Old church heating advice

Larry Gebhardt

Our old church (1904/1928) in Pocatello, Idaho is heated by ten zones controlled by old Honeywell motorized valve linkages with modutrol motors. The Honeywell thermostats are 3-wire SPDT that operate the open-shut windings of the valve motors.

We are looking for programmable thermostats. Honewell tech support advised: "Honeywell doesn't make programmable thermostats for 24 volt AC SPDT valves. You would need to have a contractor install a 24 volt switching relay to convert the SPST switching action of our programmable thermostats to SPDT. Once these are installed, you can use most of our programmable thermostats."

Do you know of other thermostat manufacturers who have SPDT programmable models? of if not, then of sources for the 24V switching relay, SPST-SPDT conversion?

Thanks,
Larry Gebhardt

Larry Gebhardt

Updating old zone control

Our old church (1904/1928) in Pocatello, Idaho is heated by ten zones controlled by old Honeywell motorized valve linkages with modutrol motors. The Honeywell thermostats are 3-wire SPDT that operate the open-shut windings of the valve motors.

We are looking for programmable thermostats. Honewell tech support advised: "Honeywell doesn't make programmable thermostats for 24 volt AC SPDT valves. You would need to have a contractor install a 24 volt switching relay to convert the SPST switching action of our programmable thermostats to SPDT. Once these are installed, you can use most of our programmable thermostats."

Do you know of other thermostat manufacturers who have SPDT programmable models? Or if not, then of relatively inexpensive sources for the 24V switching relay, SPST-SPDT conversion?

Thanks,
Larry Gebhardt

don_9

old valve

Larry I have never seen a douple throw tstat. if i may ask
is the valve energize open thru the tsat then when tsat
is satisfied it power close again. if that the case i would think you could get by with a simple multi purpose relay,energize the relay coil from tsat, with a separate transformer for damper motor and relay contact
valve open thru the normally open set of contact on relay with a call for heat, then when tsat is satisfied its power close thru normaly close contact. fan center will do the
job. that is if we talking heat only and it a 24 volt control circuit,used the extra wire at the tsat for your common terminal on the programable tsat.I hope this is what you were asking. don

don_9

sorry

I had to get the saw dust out of my eyes,after reading the thread again i can see i added nothing new. oops.

Boilerpro

Inexpensive relays

I made that conversion on some of the old Honeywell Modutrol motors on my own church last fall. A simple "ice cube" plug in relay will work fine with its matching base. Siemens' No.3TX7114-5LC13 is a good make. Since you have a 24 V power source to power the valve, you don't need another power source(like a fan relay) to power the relay. These relays are available through Johnstone Supply and other sources.

Boilerpro

John Mills

White-Rodgers

Some of the W-R 1F90 series are designed to work with W-R 3 wire zone valves. Don't know if they work the same way as these old Honeywells but might be the first place to look.

Dan Law

Alternate control scheme

I assume the driving force for the programable thermostats is energy conservation. If this is the case, you might consider a different approach than all zones reseting individually. Instead, wire a single night setback thermostat to the boiler control circuit, in series with the existing zone valve end switches. Set this thermostat to a day temperature of say 75 degrees, and a night temp of 55f. The zone stats will still control at thier individual setpoints during the day, cycling the boiler on demand. During the night cycle, all zone valves will be open, but the boiler will not fire till the night stat setting of 55F is reached. At this point the boiler will fire and circulate all zones untill the 55F setpoint is satisfied. On return to "day" mode, your back to individual zone control. This same general concept will work if the motorized valve operators are not interlocked to the boiler through end switches. Just be certain the "day" setpoint is high enough to call for heat constantly. If your boiler control circuit is 120 vac, a time clock and line voltage thermostat or relays can be employed. The specifics of you boiler and control system will determine the exact connections. Let me know if you need some wiring help.

Boilerpro

Seen this too, using a timeclock and Freeze protection stat

However, most churches need a little section of the structure heated during the week(offices , meeting room) while many other zones are setback, so zone by zone setback are much better. To use a timeclock most effectively, I'd wire the zone vavle end switches through the timeclock contacts if you can, so if no zones are calling for heat the boiler won't continue to maintain temp, if you can "cold start" the boiler. The freeze stat is usually set at 45 degrees and placed in the coldest location in the structure. It's wired to bypass the timeclock contacts so it can fire the boiler.

Boilerpro