Steam neophyte - oversize boiler issues?

joel_19

Do not even think about changing the system before tightening up the envelope more , your putting the cart before the horse . Anything we HVAC pros do is a bandaid to combat the heat leaking out of the house . First stop the bleeding , then worry about what else is wrong .

Jon_11

Steam neophyte - oversize boiler issues?

Disclaimer: not a heating pro.

My brother bought a big, old (100 years plus) house in the Finger Lakes area a couple of years ago. It's about 4,000 square feet with high ceilings. He had cellulose blown into the attic, but the walls are still uninsulated. It's heated with steam of the single-pipe variety. His heating bills have apparently been very high, and he's trying to sort out why.

For some reason the previous owners installed a 400,000 BTU commercial boiler, which a local HVAC contractor guesses is more than two and a half times as big as it ought to be for this house. That same HVAC guy would dearly like to sell my brother a forced air system, and has actually said "I'll guarantee 30% lower heating bills, and it will probably be more like 50%."

This suggests, to me at least, a few questions. Does it sound likely that the boiler is oversize for such a house? How much efficiency is lost when a boiler is oversized? Are forced air systems typically more efficient than steam and, if so, by how much?

Neither of us has any expertise in this area. I realize I'll probably need to buy a book or two to really solve anything, but I'd appreciate some help sorting fact from crap here.

Thanks for any insights.
--Jon

Bob W._3

Jon, go to the menu at the left side of the screen and click on Hot Tech Topics. Read all you can about sizing steam boilers, and the other steam articles. Then go to Burnham's website and get the charts for measuring the radiators. Steam boilers are sized to installed radiation. My home is 4000+ SF, with a 450,000 BTU input boiler, rated at 1125 SF steam and correctly sized for the installed 1087 SF of radiation. After you measure the radiators and add them up, you will know if the boiler was oversized.

This is the Burnham chart for sizing radiation:

http://www.burnham.com/Sizing.cfm

Mark Hunt

Ah geeze


There is only one way to size a steam system and that is to measure the connected load. That means measuring EVERY radiator in the house and coming up with how many square feet of steam the boiler needs to produce. Square feet of the house has nothing to do with this unless we are trying to determine if there was enough radiator to do the job.

Now since the home is that old I can almost guarantee that some remodeling has been done and probably some radiators have been removed. Blowing in insulation will lower heat loss but it does nothing for the existing radation except to make it over-sized.

So before I tell you that the boiler is over-sized,(99% sure it is) I need to know what it has to fill.

If I put a 1 million btu boiler in a 2000 square foot house and it doesn't heat, do I have a boiler that is too small??? If I put a 1 million btu boiler in a house that is 2000 square feet and it heats fine but costs an arm and a leg to heat, is the boiler too big ???

Steam boilers do one thing........they change water from a liquid to a gas. How much gas they need to create is determined by how much volume the system needs. Nothing to do with how big the house is, only how much radiator and piping is connected to the system. They need to be filled.

So you and your brother need to measure the height and depth of every radiator in the house. We also need to know the type of radiator whether it is a column type, tube type or thin tube type radiator. Then we can see how much steam he actually needs. From here we can decide how big the boiler needs to be.

Now he may not have enough radiator. Some may have been removed. So he has a 400k btu boiler connected to 200k of radiation. Boiler eats 400K of fuel but the delivery system can only handle 200K of heat. Where does the other 200K go????? Go outside and look up at the chimney and you will see it! It is being vented to the atmosphere. Still paid for it though.

So..........more info needed here. We can solve your brothers issue, but we need more info.

Mark H



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Jon_11

Thanks for the ideas so far. I'm a few hundred miles from my brother's house, so it's tough for me to start measuring radiators. I'm going to tip him off to this thread so he can follow up.

Maine Doug_22

What's a few miles

Hey, he's your brother. Order the books and drive over some weekend and help him.

Jon_11

What happened?

Did I log onto HeatingGuiltTrip.com by mistake?

I am going to start working through the steam-related Hot Tech Tips articles. The first one ("Boiler Sizing") didn't have any technical info, but it was entertaining. In the meantime, could someone clarify how to properly measure radiators? When you say "height and depth", I assume height will be from the floor-up and depth will be from the side facing the wall-out. Does the length not matter?

Also, how does one know the difference between column, tube and thin tube types? I believe they are all old cast iron items, if that narrows it down.

Jon_11

What happened?

Did I log onto HeatingGuiltTrip.com by mistake?

I am going to start working through the steam-related Hot Tech Tips articles. The first one ("Boiler Sizing") didn't have any technical info, but it was entertaining. In the meantime, could someone clarify how to properly measure radiators? When you say "height and depth", I assume height will be from the floor-up and depth will be from the side facing the wall-out. Does the length not matter? Are we measuring volume or cross-sectional area?

Also, how does one know the difference between column, tube and thin tube types? I believe they are all old cast iron items, if that narrows it down.

Bob W._3

Jon, the Burnham site lists the sq. ft. EDR for common types of radiators. If you have the old cast iron single pipe radiators, measure from the floor and count the number of columns, then find the sq. ft. EDR per section and multiply times the number of sections. This should get you close. I believe you can purchase a manual on this site that lists many specific types/brands of radiators. You mentioned the boiler had a 400,000 BTU input. That should work out to about 1000 sq. ft. of EDR. I wouldn't be surprised if the house has that much radiation.

Jon_11

Uhh, Bob?

I think something went haywire with your last response.

Bob W._3

I hit the post button before entering any info. See above. BTW, I am replacing my boiler and downsizing the installed radiation by about 45%. I'm keeping the steam system because we like the heat.

Steamhead (in transit)

Jon, the radiator sizing book you want

is called "E.D.R." and you can get it on the Books and More page of this site. There were many different types of radiators made and this book has almost all of them. Also get "We Got Steam Heat".

The contractor your brother encountered is a typical scorched-air pusher with dollar signs in his eyes. You don't need him and his furnasties. When a steam system is set up properly, it's far more efficient than scorched-air.

Have your bro post some pics. We love this old stuff.

Jeff_65

I'm the brother

Hi Everyone,
Thanks a LOT for your help so far. The HVAC guy did measure all the radiators and (of course) said that the boiler was oversized. I'll go through and do all the measurements again and post that info but right now I'm posting 3 pics of different radiators we have.

One pic is a large white one (we have 2 this size) and another is silver (we have about 6 this size). Each of these are about 38" tall. The smallest radiator we have is also pictured (it's about 20" tall). There are a variety in between and a total of 19 or 20 in the house.

One important question - please check out the picture of the large white radiator and tell me whether I should count it as having 12 columns or 24 when calculating volume with the Burnham tables. The HVAC guy told us it was 12 (because each set of 2 are connected).

I'll post the measurements but please let me know if there's more info I should provide.
Thanks again!
Jeff

lchmb

Now that's beauty

If you ever get crazy enough to remove that system let me know. I'll drive out and haul those off for you for free!!
BTW...You will never find a better way to heat a house than steam..IMHO...

Bob W._3

Jeff, I don't think the Burnham tables are specific enough to size those large ones. One of the steam guys on this board, like Steamhead, should be able to give you the numbers. Nice stuff, by the way.

Steamhead (in transit)

I bet that large white one

is a Bundy, made by A.A. Griffing Iron Works. Other possibilities are the Reed, made by H.B. Smith Co, and maybe the Nason, made by Nason Manufacturing. You should be able to find the maker's info cast into the base. Ratings for these are not in E.D.R. or the Burnham Heating Helper, but you can find them here:

http://www.heatinghelp.com/pdfs/92.pdf

If that is a Bundy, each pair of risers coming off a common base connection are looped together at the top. So the rating for these is based on the number of loops.

John_102

Airmail

Airmail those rads to me, collect! They're beautiful!

Sheila

I'm the sister-in-law

Hi All,

I'm Jeff's wife and co-owner of those radiators. Thanks to everyone for your input and for the nice comments on our radiators! Best we can figure, we have about 750 sq. ft. of radiation (including 6 large Bundys - thanks for that info Steamhead). Our boiler is 80% efficient so it is kicking out about 320K BTUs. Does this seem to be about the right size for the amount of radiation we have? Given Bob W's previous post, it seems as though this may not be that oversized (I'm not sure if we should be looking at input or output).

One thing the HVAC guy told us about our boiler is that unlike residential models, it does not have very many energy saving features. Specifically, it does not have a damper that closes automatically when the boiler is not heating. As a result (we were told), cold air travels down the chimney cooling the water in the boiler and making it work all the harder to get heating again when it cycles. He suggested that there might be someway to jury-rig a damper for the boiler so that did not happen. Does this at all sound possible? If so, how might we do this?!

Thanks!

Bob W._3

Check your email. Hopefully one of the pros will answer that damper question.

Steamhead (in transit)

Look at the rating plate again

there should be a rating "NET Output" in square feet steam radiation, or BTU per hour. If it's in BTU, divide by 240 to get the square feet EDR rating.

Stack dampers are sometimes controversial, but if your house is old enough for steam heat it was also old enough for coal-fired boilers, which required much more chimney draft than gas or oil-fired units do. Such chimneys can produce enough draft that they will suck a lot of heat from the boiler on the off-cycle. In this situation I'd say a damper is worth the expense. There are a few caveats- one of which is that the boiler must have a dual-seated electric gas valve or two separate valves, and of course the installation must be done by a pro. And if it turns out your boiler is way oversized, you'd be better off replacing it.

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