SIZING A STEAM HEAT BOILER

lellabella

Hi All. Does the US have a regulated guidelines on how to calculate the size of a new boiler? HomeServe came 3 years ago and put in an larger size boiler which cause one room to not receive heat properly. Long story short, I am in a position now to document everything and contact HomeServe corporate to make sure this addressed. Thanks.

Hot_water_fan

Good luck!

KC_Jones

There aren't regulated guidelines, but many manufacturers have information on their website about proper boiler sizing. It's not hard.

You most likely have more than an oversized boiler issue if heat is not getting to a certain room.

MaxMercy

I don't think there's a U.S. gov regulation, but to way to size the boiler is by several factors - how much radiation the house has as well as the "envelope" itself (windows, doors, insulation, etc.).

I'm sure the steam guys will give you specific instructions on how to start with measuring how much radiation you have.

As far as one room not getting enough heat, it sounds more like a venting issue.

ethicalpaul

(simultaneously posted with the above two similar answers, sorry!)

The correct sizing of the boilers is in the documentation and manuals of the various manufacturers. It's based on the "EDR" or "Sq Ft of Steam Radiation" (sometimes referred to as "Sq. Ft." on the boiler rating plate), which is the square feet of each radiator surface that is exposed to the air in the house, all added up. There are reference materials that show the EDR for most radiator designs and the installer 100% should have measured your radiators to come up with this value

I have no doubt they oversized it, but I will say that would not prevent one of your radiators from getting steam. That problem is caused by something else, such as incorrect piping, missing or inappropriate main venting/radiator venting, or possibly other cause (but those are the common ones).

KC_Jones

What brand is the boiler?

Jamie Hall

The poor heat to one room is, as has been said, likely a venting problem -- but there are other possibilities as well which need to be checked. None of them, however, are related to the size -- oversize or otherwise -- although they may be related to poor installation.

There are no regulations in the US as to how to size a boiler. However, for steam systems it is very easy to do.

Steam boilers have a rating called the EDR rating, or square feet of steam. This is the amount of radiation, expressed in terms of EDR (equivalent direct radiation) that they can power. Radiators (and other similar devices) are also rated in terms of their EDR, which is how much power they can absorb and emit into the space.

So... you go around the structure -- house or whatever -- and locate all the radiation, determine the EDR of each unit (there are handy tables and books for that) and add it up. Then you select a boiler with the same or slightly more or less EDR rating (note that many boilers have a range of power which they can be fired to, so make sure your EDR is in that range), and you're good to go.

That's all there is to it -- so far as selecting the boiler size,

Next step is installing it correctly. All boilers come with a manual with the minimum installation requirements for piping and controls. These are minimum requirements! Sadly, not all installers read them...

BobC

When a boiler gets ripped out and rep[laced the systems piping gets moved around. I suspect you may have some piping that been inadvertently moved so the slope is not allowing water to find it's proper home (the boiler). Any water sitting in a pipe will collapse steam trying to cross over it so it won't reach it's destination when it is supposed to.

Although it could well be a venting issue I'll vet some piping has been moved. Puy a level on the problem radiator and make it slopes so water can find it's way out and check the piping in the basement to make sure water can find it's way back to the steam main and then the boiler.

You have find out what got moved and figure out what to do to get the slope right. I'm assuming this is single pipe steam where the steam and wateer flow through a single pipe. If your lucky you'll just have to lifyta radiator up 1/2 to 1" to make it work, bake sure the radiator has slope so water can find it's way out.

Bob