Raypak 266 millivolt heater trouble

[byeloe]

Trying to get my heater working.

1. Pilot stays lit.
2. Heater won't fire.
3. Jumping the gas valve- fires the heater.
4. I tried jumping, pressure switch, thermastat, and limit switches. The heater doesn't fire on any jumps, so I was thinking they are all ok.
5. After jumping the gas valve, the heater fires. when I remove the jumper, the heater continues to run, but eventually shuts off(randomly within an hour)

any ideas?

 

[swamprat69]

Do you have a multimeter? A millivolt system operates at a very low voltage. Normal output from the powerpile/thermopile ( listed as the "pilot generator") is ~ 600-750 millivolts. If the thermopile output is weak combined with a voltage loss through all of the safety/operating control contacts, there will not be enough voltage left to operate the gas valve. I assume that when you are jumping out the gas valve that you are jumping from "TH/TP" to "TH". You really need a multimeter to confirm that the thermopile output is good and that the gas valve from "TH/TP to "TH" is at a bare minimum of 300 millivolts after going through the safeties/operating controls. If you don't have it, this should be the manual for your heater https://www.poolsinc.com/pdf/raypak/raypak-digital-heater-product-manual.pdf. Does the pilot assembly have a strong blue flame that has good contact with the thermopile? A weak pilot flame will result in a lower millivolt output from the thermopile.

 

[byeloe]

thanks. I forgot to list that the reading was around 535ish, I will check it again tomorrow. I installed a new pilot assembly last season.

 

[JamesW]

I forgot to list that the reading was around 535ish, I will check it again tomorrow.

Is that before or after the heater tries to fire?

Check the voltage before the heater tries to fire and then see how much the voltage drops on call for heat and as the heater tries to fire.

Clean all of the contacts on every wire and every terminal.

At less than 1 volt, dirty contacts will diminish the voltage too much.

Check the resistance of the control loop by itself to see how many ohms the millivolt power is trying to go through.

 

[byeloe]

The 535 is before the heater fires.

To check the resistance do I use the same terminals as the voltage check?

 

[JamesW]

To check the resistance do I use the same terminals as the voltage check?

Remove the wires going to the control loop and measure from one side to the other.

You're basically looking at the resistance of everything that the millivolt power has to go through.

 

[swamprat69]

Disconnect the wires at "TH/TP" and "TH" at the gas valve. That is your safety/operating control loop. Measure resistance of the loop. Less than 1 ohm is good, 1-2ohms is somewhat iffy and greater than 2 ohms is no good. Since it would be difficult to check individual resistances (due to meter resolution) in the loop, you could check voltage drop across each component in the loop with the heater set to heat to find the one with the highest voltage drop (this would indicate the specific safety/operating control that has poor internal contacts). This is after cleaning all the exposed wiring contacts in the loop as James noted.

 

[byeloe]

Clean all of the contacts on every wire and every terminal.

Do you recommend using a dremel rotary tool for this?

 

[swamprat69]

Dremel would be too aggressive and not capable of reaching into small spaces such as a slip on female connector. I normally use a small stainless steel wire brush such as this Anvil Stainless Steel Mini Wire Brushes (3-Pack)-SMB3-ANV - The Home Depot. Available at most Home Improvement and Hardware stores and also online.

 

[byeloe]

I attempted to clean all contacts.
I am getting a reading of 535 mv when not fired and around 450 mv when the heater is running

 

[JamesW]

Is it running ok now?

What was the resistance of the control loop?

 

[byeloe]

Is it running ok now?

What was the resistance of the control loop?

I still have to check the resistance. We had a thunderstorm

It won't fire without jumping
It still shuts off randomly

 

[byeloe]

resistance is .5 or 6 when I turn the thermostat up, past the call for heat click

 

[byeloe]

also when I removed the th/tp and th wires to check resistance. I found that the heater fires when I reconnect the wires.

 

[JamesW]

also when I removed the th/tp and th wires to check resistance. I found that the heater fires when I reconnect the wires.

Possibly corrosion on the contacts or a failing limit switch or sensor.

 

[byeloe]

Possibly corrosion on the contacts or a failing limit switch or sensor.

which contacts? the th/tp and th?
what's the best way to test the limit switch?

 

[byeloe]

thanks to everyone for the assistance. My heater seems to be working now