Raypak heater problem

[ps0303]

So, you turn the switch to on, it doesn't fire, but when you bypass the safety circuit it fires and stays on until you flip the power switch to off. What happens if you don't jump the safeties but jump out the on/off switch?

I would expect the system to continue to fire when all the safeties are bypassed. You could also by pass one safety at a time until the unit fires like it should. Then you have identified the safety that is bad.

 

[unome]

First time poster here and I'm hoping the WOTL can help me. The heater is a Raypak Versa 265B. Now before you go saying it is not worth saving because it is older than dirt bear with me. It all depends on the cost of the repair. I do my own work and am pretty competent when it comes to mechanical things. I'm pretty decent on electrical too but when it comes down to circuit bard repairs I throw in the towel.
So what is happening?
The heater has a Honeywell MV system. I have the pilot light lit and staying on however the heater does not turn on when I use the main power switch (all other things are in operating position, pump running, thermostat set). If I temporarily jump across the safety circuit the unit fires up and when I remove the jumper the heater stays on. Turn the system off using the main power switch and it shuts down like it should. I then re-fired the unit with the jumper and turned off the pump. The pressure switch did it's job and the unit shut down. I jumped it on again and then tested the thermostat and it too turned the unit off. But after all this the unit will not start and run on it's own.
I'm a little stumped and was wondering if anyone had any trouble shooting tips for me. I have a good multi-meter but what should I be looking for as far as voltage should be?

 

[unome]

So, you turn the switch to on, it doesn't fire, but when you bypass the safety circuit it fires and stays on until you flip the power switch to off. What happens if you don't jump the safeties but jump out the on/off switch?

I'll try that tonight.

I would expect the system to continue to fire when all the safeties are bypassed.

Thanks for the response. Let me clarify. I bypass the safety circuit by using a jumper then remove the jumper and it stays ignited. I found it odd that a switch would close only because the flame is ignited.

You could also by pass one safety at a time until the unit fires like it should. Then you have identified the safety that is bad.

That was next up. Thought maybe someone could suggest one of the switches to focus on that could react based on my details as some are a PIA to get at.

 

[k9sarretired]

Typically millivolt systems have a few components that need to be checked (I know, I'm troubleshooting my versa 405B). First, check the millivolt output of your generator. It needs to be between 250 and 750 mV, the higher the better since most gas valves have a minimum of 250mV needed to open the main valve. Mine is running about 400mV (brand new pilot assembly). Then, throw the switch and see if the voltage drops significantly. If it does not, there is something open in your circuit (or too much resistance). The next line of check would be either to jumper each individual component and see if you can tell where the main voltage drop is. timer switch, pressure switch, thermostat, on/off switch and 2 temp limit switches (one usually on the manifold on the opposite side of the input/output and one mounted near the input header near a pressure relief valve). If you can isolate which component is causing the unit not to light, first, clean the contacts. The other approach is to disconnect something in the loop (so you are only measuring one way around the system) and check the ohm values of each component and feed wire. I found that I had very high resistance in one of my limit switches until I wiggled the wire connector and made better contact. I also had bad contact within my pressure switch. I took that apart and cleaned the contacts and now it reads .1 ohm when closed rather than 60+ ohms. Once you eliminate all excess resistance, check the mV again when the system is activated. It will need to hang above a couple hundred mV under load to operate the main valve. Good luck

 

[unome]

Storms last night (and dinner out) prevented me from trouble shooting but tonight looks good so I will try all the suggestions. I suspect the generator may be the culprit. The spiral wire casing was quite corroded and it is pretty old. I did wiggle all the connectors I could easily access when lighting it (power switch, pressure switch, thermostat and the temp limit by the manifold) but will continue to figure it out.
By the way did I mention the bee's nest that was underway just by the manifold? Didn't check for chewed wires when I removed it but I will tonight.
Thanks all for the help.

 

[Pool Clown]

If you don't have enough mV to open the gas valve, the current draw will cause the pilot valve to close, and you will loose the pilot. So if you are able to fire the heater and turn it off and pilot stays lit, probably something other than the generator. my guess would be critters not quite chewed through two or more wires.

 

[k9sarretired]

definitely take the time to measure the resistance of each component. If anything reads more than a couple ohms, there's an issue and you should clean the connectors, perhaps recrimp the lugs, etc. I just finished troubleshooting mine and I went from over 50 ohms (and the system not working) to a total loop of about 7 now. Had to replace 3 lugs and one length of wire but it lights as expected. My thermostat doesn't regulate the temp so I will need to replace it but turning the dial will turn the heater on/off. btw, I'm holding about 490mV generated by the pilot and, when under load, holding around 280. Good luck