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  1. #1
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    Southbend EH-10SC won't maintain heat

    I got a call from a customer with Southbend EH-10SC oven that would not maintain the set temperature. They told me it would get up to temperature and then would not maintain the temperature. I replaced the control board/analog potentiometer and thermostat probe. That did not fix the problem. It continues to do the same thing. Does anyone have a technical manual for this oven? I got a copy of the owners manual off the web but no tech manual. Can anyone help? Thanks

  2. #2
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    I would call southbend they have emailed me manuals before.

    I usually start bt asking the customer questions. This can sometimes lead to a solution. For example its fine until they use during rush hour. They use as finishing oven during rush hour and heat demand cannot satisfy the load put on the oven. Oven loses temp.

    Or for example. Stops running after 2 hr cook (roast?) With no input. Maybe it's a limit/door switch when somebody checks the product or a motor is overheating and shutting down causing heat to cut out.

    Wiring diagram should tell you all you need to know.

  3. #3
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    Maybe the same manual you have? >>http://download.partstown.com/is-bin...H-10SC_spm.pdf

    For an operator's manual, it sure has some technical stuff in it.

    Like protocol said, a wiring diagram/schematic is usually all you need, unless some intense, technician-level programming is in order.

    You replaced the temp controls already? I'm assuming you tested its output circuit first to see that the old control had failed to call for heat by sending output to the heat contactor coil.

    Just perusing the manual myself, I see there's a hi-limit in series with the contactor. Did you test that?

    You never mentioned any condition of the heat circuit, whether it's single or three phase, etc. What's the condition of the wire connections? Did you ohm out the elements? How's the contactor look?

    There are three elements in that oven. Is the oven drawing proper amperage during a heat cycle? An empty oven will reach setpoint all day long on just one functioning element, but will drop like a rock when they load it with product needing cooked.


    "You never know what others don't know." -

    If I can't laugh at myself...then I'll laugh at YOU! -

  4. #4
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    The unit is 240 volt single phase. I checked the old temp controller and it was not calling for heat. There was no continuity between terminals 6&7. The hi-limit check out good i.e, there was continuity across the terminals. I checked the three elements and they were about 5.7 ohms each. The connections, terminals, contactor and wiring looked good. No signs of excessive heat, arcing or anything like that. Today, I went back to look at the unit. I turned it on and poof the on-off switch burned up. Now, I have something else figure out. This unit is only about 4 years old. I have worked on Blodgett, Hobart, Vulcan, Garland ( probably others) and they are all very similar. I have never had this kind of confusion. Any advice, help, criticism, will be appreciated. I really feel as though I am missing something. Thanks

  5. Likes ECtofix liked this post.
  6. #5
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    Gawd...a sixteen hour work day makes me look at what you wrote cross-eyed! Not your fault...

    There's a few minor problems in your resistance readings of the elements.

    • You didn't isolate the three elements to read them, and
    • I think your elements are rated for 208vac


    You said you read 5.7Ω per element, with three such elements connected in parallel for single phase operation - if that were true, this oven would be draw over 126 amps to cook biscuits.
    I don't think so.

    I did a few calculations and 5.7Ω is the total resistance of three 208v, 2500w-rated elements when connected in parallel (for single phase operation). FYI, those 208vac elements would each read 17.3Ω (per my calculations). Elements that are designed for 240vac use would read 23Ω each. Three of those connected in parallel would read 7.7Ω when all are still connected to each other. So...my calculated guess is that when this oven is heating, it's actually pulling around 46 amps (when factoring the motor and controls in there).

    If I just confused the hell out of you, don't sweat it. Electricity takes constant study and I've been doing it for a long time.

    Those 208vac elements will survive the ride with 240v applied. They'll just have a shorter lifespan. Your 5.7Ω reading sounds like they're all still good. I'd be more concerned as to whether the motor is rated for it...and whether source wiring can handle it.

    With regards to your present peril, I suggest taking a really good look at the wiring to the components. It sounds like some wires are crossed/misplaced. Page 39 of of the manual I linked to you in my earlier post appears to be the applicable diagram. It surely appears that the fuses should've blown before the switch fizzled out on you.

    You'll figure it out by getting methodical with it. I've been there too many times...and will confront such a situation again, fer sure.


    "You never know what others don't know." -

    If I can't laugh at myself...then I'll laugh at YOU! -

  7. #6
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    I do appreciate the replies. I work by myself and have no one to talk "technical" with. As, I was advised, I had to be methodical and slow down (I added that part). Fired it up, took readings across the control board terminals to see if, the contactor was responding, as it should. After, taking temperature readings and voltage readings and listening to contactor, I came to the conclusion that the 120v pull down coil was working intermittently. Replaced contactor and that fixed it. Now, I wonder how the temperature control and the contactor went bad at the same time. What's that all about? Thanks and best wishes

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  9. #7
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    What lead you to believe temp control/pot on original service? There could be a million reasons why coil was bad and whether it caused the control/pot to fail or not. After the fact is all speculation,really.

  10. #8
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    Quote Originally Posted by Protocol. View Post
    What lead you to believe temp control/pot on original service? There could be a million reasons why coil was bad and whether it caused the control/pot to fail or not. After the fact is all speculation,really.
    From past experience, I first check the temperature controller when there are temperature problems. In this case, the board checked out as not functioning properly ( no continuity between 6&7) when calling for heat. I agree, after the fact is speculation but speculation sometimes leads to discovery and learning. Thanks and best wishes

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