Raypak 336A - no pilot sensed

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Jmen

Jmen

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Jul 6, 2022
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Martinsburg, WV
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Our Raypak 336A (Propane) is approx 8 years old (replaced an older 266A rusted out unit). The heater has worked fine up until startup this year. We don’t use the heater much other than to extend swim season. We have a 250 gallon propane tank that holds way more fuel than needed for a season, so normally only fill the tank half way each spring.

This year the heater started fine - except the pilot light appeared a bit more yellow than previously observed. First firing of heater is an extended burn to meet desired 12 degree F temp rise. Next day noted heater off with Ignition Lockout - No Pilot Sensed. Opened the front cover and found a hardball sized area of soot on the sheet metal burner shield in front of the pilot assembly.

On restarting the heater, CFH sequence starts, and buzzing occurs around the pilot area. However no flame is visible. Eventually the ignition sequence time out and Ignition Lockout reoccurs.

Repairs attempted
Removed and cleaned pilot assembly with wire brush. No change
Replaced Pilot assembly. No change.
Checked continuity of all wired connected to gas valve and pilot. No change
Mounted pilot bracket backwards for better visibility. Good spark observed but no pilot light and no obvious gas odors around pilot.
Closed heater manual gas supply valve, opened test plug in front of internal gas valve and briefly opened manual gas valve - gas confirmed in front of internal heater valve.
Set Multimeter to 200v AC and probed PV/MV to PV terminals on main board during CFH sequence - 24-26 volts displayed during the quiet period between hi tension buzzes.

Question: should 24 v reading at PV/MV to PV terminals be constant? Main reason for asking is to try and determine if issue is definitely control board or gas valve.

Thanks in advance for sharing thoughts on what to test next or how to better test above.

Best regards,

Jo M in WV
 

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You should get 24vac across mv/pv and pv during spark, when pilot lights the mv will open. You never said what the wc was going into the valve? How full is your tank currently? Was the tubing replaced with pilot assembly and the correct orifice placed?
 
I do not have a manometer so cannot report gas pressure. Gauge at 250 gallon propane tank reads just above 30%. Pilot tubing was not replaced. I did use a mity vac connected on the gas valve side of the tube with pilot and orifice installed to verify the tube was not clogged.

I do have a new pilot tube on hand. The replacement pilot assembly did come with one orifice installed and one loose. My understanding is the loose office is propane. However, the l orifice did not have a red stripe on it.

I still have the original pilot assembly and orifice. It won’t cost anything but time to replace the pilot tube and orifice. Thank you for input.

Joe M in WV
 
I will have to recheck - but my recollection is no voltage between PV/MV to PV terminals until the CFH cycle began. Then voltage pulsed to 24-26 VAC in quiet periods between pilot spark buzzes. Buzz-buzz-buzz - 24v - buzz-buzz-buzz - 24v . . .

Tough call on adding more propane to the big tank. Tank was empty this spring. Already have $350 worth of propane in there with no heat so far. Any recommendations for a residential type manometer?

Big storm arriving here soon - further testing may be delayed until tomorrow.

Regards,

Joe M in WV
 

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Looks like the flame current is not giving good readings.

The flame no call for heat indicates a flame current being detected when there should be no flame current.

Maybe a grounding issue.

Did you check for flame strength?
 
Cannot get the heater to fire currently so flame strength = 0 :(

Measured 0 ohms between ring terminal at pilot bracket screw and ground socket at board. Please let me know if there are other grounds to check.

During CFH sequence, A/C volts between PV wire terminal at gas valve and ground measured 24-27v with brief intermittent dips to 16v. Voltage did not vary with spark signal - apologies for associating the two earlier.
 
Found some spider webs on back side of board. Used electronics cleaning spray and a nylon brush to clear the webs and detritus. Unfortunately did not help with lighting pilot.
 

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Jmen said:
Found some spider webs on back side of board. Used electronics cleaning spray and a nylon brush to clear the webs and detritus. Unfortunately did not help with lighting pilot.
Click to expand...
That ball of soot indicates that flame is getting out of the firebox, it is not a normal operating condition. May have to find out if something is sitting on that burner or if the orifice is clogged and letting flame out of where it should be. That close to the valve and wiring is not a good thing.
 
Agreee that flame and wiring do not make good companions. All visible wiring in the area was tested - zero ohms @ 2k meter setting from end to end each wire. Should pulling the burner gray be considered at this time, or wait for gas pressure testing?

Thank you WF for the barb number. Hope to stop by hardware store tomorrow.

Regards,

Joe M in WV
 

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