Sizing a residential boiler

Dave_23

Last sentence should read "...no STORM windows..." Sorry.

Dave_23

Sizing a residential boiler

My question concerns sizing a steam boiler for a residential application. My house in Michigan was built in 1926. I have a two-pipe Trane vapor system. Several energy efficient upgrades have been performed over the last five years or so, including new windows, better insulation in the walls and attic, doors, weatherstripping, etc. However, I still have the same original radiators. Most of the radiators only get partially hot before the thermostat is satisfied. Therefore, when running the calculations to properly size a boiler for my home, based on size of the rads, would you scale their size down to account for the fact that they only need to partially heat to satisfy the 'stat and properly heat the house? Let's assume for the sake of this discussion that everything, main vents, boiler, etc., work properly and that the house is perfectly comfortable and balanced with no hot or cold spots.

As a side note, back in 1926, I suspect that the boiler ran continously during the heating season, to overcome poor insulation, lousy windows, no windows, cheap energy (coal) which allowed the rads to fully heat.

Constantin

Hi David...

... and welcome to the Wall. I am a fellow homeowner and the current apartment I'm renting has steam heat, though only a one-pipe system.

It is my understanding that the emitting surfaces (called EDR) are what you need to size a steam plant with, not the actual heat loss. Way back when, the installer installed radiators that were expected to cover the heat loss, connected the piping, and then sized the boiler to meet the total steam need of the system.

If you undersize a steam boiler relative to the connected load, it'll never manage to start steaming and the result will be a cold house.

Given that you've weatherized and insulated your home, you'd think that a smaller steam plant is needed. That is not so, unless you do a room-by-room heat loss and resize the radiators accordingly. Only then would the EDR of the system decrease.

I suspect that resizing the radiators is not in the cards. However, it is still worthwhile to go through the house and measure the radiators to make sure that the boiler is not oversized. Dan Holohan has several good books on the subject of steam heating that you can buy. I recommend "We Got Steam Heat" as a primer, followed by "The Lost Art of Steam Heating" as well as the EDR booklet.

Depending on your system, you may be able to improve fuel efficiency and comfort by making small improvements in the venting and other details. In the meantime, I'd absorb the great knowledge in Dans books, and use the "Find a Pro" service to see if any great steam experts are in your area.

Mike T., Swampeast MO

Constantin:

Even if the rads in this system are re-sizable (they have small horizontal rods at top and bottom) there is still a big problem. His is a two-pipe vapor system with connections at each end of the radiator. Re-size the radiators and you have to relocate the piping! Extremely expensive and rather impractical.

J.C.A._3

Unless you're going to.....

Downsize the radiation, a new boiler should be sized to the existing radiation. If the improvements to the envelope are as good as you say, you can lower the usual piping pickup factor quite a bit, but the radiation is the deciding factor for sizing. It has to be filled for the pressure control to work properly, and venting IS the key.If it's a vapor system, is the pressure control working properly?
Chris

c.t.kay

steam capacity

2 pipe steam,put in trvs,put in orifice plates sized to the heat loss of the rooms,down size the edr of the boiler +-30%,no pick up load.put the whole system on a heat timer.it works.

Unknown

I'm with c.t.k.

I have some very good experience to share with old Trane systems, and some good tales from the trail. Because it's a Trane, I'd like to chat with you about it.

I'm at 800 873 4346, 9-5 Eastern time.

Noel

Unknown

Constantin, I admire your heating opinions.

Permit me to disagree.

Please stick to things that you are trained in.

Noel

Supply House Rick

MEGA DITTOS

The empty can rattles the most!!! Oh, wait should this be in favorite quotes thread? No it fits here also. Some people have a lot of free time and respond to every post. I am glad I am not that lonely. Another quote from Jack Sparrow "mate, you need a woman"