Raypak (Rheem) Gemini Heater from the 80's; worked last year

[bugsy714]

Howdy!

I have been whipping my old pool back into shape but so far the heater has stumped me. It is an old heater Raypak Gemini Natural Gas 309k btu circa 1980ish. The pool is from 1969 and was re-plastered in 2006. The heater allegedly worked when we bought the house in dec 09, it was left on by the house inspector and ran for a week until the previous owner noticed it was on (the pool was 85 degrees in winter lol). The home warrenty company got in a dispute with us over the pump and we dropped the policy before realizing the heater was also dead.

After we moved in I tried to fire the heater up to no avail, I had the gas co come out and light the pilot and check it for leaks, the pilot would light but that was all that would happen. When I turn the temp dial to any temp there would be no fireworks or roar of the burner firing up, I left it on with the temp knob to "spa" (the hottest setting) for hours but no dice.

Any thoughts on what needs to be replaced/serviced or on the likelihood this being a lemon/money pit to try to service? The thermocouple is over $100 and various other parts put the servicing into the $400ish range on the low end I'm guessing

I am debating cutting the old copper pipes out and bypassing the heater completely if it is a lost cause (probably scrap it)

 

[JasonLion]

Re: Raypak (Rheem) Gemini Heater from the 80's; worked last

Welcome to TFP!

As long as it isn't leaking, it can be repaired, though it may well be several hundred dollars to repair it. Depending on how handy/DIY you are feeling, there are a couple of simple tests you can perform. There is nearly always a wiring diagram in the manual showing the different sensors that can cause it to stay turned off. They can be checked fairly easily with a multi-meter.

 

[Dalandlord]

Re: Raypak (Rheem) Gemini Heater from the 80's; worked last

If the pilot stays lit the thermocoupling is good.

 

[bugsy714]

Re: Raypak (Rheem) Gemini Heater from the 80's; worked last

Excellent advice! I figured it is repairable if the parts don't make it cost prohibitive

I am going to relight the pilot and see if it stays lit over night, if it does can you recommend where to look next? I was thinking the temp knob assembly, it's all so ancient inside of the heater it's a bit intimidating to start tinkering too much

 

[PoolGuyNJ]

Re: Raypak (Rheem) Gemini Heater from the 80's; worked last

The thermocouple may still be bad. The gas regulator usually needs 250mv to keep a pilot lit but somewhat more for it to be able to open the main gas when the call for heat is made, typically 400mv or more.

Make sure the pilot flame is not whimpy.

When lighting the pilot, you hold the knob down. If you disconnect the leads from the thermocouple and put you volt meter on the leads, you'll get an accurate reading of it's output. It might take a couple minutes to get the full voltage. If you get 400 or more, it's good and it's time to start checking the rest of the sensors.

Next is pressure switch. It stays open until there is pressure. Pump on = zero ohms.

There are two high limits. They should be closed, or zero ohms.

There is also a fusible link or two that ensure flames aren't back drafting of the chamber between the flames and the heat exchanger isn't getting too hot. Normally zero ohms there.

The thermostat is normally closed until it's probe passes enough heat to it. When set on high, it should be zero ohms. When the water is warm enough, the thermostat opens.

The On Off switch should also be checked.

Check for burn wires.

All these sensors are in series, one after the other. It's called the safety circuit. Do not disable/bypass anything there!!!! If it isn't 100%, do not use the heater.

Scott