Need help. Pool heater is old but has been working until 2 weeks ago. Started pool heater and cked in the evening and noticed it off. Heater pilot off so thought wind. Has done that before in the past. I couple start the pilot but as soon as I tried to go on, turns off. Got my multimeter out and removed the 2 wires from thermopile. Start the pilot and after min, 600mv. Ok, so must be gas valve. Ordered new one and same thing. When u put thermopile on valve, no mv. Should I get a reading?
Mv pool heater issue
- Thread starter madelectrical
- Start date
- Jul 21, 2013
- 52,964
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Welcome to TFP.
What model heater are we discussing?
@swamprat69 may know his way around MV heaters.
What model heater are we discussing?
@swamprat69 may know his way around MV heaters.
Mini max Pentair about 18 yrs old. Just ordered a thermopile to replace the old one. It is rusted and corroded. With new valve on, it’s the only other thing.
swamprat69
Well-known member
Even though the thermopile may be good the output is in millivolts (very low voltage). The output from the thermopile has to go through all of the safeties before reaching the gas valve. What is the voltage in millivolts at the gas valve? Any deterioration of any of the safety contacts will drop the voltage below what is needed to operate the gas valve.
With the wires attached to the valve, no reading what so ever. With the wires removed, over 600mv. We are not trying to fire the valve up to heat. When I have the pilot on for over a minute, u try to switch over to on from pilot and the pilot light goes off. The safety goes thru the press sw, thru the temp switch and waits at the on/off switch. So normally open. When I put the pump on high. Now the press sw makes and I can turn on the on switch. If that series connection is open, gas valve will not start heater. I just need to keep the pilot lite.
swamprat69
Well-known member
As I understand it you have 600mv measured at the 2 leads from the thermopile, presumably at TP and TH/TP on the gas valve with a 2 lead thermopile. When you let up on the knob on the gas valve in the pilot position, the pilot stays lit ( the magnetic pilot safety engages ). When you try to move the gas valve knob from pilot to on, the pilot goes off ( is this with the heater not asking for heat or with the heater calling for heat?).
600 mv with leads flying. Not attached. If I put leads on the valve, reading is zero. If I attach the leads to valve and start pilot, after 90s, I let the pilot button on the valve and it goes off. Cannot switch to on. Heater is not asking for heat. Sw off and pump in low. Pressure switch would us open. Thank u for trying to help me!
swamprat69
Well-known member
There is no need to disconnect thermopile leads from the gas valve. Thermopile out put can be read from TP to TH/TP when you are attempting to light the pilot. You state that you are getting 600mv when you are attempting to light the pilot. Does the pilot stay lit when you let up on the gas valve knob when it is in the pilot position?
If I don’t disconnect the leads, no voltage. When I remove the leads, I get 600 mv. So that answers a big question do u get the reading at the valve, which I should. So I press down on the pilot it lites. I count to 60 seconds and let the switch up. Pilot still should be lit, but it doesn’t. That is why I thought valve but the only other variable is thermopile.
swamprat69
Well-known member
The connections at TP and TP/TH that the thermopile is connected to also connect inside the gas valve to the magnetic pilot safety. You could try cleaning up the gas valve terminals and wiring connections to see if that makes a difference. If not it would indicate that the gas valve needs to be replaced. That does not look like a "new" gas valve???
If I take the safety circuit out, should the pilot lit and hold the pilot? It’s an open circuit. Safety stuff will be normally closed waiting for the on/off switch. Correct?
swamprat69
Well-known member
It is an open circuit if the heater is not turned on and will have no effect on the pilot. The only thing in the circuit with the heater off is the magnetic pilot safety.
It’s fixed. Thank u for ur help. The Thermopile was bad. Wires off valve, could get the 500 mv, but put on valve, nothing. It is old at 18 years and burnt. Put new one in and works well. Just wanted to finish the thread.