steam radiator

kmj

Single pipe steam - the old steam radiators in the house have a vent one third of the way down the radiator. Upstairs, there is baseboard which does not work very well in a single zone system. The radiators stay warm for 30 minutes and the baseboard is cool 5 minutes after the system shuts off. I have found old steam radiators with the vent near the bottom of the radiator. Why the difference? Will it mix with the system I have?

Just finished reading about high heating costs, vents and the pressuretrol. I think my pressure is set way too high, my main vent has never been touched and many vents in the house are old. If they hiss are they fine?

I have had too much water in the system too. Now I add water manually and keep it low. How do I tell if the boiler is too large for my house. I did have insulation blown into the house to save costs but I never thought it worked and I don't think the house is that warm. The boiler is a new Weil Mclain. The boiler was bought before the insulation was done.

Brad White

Where do we start?

1) Baseboard (copper tube and fin type) is not compatible with cast iron for the reasons you are finding out. It cools and heats at an entirely different rate and leaves you at the altar while the honeymoon goes on downstairs.

2) Vents are nearer the bottom of steam radiators because if near the top they would close sooner and the radiator would not be fully filled with steam. Steam hugs the top of the radiator and finds it's way to the lower opposite side last. Water forces air to rise high, that is why the vents are there on water radiators.

3) Pressure: You should be able to heat with 1.0 lbs. or less in most systems if you are properly vented and insulated on the piping.

4) Hissing: Vents that hiss are working too hard. If a radiator vent is hissing then it is likely the mains are not vented well if at all. Radiator vents are responsible for venting their own volume and that of their serving piping, that is it.

5) Water level- that should be indicated on the boiler jacket. Typically the sight glass should be 1/2 to 2/3 full when at rest. Do note your makeup rate though.

6) Boiler size relative to heat loss. First of all- by insulating you still did a very good thing. But steam systems are different than hot water in that the boiler is sized for the interconnected radiation it serves.

Ideally, your radiation would match your heat loss and the boiler then matches the radiation. If you have too much radiation, it still has to be served.

If you can determine the connected SF or EDR of your radiation you can compare that to the SF rating of the boiler. Many I have seen are still oversized. You may be surprised to find it properly sized.

Mike T., Swampeast MO

So many problems...

The worst problem, by far, is the baseboard. There is simply no way to make it compatible with standing iron rads on a single-zone steam system. Before you think, "I can just zone the system!", think again. Zoning a small, residential, one-pipe steam system is a practical impossibility.

Yes, you should replace the baseboard with standing iron. Salvage rads are FAR less expensive than new. To preserve system balance however, the new iron rads MUST be sized proportionate to the other radiators in the system. They CANNOT be sized to the room heat loss based on the new insulation. The best way is to conduct a room-by-room heat loss based on the pre-insulation (e.g. original)condition. Compare the EDR of the existing standing iron to the heat loss and size the new radiators similarly. You [should] find a reasonably tight correlation between loss based on original condition and EDR of the rads.

Be aware that anyone who would install fin baseboard in such a system was essentially incompetent to work with steam systems. Unless they removed existing radiators and replaced them with the baseboard, the piping to the baseboards is very likely terrible with replacement required.

My best suggestion is to find a good steam man. "Find A Contractor" at this site is a great starting place. DIY is possible, but it will take a LOT of study before you ever put your hands on a wrench...

kmj

This is a wonderful resource. In addition to these posts I have received email assistance as well.

Thank you Brad and Mike.

I do want to keep my steam system but I will not add zones or anything like that. You do have a good sense about my house or a lot of experience! It is maybe a 1600 square foot house. An earlier owner did a lot of home improvement on his own (ugh)! He was fearless I think.

Yes, someone else should replace radiators but I thought I might replace the main vent myself and reduce the pressure.

The original bedroom radiators were tall, 3 tube, 6 section radiators. I have found some beautiful old radiators, same height, 3 tube, 5 sections. I thought they might work since it would be so much better than the baseboard. Also, since they have the vent near the bottom of the rad and mine have the vent at the 1/3 (from the top) mark, I thought they might actually function a little better and it would all work out fine. It seemed logical to me but maybe not.