13 replies to this topic

[Larbo]

This venerble wall oven c1985 has worked for many years but the temperature varies by +/- 30 degF. Since my daugher has graduated a baking and pastry program, all I get now is an angry look accompanied by a cake that didn't rise, or got burnt.

I guess that I should first ask if this is considered normal for a non-commercial oven?

The convection fan works fine and the door seal is almost new. What other factors should I look into? Essential parts (like thermostats) are scarce or non-existent. Are there any cleanings, adjustments or calibrations that one could perform? .

Thanks!!

[RegUS_PatOff]

off by + 30 and sometimes - 30 ?
How are you measuring the temperature ?
Has the Thermostat ever been changed ?

[Larbo]

Meaurements were with a Taylor dial thermometer.

Thermostat was replaced in 06 (I didn't see it actually happen.. but I was certainly billed for it).

Thanks

[RegUS_PatOff]

off by + 30 and sometimes - 30 ?

[Larbo]

I just got a digital thermometer from my neighbor and did two full cycle tests. Here are the results...

The oven was set at 350degF on Bake-Convection:

#1- Heated up to 409, took 8 minutes to drop to 352 (-57), then took 3 minutes to rise to 404 (+52).
#2- Heated up to 404, took 10 minutes to drop to 348 (-56), then took 3 minutes to rise to 403 (+54)

So, average temp was about ~378 (off ~28degF from the 350 setting) and the temp variation is about +/-27degF.

Is see that the dial thermometer is useless, after all.

I can try to calibrate the control panel to some degree. Is the variation normal or even significant considering that it has a 10 minute cycle?

Thanks

[RegUS_PatOff]

The digital thermometer may be "too fast"
the dial thermometer may be better,

from the service manual:
THERMOSTAT
• TO CHECK CALIBRATION
1. Place thermocouple or mercury thermometer in center of oven.

2. With thermostat dial in the OFF position, make certain OFF mark on the dial
agrees with reference point of the bezel or panel; misalignment will affect calibration.

3. Set temperature at 350°.
Allow oven to heat until control cycles "ON and OFF" thermostatically at least three times.
This will allow oven temperature to stabilize and eliminate possible error resulting from
initial oven temperature overshoot and/or undershoot.

4. After the control has cycled thermostatically three or more times,
note the oven temperature when the unit cycles off, and the oven temperature when the unit cycles on.
Recalibrate only if the average of these two temperature readings varies greater than 25 degrees from the dial setting.

[Larbo]

Turns out that the original +/- 30 estimates were based more upon my daughters baking experience and not the dial thermometer. I noted during my cycle tests that the dial went up to 360 down to 350. There seemed to be a 5 or 6 minute lag compared to the digital thermometer. Since the two tests were pretty close, I imagine that a 3rd would not have been much different.

Regarding the service manual... I am not clear what it means. I don't have a high temp mercury thermometer and what is meant by a thermocouple? I get making sure that the ambient temps are zero'd out but on what? Also, I don't think the display shows when the elements are being powered or not ("unit cycles on and off"). Sorry.

Edited by Larbo, 25 August 2012 - 05:09 PM.

[RegUS_PatOff]

... what is meant by a thermocouple?
... I don't think the display shows when the elements are being powered or not ("unit cycles on and off")

1) multimeter with temperature reading abilities
2) just let the oven "warm up" for 20 or 30 minutes should do it ... to stabilize

[Larbo]

1) multimeter with temperature reading abilities
2) just let the oven "warm up" for 20 or 30 minutes should do it ... to stabilize

I'll look for one of those multimeters (with high temp probes, I assume!) but my meter is just a std electrican's type meter. I may have to call in a service tech to do that. Arigatou.

Edited by Larbo, 25 August 2012 - 05:24 PM.

[Larbo]

I was wondering.

1. Is there a generally accepted temperature range for residential and commercial ovens? Like +/-10%? I had been looking at new ovens, too, and one of the reviews complained about this very issue. Granted, my situation appears to be both range and median temperature issues.

2. Is there ever an adjustment for this range or is it a non-adjustable built-in function of the oven? Or, put another way, Is turning the oven's elements on and off controlled by the thermostat or by the control board?

Thanks.

Edited by Larbo, 25 August 2012 - 07:19 PM.

[RegUS_PatOff]

... Like +/-10%?
... median temperature issues
... controlled by the thermostat or by the control board?

1) I don't know, but 10% of 350 would be 35
2) When the Thermostat was replaced, there are some switches on the Controller Board that should have been set according to the underlined number stamped on the Thermostat
3) both (see #2) .. although I don't think either are available anymore
Pages from jennairwallovenwiringbook.pdf

[Larbo]

Hi Sensei,

Yes, I have those instructions and I don't know if the tech set them or not (thanks for the pdf). I will have to yank the oven out of the wall to see the thermostat on the back for the setting code. Though, I assume from my reading that this may improve the accuracy but not the range. The rocker (DIP?) switches can account for up a +/-30degF calibration adjustment.

And yes, 10% (35degF) would cover my appx range of +/-8% (27degF). That is kind of why I wondered if it is normal or not. Maybe my expectations are too high regarding thermal consistency in a (at the time) higher end residential wall oven. Thanks!

Edited by Larbo, 25 August 2012 - 10:00 PM.

[RegUS_PatOff]

... accompanied by a cake that didn't rise, or got burnt.

didn't rise ? ... it would still rise at the lower temperatures, may just take longer ..

burnt ? ...that would take higher temperatures .. or if there are "hot spots" in the oven
or if the cake pan was on one of the lower shelves .. to close to the Heating Elements

[Larbo]

Apparently, she was occasionally (over-)compensating on the temp setting due to its being too hot.

Edited by Larbo, 26 August 2012 - 12:25 PM.