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Mark Henley
Mark Henley, Journeyman Technician
Category: HVAC
Satisfied Customers: 3217
Experience:  UA Journeyman Pipefitter , HVAC, Refrigeration, DDC controls. 26 years.Commercial & residential
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I have an old two wire thermostat that I have purchased a TX9600TS

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I have an old two wire thermostat that I have purchased a TX9600TS 7-day touchscreen w/ lockout function. I can make my Oil fired boiler operate by toching both white and red wires together so I know that part works. I checked with a meter to verify which contacts will energize the and it looks like C+ common and W1 for NC with set point of 73 F and inside temp below 72 F.

It will open contacts above 73 or 74 F.

But when I put it all together it does not control boiler. What is wrong?

Mark Henley :

Hi, you don't have a wire for C, you can only connect to R or it may be RH, and then W1, if that doesn't work you won't be able to use this thermostat unless you run more wires, let me know. thanks Mark

Customer:

Mark, Again I have used a meter to verify what I have for contacts.

Mark Henley :

Hi, you can't verify those contacts with a meter.

Customer:

Mark, w/he set point at 74F Blk lead on "C" Pin 1 and Red lead on pin 2 was open; pin 3 was closed; pin 4 was Open; Pins 5&6 were closed pins 7&8 were open; pin 9 was closed and pin 10 was open.

Mark Henley :

You have a two wire system, so you will have 24 volts on both wires red and white, when your thermostat calls for heat The C terminal is common and you don't have a common wire present. You can't really check these contacts with a meter because they are triac outputs not your typical relay contact, they need a load on them to make and be able to measure them with a meter.So if you connect to R and W on the thermostat it will work as long as the thermostat is still powered up or on battery power.

Customer:

when set point was at 73F Pins 5,6 & 9 were closed as before and the rest were open. Pin 3 went open which is what I need to operate the oil fired boiler.

Customer:

Okay i will try that. Hold please.

Customer:

You were right. it has fired the boiler.

Customer:

Thanks

Customer:

What UA local are out of? I am out of UA 716 Augusta Maine

Mark Henley :

yeah I'm not allowed to say, sorry about that.

Customer:

Okay, Thanks for the help!

Mark Henley :

no problem, take it easy

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