Questions on Thermostatic operator vs TRV

[vlad_nada]

Hi, I own a condo built in 1972. There are 9 other units in the building. We have baseboard heating powered by a steam boiler. The Danfoss RA-33 Thermostatic Operator separate remote mounted dial and sensor is installed on the baseboard.
Some questions that I had:

1. How does it work? How is a thermostatic operator different then a TRV?

2. Is the condition of the valve/capillaries a problem?
It works. There are NOS units on ebay and danfoss does list the replacement valve and operator for the RA-33.

2. Can this be upgraded to a smart thermostat like nest?
Ive read about some issues w/ boiler temps/cycle times in homes but havent seen anything on condos or apartments. It would just be adjusting the valve and not turning the boiler on/off so I dont think it would have the same issue right?

Any info is appreciated. Thanks!

-Dan

 

[Dana]

This is essentially a TRV, but it places the temperature sensor (a thermocouple) away from the radiator, which gives it more precise room temperature control.

There is no simple way to replace or integrate these things with a smart thermostat. Thermostats such as the Nest are making switch contacts for low voltage electrical controls. These things operate on gas pressures changing with temperature, as described in this document:

The RA 2000 thermostatic operator consists of a saturated vapor charged bellows and a setting dial. The dial is set to the position equal to the desired temperature. When the ambient temperature lowers, the pressure from the bellows will reduce, allowing the valve to open. A rise of temperature increases the pressure in the bellows closing the valve. The balanced pressures between the adjustment spring and the bellows ensure a smooth and modulating operation of the valve.

If it's working, keep it, but given the amount of corrosion it's good keep the replacement part information handy.