Need help understanding what I am looking at

kmbit615

Folks, I stumbled upon this forum while searching for answers on what these old thermostats are and what they were connected to. First off allow me to confirm that these old stats were inactivated years ago when the steam system was upgraded with electronic controls. but the company that did the upgrade left all of the old stats on the wall and this one is in the way of a new projector screen to be installed. The stat is a old Honeywell with two copper pipes coming out the back... one would hope that these pipes were not connected to anything anymore - but since they are still connected to the thermostats who knows if they are connected else where.

My problem is I have no clue how these work or where to check to see if they are still connected to anything. I do see in each class room that there is a copper tube ( about the same size ) that is disconnected and capped off with a compression fitting - leading me to believe that if that is from the thermostat in that room - that there was a reason to cap it and not just cut it back.

So other than figuring out what this was connected to, can any of you tell me what size the copper tube is - cause I could just cap it with a compression nut and be done with it as well ...

Thanks for any insight you could provide

ratio

That's a pneumatic stat - it uses compressed air to operate the valve. If the compressor's gone the system is not functioning, but if it's still present & running then you still have some part of it working.

What operates the valves now? electronic/DDC controls? Or are they still pneumatic?

If the pneumatics have been abandoned completely, the copper pipe can be cut off & poked back inside the wall as it's not too likely to be returned to service.

Hap_Hazzard

If I didn't know better I'd say somebody wired them with lamp cord and the insulation has fossilized. If I'm right, you can bend it and the insulation will crack and you'll see stranded copper inside. If you're afraid to try that, look at it closely and you should see that one side of the jacket has two or three thin ridges running lengthwise. These were used to mark polarity. I can't imagine why there would be anything other than electrical wires coming out of this thing. It's basically a mercury switch riding on a bi-metal coil.

If you dispose of these, you need to treat them as hazardous material because of the mercury, but I know of some people who would be happy to take them off your hands because they worked very well, and you can't buy them anymore.

kmbit615

ratio said:

That's a pneumatic stat - it uses compressed air to operate the valve. If the compressor's gone the system is not functioning, but if it's still present & running then you still have some part of it working.

What operates the valves now? electronic/DDC controls? Or are they still pneumatic?

If the pneumatics have been abandoned completely, the copper pipe can be cut off & poked back inside the wall as it's not too likely to be returned to service.

Ratio,

I assumed they were some kind of pneumatic but I though they may be tied into the Steam pressure of the boiler. Keep in mind these are from the original Steam boiler install. When these were in service would one side of the stat be tied to the pressure and the other side to a valve on the steam radiator? Or was it some kind of loop?

kmbit615

Hap_Hazzard said:

If I didn't know better I'd say somebody wired them with lamp cord and the insulation has fossilized. If I'm right, you can bend it and the insulation will crack and you'll see stranded copper inside. If you're afraid to try that, look at it closely and you should see that one side of the jacket has two or three thin ridges running lengthwise. These were used to mark polarity. I can't imagine why there would be anything other than electrical wires coming out of this thing. It's basically a mercury switch riding on a bi-metal coil.

If you dispose of these, you need to treat them as hazardous material because of the mercury, but I know of some people who would be happy to take them off your hands because they worked very well, and you can't buy them anymore.

Hap_Hazzard, not lamp cord - but copper tubing... no electrical for this at all .

Hap_Hazzard

kmbit615 said:

Hap_Hazzard, not lamp cord - but copper tubing... no electrical for this at all .

I guess Honeywell made a lot of different types of thermostats that look superficially the same while having completely different guts inside just to fool guys like me.

Are you able to see where any of these copper tubes end up in the boiler room?

kmbit615

Hap_Hazzard,

I believe that one side of this goes to the radiator in the class room ( but it is disconnected and capped ) I have no clue where the other line goes - that is why I am concerned - not knowing where it goes ( or where it should have gone) I do not know if it is still hooked up. I do not see any cluster of thin copper tubing in the boiler room.

Steamhead

Is there an air pump and tank in the boiler room?

kmbit615

Steamhead said:

Is there an air pump and tank in the boiler room?

Steamhead,

I do not believe that there is. Would this type of stat always be connected to compressed air? never the steam ? I assume that the way they worked was when they fell below the set point they allowed pressure to flow to the valve on the radiator allowing the steam to pass and heat the room. is my understanding correct.

ratio

Always air, as clean and dry as possible. We actually have a refrigeration-style dryer on our pneumatic system.

That's about it WRT operation. They were top-end in their time, offering PI control & centralized night setback way back before electronic controls even existed.

kmbit615

ratio said:

Always air, as clean and dry as possible. We actually have a refrigeration-style dryer on our pneumatic system.

That's about it WRT operation. They were top-end in their time, offering PI control & centralized night setback way back before electronic controls even existed.

Ratio,

Thank you so much for your insight and knowledge. that last thing I wanted to do is find out these pipes were connected to the plumbing in some way. The system was converted to electronic burner controls nearly 10 years ago so these are no longer used to control anything.

JUGHNE

There may be only one copper tube into the boiler room to the previous air compressor. Would probably be larger than the 1/4" tubing at the T-stat. Maybe 3/8" OD or larger.

If in doubt you could put a compression fitting with a cap on each and push them back into the wall . Who knows what the future might bring.

John Mills_5

Honeywell round pneumatic? Neat. I remember from high school, we learned just how to use a paperclip in the stat to get the steam valve to open and warm the room up. This was in the energy shortage years and the place was kept cold.

bob_46

usually the supply pressure is 15PSI the valve on the heater is normally open as you apply air pressure it starts to close, at 8PSI it's closed. The system fails to the full heat position. I would cut them and push them in the wall, if one has pressure just crimp it .