Middleby-Marshall PS536 GS

[howardgt]

Anyone had any trouble with ignition on these ovens? I got one that really gives me fits. It will light 3 out of 4 times usually. Good gas pressure, good spark. I'm beginning to suspect building air pressure as a possible problem. It is the top oven in a triple stack. This is the oven with no pilot or burner blower. It's at a small pizza franchise. (Nobel Romans) Also no MUA that I can find. Is under a hood.

[ckone180]

They are problematic, but easily repaired. MUA? Not familiar with that acronym, also, check for draft. The exhaust hood could be pulling enough to cause outage. If the unit is lighting, but failing to stay lit, clean the flame sensor. These thing are easy to repair. There are thousands around the country, I work on atleast 5 locations with these ovens. They are simple compared to CTX.
Also, the cover may need to be in place for the exhaust not to hinder it.

[howardgt]

I agree, they are simple. There are no adjustments. MUA= make up air. Sorry for poor acronym. If it lights, it stays. Not a problem with sensor. It just doesn't always light. Any fixes for problematic ones?

[Mstrav]

it does have make-up, they are using a/c for it. that is a type-2 and some places will use a/c air instead of a supply fan. the mua has nothing to do with your problem.


it sounds like it is not proving flame every time. have you removed the pilot assembly and cleaned it? Most of these places are horible about cleaning these. I have installed several in the little ceaser's and costco stores all doubles and only one little seasers with a triple. I am glad I only do first year warranty on these, the hardest part is getting them through the door and stacking them, super heavy.

good luck, matt

[ckone180]

We actually had a guy die in the Atlanta market last year when a Middleby oven fell off a truck lift of a rental truck. The lift just broke, and the guy didn't have time to react.

Anyway, the gas valve may not be opening, several of these have had this problem. If it doesn't light, then it isn't the flame sensor, it has to do with the gas supply, so check the valve first.

[howardgt]

Thanks for info. The unit is 7 months old. The igniter/sensor has been replaced. It's not a problem proving flame. If it lights, it stays. It just doesn't light every time. I've even played with gas pressure a little to try to help it. It's also about 160-170 degrees in the burner control compartment. I asked MM about installing a cooling fan in the cutout, they said no. I've pulled burner, checked fingers for airflow. I do not have the means to test air pressure or flow on hood.

[ckone180]

I understand, it isn't your job anyway, that should have been balanced long ago. Check the gas valve, I have seen it a couple times, should hear it click to open, if it doesn't do it everytime, it has a bad connection or need replaced. Good luck.

[wwcole]

Gotta be missing something... Swap modules with another oven. Make sure it is sparking in the correct place, not through the porcelain somewhere. Ckone is correct about the gas valve. Make sure its opening.

[ckone180]

Gotta be missing something... Swap modules with another oven. Make sure it is sparking in the correct place, not through the porcelain somewhere. Ckone is correct about the gas valve. Make sure its opening.

Good addition, it may be shorting itermittently on the spark circuit.

[howardgt]

Module was just replaced. Same result. I have another tech thats gonna go out with me on this unit when we get the new blower belt in. I just hope another set of eyes will help. If I am missing something, I don't know what. I test it with a manometer hooked up. Gas every time, spark every time, ignition 75% of the time. Sometimes it will take 4 or 5 times to light, other times first time. One thing is constant, if it ignites, it stays.

[CFESA MASTER]

Module was just replaced. Same result. I have another tech thats gonna go out with me on this unit when we get the new blower belt in. I just hope another set of eyes will help. If I am missing something, I don't know what. I test it with a manometer hooked up. Gas every time, spark every time, ignition 75% of the time. Sometimes it will take 4 or 5 times to light, other times first time. One thing is constant, if it ignites, it stays.


you have a dirty ignitor, replace it. part #44982 list $328.28

[howardgt]

Igniter was replaced with module, so was ignition cable. I've covered the basics.

[ckone180]

Igniter was replaced with module, so was ignition cable. I've covered the basics.

Still no solution?

[CFESA MASTER]

Igniter was replaced with module, so was ignition cable. I've covered the basics.

What was the gas pressure? nat or lp? Have you made sure of the correct oriface?

[CFESA MASTER]

Sorry for posting info that had already been posted, i am tring to figure out how to change the posts, I am getting them backwards first

[howardgt]

The unit is operational. Just have to cycle it when turning it on. Once lit, it's fine. We are scheduled to go back there when we get in some non-related parts.

[howardgt]

What was the gas pressure? nat or lp? Have you made sure of the correct orifice?

It is nat. I have played with the GP. It is now set at 3.5 WC. I've gone higher and lower, same result. The orifices are 42, which I verified through M-M. What's so aggravating is that this ignition system is very simple. So simple that there are no adjustments.