Raypak propane heater issue. M266A

Poolbreh

In The Industry
Jul 31, 2021
300
San Diego
I found a small spider under the plastic cover, but no evidence of any contacts being bridged. I even took the circuit board for the valve out. Nothing unusual on the back. I just don't see how this can be happening. No way you can see the other side of the board without destroying it, so maybe I'm not seeing something. In summary... it appears when the pilot solenoid activates, the main solenoid also activates.... even with the MV wire disconnected from the main valve.
Yea I wouldn’t know man. The gas valves say no serviceable parts so if I ever had an issue with one I would just replace it. Was the heater under water?
 

hoosierrun

Well-known member
Mar 28, 2012
196
Tampa Bay, Florida
Yea I wouldn’t know man. The gas valves say no serviceable parts so if I ever had an issue with one I would just replace it. Was the heater under water?
No, never under water, but here in Florida there are all kinds of bugs that get into everything. Yeah I wouldn't get into the guts of the gas valve, but I didn't see a problem looking at the electrical parts by removing the top plastic cover. I should get the new valve by Wednesday, but going out of town so it might be over a week before I get to this. It really shouldn't be that difficult since the new valve will be set up for propane and is the exact Raypak part# for my heater. That is providing my gas pipe union holds OK. Sometimes re-using and getting it into a different position can result in a small leak. If I have to replace it, that might add some time.
 

swamprat69

Well-known member
Mar 30, 2019
600
Las Vegas, NV
It seems very inlikely that the main gas valve is open/opening with no voltage input to MV. That would mean that both redundant main valve solenoids were stuck open or that somehow voltage to PV was also being applied to MV as you surmise. If both solenoids were stuck open, it would empty your propane tank fairly quickly. I would disconnect the wire from MV and then connect your multimeter set to AC volts from MV/PV to the MV terminal on the gas valve that you removed the wire from. Connect your " WC manometer to the outlet tap of the gas valve. When the heater is not set to fire up, you should read 0.0 " WC at the outlet of the gas valve. Fire up the heater without reconnecting the wire at the MV terminal on the gas valve. You should then be able to tell with the manometer reading if the main valve is opening with the wire disconnected and with the multimeter whether or not the main valve is receiving 24 volts with the wire disconnected.
 
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hoosierrun

Well-known member
Mar 28, 2012
196
Tampa Bay, Florida
I agree... very unlikely, but that is what is happening. Right now I've got the spa heating with the MV wire (purple/black stripe or bottom MV ) disconnected. It did start with the boom this morning but fired up with no MV wire connected. I can assure you that no valves are open until power is applied to the PV (I would smell gas otherwise). Once the heater is running, the pressures appear normal, both in and out. I did notice that the static pressure into the valve, before any voltage is applied was about 13., but that should bleed right off as soon as the pilot valve is opened. In my previous work on gas appliances, I noticed it is not unusual to get a slightly higher static pressure. Here is a picture I just took with the wire disconnected and the main valve open. Once I get this valve replaced, I hope to do some bench testing with 24 VAC source. I should be able to observe what the heck is going on.

EDIT in. Furnace just hit the set point 20 minutes later without cycling. It shut down normally and now I have it completely shut off due to safety reasons. MV wire disconnected the entire time.
 

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hoosierrun

Well-known member
Mar 28, 2012
196
Tampa Bay, Florida
Resolved! It was the gas valve. That part was not difficult to swap except that the original valve was difficult to get off the manifold tube. I had to heat the connection and use two persuader pipes on my wrenches to break it loose.

The worst part was I hooked everything back up, and it didn't work. Spark came on and pilot lit, but main valve would not open. After some troubleshooting, I saw that it wasn't sensing pilot. So no 24 v sent to main valve. I went and swapped back to the original control board and it fired right up, as quiet as new. The pre-owned board was bad, so I hope E-Bay comes through with a refund or replacement.

I'd like to thank everyone for their suggestions. I may be one of the first to have this problem where the main valve opens with the pilot valve opening (resulting in a boom on startup) My resistance checks of comparison between the old valve coils and the new valve coils are the same, so my next step is to take an external source of 24 volts, apply it to the pilot connection and see if there is a way to detect if the main valve is opening (bench test). That will happen within the next few weeks or when I have time. My patience was definitely tested here.
 

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