on/off thermostatic valve?

jumper

Some sort of snap actuator for radiator valve. To control one pipe heating in each room. Surely somebody must have tried this idea?

jesmed1

Do you mean like this?

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/013G8019-Submittal.pdf

AdmiralYoda

As in….a TRV? A Thermostatic Radiator Vent? These adjustable vents sense the temperature of the room and close the radiator vent before the radiator 100% fills up with steam. Some fancy models come with a remote sensor that allows you to place the sensor somewhere else that makes sense too.

By the way it is easier to electronically shut off the exit (the vent) than it is to electronically shut off the inlet (the valve). The valve has steam coming in and water going out, the vent is just air.

ChrisJ

TRVS use a wax motor and it's 100% variable, it can be fully open, fully closed and everything in between depending on the temperature of the wax.

The OP is asking if anyone makes a valve to go on the pipe that snaps totally shut to cut off the steam, and snaps wide open so not to block condensate.

I suppose it's possible, if you find a refrigerant to charge a oil can like capsule (like in some steam vents) with that expands at around 70F. But it'll have one set temperature, and probably a fairly wide swing. What seems far better is a solenoid controlled valve with a thermostat. But, that too is only on or off, where a TRV on the vent side is variable, it can slow it down at times rather than totally shut it off.

In my opinion, even with a solenoid controlled valve it's still best on the vent of the radiator.

Jamie Hall

@ChrisJ puts it well. There is no good theoretical reason why one couldn't have a full open/full closed valve. There are ways to make one which is fully mechanical, but it is actually easier to make one which is electric.

But.

First, on one pipe steam it goes on the vent, not on the service valve. The service — inlet — valve — must be either fully closed or fully open — and when closed must be steam tight. It is intended for one purpose only — to allow servicing the radiator without having to turn the boiler off.

Second, it is important to realise that closing the vent on a radiator can only reduce the heat output from the radiator; it cannot increase it. Further, it can only exert control if the system pressure drops to atmospheric from time to time.

But all that said — there are a number of readily available thermostatic radiator vents on the market, with a variety of control schemes.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1890460#Comment_1890460

even a hydraulic thermostat is linear, it has a mechanism attached to it that is bistable so it flips discreetly between and on and off state at discreet points in the force/travel of the hydraulic element. I think the remote bulb type actuators are hydraulic rather than wax pellet type actuators.

jumper

For many speedy warm up is a big advantage of steam heat. Shut off controller may require some sort of anticipator to prevent over shoot.