Raypak propane heater issue. M266A

[hoosierrun]

In the morning when I first fire up the heater, I get a boom. The unit comes on and heats normally and seems to run fine. When it reaches heat setting it shuts off normally. Then when it calls for heat again it ignites smoothly. To me it sounds like a tiny leak that occurs from several hours of no usage, but I have not detected any smell when I put my nose to the floor near the burner tray. There is no fan in this style of furnace. The unit error display doesn't really provide me any clues. Flame strength is 8. voltage is 28 volts. The errors are all CFH/no flame. I don't know if that is caused by how it is shutdown which is done by turning off the pump and causing the water pressure switch to open (original installation by pool builder).

So far here is what has been done:
1. All leaves/debris vacuumed up, top removed and cleaned inside.
2. Fittings around gas valve/pilot tube leak tested with soapy water - all OK
3. Pilot igniter removed, orifice replaced with new propane piece, Pilot tube blown out and inspected.
4. Ground wire removed, all connections cleaned and reinstalled.
5. Control board inspected for any obvious moisture contamination or bad solder joints - nothing found
6 Burner tray completely removed and inspected. All holes clean. Minor rust tapped out. Very little debris
7. All burner jets removed and openings checked with large paper clip. Tube checked for debris/webs - nothing found and no clogged ports.
All this was done over a few days. Same result. Looking for any further suggestions. I suspect an undetectable leak and will put my own fan in front of it at the next attempt. Also, I will tap the valve with a rubber mallet to see if I get any change. I will check the pressure too but since it performs good after initial start, I have my doubts. I'm hoping it is not the board or the valve.

Thanks for any suggestions.

 

[ajw22]

Let’s see what @swamprat69 or @ps0303 think.

 

[swamprat69]

A "boom" on firing up sounds like "delayed ignition". Common causes are: restricted burner ports, restricted burner tubes, restricted pilot orifice, restricted gas manifold orifices, misaligned pilot bracket, low gas pressure ( pilot or main). Looks like you have covered almost everything although just tapping out burner tubes would not remove any spider webs restricting the gas/air flow in the burner tubes. You might want to try something like these burner brushes McMaster-Carr they are also good for cleaning grill burners. Have you observed the burners as they light off (not from too close if you are getting delayed ignition, try from the side and not directly in front) to see if the burners light off immediately after the gas valve opens (should hear a click). Observe the pilot flame. Also observe burner flames after they have stabilized. I suspect that the reason for it not happening other than a cold start might be that residual heat may be creating a natural draft that is altering the flow slightly? Natural gas residential furnaces have a very slight natural draft when cold due to flue height and weight per unit volume difference between inside and outside air measured in hundreths of an inch WC. Since a pool heater essentially has no flue stack height or weight per unit volume difference between the inlet air and the outlet air on a cold start, it has no to extremely little natural draft when cold fired.

 

[hoosierrun]

I like the thought of insufficient draft when cold. I am in Florida and this time of year the air is totally stagnate in the morning and very heavy with moisture. I may try again to blow out the insides of the furnace body with compressed air to see if I can get anymore debris out. I'll update with any new news.

 

[ps0303]

This is a tough one and it appears you have looked at many of the causes why this might happen. Could be an issue with the gas valve. One would need to put a manometer on it to see what the pressures look like. Could also have something to do with the gas regulator.

 

[hoosierrun]

More tests today after another cleaning attempt. First, I took much of the shell apart (dozens of screws). I used compressed air and a vacuum. I found most of the inside to be pretty clean. I noticed some evidence of suspected overheating since there was just a little bit of paint blistering on a few small areas. I put everything back together, and with the front off, furnace set to ignite, I turned on the pump breaker. It took longer then I thought to ignite and it did start with a boom and flash of yellow flame. It remained running and was heating the water. If you look at the furnace straight on, it appears the flame is nice and blue, but the top of the flame is not visible because of a metal shield in the front. I moved to the side of the shield and looked in. The flame tops are quite yellow. I'm thinking the pressure may be a little high. Stage 2 regulator is about 7 years old on the propane supply line. Pictures below: The picture from the side looking at the flame tops looks bad. Any opinions?

 

[swamprat69]

Burner flames should be well defined and blue. The amount of yellow in the flames is troubling. Try using an extension mirror to check the underside of the heat exchanger for sooting/blockages ( caused by incorrect propane/air mixture). Definitely check the gas valve pressures also. Also realize that propane is only combustible between 2.15% and9.60% propane/ air mixture.

 

[hoosierrun]

I checked the pressures today. The incoming source pressure is 11 in WC which is perfect for propane. The gas valve outlet pressure is 10. I think 1 inch drop is probably right, but any experts please comment. All this with the furnace running. I also took another picture of the flame. I'm still not sure it is right.

One thing I observed today: When starting the furnace from cold, I get 2 clicks which results in a bit delay before it fires off with the boom and yellow flash. When I cycle the furnace a 2nd time (with it a bit warm), it fires up quiet and smooth on the first click. Further, but probably unrelated, if it does not fire up on the 2nd click the furnace locks out on main ignition failure. I think it only did that because I had bled off the propane when testing.

So perhaps one of two possibilities:
1. The pilot lights and signals the control board to open, but the pilot dies when the igniter shuts off. Then on the second click the igniter fires with a flood of propane and I get the boom. Fault of valve?
2. There is just not enough draft in the area where the pilot is located and main burner gas discharges more on the left side causing some delay for the pilot to light off the gas.

It is very difficult to see what is happening and I would not want to get too close with it acting like this. The view is mostly blocked anyhow. Still looking for suggestions. I would replace the pilot igniter if I thought it might be an issue, but I suspect I would be wasting my money.

 

[ajw22]

Your propane heater is failing to light the first time when cold. I suspect someone converted a NG heater to propane and did not do it properly. The heater should lockout on the first failed attempt and not retry.

The board on the propane heater, depending on the age, will have a tab that has been broken off. I suspect your board still has the tab.

Propane is heavier than NG when its in gas form and it likes to sink to the floor and pool, making for some lively outcomes if it happens to pool in the right place. The designers at Raypak found a way around this. When the tab is broken off, the system will only try to light one time before it locks out, instead of the three tries for NG.

I recommend you call in a heater professional experienced in Raypak pool heaters to checkout your unit.

RayPak Heaters - Further Reading

www.troublefreepool.com

 

[borjis]

Ya I'd have it checked out by a pro at this point.

 

[Poolbreh]

Are your mv pv common on the gas valve in the right place? And when you say clicks are talking about the igniter or the gas valve? It could be the mv is opening first and the pv second which would be backwards.

 

[hoosierrun]

Don't know how to delete this

 

[hoosierrun]

Your propane heater is failing to light the first time when cold. I suspect someone converted a NG heater to propane and did not do it properly. The heater should lockout on the first failed attempt and not retry.

The board on the propane heater, depending on the age, will have a tab that has been broken off. I suspect your board still has the tab.

Propane is heavier than NG when its in gas form and it likes to sink to the floor and pool, making for some lively outcomes if it happens to pool in the right place. The designers at Raypak found a way around this. When the tab is broken off, the system will only try to light one time before it locks out, instead of the three tries for NG.

I recommend you call in a heater professional experienced in Raypak pool heaters to checkout your unit.

RayPak Heaters - Further Reading

www.troublefreepool.com

The furnace was put in by the pool remodeler about 3 to 4 years ago. It is definitely propane and has the tab broken out on the board. This problem only started 2 months ago. Here are some pictures.

 

[hoosierrun]

Are your mv pv common on the gas valve in the right place? And when you say clicks are talking about the igniter or the gas valve? It could be the mv is opening first and the pv second which would be backwards.

The gas valve wiring has never been changed. and the fact that it works perfectly on a warmed up furnace, i.e cycles perfectly with no boom, suggests all is fine with the wiring. The question regarding the sound is a good one. I just fired it up accidently a little while ago, cold. I stood right in front of it with the door off trying to manipulate the screen and I heard a buzzing sound which was probably the igniter. I actually didn't hear the click of the valve, but my hearing is often bad unless I'm concentrating. So on the 2nd buzz, it ignited with a boom and even singed a few hairs on my legs. LOL. This morning when I fired it up, I was a little distance away and used the circuit breaker to start the pump. When I did that, I heard 2 distinctive clicks which had to be the gas valve. I was probably too far away to hear the igniter. According to the previous poster, I am only supposed to get 1 attempt at igniting according to what he said, so I am really confused by this. It seems like the boom always occurs delayed once the ignition is tried a second or two later after I turn on the pump.

 

[Poolbreh]

Yea Allen is right, the propane boards only open the main valve once than ignition lockout occurs. Which is different from the igniter. The gas valves rarely go out. But it sounds like the gas valve may not be closing all the way. It would explain the problem only happening on cold starts.

 

[hoosierrun]

Yea Allen is right, the propane boards only open the main valve once than ignition lockout occurs. Which is different from the igniter. The gas valves rarely go out. But it sounds like the gas valve may not be closing all the way. It would explain the problem only happening on cold starts.

Do you think the igniter itself might be bad? Maybe the pilot confirmation signal back to the board is dropping out. So perhaps it is dropping out at the same moment the call for valve opening occurs, but if there is a fraction of a second delay and the pilot confirmation fails, it cuts power to the valve but then immediately restarts. Maybe a dirty signal? I think I'll spend the $60 for a new igniter. I can't think of why the gas valve would operate twice when it is not suppose to. I'll keep you all updated and I really appreciate all the comments.

 

[Poolbreh]

The igniter will keep buzzing multiple times through the fire up sequence. The main valve should only open once(click)Does the pilot light right away? Before the main valve is open? It could be sensing pilot flame before it is actually lit than opening main valve and pilot lights after. I could be wrong but from what I recall there is usually more buzzes than 2 from igniter before pilot is sensed and heater fires. The manual says usually 15-90 seconds to sense flame at pilot.

 

[hoosierrun]

The igniter will keep buzzing multiple times through the fire up sequence. The main valve should only open once(click)Does the pilot light right away? Before the main valve is open? It could be sensing pilot flame before it is actually lit than opening main valve and pilot lights after. I could be wrong but from what I recall there is usually more buzzes than 2 from igniter before pilot is sensed and heater fires. The manual says usually 15-90 seconds to sense flame at pilot.

I can't actually see if the pilot is lighting since it is pretty far back in there and the way it is acting, I don't want my face anywhere near the bottom of the unit. Just no good way to view it. To open the main valve before the pilot was actually lit would be a serious safety breach and could suggest a bad board. I think there has to be a small voltage generated by the igniter that has to feed back to the control board (pilot confirmation signal) before the 24 volts is applied to the valve. The other thought (as previously mentioned) would be clogged burners right around the pilot, but why only when cold? Why am I getting 2 clicks from the valve? I'm pretty stumped here and I really think a pro is going to do exactly what I have already done. A lot of money will be spent in diagnoses and considering the condition doesn't occur for several hours between startup makes it really tough. As I said before, there are no error codes and obviously the rollout safety fuse hasn't burned out.

 

[Poolbreh]

I wonder if you can turn the gas off, try firing heater and check the flame strength. It should be 0 but if sensing flame through the igniter when there isn’t a flame it could possibly a board issue.

 

[Poolbreh]

To rule out a slow leaking gas valve I suppose you can place a fan near the face of the heater to try and air it out for a while before firing on a cold fire.