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Rick, Construction Supervisor
Category: Plumbing
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Experience:  Licensed Master plumber with 40+ yrs. experience.
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old Robertshaw Unitrol water heater gas thermostat control

Resolved Question:

old Robertshaw Unitrol water heater gas thermostat control valve R110rtsp, 66-138-335

replacement sold at Lowes looks identical, but has 2 extra wires, which are called thermal switch wires. Whirlpool 295098, R110RATSPLC

Can I use this valve? Thermocouple replaced and pilot won't stay lit
Submitted: 4 years ago.
Category: Plumbing
Expert:  Rick replied 4 years ago.

Rick the plumber :

Welcome to Just Answer, I will do my best to help with your problem

Rick the plumber :

You have to connect the 2 wires together. They are for a thermal cut off switch that's in newer models

Rick the plumber :

Once you connect the 2 wires the pilot should stay lit


It still does not stay lit.

Rick the plumber :

Do you have a good connection between those 2 wires? This a very low voltage connection, millivolts, so a bad connection will kill the current

Expert:  Rick replied 4 years ago.
The other thing to check is to be sure the pilot is tring and is heating up the thermocouple. You sometimes need to hold the pilot light button down for over a minute
Customer: replied 4 years ago.
The pilot is 1/2" tall at best.
Expert:  Rick replied 4 years ago.
Sounds weak. You probably have to clean out the pilot burner orifice. It's a small thimble shaped object at the end of the pilot tubing where it connects to the pilot burner. When you disconnect the tubing at the pilot burner it may stay in the pilot burner but it should pop out. You need to pass a very small wire (~.01") through the tiny hole in the orifice. Take care not to enlarge the hole. You must do this even if you can see daylight through the hole
Customer: replied 4 years ago.
Should the thermocouple adapter be installed on this valve? It has 2 wires that go from the thermocouple connection on the gas valve to the exhaust gas chimney.
Expert:  Rick replied 4 years ago.
You have an after market power venter on this water heater?
Customer: replied 4 years ago.
no, just a std chimney hookup that tees with the boiler

FYI gas supply and pilot ok with it
Expert:  Rick replied 4 years ago.
So I have no idea what you mean by a thermocouple adapter. Unless you have one of those wonderful American water heater thermocouples with a left hand thread. To simplify you may need to get a new conventional (right hand thread) thermocouple. The only reason for a terminal block in the thermocouple is if you have a power venter with spill switches on the draft diverter. If this doesn't clarify things then post a picture of this adapter here.
Customer: replied 4 years ago.
I took out the adapter and it lit right up!

It is shown on the instruction sheet for the Whirlpool BFG Gas Thermostat instructions.

No left hand threads involved.
Expert:  Rick replied 4 years ago.
Glad it worked out. Like I said I didn't see the need for the adapter
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