Seems like a simple question, but I've had a very hard time finding a definitive answer to this.

I went to the hardware store to buy a replacement for a faulty thermostat and when I arrived and looked at what was available there were specific TYPES of heating & cooling system (single stage, multi stage, heat pump, electric baseboard heat etc) that each thermostat supported or didn't support. I ended up not purchasing anything because I didn't want to buy the wrong one - and to be honest didn't trust the recommendation of the employee.

In my specific case, I have a Rheem Criterion ii heater, but can't find any description online of which of those types of heating system types mine is. For my benefit and others, it would be great if someone could detail how to determine this?

2 Answers 2


Rheem's Digital Programmable Thermostat Model# RHC-TST411MDMS. This Thermostat is Required for Enhanced Modulating Features. Check this site to determine the exact model and specs.(PDF file) http://www.expresshvac.com/res_components/gas_furnace/hvac_rheem.asp Most of these Rheem furnaces are gas fired, forced hot air.

  • It seems that my heating system didn't include that thermostat, but I may be because mine is older than the ones listed on that page (mines is Criterion II, not Criterion II Plus 2 LXE). Assuming mine is also gas fired, forced air - would I be able to use this kind of thermostat with it? lowes.com/…
    – drewdah
    Feb 8, 2011 at 23:47

If you post a photograph it may help.

By the sounds of your description you have some sort of electric heater. Could be baseboard or a convector. But this is only a best guess.

Single stage, multi stage and heat pump refer to more complex systems than a single radiator (or heater).

  • I can provide a picture of what my unit looks like, which might help identify mine - which is helpful, but I was hoping someone had some kind of definitive "If you have one of these identifying features on the furnace unit, then its a heat pump system". Mine looks exactly like this image from the link that @shirlock homes posted -expresshvac.com/images/rheem/Rheem_RGRA.jpg
    – drewdah
    Feb 8, 2011 at 23:41
  • Whoops, definitely not an electric heater then, forget that. You say furnace. So do I understand that you have either oil or natural gas to power this, can you say which? And does it heat water or air? I.e. is the heating in your rooms distributed via hot water radiators, or is it pulsed air? In any case if you say furnace, you almost certainly do not have a heat pump (as far as I understand those things) - but here you go way beyond my knowledge area - so I hope others will chime in and help you out.
    – asoundmove
    Feb 8, 2011 at 23:53

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