Gas boiler question

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Hello, I'll be real brief with this one as my research has just begun.

The Peerless boiler for our hot water baseboard heat is ancient. People say it's way overdue for replacement.

It's a 140,000 BTU input. These are small units (30"H X 30"D X 19"W)

The first local plumber I spoke with installs Slant Fin brand boilers.

He dissuaded me from the "new breed" of super efficient boilers claiming that they break down "every 2-3 years".

It all sounded a little too pre-recorder to me. Add to that the fact that I don't want to make a purchase based on what he's comfortable with.

Has anyone any useful info on this size of boiler? I have no problem periodically replacing some widget in a box. Kira
 
Boilers can last a long time.

My 2 cents: don't incur the expense of replacing a perfectly functioning machine for the sake of fuel savings.
 
Originally Posted By: oilpsi2high

My 2 cents: don't incur the expense of replacing a perfectly functioning machine for the sake of fuel savings.


Agreed.

There would have to be a SUBSTANTIAL and significant energy savings to warrant replacement cost.
 
Kira, assuming your baseboard hot water heat is low pressure, I've got the same thing. An old Dunkirk 140,000 BTU unit under the "Bryant" name, with a single Grundfos sealed circ pump. I have two zones each with their own 24vdc switching valve. One for the basement, one for the rest of the house. I'm with the others in that if it works, keep it. I dunno of any super advancements in technology for these hot water baseboard dinosaurs.

My house is ~2800 sq/ft, family of 6 and my worst gas bills might be $160-180/mo in the coldest of months.
 
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Mod-con boilers are awesome, especially if you also use it for indirect hot water.

Water heaters getting old scare me a bit. Boilers dont. Its a closed system, so once the dissolved oxygen in the water is used up, theres really not much corrosion.

We have a 30+ yo oil/coal stoker at the mountain house thats perfect.

We changed our 30 yo gas fired boiler at our house because of the fact that our water heater was getting up in age, and there were utility rebates and tax incentives to go from a fired water heater and a 78% boiler to a 96% mod con with indirect hot water tank. Id recommend this setup to anyone. I think its better than instant water heaters because you can still modulate and condense, and the tank have next to no losses, and you can recover remnant heat in the working fluid for home heating or vice versa if set up right.

Since we use ours for hot water, it runs all year round, not just in the winter.

Weve had ours for much longer than 2-3 years, and if you consider our 12 month use vs 4 month use, ours has many more "year-equivalents". If it has ever broken for sny reason, ive never got the memo.

Peerless Purefire with Peerless Partner indirect. 110k btu, IIRC. You can go lower rating with these too because of the efficiency, but I forget the details.
 
My boiler is a cast-iron unit from 1961. I've replaced the expansion tank, pilot assembly, and water pressure regulator. If it isn't broke, why fix it?

I anticipate the cast-iron body of the boiler to outlive me. Why shouldn't it
 
Originally Posted By: Kira
Hello, I'll be real brief with this one as my research has just begun.

The Peerless boiler for our hot water baseboard heat is ancient. People say it's way overdue for replacement.

It's a 140,000 BTU input. These are small units (30"H X 30"D X 19"W)

The first local plumber I spoke with installs Slant Fin brand boilers.

He dissuaded me from the "new breed" of super efficient boilers claiming that they break down "every 2-3 years".

It all sounded a little too pre-recorder to me. Add to that the fact that I don't want to make a purchase based on what he's comfortable with.

Has anyone any useful info on this size of boiler? I have no problem periodically replacing some widget in a box. Kira


If your boiler is mounted on the floor and vents to a chimney if it has a major problem replace it with a modulating/condensing boiler that mounts on the wall and vents with PVC pipe to the outside.
 
When you do go to replace, which I agree you should not yet, anyone selling you a replacement should survey the house to determine the proper size you need. That is a mark of a better-qualified company. So many existing boilers are oversized.
 
Originally Posted By: mk378
When you do go to replace, which I agree you should not yet, anyone selling you a replacement should survey the house to determine the proper size you need. That is a mark of a better-qualified company. So many existing boilers are oversized.


That is called a manual J calculation. If they are lazy, they will just suggest something close, but probably a little higher than before. But the new ones are much more efficient. The old one might only be 70 to 80℅ efficient, but new direct vent can be 95-97℅ efficient so you don't need as many BTU as the old one, otherwise the new one will start short cycling which is less efficient.
 
Originally Posted By: Wolf359
Originally Posted By: mk378
When you do go to replace, which I agree you should not yet, anyone selling you a replacement should survey the house to determine the proper size you need. That is a mark of a better-qualified company. So many existing boilers are oversized.


That is called a manual J calculation. If they are lazy, they will just suggest something close, but probably a little higher than before. But the new ones are much more efficient. The old one might only be 70 to 80℅ efficient, but new direct vent can be 95-97℅ efficient so you don't need as many BTU as the old one, otherwise the new one will start short cycling which is less efficient.


HUGE, HUGE +1

Step 1: a PROPER heat-loss calculation. A properly sized boiler is reduced short-cycling and fuel use. However knowing infiltration (how drafty) is key as its the single biggest variable in heat-loss calculation. In my state, the local utilities will do an energy survey of your home for $100. Part of the survey is a blower-door test. Essentially a fan mounted in an exterior door sucking/blowing air in/out the house. The results of which will tell you how well sealed the home is.


I replaced the entire heating system during my remodel. Did a heat-loss calculation myself using the IBR method (slant-fin tool) and checked it against online manual J calculators. The 30+ year old CI boiler was 120k+ input, but it is used a hot water coil (demand). Anyway redid the system with a Lochinvar condensing/modulating gas boiler (ODR), Crown indirect tank and Buderus panel radiators.

1400sqft single story ranch, 55k input boiler (smallest unit) and it hasn't run full throttle during the coldest nights. My calculated heat-loss was around 26k and based on gas usage its 21-22k. I still have reserve for planned additions.
 
Yeah, it's crazy how over sized most boilers are. Slant-Fin used to have a manual J calculation tool on their website and once you plug in some numbers, I ended up with about 30k BTU's to heat to heat a 3 bedroom apartment, but it had 95k BTU's worth of heating equipment and even at 75% AFUE, that was still in the 70k range and just way more than needed.
 
Originally Posted By: Wolf359
Yeah, it's crazy how over sized most boilers are. Slant-Fin used to have a manual J calculation tool on their website and once you plug in some numbers, I ended up with about 30k BTU's to heat to heat a 3 bedroom apartment, but it had 95k BTU's worth of heating equipment and even at 75% AFUE, that was still in the 70k range and just way more than needed.


Yup, but the "downside" is a house won't heat up in 30 minutes (coming back from vacation), no deep setbacks, and no on-demand hot water (limitless). Then again my parents house and mine were built in the 50s. Oil was cheap, houses were barely insulated and hot water was on-demand off a coil in the boiler. So you "needed" a large boiler...

The only downside to a larger boiler is upfront cost and efficiency... both of which are easier to sell than installing a boiler too small that doesn't keep up. Everyone I talked to said I should be looking in the 100k range for a boiler. The good thing with modulating boilers is they allow a bit more wiggle room. Mines, 5:1 IIRC but I'm hearing 8, 10 and even 15 in Europe for mod/cons!
 
I think a standard gas hot water heater is about 30k BTU's. The recovery rate on a 40 gallon tank is typically about 50 gallons in an hour.
 
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