Combi Oven Uneven Cooking

[fixbear]

Ah, a difficult one. Sorry you seem to get them. 

Exactly where is is slow cooking?  Top, Bottom, left, right, Front back?  

 

The monitoring system checks fan motor internal temp and speed,  But not the actual air flow. Build-up in a blade, Foil, blockage in the flow will cause problems with even cooking. As will something foreign on the racks disturbing the flow.  Convection ovens are fast, but they do rely  on proper and even flow to cook right.

[olivero]

Lol, I should write a book.

 

Its on the entire lower section of the rack, all the meat on it was undercooked and had to be recooked.

 

They haven’t really changed anything, but something changed.

[fixbear]

Lower burner or lower fan

Do you have like a Fluke 52 temp unit. Place one probe high and one low.  Watch the delta

[olivero]

No I don’t I was thinking that’s one way to tell. Put 2 different thermometers   or probes in there and see if they are any different.

[ectofix]

I’ve never addressed (or even heard of) that problem on a combi-oven of ANY size, since they usually (but not always) are designed to reverse blower direction in a cyclic manner.  Additionally, combi-oven blower wheels are far more substantial than the diminutive squirrel cage in standard convection ovens.  AND…(unlike standard convection ovens), I’ve never seen foil or debris get caught up in a combi-oven blower wheel – since the wheels vane spacing is wider.

 

SO, a dumb question…since I don’t know if this even possible, but –  are the upper and lower blowers possibly turning opposite directions within a simultaneous cycle?  I’m pretty sure they should both be turning the same direction (within a cycle).

I’m not sure if that matters, but just something I thought of.

 

Is the door gasket sealing properly at the bottom…around the trolley?

 

°     °     °     °     °     °

 

I don’t know what else to think of…other than heat source malfunction.  Yet, if there were issues with the bottom heat exchanger burners, the oven controls would certainly inform you of that.

 

I also considered the possibility of loading of the oven racks a different…or wrong way.  I can’t see that as being an issue, since the oven IS DESIGNED for accepting a trolley FULL of pans of product. 

But on that note, I’ve never read the operator’s manual.  So, really don’t know of the stipulations on proper loading of that oven size.

 

Hmmm…  There’s a thought.  Additionally, I seriously doubt that the Chefs have read the manual either. 

 

OH…one other thing:

 

I’m not overly familiar with Convotherm’s (old or new).  Although I got factory training on the original ones a dozen years ago, I can only remember working on two during my next six years in the field.

 

ANYWAY – my Rational ovens require a self-calibration cycle to be run whenever any major parts, controls or sensors are replaced.  The intent is to make the oven computer RE-LEARN & adapt to any changes between old and new components or operating environment. 

– YES – even if the oven is MOVED, Rational says it should be recalibrated. 

The self-calibration cycle is something a technician must set up properly and initiate by following instructions in the service manual.  A fully functional Rational takes forty-five minutes to complete that process. 

 

So I was just wondering.  Do Convotherm maintenance procedures call for doing such a thing as well?

If so, have you attempted to run the ovens through that?

[fixbear]

Ectofix’s thoughts have triggered a idea.  Is it possible the the oven sensors have drifted so that the top is cooking faster than the bottom.?

[olivero]

To answer both questions,

 

Ectofix

 

“

SO, a dumb question…since I don’t know if this even possible, but –  are the upper and lower blowers possibly turning opposite directions within a simultaneous cycle?  I’m pretty sure they should both be turning the same direction (within a cycle).

I’m not sure if that matters, but just something I thought of.”

 

I guess its possible but I seriously doubt it, nor is there a good way to confirm it other than trying to see through the glass door and then through the suction panel.

 

This unit leaks steam still, can’t seem to get a grip on it regardless of what I try, my last conclusion is that the trolley is not level due to the floor not being level. Offered to put spacers on the casters and make the racks specific for the 1st or the 2nd one but they didn’t want that. So leaky combi it is.

 

The oven hasn’t particularly changed anything or had anything majorly changed, this is the good one whereas the convotherm 4 has pretty much had 30-40%  of its parts changed already.

 

Convotherm has never mentioned a calibration type test, never seen it in the service, repair, install or user manual. 

The chefs have read the manual, they can’t operate the equipment unless they have read them. 

 

Fixbear,

 

I had a similar concern but as far as I know, there is only one temperature measuring point in the cavity of the oven, sits a little but above the middle point of the oven, or it might be near the top, can’t remember. It also has a core probe which is another way to cook but from what I know, its measuring cavity temperature only by this 1 thermometer, That’s as far as I know.

[fixbear]

You mentioned that the carts don’t seal.  Is it possible that the oven ventilation  blower system has changed.  If a closed system and house atmospheric pressure has changed, it could be sucking air in the bottom there by cooling that area.

As I recall, the blower wheel is inside the heat exchanger and blows air 360 over it.  But how does it get ducted to the specific areas of the oven cavity?.  Do they use plates to portion the flow more to one area than another? 

 

A smoke generator may be of some assistance here.

[olivero]

Fixbear,

 

I don’t know how it would have, its part of the core programming as far as I know, its not something the chef or myself could just go and change if we thought the lower fan should run faster. The unit has a vacuum relief on top of the oven so I doubt any suction is happening.

 

The way these work is the heat exchanger kind of wraps around the fan wheel and blows air over it which is how the hot air moves. The suction plate that I mentioned earlier is what controls that “ducting” of the air.

 

Cleveland C2216467 PLATE,GUIDE,AIR FLOW | Parts Town   that’s one of them, just mounted on the wall.

 

Can’t find a picture of the fan guard /suction plate but here is the internals and everything in it from Convotherms Service Manual

 

It looks like there is only the B6 which measures oven temperature, its placed higher though, right above the top HE’s fan wheel. Kind of an odd place I think.

 

yeeeeeeah. smoker, they don’t offer that for this unit. We tried to figure that out.

[ectofix]

olivero wrote:

 

It looks like there is only the B6 which measures oven temperature, its placed higher though, right above the top HE’s fan wheel. Kind of an odd place I think.

 

That’s the standard place for a cavity temp probe.  Same with convection ovens.  Hottest spot in the oven is towards the top.

 

Olivero,

Any issues with the quench (condensate) solenoid valve?  I believe it cycles at something like 140° in the drain box.  If it’s stuck open, then it effectively could facilitate too much venting through the drain.  

I’ll explain that theory if you need me to.