Boiler temp on Burnham

[Tom3holer]

Hi,
Its been quite a while since I posted last. I learned a lot and was/am very grateful for all the help.
With the very cold wx here in New England some new problems popped up.
I have a Al80 Burnham Alpine. In these temps it barely can keep the house up to 70. My question is what is the highest temp one can normally run in a baseboard heating system? My Al80 was set at 180 but was not doing the job at that temp so I upped it to the max which is 190 which helped. Is 190 a normal max or do other boilers have higher available temps?

Thanks,
Tom

 

[Dana]

A lot of cast iron boilers can go up to 220F, some even 230F. Most condensing boilers stop at 180F or 190F, like yours. Distribution losses go up at those higher temps for lower as-used system efficiency, and the burn risk of skin in contact with exposed distribution plumbing does too. If the distribution plumbing isn't insulated and in a cold basement or crawl space that can sometimes make a measurable difference in the amount of heat that even makes it to your baseboard. If the amount of baseboard is marginal at 190F boiler out under this type of weather and the distribution plumbing isn't insulated, consider insulating what you can (both supply and return lines.)

At temps north of 200F plumbing in direct contact with wood can even give it a (very) slow charring. The charring effect is pretty commonly seen in old 215F steam systems in service after decade (or 9) if there isn't sufficient clearance or insulation between the piping and wood. Pumped hot water operating at those temperatures isn't immune. A temperature of 190F isn't going to mar the wood though. Some PEX isn't technically rated for 190F, even though it takes 200F+ to really do any damage.

 

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[Tom3holer]

Dana,

Very nice to hear from you again.
I took your recommendations from a couple of years back and have learned a good deal often refering to my Bible "Modern Hydronic Heating"
The basic problem was that the plumber installed a 150K BTU Burnam Alpine but all it did was short cycle in the smallest zone the kitchen. He didn't have a clue how to set it up. I had him meet with the Factory rep at my home and the rep asked how he determined the house needed such a large boiler. His reply was I just took the old one and added 20% which is the normal way I do it. I still remember the look on the reps face.
I had him replace it with a AL80 which has worked more or less OK. All lines are insulated with foam pipe covering. Anything below the low teens it cannot keep the water above 170 and I have to shut off the HW as it has priority running a 40 gal Superstor.
That it seems was the main problem with a larger boiler was the inability to modulate down enough in the warmer temps or for the smaller zone to not over temp and short cycle.
Been thinking about it for a while and looked at the Burnham website and see they, probably others also, now make a 10:1 boiler now. My al80 modulates from 16-80 whereas the new Aspen 110 mods form 11-110.

 

[Dana]

It's not a crime to use auxiliary heating sources to stay comfortable on days when even the high for the day is below the 99% outside design temperature, just a PITA.

I vaguely remember you had a fair amount of air sealing and insulation work to do on the place too, and if any of that stuff is still pending it could make ALL the difference under conditions like these. I have one high-loss zone heated by radiant floors in my house that's been running 60-65F in the recent sub-zero morning with daily highs in single digits (my 99% outside design temp is +5F), but my solution there for the time being is to watch TV laying on the warm radiant floor with a fleece blanket. . At condensing water temps the floor just isn't putting out enough. The longer term solution is in two phases: Re-glaze the ~100 square feet of clear glass U0.5-ish double pane window with double low-E U0.20-ish double pane glass (Cardinal LoE180 +i89) . The second low-E coating is on the interior facing side of the glass (surface #4 in window-nerd speak), and reflects body heat back at you, which makes it more comfortable at any room temperature.

If that still doesn't cut it at -5F, I'll use the remaining unused manifold port on the radiant floor loop manifolds to feed some Euro-style flat panels under the largest windows. That would be more responsive and higher efficiency than just cranking the water temp up. My system is a single temp design centered on a buffer tank, and all other zones are keeping up at ~125F AWT. It would be silly to blast it on up to 150F just for that one zone. I was planning to re-do the glass on a comfort-basis alone due to the large glass area reducing the mean radiant temperature of the room, independently of the floor's inability to maintain the air temp. Every year it's been one more incremental improvement- by the time I'm dead it'll be nearly perfect!

 

[Tom3holer]

Thank you again Dana for the insight. I did have most of the insulation done and the final will be at the end of this month having had a new survey.
One thing I am thinking of doing is to get a instant gas hot water heater. With the boiler running the HW we cannot take more than 2 showers without waiting. In the summer that becomes a problem with company. Ma has a $800 rebate on them so may look into the total cost and see if its worth it. the Superstor temp is set fairly high with a mixing valve but still is inadequate much of the time.
Wondering what the thoughts are on the newer instant gas water heaters?
Tom

 

[Dana]

A bigger indirect is usually the right solution, but if you're running out of raw BTUs for space heating that won't work as well if you have multiple wintertime guests.

Some of the Korean condensing stainless tankless units sold under HTP or Noritz nameplates are good values, as are some of the Naviens. But Rinnai has the better rep for reliability and support. A tankless never runs out of hot water, but has a limited gallons per minute rate. In this climate you'll need to max out and go with a 199,000 BTU/hr unit if it has to support more than two simultaneous low-flow showers.

If it's showering performance (and not tub-filling) you're after, a drainwater heat recovery heat exchanger at least 4" x 48" (taller is better) can more than double the capacity of the indirect when there's an 80K boiler backing up the indirect, and doesn't use any fuel.

Shorter versions might do it too, but at 4" x 48" and up you're in the ~50% heat return, cutting the BTUs pulled from the tank during every shower in half. I don't think there's a MassSave rebate for them, but direct from the manufacturer you're looking at about a grand, and it's much simpler to install than a tankless.

They do nothing for tub-fills, since the drain has to be flowing at the same time that the tap or showerhead is running to work.

They also need to be mounted vertically to work, which is sometimes a limitation for first-floor showers over shallow crawlspace foundations (or slab-on grade.) (A 3" diameter PowerPipe can just squeeze into a 2x4 stud bay for second floor showers, if there's no space under the first floor and no fat plumbing chase for a 4 incher.)

It doesn't have to be right next to the water heater either, but if the main drain is far from the water heater it means more plumbing to install it than if they're reasonably close.

Ecoinnovation's Theromdrain and Renewability's Powerpipe drainwater heat exchangers are on the pre-approved MA plumbing list, and would not need to have a variance to install. It's not clear if Ecoinnovation still sells direct (they used to)- it may be distribution only, but Renewability units can still be purchased onsie-twosie directly , or for a bit more money through the big orange box store.

 

[Tom3holer]

Dana,
As always thank you very much for the advice and wisdom.
My upstairs laundry and 2 showers drain through a small 12x12 chase that eas filled with insulation and foam during the last Mass Save inspection.
As a bit of information: The wife unit just took a 7-10 min shower then ran a load of wash. I noted when the furnace switched over to HW and it ran for about 22 min. During that time the downstairs went from 71 to 68 with a rather mild 30df outside temp. It will take probably over an hour to get back up to 71. Saturday and Sunday I will disconnect the HW thermostat less we wind up with low 60's in the house.
This is why I am looking at a gas instant HW water heater. The Superstor is only 3 yeras old and is a 40 gal stainless lifetime model but along with the furnace it just doesn't do the job and I can't allow the HW to have priority on the real cold days.
It also seems to me that keeping a 40 or 50 gallon tank of water hot all the time isn't very efficient. I believe the HW comes on about twice a day with little or no use. I guess there is some downside to these new heaters like longer to get hot.
I need to get a couple of plumbers over here and get an estimate in the installation. Any idea on what installation should cost?
Tom

 

[Dana]

If the boiler-to-tank plumbing, as well as all accessible hot water distribution pluming and even the cold feed within 10' of the tank is all insulated to at least the current code-min R3, the standby losses of a 40 gallon 160F-180F tank is pretty small, much smaller than that of a 50 gallon standalone gas-burner.

Typical tankless installations run in the $2-3K, range, & 4K at the outside in central MA, assuming the gas service to the house doesn't need upgrading. Since your space heating boiler is an 80K you probably won't run out of meter capacity when adding 199K of tankless.

Hooking up some of the newer Navien models is often cheaper than other vendors, since in most cases doesn't need the 1" to 1.25" dedicated gas line back to the regulator/meter that most big-burner tankless unit need, due to their proprietary internal compensation features. Being able to hang it on 3/4" gas lines that used to serve a 35-40K burner on a tank type water heater has been a real selling point!

 

[Tom3holer]

Dana,
Thanks I will look into that Navien. I did have to have the meter upgraded a couple of years ago due to a generator installation.
The gas line coming in is 1 1/2" then goes down to 3/4 to feed the boiler. We have a gas cooktop and gas drier also. Right now the boiler is running at 100% and with a set temp of 188 it is holding 180 and the house is 66-67 with stats set at 70. This is fine for this 6df early morning. I did disconnect the HW thermostst to keep it from coming on and will leave it that way till probably Monday when it warms up.
I have contacted two plumbers to come over and discuss the issue here with a tankless in mind.
A call to Mass Save yesterday confirmed the rebate program ran out Jan 1 and they have no idea right now if it will be continued. The $800 rebate was going to be a big help, so hopefully will know in a couple of weeks.
Thanks again,
Tom

 

[Tom3holer]

Was talking to a friend today and the subject came up and he told me of being very pleased with a hybrid water heater he is using at his camp in Greenville Me. Its a heat pump/electric unit. It uses a top mounted heat pump with a fan and has been very efficient. He said with temps above 45 or so the heat pump handles much of the demand. It has the side benefit of acting as a dehumidifier which I need in my cellar. The temp runs at a low in this wx around 45 up to the high 60's to low 70's in the summer.
Wondering if they make a hybrid with gas?
Any thoughts on this?

 

[Dana]

I'm not aware of any hybrid heat pump water heaters that use gas. The recovery times are pretty slow (even in hybrid mode), with pretty wimpy first-hour gallons numbers. A 50 gallon version would handle 2-3 people just fine, maybe even 4, but you'll want an 80 gallon unit if the showers are long or the guests bring the numbers above that.

The operating cost for most will be slightly more than with an indirect in most MA locations, and be aware that half the heat or more will be coming from the house, representing an additional heat load to be served during the heating season. But it also dehumidifies the space, taking a decent bite out of the latent cooling load in summer.

 

[Tom3holer]

It was a thought but probably won't fit my needs as well as I first thought. It would be located in the basement which is currently 43df, although the dehumidifying effect would be useful.