What is the highest efficiency residential boiler?

NateCH

I'm likely going to need to replace our Weil-Mclain EG40 one pipe steam boiler (102k BTU/HR) that was installed in 1987 in a 3000 sq ft 1880s two story house with foam insulation and new windows.
Replacing because it leaks water pretty badly (Last winter it would hit the cut off every night) and I'm told its too difficult to repair and that repairs are too unreliable.

I was hoping to find a newer unit with unbelievably high efficiency, but it seems like I can pretty much only expect similar efficiency to what I have now. I can't find any steam boilers that are more than around 82% efficiency. Am I missing anything? Is there a cute wall mount boiler out there with 90% plus efficiency? It would be nice to be able to use a smaller diameter chimney and take up less space in the basement, but I'm mainly thinking that if I have to suffer with replacing, I would like to see some savings on propane.

Thanks for your help.

ChrisJ

NateCH said:

I'm likely going to need to replace our Weil-Mclain EG40 one pipe steam boiler (102k BTU/HR) that was installed in 1987 in a 3000 sq ft 1880s two story house with foam insulation and new windows.
Replacing because it leaks water pretty badly (Last winter it would hit the cut off every night) and I'm told its too difficult to repair and that repairs are too unreliable.

I was hoping to find a newer unit with unbelievably high efficiency, but it seems like I can pretty much only expect similar efficiency to what I have now. I can't find any steam boilers that are more than around 82% efficiency. Am I missing anything? Is there a cute wall mount boiler out there with 90% plus efficiency? It would be nice to be able to use a smaller diameter chimney and take up less space in the basement, but I'm mainly thinking that if I have to suffer with replacing, I would like to see some savings on propane.

Thanks for your help.

82-83% is as high as you're going with an atmospheric natural gas boiler.

Which is fine.
Concentrate your efforts on improving insulation, windows and infiltration. Having an 82% boiler run less will save more money than a 96% running often.

Ironman

The highest efficiency will be the one that’s properly installed with all the system components functioning correctly.

The Steam Whisperer

Ironman is giving solid advice... you can often cut fuel consumption 20 to 30% just by making sure the system is working optimally...i,e. installing and properly setting up the thermostat for steam can cut fuel usage about 12% if the current thermostat is not set up properly. For a boiler replacement, you may want to first make sure the new boiler is properly sized. You may want to look at small power burner boilers ( ie. Peerless EC) These should give you even better efficiency. This type of boiler is used in large commercial applications, but can be had in a small size. The EC heat exchanger is designed for use both for gas and oil firing, while most small power burner boilers are designed mainly for oil firing.

Also, another thing to remember is that the simple atmospheric boiler uses about 1/80th ( not 1/8th) the electricity of a "high efficiency" forced air furnace and somewhere around a quarter of a "high efficiency" hot water boiler. The efficiency numbers on equipment are extremely misleading when comparing different types of equipment as they are not based upon the total energy consumption of the equipment and the losses in a typical system.

Jamie Hall

The thermodynamics is very much against you. So-called "high efficiency" boilers get their high efficiency by condensing the water vapour in the combustion exhaust. This simply can't happen when the boiler and return water is much above 140 F, and doesn't really kick in until down around 100. Water boils and produces steam at 212 F. Too high a temperature.

That said, you can get slightly higher efficiency out of a properly installed and tuned oil burner than you can out of a properly installed and tuned gas or propane burner (around 85% vs. around 82%). Again, the thermodynamics are at play -- a good deal of the heat from oil comes from combusting the carbon to carbon dioxide, and less to combusting the hydrogen to water. Gas is much more hydrogen and much less carbon.

A poor installation or sloppy tuning can easily drop either one to around 50% or worse, no matter what the manufacturer's sticker says.

Hot_water_fan

Also, another thing to remember is that the simple atmospheric boiler uses about 1/80th ( not 1/8th) the electricity of a "high efficiency" forced air furnace and somewhere around a quarter of a "high efficiency" hot water boiler. The efficiency numbers on equipment are extremely misleading when comparing different types of equipment as they are not based upon the total energy consumption of the equipment and the losses in a typical system.

Sure, electricity usage is less but doesn't outweigh the increased gas usage.
For example: 60,000 peak load, $1/Therm and $.20/kwh. A 82% steam boiler using 0 electricity costs 5% more than a 95% furnace using 300W. When load is less and the blower is moving only a 1/3 of the air, the savings increase.

ChrisJ

Hot_water_fan said:

Also, another thing to remember is that the simple atmospheric boiler uses about 1/80th ( not 1/8th) the electricity of a "high efficiency" forced air furnace and somewhere around a quarter of a "high efficiency" hot water boiler. The efficiency numbers on equipment are extremely misleading when comparing different types of equipment as they are not based upon the total energy consumption of the equipment and the losses in a typical system.

Sure, electricity usage is less but doesn't outweigh the increased gas usage.
For example: 60,000 peak load, $1/Therm and $.20/kwh. A 82% steam boiler using 0 electricity costs 5% more than a 95% furnace using 300W. When load is less and the blower is moving only a 1/3 of the air, the savings increase.

And when the high efficiency furnace breaks?

Big Ed_4

As stated you need to look at the whole system to up efficiency ...

If had a steam system the boiler would be Burnham MPO ....

SuperTech

Big Ed_4 said:

As stated you need to look at the whole system to up efficiency ... If had a steam system the boiler would be Burnham MPO ....

The steam version of that is the Burnham MegaSteam. Not available with a gas burner.  Can it be converted? Sure it can, but it will void the warranty unfortunately. 

Big Ed_4

MPO and Riello gas burner .... It would be in my cellar... if I had steam .

NateCH

Thanks, everyone. So if a new unit isn’t much more efficient  than my current one, does it make sense to fix the current one? It seems like my old one is the same efficiency but no on fixes them at this point.

I’m currently attempting jb weld a couple of leaks on the heat exchanger. We’ll see if they hold at least long enough for a new boiler to arrive.

My HVAC guy recommends replacing with a NEW YORKER CGS40CNI-H STEAM 103MBH INPUT 263 SQ FT 82% AFUE
Is that a good boiler?

Before install I’ll do some calculations to make sure that’s the right size.
I’m also considering solid fuel as well, but that is probably unlikely.

We have done all of the obvious insulation work we can do.

ChrisJ

If the block is leaking and it's that old no, don't try to fix it.  Replace it with another EG40 assuming that's the proper size for your building and radiators.


I just installed an EG40 in my own house in 2011 and I would again.



Keep in mind piping is extremely important on a steam boiler so there's a chance you could improve on that.  Share some pictures of your current install.

NateCH

Here are pictures. We removed the asbestos insulation when we bought the place two years ago. I have it on the list to class up the pipe insulation but here you have it. 

Do the pipes look correct?

jb weld on the side of the boiler is dry but apparently the leak is on the bottom right above the burners. It is a fast leak. I think we need a new boiler now. 

Last year I would say the boiler heated tolerably well, but it wasn’t possible for all radiators in the house to get fully hot at once. I had to have some rooms turned off completely. I have fiberglass insulation on 90% of the pipes in the basement. I replaced the main vent and the vent on the return vent last year.


We have a Weil-Mclain EG40 one pipe steam boiler (102k BTU/HR) that was installed in 1987 in a 3000 sq ft 1880s two story farm house with foam insulation and new windows. 

Thank you all once again!

Ironman

No, that’s not piped correctly.

This is how it should be:

STEAM DOCTOR

NateCH said:

Thanks, everyone. So if a new unit isn’t much more efficient  than my current one, does it make sense to fix the current one? It seems like my old one is the same efficiency but no on fixes them at this point.

I’m currently attempting jb weld a couple of leaks on the heat exchanger. We’ll see if they hold at least long enough for a new boiler to arrive.

My HVAC guy recommends replacing with a NEW YORKER CGS40CNI-H STEAM 103MBH INPUT 263 SQ FT 82% AFUE
Is that a good boiler?

Before install I’ll do some calculations to make sure that’s the right size.
I’m also considering solid fuel as well, but that is probably unlikely.

We have done all of the obvious insulation work we can do.

What was his basis for recommending that boiler? Did he measure the radiators, and determine the heat output of the radiators? If not, he is a minor leaguer at best and should be sent back down to the miners until he is ready for the Major leagues. 

ChrisJ

STEAM DOCTOR said:

NateCH said:

Thanks, everyone. So if a new unit isn’t much more efficient  than my current one, does it make sense to fix the current one? It seems like my old one is the same efficiency but no on fixes them at this point.

I’m currently attempting jb weld a couple of leaks on the heat exchanger. We’ll see if they hold at least long enough for a new boiler to arrive.

My HVAC guy recommends replacing with a NEW YORKER CGS40CNI-H STEAM 103MBH INPUT 263 SQ FT 82% AFUE
Is that a good boiler?

Before install I’ll do some calculations to make sure that’s the right size.
I’m also considering solid fuel as well, but that is probably unlikely.

We have done all of the obvious insulation work we can do.

What was his basis for recommending that boiler? Did he measure the radiators, and determine the heat output of the radiators? If not, he is a minor leaguer at best and should be sent back down to the miners until he is ready for the Major leagues. 

I'm not sure what they did, or didn't do.
But if that improperly piped EG-40 is working, I have a feeling it's probably not oversized.

I have an EG-40, was, EG-45 based off of radiation in a 1600sqft 1860s house.
If they're doing ok with that in 3000sqft it can't be too far off.

NateCH

He recommended that one because it is pretty close in specs to our current unit. The New Yorker is a couple Grand cheaper than the Weil-McClain.

I did the load calculation I have 465 sq ft of radiation from radiators. I followed the procedure here:
https://www.usboiler.net/sizing-steam-boiler.html


my calculations are here
https://docs.google.com/spreadsheets/d/12Zem4eB0ZwUs9IJukSTNbtcz13g2SoUTpXweiJFzHyE/edit

What am I to do? That’s double what my current boiler had. Last winter we only ran about half of the radiators at a time to ensure the most important ones were hot. I chalked that up to the boiler being close to the end of its life and having a leak. I guess this makes sense if our boiler is so undersized. 

So should I get a boiler that has 465 sq ft of steam for a 3000 sq ft house even though the previous boiler was way smaller?

Granted, I am going to heat a room that previously never had a radiator, but that is only a one room increase. 

Am I missing anything?

mattmia2

The ratings plate edr has a 30% pick up factor added to it to account for piping losses. Most systems have far less loss than that especially if they are insulated. If the system is well balanced and doesn't have issues with inadequate venting or trapped water or bypasses between mains if the boiler is a little smaller than what it is connected to it should heat ok. 50% undersized will have trouble filling all of the radiators on the system. I would size it to the connected(and planned) radiation with a smaller pickup factor and control it with a vaporstat. The vaporstat will control the boiler more precisely if you continue to shut off some radiators sometimes.

A properly sized boiler will be most efficient. A boiler that is too small will run a lot and not get heat out to the radiators as well, a boiler that is too big will heat the water hotter than necessary and cycle on pressure. A properly sized boiler will generate just the amount of steam that the system can consume.

The Steam Whisperer

Are you one pipe or two pipe steam. Two pipe steam can often go with smaller boilers.....especially if it was an original orifice system. The big one was Moline, but other big two pipe steam names started using orifices in the 1930's.

STEAM DOCTOR

There are two separate questions at hand over here. Question number one is what size boiler do you need. Question number two is should you hire that amateur. I certainly know the the answer to question number two. And the answer is no. He is guessing. Even if he's lucky and he guesses right, you do not want a guesser involved in the major investment of a steam boiler replacement. 

STEAM DOCTOR

And assuming your calculations are correct, then definitely get a boiler sized to the radiation.

STEAM DOCTOR

Using industry standard pickup factors, Weil Mclain EG-50 would be a perfect match. But nothing says you need to go with Weil Mclain. You can get a Williamson boiler, which is essentially a WM in disguise.. Or you can go with Peerless. But without question, you want a major leaguer to do the installation.

NateCH

Thanks!

It’s a one pipe steam system.

Is New York Boiler acceptable? Or are Weil-McClain, Williamson, and Peerless my only options?

STEAM DOCTOR

All boilers are acceptable. Just some will probably last longer than others. I personally prefer Peerless, WM, Williamson but each tradesperson ha their preference. But that is really step two. Step one is to find a qualified installer. The installer is considerably more important.

AdmiralYoda

NateCH said:

Last year I would say the boiler heated tolerably well, but it wasn’t possible for all radiators in the house to get fully hot at once. I had to have some rooms turned off completely.

This tells me that your boiler is likely undersized and backs up your EDR calculations. A small boiler will have to run much longer to provide adequate heat and by turning off radiators you lowered your overall EDR which made your boiler more effective.

A properly sized, perfectly piped and insulated boiler with good venting will run circles around what you have now and your system as a whole will be way more efficient. With an undersized boiler it is running a lot just to provide heat.

Where are you located? You need a real steam pro for this one. Check out the "Find a contractor" link at the top of this site.

This forum is full of posts of people asking for advice, getting it and then ultimately going with the lowest bidder...just to come back in a month begging for more help because the system isn't working right and it turns out everything that they were warned against did happen and they need a complete do-over.

NateCH

Thank you all. This certainly gives me a reason to get bids. 

One more question. The house is certainly better insulated than it was 30 years ago when the last boiler was installed or 100 years ago when I assume the steam system was first installed. 

Could my radiators now be oversized for each room? In the last thirty years the house has gotten vinyl siding, windows, spray foam insulation. Seems like that would cause you to need smaller radiators and thus a smaller boiler.

AdmiralYoda

@NateCH More than likely yes, they are oversized for the rooms compared to decades ago. The cost to replace the radiators with smaller ones to utilize a smaller boiler would be excessive. Unless you are able to find good used radiators it can become a non-starter. Good, new radiators can get pricey.

You'd have to do the heat-loss calculations for each room and figure out how much EDR is needed to balance that heat loss.

The beauty of steam is that the radiators only fill with enough steam as needed. If the thermostat is satisfied the radiator won't always fill all the way up and be screaming hot. Balancing radiator venting so that all the radiators heat up at the same time will prevent them from cooking you out.

ethicalpaul

It's a complicated subject and controversial. Yes your radiators are likely larger than you (now) need. You have been running with some of them turned off, correct?

In most calls for heat, your radiators aren't going to fill up completely with steam anyway. Is a massively oversized radiator really massively oversized if it never fills up with steam?

If you have rooms that are too hot, you can slow down the venting on those rooms, or cover part or all of the radiator with a blanket. Both of these have the effect of reducing your radiation (caveat: on a long call for heat, slow venting becomes moot-- eventually it will fill with steam. This is one reason why large setbacks are not great with steam heat).

I would say size for your radiation, but if you're between two boiler sizes, definitely choose the smaller one.

The 30% pickup factor that is built into the sq ft rating of steam boilers is way larger than it should be IMO, this lets you go with a smaller boiler than the numbers may indicate.

KC_Jones

If your 465 number is correct, I would do an EG-50 and no bigger. I definitely wouldn't go smaller especially since you already said you aren't getting enough heat.

All that piping is wrong, so make sure they pipe it properly. That include the tee connecting the 2 mains, they should be connected to the header indivicually.