Triangle Tube Prestige Boiler Problems, Solutions & Question

[larryleveen]

Well, we just had a new green-dot controller installed and so far the thud noises are gone as are the E02 lockouts from failure to ignite. If there is one thing that I've learned about mod cons is that they need an experienced professional to design the system and install it. Might be time to pick up the phone and take out the checkbook.

I am still looking into the issue of my system's efficiency. I was using setback on my thermostats, but have stopped doing that based on what I have heard/read on several online forums and articles. Oddly, I got the following email from Triangle Tube regarding the matter when I emailed them a question about this issue:

Sorry for the delay in responding. The question of night setback does come up. The good news is that you can use night setback thermostats with mod con boilers and you will see some savings. Here is the impact of using night setback.

1) It will take slightly longer to bring the house back up to temp when using outdoor reset as compared to traditional cast iron boilers. This is obviously due to the lower supply temperature that the mod con will usually have. This will especially be true when using radiant flooring.

2) You will lose a small amount of efficiency while bringing the temp back up as the boiler will be running at a higher firing rate. This should be rather small but it will be there in theory.

My advice is that I would use the night setback feature of the thermostat, but recognize that you may need to set the recovery time a little earlier that you may have thought. Anything that can improve fuel efficiency should be tried. Each home is different so we can’t give specific savings amounts, but I would experiment to find the optimum settings for your house.

I'm surprised that TT says to use setback!

[Dana]

"Each home is different so we can’t give specific savings amounts, but I would experiment to find the optimum settings for your house."

No kidding!

Whether or not you gain anything at all with setbacks is mostly a function of how tight & well insulated the house is, and the amount of thermal mass inside the thermal & pressure boundary of the house. Low-mass leaky houses cool off faster, reducing the delta-T between indoors & outdoors, which reduces the rate of heat flow out of the house. But a tight higher-R house with some amount of interior thermal mass (like maybe a radiant floor slab?) will almost never hit the setback limits, with very low, sometimes unmeasurably low reductions in fuel use. If you saved 3% in heat loss by going to setback, but lose 3% in efficiency on the recovery ramp by firing away at a higher temp you've gained nothing, and perhaps lost a bit of early morning comfort.

The raw efficiency of a mod con is determined by the entering water temp coming back from radiation, and the firing rate of the burner. With most the sweet spot on the firing rate is at or near the lowest modulated range, and going more than 50% of full fire cuts into condensing efficiency at any return water temp by a significant more-than-theorectical amount, which you'd somehow have to make up for with lower return water temps:



Setback is a better strategy with bang-bang cold-fired boilers and higher temp radiation, where standby losses can be reduced by letting the boiler cool off, and the efficiency curve is in the long, linear fairly flat non-condensing zone, where the firing rate is what it is, and the combustion efficiency not much affected over a 10-15F return water range.

[larryleveen]

I have never understood what high-mass and low-mass are in this context. Is it the mass of the hydronic heating water? Is it the mass of the radiators/other heat sinks?

Is efficiency the result of just getting low return water temps, or is is the result of a specific temperature loss across the system? I would guess the former, since it creates a bigger gradient to exchange heat across in the boiler, but please confirm that.

If I was right, what is the lowest realistic OUTGOING water temperature to use? It seems like that would be desirable so that the return temp was as low as possible. Again, I have radiators, not radiant floor heating. The house is small 1200 sq. ft., fairly well insulated in a moderate temperature area (zip 98502), though I suspect the house is not very tight (something I want to improve this year).

Here are readings from the boiler display:

Supply Water Temp: 174
Return Water Temp: 144
DHW Temp: 132

What to do? Maybe the installer left a default reset curve (based on a colder area) in there.

[jadnashua]

If a boiler is designed to condense, then it can tolerate return temps a lot lower. Otherwise, it's prudent to keep it at or above 130-degress for the most part (there are some exceptions). Radiators will still continue to heat when the supply temp is lower and is more efficient as long as the house remains comfortable. you only need the higher temperatures (and you may not actually need them) when it is colder outside. One thing common to all newer condensing boilers, and available for others that don't have it, is an outdoor reset. This adjusts the supply temperature based on the outside temperature and the return water temps to keep the supply as low as possible while maintaining comfort and maximizing burn time. In a perfect world, the boiler would run all the time at the proper supply temp while maintaining the desired comfort level. This is accomplished, up to a point, with a mod-con by adjusting both the boiler's output level (burner) and supply temperatures. It's just that they don't have infinite range, and on a mild day, the minimum burn is likely going to be larger than the house's needs. There are other controllers that can help maximize efficiency, but the one biggest factor is to have a boiler that is 'right' sized for the load. it's just that with a mod-con, it can adjust its 'size' to the load over a fairly good range. On a fixed burner, it must cycle more often. Each time it cycles off and on, it loses some efficiency. Controlling it with some anticipation (i.e., turning off before the house temp is reached while allowing the latent heat to finish the job) can help, and there are devices that can be setup to do that as well.

[Dana]

I have never understood what high-mass and low-mass are in this context. Is it the mass of the hydronic heating water? Is it the mass of the radiators/other heat sinks?

Is efficiency the result of just getting low return water temps, or is is the result of a specific temperature loss across the system? I would guess the former, since it creates a bigger gradient to exchange heat across in the boiler, but please confirm that.

If I was right, what is the lowest realistic OUTGOING water temperature to use? It seems like that would be desirable so that the return temp was as low as possible. Again, I have radiators, not radiant floor heating. The house is small 1200 sq. ft., fairly well insulated in a moderate temperature area (zip 98502), though I suspect the house is not very tight (something I want to improve this year).

Here are readings from the boiler display:

Supply Water Temp: 174
Return Water Temp: 144
DHW Temp: 132

What to do? Maybe the installer left a default reset curve (based on a colder area) in there.

But the thermal mass of the house (relative to setbacks) is the sum total of the specific heats x mass (kinetic) of everything inside the exterior edge of the thermal boundary (insulation layers, including studs), and that would include the heating system, wood, flooring, walls, plaster, furniture, pets & people, etc. which can vary by quite a bit. Concrete & masonry construction tends to be significantly higher mass than stick-built, tile floors have more thermal mass than carpet, etc.. The greater the thermal mass of the house, the more BTUs it needs to lose to fall to a particular setback temp, and a very high mass house may lose very little in the way of temperature, even with large amounts of heat loss over night. Setback only saves if the indoors temperature drops, reducing the rate of heat loss, so a lower-mass house derives greater benefit from a setback strategy than a high-mass house where the temp barely drops during the setback period.

The mass of the heating system the thermal mass, of the entire system, which is related to the the specific heat x mass (kinetic) of all the materials in the system. The specific heat of water is 1BTU/lb per degree-F, but the iron in cast iron radiators etc is about 1/9 that of water, and most of the thermal mass in a radiator system well be the water, but not all of it. It's considered "high mass" radiation if it's big old radiators, but some will argue that thin Europanel is more like "mid-mass" due to lower water volume and less iron.

The specific heat of concrete is ~ 0.2 BTU/lb-F, and concrete slab radiant floors can have quite a LARGE amount of thermal mass relative to say, a 40 gallon tank or most heavy radiator systems despite having 1/5 the thermal mass per lb.. Concrete is pretty dense stuff and there's lots of it in a slab.

With fin-tube convectors as the heat emitter and a low water volume mod-con nearly all the thermal mass is accounted for by the water- the rest is negligible- a few percent of the total at most. With staple-up radiant floor, same thing, but there's usually 5x or more water in the system than with fin-tube, but both are considered "low mass" radiation.

Similarly with a big cast-iron beasty-boiler the iron can count for some fraction that may equal or exceed the water-volume of a boiler, but with mod-cons the thermal mass of the heat exchanger is pretty small even compared to the gallon or so of water volume in the boiler. The same is true of copper-fin water tube boilers and their cousin, the tankless water heater.

Enough with the mash-schasch- getting to the real issue for YOU:

If your return water temp is 144F it's only getting ~87% efficiency out of the boiler, and you'd need to drop the overall temp by another 15F to break 90%. The lowest output temp that's "reasonable" depends on the heat emitter type & size. With fin-tube going below 120F becomes wird since it's output becomes non-linear with temp, but big old high-mass radiators have decently linear output even at sub-100F, and usually enough thermal mass to keep the boiler from short-cycling even at low-output (a common problem with low-mass fin-tube.) I haven't programmed this series, but if it's a standard set of curves, start at the bottom and see if it keeps up. The lower the water temp, the lower the output of your radiators- to squeak the best efficiency out of the boiler, run the temp curve at the lowest temp that actually keeps up with the load. With high-mass radiation it shouldn't short cycle no matter how low the water temp is, but keep track of what it's doing burn-length wise when it's "bumping off the bottom" at heat loads below the minimum firing rate of the boiler (which may be much of the time, for you.)

The 30F delta-T at 174F output is fine- expect that to shrink a bit with lower temp output, but it'll still be >15F with 120F output, and lower still at 100F output.

It's been mostly in the 40s in 98502 for the past few days, and I'd be shocked if the heat load ever exceeded 20 KBTU/hr during that time period unless you left some windows open. If this is a retrofit installation to a house with upgraded insulation & windows (or storm windows), and all radiators are original, there's probably enough radiator to deliver 100K @ 174F, and you should be able to drop the temperature quite substantially and still keep up. With the curve set too high you end up overheating for awhile, then it undershoots the setpoint as it brings the mass of water up to the (too-high) temp, repeat. With curve dialed-in the burns will be long, slow, and efficient, with a much more stable room (and radiator) temperature, and higher comfort level.

[ericg]

(1) I have a Solo 110 that makes a horn-like sound just after firing, goes away after about 15 seconds as boiler moves to "high fire". (2) Also, I smell raw gas coming from the intake elbow that connects to the venturi when in standby. TT told me that there should not be a gas smell anywhere! So they arranged to have a guy put in a new gas valve. That didn't fix it. Sometimes I smell gas in the room. Anybody have trouble like this?
Jack

I had the same issue with my Solo 110 and to some extent i am still having it. First the gas, it seemed to be intermittent, sometimes stronger, sometimes weaker smelling. My gas company went through the unit and was able to detect a small leak which they fixed. I would do this first. I have the same trumpet or train whistle sound on low fire. The conventional wisdom was to make sure the unit air/gas was calibrated correctly, i.e. make sure it's not a lean mixture. Some purport to have fixed the problem by calibrating the unit correctly. I had my unit tested by a TT factory-trained plumber with a digital combustion analyzer and the unit was spot-on. He was able to re-create the trumpet sound issue on a low fire test (amazing! when does this ever happen when the repair guy is there?). He indicated that there were no specs for a low fire calibration. He also tested the LP gas pressure which was 11" - also on-spec. He contacted TT who told him that i should have my pressure lowered to 9". I think the theory was that the regulator may have shown 11" but during the morning (when the sound typically happens) it may be fluctuating above. My opinion is that TT doesn't want to send new parts until they can't point fingers anywhere else. One piece of additional info, I've had the boiler for about three years and this issue didn't happen until about 2 months ago.

[BadgerBoilerMN]

The key to efficiency and comfort in any hydronic heating system, is control. Control is gained by understanding the thermal dynamics of the distribution system you have and the heat source you want to drive it with. I just so happens that that a low-mass, condensing boiler with modulating output will drive nearly all hydronic heating systems, be they radiant panel, panel radiator or slab-on-grade, with better control and higher efficiency than anything previously devised. The reasons for this fact can be surmised in one word: microprocessor.

The "mass" in cast iron radiation or concrete for that matter is better controlled with weather sensitive controls. The odd fact that both systems normally have more radiant surface than is technically necessary (given the 167 to 200°F max. water temperatures of ModCon boilers), the result of over-sized radiation is a low design water temperature. Low-mass, high efficiency, condensing boilers love low water temperatures and can easily cut fuel bills in half with stack (chimney) temperatures in the 100°F range instead of the 350° common in high-mass, low efficiency (<88%AFUE) cast iron boilers.

Because of the modern condensing boiler has built-in outdoor reset (ODR), even low-mass emitters like fin-tube baseboard will create more comfort at lower operation cost than when matched with an old-fashioned boiler.

European "panel" radiators are really one of my favorite design tools as I can over-size a panel to any design water temperature I choose creating radiant comfort where fast response time is essential.

It is why I no longer use tin.

[larryleveen]

Badger, what you say makes sense. I think that my installer did not truly understand how much heat needed to be "dumped" from the system to the living space to adequately lower water temperature so the boiler can operate towards its peak efficiency. Our house is small (1200 sq. ft. (fairly well insulated), and has two zones, which I think make it harder for the system to have adequately low return water temperatures for efficiency. As a result, our utility bills have not decreased from when we had an older gas forced-air furnace.

What do you (or anyone else) recommend I do at this point? Could the Runtal radiators we have be switched out for ones with higher BTU output to "dump" more heat into the living space and lower the return water temperature? That is the only solution I can think of. Thanks.

[Dana]

More radiation and more thermal mass can be your friends, but have you tried programming the Solo 60 to a lower reset curve to see if it still keeps up?

Runtal radiators have at least some thermal mass and work well with low temp (compared to fin-tube which have very little thermal mass, and is pretty unreliable at low temp.) As long as it's not short-cycling like crazy on zone calls you should be able to run a lower temp curve to pick up condensing efficiency.

A well insulated 1200' house in Seattle may have a design condition heat load not much more than the ~15,000 minimum modulated output of a Solo 60. To keep a low-mass zone from short cycling itself silly at low temp it needs to be able to deliver at least half the min-mod output of the boiler at your minimum temp, but with the Runtals you have some thermal mass to help out, and you can probably do fine with 1/4 the output, and maybe even less, but let's go for half the rated oiutput at min-mod. (This is a WAG, don't have all of the necessary specs in front of me.) So, you'd want at least something on the order of 15K/2=7500BTU of output @ 140F to get you into the condensing zone. Runtal UF2 radiant baseboard is rated ~600BTU/foot @ 180F, and should deliver ~300BTU/ft @ 140F. If your's is UF-2 two-panel baseboard (or tell us what model & size Runtal you DO have), you be looking at only 7500/300= 25 feet or more. If you have 25' of it on your smallest zone you should be able to run in condensing mode 100% of the time without short-cycling, and may be able to drop the bottom of the curve to 110F without short-cycling and hit the mid-90s or higher.

I'm guessing you may already have radiation worth at least 7500BTU @ 140F on your smallest zone, if certainly more than half that. If so, you should be able to set up the boiler to run in the condensing range nearly 100% of the time and still meet the design condition load without it short cycling itself into an early grave. Why you're running with 174F output is beyond me. I doubt the heat load of either of your zones exceeds 10K at 20F outdoor temps, and even 20' of baseboard would deliver 8-9K at your ~160F average water temp. At 40F weather (the mean temperature for Seattle in January) you should be able to meet the heat load comfortably with sub-140F output, and condensing-range return.

So, whattaya got for radiation, zone for zone?

[larryleveen]

Quick and important question: I just programmed the boiler's outdoor reset curve points to the minimum allowable values which I now realize could have been a really stupid thing to do. Was it? I did it because I am interpreting the situation as: we have a very small house with insulation and two zones in the heating system and we don't keep it the thermostats up very high, therefore we need to "throttle down" as much as possible. That is, our needs are still very undersized compared to the mod-cons commonly available in the US market so we need minimal temp settings to get efficiency. Please tell me if I am on the mark or not. Now onto your questions:


Nice guess on the Runtal UF-2 units, Dana -- that's mostly what we have :-)

Zone 1 total lineal footages by radiator type:
UF-2: 16' (2x6' & 1x4') 600 BTUH/ft = 9600 BTU*
TW9: 2' = 2400 BTUH**
Turbonics Toester (toekick heater in kitchen): 2200-3000 BTUH depending if fan speed is low or high.***
Zone 1 Total BTUH: 14200-15000 BTUH

Zone 2 total lineal footages by radiator type:
UF-2: 8' (2x4') 600 BTUH/ft = 4800
Zone 2 Total BTUH: 4800

House Total: 19000 - 19800 BTUH (We intended to almost never need both zones running at the same time, we are either asleep in zone 2 or awake in zone 1).

* http://www.runtalnorthamerica.com/re...eboard_uf.html
** http://www.runtalnorthamerica.com/to...omnipanel.html
*** http://www.turbonicsinc.com/TOESTER-UNDERCOUNTER.pdf

BTW, does running each zone's circulator pump at a slower speed help? I was thinking that it could "give the hot water more time" to dump heat to the living space through the radiators and bring the return water temperature down.

[larryleveen]

Hey weird, after lowering the reset curve points all the way, my Solo 60 is making that horn sound too! I wonder if the unit is throttled all the way down and the rate of gas flow is now low enough to create the noise at some adjustable regulator. I know I'm just "talking out my exhaust port" here, but it's the only thing I can think of, since the gas line is pressurized and some mechanism must be trying to restrict it's flow. Thoughts?

[Dana]

Running the boiler at the min-allowable values is not a stupid thing to do- if the house stays warm that would be THE most efficient way to run the system from a condensing point of view. If it's not keeping up when there's a real heat load, bump the curves up a bit at a time until it does.

But with only 8' of UF2 on the second zone it's likely to short-cycle on that zone at low temp. The 4800BTU output rating is what it delivers at 180F, and it's more like 2600BTU @ 140F, and would be 1300 BTU @ 100F output. When the boiler is at min-mod and dumping ~15,000BTU/hr into a zone that's only able to dump 1300 BTU/hr into the rooms the temperature of the system water rises pretty quickly (how quickly depends on how much thermal mass there is on the zone), and it will cycle on/off even with a steady call for heat from the thermostat. That's OK as long as the burns are reasonably long, and what's "reasonable" depends on the mass & standby of the boiler. For a low-mass mod-con like the Solo 60, if the burns are 3+ minutes and it's doing 5 burns or fewer per hour you're fine. If the burns are under 1 minute long and it's doing 15+ burns/hour it's wearing out the boiler and losing efficiency to flue-purges and ignition cycles.

Some mod-cons also allow you to program the hysteresis (the amount of water temp overshoot it allows before turning the burner off), which would be the first place to start to fix a short-cycling issue. If that doesn't do it, if it's possible to set just the min-temp of the curves without moving the rest up, try bumping it up 5F at a time until you get number of burns down under light to moderate heating loads, and the minimum burn times to at least 150 seconds, if not 200+. With any luck there's enough mass in a 8 feet of UF-2 to run reasonable burn times at some modest hysteresis with sub-140F water. (But I don't have the specs for either the boiler or the mass/volume specs for UF-2 to be able to tell you if that's a given.)

Zone 1 is less of an issue at 140F, but even that might have short-cycling problems at 100F output, but with 16' of UF-2 + the towel rack the thermal mass is probably going to be sufficient help you out there. (The toe-kick is very low-mass and hardly counts from a mass point of view.)

As for tooting the horn, are you sure it's on the gas line, not the venting?

[larryleveen]

Firstly, thanks for all your help.

Second, no, I am not sure about the noise going from the gas line and not the venting. I'll certainly look as it is safer to inspect/look at/monkey with (you know what I mean).

Lastly, I'll be paying attention to the house temps now that some time has passed and the thermal inertia the house had shouldn't be masking the curve changes I made. I'll also consider timing the burns to see if it is short cycling.

You are probably familiar with how toe kick heaters work. They seem to turn the fan on when they sense water temperature is at a certain point and just shut off below that. Ours used to run all the time, which annoyed me because it is not as quiet at I expected (it also isn't in a complete enclosure due to an impending kitchen remodel, so I can't blame it that much). Since I made the change, it hardly runs at all. To me that says, yup -- the system water was consistently too hot, and even when there was no call for heat and the water wasn't being circulated, the heat could travel through the still water and keep that toe kick fan going all the time. It seems like evidence of the curve needing to come WAY down. Do you agree?

Lastly, and I might have to call TT on this one. The display on the boiler seems to hang out a lot at code/status 6 with the water temperature also showing, instead of at code/status ZERO ("standby/no call for heat") like it used to. Any idea why? Is that also evidence of the issue I had/change I made? Seems like it could be:

BEFORE curve change: Curve WAY too high, unit short cycles, water temp very high, takes a long time to drop down due to small house/small BTU emitters, toe kick runs all the time too. Boiler is thinking "Man, they don't need me -- I'm going to sleep".

AFTER curve change: Unit hopefully not short cycling (I'll report back), water temp NOT way too high for the small house/BTU emitters, toe kick only runs when it should, and boiler doesn't go to "full standby" because it sees the system water temp as close to its minimum and it will be needed for a slow burn soon.

Scary but perhaps accurate metaphor: An airplane pilot can take a nap when flying at 20,000 feet, but not at 2,000 feet.

[Dana]

I would hope that the toe-kick has a adjustable aquastat to be able to set it to come on at a suitably low temp for running the boiler in a condensing mode, but that alone might establish an operating low limit. If it's not running at all even when the rest of the zone is calling for heat it means the outdoor reset curve has gone below it's turn-on temp. But since that probably only happens when it's relatively warmer outside that may not be a problem. With lower temp water it should take LONGER to satisfy the thermostat on a call for heat.

The thermal mass of the house isn't likely to be so great that it would coast a few days with the heating system's output under-shooting the heat load. If you've gone 24 hours with outdoor temps below 55F and the room temps are still where you expect them to be, the system is keeping up. If you go a day when it's consistently below 40F and the indoor temp isn't dropping, the top end of the reset curve is almost certainly going to be high enough.

DO time the burns at modest load and relatively high outdoor temps. When it's 50F-55F outside there is still a real heat load, but the boiler output should be near the low-temp end of the curve where short-cycling is most likely to become a problem. If you turn off the bigger zone and bump up the smaller zone a couple of degrees you would be able time both the on & off cycles under a continuous call for heat for a few cycles to get a sense of it. If it's not short-cycling on the smaller zone it means it also won't on the bigger one.

From a quick read of the manual it looks like you have just two points to monkey with on the curve and it's a line, but you can adjust a min-temp between 60F<=>140F output to correspond to any arbitrary outdoor temp between +50F<=>+78F, as well as a max temp between 96F<=>194F to occur at any arbitrary (lower) temp between -22F<=>+50F to define the line. With a room-by-room heat load analysis you'd able to set it up right from the get-go. To run it at absolute minimum temp would mean you set it to run 60F boiler output when it's 78F outside, and 96F when it's -22F outside, but I sincerely doubt that's how you are set to run right now. What do you have for parameters 4, 10, 11 and 12?

I can all but guarantee you that the prior curve was too high if it was running near 180F output water. With that much radiation my non-superinsulated house with 2-3x the conditioned space would keep up at +25F outdoor temps with 170F water, and in western WA in a tight well insulated 1200' house you probably will never need more than 150-160F at design temps of ~20-22F. (Manual-J on my mother's not-so-insulated place in Port Orchard came in at about 18K, and MOST houses are better insulated & tighter than hers. You are probably under 15K even at design condition.)

[Buffalobillpatrick]

Larry, hello again. Dana is a constant source of great info.

TT Solo seems to have lumped 3 conditions into a Standby Display of 6*** = Burner off.
1. It quickly goes to 7*** if thermostat is satisfied (space heating post pump cycle)
2. It quickly goes to 8*** if DHW is satisfied (post pump cycle)
The 3rd is interesting, it sits at 6*** for 10 minutes & refires, repeat until thermostat satisfies.
Solo has a smart way of "bumping off the bottom" by waiting 10 minutes before firing again.
This happens when the thermostat is still calling for heat AND the boiler output temperature reaches the max set by outdoor reset AND boiler can't modulate any lower.