Single Pipe Low Pressure Steam (thermostatic??) valve thermostat


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Old 10-10-09, 08:49 PM
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Single Pipe Low Pressure Steam (thermostatic??) valve thermostat

Hi All!

First of all, thanks for keeping me up late nights totally engrossed in what other people are experiencing with their steam systems!! I think I'm addicted... I have lots of questions but we'll start with this problem first.

Some background: I have a 9000 sq building that is currently a triplex. I purchased this property in 2003 and have been learning about the boiler since then. I'm a novice so please bear with me! I have a Burnham boiler (shows ANSZ21-13 1991 and Boiler # k-5011B) on the plate inside. The main thermostat is located on the opposite end of the building of the boiler on the main floor. There are 2 bedrooms on the 2nd floor of that unit that have what I think are zone valves that are in place before the steam reaches the radiator (right where the turn off knob would be for the radiator) that are connected to a 24V transformer and Honeywell T87F1959 thermostats. I have not been able to identify any model number info on the zone valves although they are made by Honeywell. From what I understand these are normally installed on hot water systems (not steam). Recently, one of the thermostats (T87F) died. These are old mercury thermostats. I happened to have a Honeywell CT8775C Digital Round Thermostat and tried to get it to work to no avail. The old thermostat had 3 wires (Red, White, and Blue) and was connected this way:
red wire -> R terminal
white wire -> Y terminal
blue wire -> W terminal

The manual says that if I am replacing a thermostat that is connected to three wires on a zoned hot water heating system (which I am, just on steam) the thermostat will only work if an isolation relay is installed. So, the first question is: What is involved with with installing this relay?

It's my understanding that this valve has a hot (R) and the white and blue wires get connected to open and close the valve. When I connected the the red white and blue wires to the R, Y and W terminals and moved the selector to heat nothing happened. When I moved it to cool the thermostat lit up and I got a current temperature reading. When i tried to set the thermostat up or down it did not do anything to the valve.

I ended up buying a CT87K (manual thermostat) that had just the R W Y terminals and that works fine. Should I just stick with that? Can I use a digital thermostat with these valves?

Also, while I'm asking. Should these valves even be installed on this system? From what I've read single pipe low pressure steam should be using TRV's such as the

Danfoss:

http://na.heating.danfoss.com/PCMPDF...0%201PS-DS.pdf

or

Macon:

OPSK - One-Pipe Steam Valve Assembly

 

Last edited by NJT; 10-11-09 at 07:01 PM.
  #2  
Old 10-11-09, 08:13 AM
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If you want to change stats, check further for more Honeywell options. They make some stats that are steam-oriented if not steam-specific.

Also get a copy of Dan Holohan's "We Got Steam Heat". You'll love it. Talks about everything in your questions regarding venting, TRVs, and then some.
 
  #3  
Old 10-11-09, 06:14 PM
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Thanks!

I'll see what I can find. If anyone has any suggestions they would be appreciated! I don't NEED a digital. Just a nice to have. I have already ordered the book so it should be here sometime next week =)
 
 

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