Convotherm 4 Combi Oven burner making gunshot noise

[fixbear]

OH yea!  Definitely a delayed ignition.  Seen it on many makes of gas equipment before.  And yes it can shake the house,  make flame roll-out, and literally scare the hell out of you. I’ve seen combustion chambers distort and split from it.  Even vent pipes blow out of walls.

 

You are getting a combustible mixture of gas accumulating in the combustion chamber and venting. When it does ignite, it all goes at once.  Like gun powder.  But why is your big problem.  It can be the igniter, or igniter wire, Gas mixing (nozzle, orifice), or even the ground.   Once it does it, one needs to inspect the combustion chamber for cracks.   Igniter gap, position, and mixing/carburetor have a big effect on this.  But don’t overlook that a leaking gas valve may have made a accumulation of fuel in the chamber.  Not possible with a pre-purge and why they use them.

[olivero]

Wow, happy I’m not the only one seeing it.

 

I pulled out the bottom burner, igniter was almost laying on the burner so I realigned it all and now I put it back in but the ignition module smelled fried so I’m mid inspecting it right now and I might have to switch it.

 

Thanks for all the information though, since it blows air through the HE before lighting it, I think that’s the “Pre-purge” I’ll make sure to look for cracks though.

 

Another odd thing is the top burner with a new igniter goes up to about 20 MA and then slowly drops down to 0 and relights, it was between that and bottom burner lighting the pop happened so I’m not sure which one, I’m thinking the bottom one more now that I saw the igniter but I’ll find out soon.

[fixbear]

I believe they share the vent. So if one is not lighting quick enough, The combustible gas can reach the other and you get a big BOOM!

[fixbear]

OH yea, I’ve lost eyebrows, arm hair, and lashes more than once on a delayed ignition call.  Not one of my favorites.  The new ignition control systems have cut down on most of them.  Worst yet is a burner valve regulator going over-pressure.. Had a face-full of flame on that one.

[olivero]

Wow, glad your here to help a noob like me, lol.

 

I put it back together, bottom burner lights and holds really well. Top burner lights but MA signal drops like a rock after a couple of minutes. I’m gonna try to put the old igniter in, realign it and see how it goes. Ended up putting a used ignition mod into the bottom burner since the one there smelled like something fried.

 

I guess we’ll see. You’re better than Convotherm tech support, you answer after hours, it’s fast. You should start charging for it.

[fixbear]

Accually the pro on this is Ectofix.  I just know a bit about gas.

[olivero]

Well, between the 2 of you, you seem to be able to answer pretty much anything.

 

I put the old igniter back in, realigned it and it’s holding steady. It’s a joke honestly, this is the Gen 4 igniter and they keep changing the insulation around the capacitor on the wire, perhaps that’s the problem, I have no clue. 

 

I’m just tired of calling them and getting the

“Oh, is it this igniter?”

“Ah,,, no”

“AH! well, there’s your problem, order 2 and put them in and that will fix it”

“But it’s been running with this type of igniter for 6 months with no issues?”

“Doesen’t matter, and what’s your software”

 

Pretty commonly how it goes. I once went through 3 sets of igniters until 2 of them worked, they were showing this same phenomena.

 

Drives me nuts.

 

Looks like it’s doing pretty good now, ignition seems consistently on point and in good time so We’ll see how it runs tomorrow.

 

Thanks for the help, glad to know it’s actually caused by that delayed ignition, keeps me sleeping better at night, lol.