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Author Topic: Why is 9 actually 11?  (Read 2402 times)

James

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Why is 9 actually 11?
« on: January 20, 2014, 05:59:31 AM »
I have my differential set at 9 degrees right now.  Why is 9 degrees actually 11?

In other words -in my logic- if I have my high set at 195, the fan should come on at 186, right?  Nope.  It comes on at 184.  It doesn't matter what the differential is set at, the fan comes on 2 degrees lower than what I would expect.
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slimjim

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Re: Why is 9 actually 11?
« Reply #1 on: January 20, 2014, 06:54:05 AM »
You know james I've wondered the same thing, I would guess that's the way that Jonson sets them up, they are very accurate but that swing has always puzzled me as well, thanks for running her hot and don't be afraid to tighten up that differential a bit if you want/need to.
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willowbk

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Re: Why is 9 actually 11?
« Reply #2 on: January 20, 2014, 08:44:17 PM »
james
my 250 controller(Johnson) is the same exact thing off by 2pts. just remember to figure in.
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RSI

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Re: Why is 9 actually 11?
« Reply #3 on: January 20, 2014, 10:19:10 PM »
I was just looking in the manual for the controller and noticed a switch offset setting. Is it possible that P&M is putting in a jumper and setting it to 2 degrees offset to to compensate for temperature overshoot? Does it actually shut off at the set temp or 2 degrees low?
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slimjim

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Re: Why is 9 actually 11?
« Reply #4 on: January 21, 2014, 04:44:51 AM »
Shuts off at setpoint RSI, I sent you another PM
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James

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Re: Why is 9 actually 11?
« Reply #5 on: January 21, 2014, 06:26:50 AM »
Yup, it shuts off at the set point but comes on two degrees below the differential number.  So, I guess like was said above, if I want the stove to come on at 185 then I need to set my diff at 8 instead of 10.
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willowbk

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Re: Why is 9 actually 11?
« Reply #6 on: January 23, 2014, 05:49:56 PM »
james
well i guess i lied, my controller has always been 2 pts off, but now i watched today and i'm 4 pts off.
my set point is 195 and diff was at 6 and unit didnt kick on til 185. im not sure how long it has been off by 4.
i discussed w/ my cousin who has a 250 born 2 months before mine and now also has a 4pt error.  getting to be frustrating- if it is consistent thats one thing now what will it be tomorrow.  slim- let me know your thoughts.
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slimjim

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Re: Why is 9 actually 11?
« Reply #7 on: January 23, 2014, 05:54:30 PM »
Hiccup?
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ITO

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Re: Why is 9 actually 11?
« Reply #8 on: January 23, 2014, 07:40:29 PM »
 2 degrees? Could OCD account for any of this?  :P
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