TRVs and pressure

Steamed2

A contractor told me that when a TRV is placed on a radiator they have seen that only the top part of the radiator gets hot. They also stated that TRVs work best when the pressure on the system is turned up -- to like 10. Does this contract know what they are talking about?

Jamie Hall

No.

There are, of course, two sorts of TRVs, and one has to be sure -- assuming we are talking steam here -- that one is looking at the right sort. One is used on one pipe systems, with vents, and controls the vents. The other is used on two pipe systems, and controls the inlet valve. Neither will affect how the radiator heats -- or the steam pressure needed -- in any way differently from what closing the vent (in the one case) or the valve (in the other) would do.

bburd

Steamed2 said:

A contractor told me that when a TRV is placed on a radiator they have seen that only the top part of the radiator gets hot. They also stated that TRVs work best when the pressure on the system is turned up -- to like 10. Does this contract know what they are talking about?

TRV’s may admit a small amount of steam into a radiator if the room does not need much heat. This means the radiator will heat partially, usually the first section or two if the steam enters at the bottom; then along the top. If the room temperature is maintained, it’s perfectly fine.

In most residential steam heating systems the pressure should be 2 psig or less. Vapor systems operate at less than 1 pound. All sorts of bad things happen at higher pressures, including water hammer, water spitting from air vents and damage to air vents.

There are exceptions, but they are uncommon.