www.buderus.us/files/201111202231520.44499096-GC124%201010.pdf) or GA124 (http://www.buderus.us/files/201111202226510.44499108-GA124-GA244_GasBoilers.pdf) would be in that class, but usually for more money. The GA124 is designed with smart controls in mind, the GC not so much.

The smallest Biasi B10 (http://www.qhtinc.com/wp/wp-content/uploads/2012/04/Biasi-B-10-Boiler-Literature-040111.pdf) , the B-3 is a 3 plate boiler, but retrofit heat purge controls would be necessary to get the most out of it.

The smallest Weil McLain CGi-25 (http://www.weil-mclain.com/en/multimedia-library/pdf/weil-mclain-pdf/products/boilers/gas-boilers/cgi/cgi_lit.pdf) is a 2-plater with 42K of output, as is the Utica MGB50HID (http://www.ecrinternational.com/secure/upload/document/2984.pdf)

The three-plate Burnham ES2-3 with the smarter controls seem like a better product and easier to deal with than those that would require some smarts on the installer's part to get the efficiency out of it without ruining it from excessive condensation. But it's really a matter of how much support there is from the distributors & installers in your area. Just don't let some idiot installer tell you that it's not enough boiler without doing the heat load math.

08-27-2013, 08:14 AM
One reason for my interest in a high efficiency mod-con boiler (besides the efficiency) is the fact that they use direct venting.
Previous estimates for mid efficiency cast iron boilers came with the notion that we needed a chimney liner.
Installing a chimney liner turned out to be expensive in our neck of the woods, $1700 dollars was the cheapest.

Adding the cost of a chimney liner to the cost of installing a mid efficiency boiler almost equals the installation cost for
a high efficiency unit.

If only, I could find a contractor that would know how to deal with the two baseboad micro zones and would be willing
to install a correct sized boiler ..... That's not too much to ask, is it?

08-27-2013, 08:43 AM
Replace those crummy baseboards on the micro-zones with low-temp panel radiators capable of delivering the min-mod output of a more appropriately sized mod-con at 120F AWT. Most of the smaller mod-cons can modulate down to ~ 15KBTU/hr.

The there are direct vented versions of these cast iron boilers out there too, such as the Burnham ESC3 (http://s3.pexsupply.com/product_files/ESC3-Brochure.pdf) for only a couple hundred more than the ES2.

There others (http://cdn.usboiler.net/products/boilers/revolution/assets/literature.pdf).

08-28-2013, 11:37 AM
Regarding the suggestion for the Burnham ESC3, is there any risk of short cycling if I kept the basenoards on the micro zones?

08-28-2013, 02:14 PM
30' of baseboard at 200F emits abotu 22,000 BTU/hr into the zone. The output of the ESC3 is 60,000BTU/hr, so you have about 38,000 BTU/hr (633 BTU/minute) of excess. There's about 17lbs of water in the boiler, figure another 15 in the heating loop, and about 200lbs of iron with a specific heat of 0.11 for about a water-equivalent of 22lb, call it ~55lbs water-equivalent thermal mass. With 633BTU/minute of excess heat the temperature is slewing at (633/55= )11.5F/minute.

The max programmable differential on the controls on the ESC-3 is 30F (according to page 15 of the manual (http://cdn.usboiler.net/products/boilers/esc/assets/manual.pdf)) you'd be able to get (30/11.5=) ~2.6 minute burns out of it serving just one zone, which is far from great, but less than a total disaster. Clearly you'd like to be able to get more. If it's turning off at ~210F output and turning back on at ~180F, with 30' of fin tube emitting that heat it'll be ~7-9 minutes between burns, and 6-7 burns per hour. You can play around with it, try running it with 180F at the high limit, turning back on at 150F if you like- the burns will be slightly shorter, but the time between them longer. Ideally you'd be getting ~10 minute burns, not 3, but that's rarely going to be the case when micro-zoned like that. If you had space to add even 10 more feet of baseboard you'd be looking a only a 30,000 BTU/hr excess, lengthening the minimum burns to over 3 minutes.

Measure the diameter & lengths of the distribution plumbing between the boiler and 30' zone. If you have a bunch of 2" iron that can add quite a bit to the minimum burn times too- my napkin sketch was for just ~40' of 3/4" copper pus the 30' of fin tube (70' of total 3/4" copper on that loop.)

If you want to run it in outdoor reset mode you'd do better to replace the 30' of baseboard with panel radiators (http://www.decorisland.com/uploadedimages/spec_files/myson.pdf), as big as can reasonably fit. Replacing the 30' of baseboard a pair of Myson SD-70140G (http://www.decorisland.com/details.asp?productid=67448&optionid=349819&feedid=2&utm&zmam=85702793&zmas=1&zmac=68&zmap=SD-70140G&gclid=CIyRzsSAobkCFYak4AodSFoASg) (55" x 28") panel radiators could deliver ~30,000BTU/hr @ 200F, but would also add about 75lbs water-equivalent of thermal mass to the loop if you run the numbers on the steel weight + water volume in the spec (http://www.mysoncomfort.com/Content/Media/PDF/Select21_22Page.pdf), so even running it a lower temp/lower output would still deliver reasonable burn times.

Panel rads are not super cheap, but they are super comfortable compared to fin-tube, and you'd get it down to under 5 burns/hour with stabler room temps and cushy radiating heat emitter.

With that much panel radiator & mass on your smallest zones you'd be able to heat just fine at condensing temps with a mod-con as small as the TT...-60 without short-cycling it, if you could find a competent installer, since at mid-mod in condensing mode is ~15,000BTU/hr, and a pair of SD-70140Gs at 120F AWT would be delivering at around 8000 BTU/hr, for a 7000BTU/hr (117 BTU/minute) of excess, and with something like 90lbs of water equivalent in the loop that's an overheating slew rate of ~1.3F/minute. With a differential of even 10F you're looking at a 7-8 minute burn time, and 4-5 burns/hour.

08-29-2013, 05:01 AM
There is really no excuse for a sealed combustion non-condensing boiler and micro-zones are not a sin unless they are in high load/sq.ft. areas and allowed to call the boiler independently. Still the answer is more radiation. European wall-hung panel radiators are the thing for sure, easily designed to 140 AWT and assured full-time condensing mode. 3 minutes run time is acceptable but if this only occurs under design conditions, I would not tolerate it.

08-29-2013, 07:48 AM
The excuse here is that he can't seem to find anybody who seems to understands how to deal with a mod-con. The 3-plate c.i. beast that tolerates 110F return water could be DIY install. (Why pay hacks plumbers union scale + overhead if they're just a bunch of hacks who couldn't design an effective escape route from a paper bag? I still don't get how anybody would recommend simply swapping in the -110 here.)

Increasing the radiation is strongly advisable no matter which way he goes on the boiler. (Who in their right mind would even install a 30' fin-tube zone in the first place?) You could take a buffer tank approach I s'pose and save a few hundred but he'd have do actually design it. Swapping the fin-tube for panel radiators would improve both comfort & capacity in these zones described as "cold", and are easier to deal with.

09-04-2013, 10:49 AM
Still talking to various heating experts. Off course there are lots of opinions out there.

One installer claimed that installing an extra buffer thank was very expensive ($1500 to $2000) and was wondering if just a larger expansion thank would do...
He also wanted to use the delay-to-fire feature on the TT boilers to prevent short cycling.

Another installer only wanted to install an atmospheric vented Buderus GC124/4 (103k BTU/hr) and claimed that a direct or power vented
model would be more prone to failures due to the added electronics ...

Yet another installer prefers the IBC boilers over the Triangle Tubes...

09-04-2013, 11:44 AM
FWIW, every installer will have his preferred equipment type, and that is not necessarily an indication of quality, just his availability and pricing, and if you're lucky, training. It's much easier to install something you've done before and have been trained on than have to take the time to read the instructions (if that happens?!) on something new. To get the most out of any install, it takes someone who is familiar with the equipment and can tweak it properly. Once you decide on a brand, you might want to call the distributor and find out who is buying them...at least they'll have a better understanding of the equipment than someone who has never seen one.

The more electronics, the more potential for failure. Now, is that a common thing? Hopefully not! If it were very common, with the typical warranty period on these things, the manufacturer would have problems staying solvent.

One thing that I firmly believe in, though, is both whole-house surge suppression, and point of use suppression on expensive items. Electrical noise and spikes on the power line are a reality. They act like an ax chipping away at the junctions on the electronics input circuits. Suppressing or minimizing them can make things last longer. Some devices have some built-in, but extra stuff isn't all that expensive, and is pretty good insurance.

09-04-2013, 12:32 PM
Still talking to various heating experts. Off course there are lots of opinions out there.

One installer claimed that installing an extra buffer thank was very expensive ($1500 to $2000) and was wondering if just a larger expansion thank would do...
He also wanted to use the delay-to-fire feature on the TT boilers to prevent short cycling.

Another installer only wanted to install an atmospheric vented Buderus GC124/4 (103k BTU/hr) and claimed that a direct or power vented
model would be more prone to failures due to the added electronics ...

Yet another installer prefers the IBC boilers over the Triangle Tubes...

He's an idiot- buy him a box of crayons & a coloring book and send him on his way.

An expansion tank instead of a buffer? Huh? It's like topping off the windshield washing fluid rather than filling up with gas to have enough range to make it across the desert. I'll BET he's wondering!

A $200 bargain-basement electric hot water heater (not wired up as a heater) can be impressed into service as a buffer tank at the flow rates seen in most residential systems. A commercial buffer tank with big fat ports might be necessary for any high-flow system loops, but if you used the buffer tank only in series the 1-4 gpm low-mass fin-tube zones (the only part of your system where it's needed) an electric hot water heater does just fine as a buffer.

The delay feature can only reduce the number of burns per hour, not the time per burn- it's still a short cycle, just fewer of them. With boilers way oversized for the zone using the delay will sometimes mean that there isn't sufficient burn time in an hour to actually meet the load- it's (almost) NEVER the right solution to the heating problem, but it'll keep the boiler from burning out prematurely from doing 25 burns/hour.

The Buderus guy has a point, but it's an extremely minor point. If the grid near house gets hit by lighting there's a somewhat higher risk of damage to the electronics than you'd get with heavy electromechanical components, which is why you should never use electronics (like say heating zone controllers, microwaves or TVS) in your house. This is a solved problem. He's also recommending a boiler more than 3x your actual whole house heat load, and 4x more heat than the 30' zone can deliver at 200F.

IBC boilers look pretty decent, but even the smallest one roars, but can still get down to the ~15K range. I'm not sure how they get the 10:1 turn down and still have high efficiency at the low-fire end, and they might not be all that efficient at the low-fire end given their "Best net stack temperature in the industry – typically 5-10F at full fire" marketing. Since you'd literally never run the 15-150 at full fire, only the low-fire end of the range, it matters what the efficiency at the low end is. The sweet-spot on most mod-cons are on the lower 1/3 of the firing range, and below the sweet spot the lack of turbulence on the fire side of the heat exchangers becomes insulating laminar flows, with less effective heat exchange, and higher net-stack temps (=lower raw combustion efficiency.) I don't know enough about IBC to say if or how they've managed to solve that fundamental issue.

09-13-2013, 06:36 PM
Still talking to various heating professionals. Had the Home Assessment Energy audit in the meantime,
found a couple of small airleaks in the basement, but nothing serious.

Found one installer that is willing to install the Triangle Tube Prestige 60.
As great as that is sizing wise, he did not see the need for a buffer tank.

Waiting for another quote from installer number two who seems more familiar with the whole buffer tank approach.

1. How is a buffer thanks going to prevent short cycling of the boiler when only one of the small baseboard zones
is asking for heat?

2. From a cost point of view, is it better (cheaper) to install a buffer thank or add more radiation?



09-16-2013, 11:29 AM
The simple-math the burn time you get out o putting a cheap buffer such as a 40 gallon hot water tank (not wired up) in the loop is that it's adding 40 x 8.34= ~333lbs of water to the system.

To raise 333 lbs of water 7 degrees (assuming that's the approximate differential hysteresis of the boiler around it's outdoor reset setpoint curve) takes 333lbs x 7F= 2330 BTU.

At a minimum modulated output of ~15,000BTU/hr that means the minimum burn time is 2330/15000= 0.115 hours, which is 0.155 x 60= 9.3 minutes.

The hardware for the buffer can be pretty cheap if you're using a HW tank- $200-250, but the cost to install it (and getting it installed correctly by a hack with no clue as to what they're doing and why) may be a cost adder, especially if you have to do it twice.

Replacing a 30' stick of fin tube (or adding to it) with a $450 radiator (http://ecomfort.com/b-2471-eco-flat-panel-hot-water-steel-hydronic-radiator-24h-x-71l-13656-btu-3036.html) capable of delivering over half the output of he Solo-60 at 140F, while adding about 40lbs of water-equivalent thermal mass might be more expensive, it offers a big uptick in comfort, and doesn't require much design-smarts on the part of the installer beyond plumbing skills. The thermal mass of that radiator adds about a minute to the min-burn time above what would have been happening with 30' of fin-tube. At 120F average water temp that radiator would be only delivering about 5000BTU/hr to the room, and assuming you have both the 40lbs water equivalent of the radiator and another 30lbs to work with (the Solo-60 itself has 25lbs of water in it), with 70lbs total it takes (7F x 70lbs=) 490 BTU to heat it's mass 7F, and with (15,000-5000=) 10,000BTU/hr that takes 490/10,000= 0.049 hours, or (0.049 x 60=) ~3 minutes- on the short side, but not a disaster. But with the 30-34' of fin tube you'd be under 2 minutes, which kind of is a disaster.

Clearly 120F would be the low end of where you'd ever want to operate it, but 120F AWT(125F out/115F back, or 130F out/110F back) that's good for mid-90s combustion efficiency at the boiler. At 140F out/120F back you'd be well into the 90s, on efficiency and over 6 minutes for a minimum burn time. You can dial in the curve to see where it needs to be to keep up, but you'll probably want to set the temperature-floor at 125F as the minimum, and only drop lower if you're getting 5+ minute burns out of it with just the smallest zone calling for heat.

09-17-2013, 09:00 AM
Ok, the information from the Home Energy assessment is in. The blower test determined the building shell leakage to be 2816 CFM50.
Does this information solidify the choice for TT prestige trimax series 60 solo with an input modulation of 16 to 60K BTU/hr?



09-18-2013, 11:16 AM
Thanks to all the suggestions on this forum and this particular thread, we now have a heating replacement plan
that at least seem to include the right ingredaints: an IBC SL 20-115 MOD/CON Boiler (20k - 115K Btuh),
a 33 Gallon buffer tank and an 40 Gallon indirect water tank.

09-18-2013, 11:35 AM
Ok, the information from the Home Energy assessment is in. The blower test determined the building shell leakage to be 2816 CFM50.
Does this information solidify the choice for TT prestige trimax series 60 solo with an input modulation of 16 to 60K BTU/hr?



Blower door tests give you the order of magnitude, aren't a precise way of determining the infiltration losses since it actually matters where those leaks are. (I hope you chased around during the test and figured out where the worst leaks are so you can remediate?) 2816 cfm/50 isn't super tight. It's also not super leaky about 2 air exchanges per hour, but it's usually cost effective to improve upon that a bit if you found the leakage paths. At 1500cfm/50 and lower the leakage is often harder to find and fix.

Using really crude "N-factor" modeling (http://virginiahomeperformance.com/yahoo_site_admin/assets/docs/Green_Sheet.185172833.pdf), in your area you can divide the cfm/50 by 17-20 for the max infiltration rates to expect. So if we divide 2816 by 17 (the worst case) you're looking at 166cfm infiltration in a high wind, which is 9960 cubic feet per hour. At a delta-T of 60F (10F outside, 70F inside) the dumb heat loss number that adds up to is 9960c.f. x 60F x 0.018BTU/c.f. per degreeF= 10,756 BTU/hr.

In reality it's literally never that high, since there's a "heat exchanger effect" along the infiltration & exfiltration paths, but it might be as much as half that figure- call it 5K. To be the full 10,756 BTU/hr requires that the leakage paths be large and low-impedance, so that the volumes of air entering the innermost skin is truly at the outdoor temperature, and the air leaving the outermost skin of the building is at the interior air temperature. It's still reasonable to go with a Solo 60, and continue air sealing.

The 115KBTU/hr IBC is really extreme overkill here, but if the installer seems competent on the system design, it'll probably give reasonalble service, and the boiler & system should be tweakable to modulate most of the winter.

09-29-2013, 05:31 PM
Would a 22 Gallon Buffer tank be large enough to prevent short cycling with a boiler with a minimum output of 20K Btuh and 2 mirco zones?

zone 1: 34 feet fine tube baseboard.
zone 2: 30 feet fine tube baseboard.



09-30-2013, 01:19 PM
Probably. Do the math. 22 gallons at 8.34lbs/gallon adds 183lbs of water to the system. You need to figure out how much else there is on that loop.

20KBTU/hr is 333 BTU/minute. If we assume you get 5F of hysteresis around the outdoor-reset setpoint it takes 5F x 183lbs= 915 BTUs to slew that much, which takes 915/333= 2 minutes 45 seconds, even if you assumed the rest of the system mass was zero, and the fin tube emitted zero.

It's safe to say that you'll be getting 3+ minute of burns out of it even in worst case conditions if you tweak in the reset curves & pumping rates, etc, which is OK for a low-mass boiler.

11-28-2013, 05:50 PM
In the interest of full disclosure, we ended up with the following system:

1. IBC SL 20-115, a high efficiency modulating boiler with outdoor reset control,
2. a 40 Gallon Domestic hot water tank.
3. a 22 Gallon buffer tank.

The buffer tank is used to add thermal mass to smaller baseboard fine-tube baseboard zones.