continued from circuit forum...

[meadowstonefarm]

http://www.eng-tips.com/viewthread.cfm?qid=179254&page=1

i need advice, in hind site i should have just dropped the money on an actual unit that would do exactly what i need.

basically, i have a cheese aging room that needs to be at 55F, but the inverter driven heat pump i want to use only goes down to 62F. i want to put a resistor in parallel to offset the thermistor curve and fool the control into thinking it's warner than it really is. the unit will run in cooling almost year round except for a few months in winter when a few btu's might be needed for heating.

the temp off the coil is about 40F, so i don't think there is a thermo problem here, just not sure about affecting the control circuitry.

kris

 

[MikeHalloran]

Since the unit you bought was damaged in shipment and is being returned, could you persuade the manufacturer to supply the exact controller you need with its replacement?



Mike Halloran
Pembroke Pines, FL, USA

 

[meadowstonefarm]

the controller is in integrated circuit, so no, it can't be changed.

 

[itsmoked]

Got a unit link?

Cheese...yummmm.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[zekeman]

Looks like a tempest in a teapot. You should have no problem with your "fix". and it should not lead to instability.
But I am amazed at what looks like overkill unless you have a compelling reason to control this to within hundredths of a degree . What is wrong with a garden variety thermostatic control that can handle this within a few degrees? I don't think the cheese will know any difference.
I have been in this control business for 4 decades and I must say, people are overdesigning unnecessarily with these overpriced fancy controllers. Don't let those EE types freak you into things you don't need and moreover sometimes cause more instability in an otherwise benign system.