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rvz 12-02-2012 09:34 AM

Modine PA 105 Unit heater. Questions and/or manual.
I have an ancient PA 105 Unit heater with a bad limit switch. This switch is an odd design, combines both the temperature high limit with the fan cut-in. It appears to be a poor design which Modine changed in 1986. Two questions. Would anyone know where to find a manual for this thing? It's not on the Modine site. I'd also like to find the temperature cut-in/out numbers for the switch, and replace it with a more conventional setup, IE separate switches for the fan and gas valve. Put more simply, what's the high-limit temperature on these things?


old_squid 12-02-2012 09:57 AM

Usually, not always, the temperatures are on the unit itself. They are not always evident, but can be "buried" in the information stamped or printed on it. Usually a fan control will have numbers like 175/30 or something of that nature. The 175 means it turns on at 175 and the 30 means a 30 degree differential (shuts off at 145).

I did a search of Modine's website and found a parts breakdown of the unit. Just depends on how you type the search into Google probably.

rvz 12-03-2012 11:55 AM

Hi Old_squid,

Thanks for the quick reply. I was able to find the parts breakdown, and even the original part number, on the site. What I haven't been able to find anywhere on the net are specs on the limit switch in question. I'll take a closer look at the numbers stamped on the old switch, maybe it'll have the temp ranges as you suggested.

I was looking at the side of the heater again, Modine must have known that it was a bad design from the start. The sheet metal already has the mounting holes (plugged) for a second limit switch.


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