Small Diesel Heater with Adj Temp

[buzzp]

I have recently started with a company that makes industrial vehicles and we use a lot of diesel fired heaters for heating material. The heaters I am referring to are a compact unit with circulating pump, heat exchanger, etc in one package. The only kind I can find has a fixed temperature for on and off temperatures. We need to be able to change the temperature that the furnace comes on at. It is easy to fool the heater by placing the proper resistor where the RTD sensor is. This will give us a fixed temperature that is less than the temperature the furnace comes on at. This works fine. My problem is, I am not in favor of modifying the manufacturers electronics, although they have done it here for quite some time. Are there any heaters available that have a user adjustable on/off temp? Or are there some that have a switched contact to tell the heater when to come on AND only use the temp sensor for safety shutdown when things get to hot? Thanks for any help.

 

[Goorah]

Buzz:

Nice to see you "play it safe". When at Trane, we use decade boxes all the time as service tools to "fool the RTD"; afterall: RTDs are just "dumb resistors"

As long as you have safety overrides (which it sounds like you do) I would think you're O.K.. But to be "safe" confirm your modifications with the equipment manufacturere. Yopu probably will be voiding UL listings and warranties. Buddha's advice 2,500 yrs ago (I'm Christian!!???!!): "After deep, careful observation/analysis; and it agrees with reason, is conducive to the common good: accept it and live up to it."

 

[buzzp]

Yes I contacted the mfg and they did not like the modifications we were making at all. They even sent us a nasty letter. Part of the problem was I told them the wrong operating temp. This was a big problem as they told us not to use their products for this application. This was mostly based on exceeding the operating temp (which we're not). Anyway, I have not found a COTS heater that will work in this application. I believe we will use a reservoir and let the heater run its course with the fixed operating temperature and then pull from this reservoir, with another circ pump, when the application requires heat. This means no modifications, which makes me feel better. Thanks for the input.