T87 NOS
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Nice. Where did you run across those?0
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PC they have been sitting on my shelf for 20 years or so3
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Classic NOS with a Hazmat twist!
I’ve got a couple units I pulled when I update the boiler and HVAC Systems. Not new but still worked fine after 40 years.0 -
PC, I’ve got a couple hundred sitting in a plastic tote. Those are considered new though, lol1
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seems like shipping could be an issue0
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The mercury inside the hermetically sealer bulb in a typical T87F thermostat will oxidize after a period of time rendering the thermostat useless. I do not know their life expectancy but they do normally last a long, long time.0
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I always assumed mercury switches were vacuumed out or filled with an inert gas along with the mercury?retiredguy said:The mercury inside the hermetically sealer bulb in a typical T87F thermostat will oxidize after a period of time rendering the thermostat useless. I do not know their life expectancy but they do normally last a long, long time.
Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.
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No surpsise -- Gary's sending me one. The mercury switch should be forever, for all practical purposes -- they were vacuumed out and refilled with nitrogen, so unless the little bulb gets cracked... and oxidation of the terminals isn't a problem, as mercury aggressively wets them every time they operate. What does fail sometimes is the wire connections outside the bulb, from fatigue, or rarely the anticipator can burn out.Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Jamie If you were me, dragging many thousands of dollars out of homeowners pockets, would you leave a T 87 on the wall? A pro and a con everything I guess.1
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Depends on whether they want programming or remote sensing or control -- or might. If they do, out the T87 goes. I suspect that in many if not most situations I would pull brand new 5 or 6 wire thermostat wire and at least hook it up at the boiler end so that they really did have a common at the thermostat, so that when Joe Sixpack decides to put in a Nest or something they can hook it up... !GW said:Jamie If you were me, dragging many thousands of dollars out of homeowners pockets, would you leave a T 87 on the wall? A pro and a con everything I guess.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England2 -
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some old gas regulators used a column of mercury but i don't know how much or if it was field serviced.
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This is the only one I could find… Not cheap but exactly what I am looking for.
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& maybe these. Am I right to assume that anything with "A" is millivolt?
TS86A or T855A ?
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At 55, I"m beginning the "old timer" era...and I relish it. You get instant "street cred" with the youngsters....hee hee..you can have ALOT of fun with that..I DO! I used Mercury Column Gas pressure test units up until atleast 2001 or so. You'd keep them in a 5 gallon bucket, so they wouldn't tip over and spill all over your truck or worse yet,the Homeowners basement. Inevitably, they'd fall over in the truck once in awhile, and you'd need more Quick-Silver as we called it. I had an lovely Old Timer named Joe Greenfield from "Matzo-Pizza 🍕 " (Massapequa Long Island, NY) who I bought my Ridgid 300 Pipe Threader off of...practically new. $125!!!! Along with that, we hit it off, I he gave me ALL HIS stuff..whether I liked it or not!!! Ha ha. A Hellmans Mayo Jar full of Mercury (Do the Mathl) this Bio-Hazardous Fragile jar weighed A TON.....He threw in 2 ancient rusty green Mercury Test Columns too! A Had them carefully stored for years. I saw 5 Honeywell T-87s in the original Plastic for sale at a neat Church ⛪ antique sale about 8 years ago. 20 bucks... I savor them and use very rarely to dial-in a quirky steam or Vapor system. I still have found NO SUBSTITUTE for control of a Steam system! Magic! Gary, I met you about 2000 at a Jim Davis Seminar in Penna? Met Mark Hunt and Darin Cooke there too! You can't be too far from me? Mass? Connecticut? PENNA? MAD Dog
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(hand raised) not sure what the legal limits are if there is such a legal thing, I have stuff
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Matt yes that was a good long time ago!
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Yes i have some but seems like they can't be shipped
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Thanks everyone—I'm having trouble with my 2-wire millivolt system. It controls an (ancient) gas wall heater in our rental unit.
No thermostat has worked properly… but the unit starts up when I touch the 2 wires together. Any suggestions??
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Not all thermostats are compatible with millivolt systems — in particular, it is unlikely that any digital thermostat will be, unless it is specifically designed for the purpose.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
If the thermopile is getting weak it may produce enough current to open the valve with the wires touched together but not through a thermostat, especially if it has an anticipator. Measure the voltage from the thrmopile open circuit and with the wires shorted together.
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Hello @arad500,
You probally can use any thermostat you want with a milivolt system. To do so you would have to add a 24 VAC transformer for the non-milivolt thermostat and a relay. The non-milivolt thermostat controls the relay and the relay contacts control the milivolt system. Keep in mind you probably would loose the functionality of having heat during a power failure.
Milivolt system thermostats did not have (or use) the heat anticipator resistor.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
oh and @Mad Dog_2 has the answer about the vials of mercury, they were for filling/topping off manometers.
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could be the thermostat or the wiring to the stat. Millivolt circuits need low resistance. You could also use a relay near the boiler to reduce the circuit length
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This is a good suggestion. The problem with modern thermostats and millivotl isn't so much the anticipator, as it is that the "switch" which most of them use is actually a triac — and the millivolt system simply doesn't have enough voltage to see that as a closed circuit and worse, most triac circuits only work properly on AC.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
I think all of the modern ones I've had all seemed to use mechanical relays.
The VisionPro 8000 green screen thermostats and now the Prestige with the remote EIM all seem to use mechanical relays. Omron brand, I think.
Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.
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Lots of variety out there, dry contacts, Mercury, Thyristors, Relays and MOSFETs
T87F 👍️
Repairing a Nest Thermostat!
https://youtu.be/avoJiqOE9ecNational - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
If they are sealed relays, they may or may not work. If they are battery or otherwise externally powered, they should be OK, provided they don't have an anticipator — but if not, not, as the millivolt generators have nowhere near the power needed.
Open relays may work for a time, but unless they are contacts designed for very low resistance they may fail after a time.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England1 -
Yes, even Mcdonnell & Miller has special LWCO switches for milivolt systems.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0
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