Replacing thermostats


Old 06-13-01, 01:28 PM
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I have a home with dual zone heating / cooling. The upper zone has a heat pump. I currently have regular (dial) thermostats. I would like to replace this with digital thermostats. I had a few questions regarding this:

1) Can I get the same kind of digital thermostat for both zones? Or because the second zone has a heat pump I need to get a different kind of digital thermostat for that?

2) Is this a simple task and qualifies for a do it yourself task?

3) Do digital thermostats come with the necessary instructions to install them?

4) Do dial thermostats have different wiring from digital thermostats?

Thanks in advance for any info on the above questions.
Old 06-13-01, 02:02 PM
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First of all, it seems you are talking about two independant heating systems and not a single "two zone" system. A two zone system would have a special controller as well as two thermostats. The system with a heat pump requires a thermostat designed for heat pumps, since such a thermostat contols a compressor and a reversing valve, as well as any auxiliary heating. On the other hand, yes, you could use a heat pump thermostat to run a regular furnace if you absolutely want identical thermostats, but make sure you understand the wiring differences for the two types of systems. You might also need to provide a seperate 24Vac transformer to power the thermostat running the furnace as well as a relay to convert the thermostat's 24V signal to a contact closure, which is what a furnace thermostat usually provides. As you can see, more information is needed to set this up.
Old 06-13-01, 04:12 PM
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Assuming that these are indeed two seperate systems. You do need a heat pump specific thermostat for the heat pump. Fortunately, for most brands, the operating controls and exterior appearance are going to be the same or very close if you buy the same brand.

I personally recommend the Hunter brand. I install a lot of thermostats, and they are the most straight forward and least hassle; and their shape covers a wide variety of old thermostat holes.

If the second system is straight cool with a furnace or heatstrips, buy the simpler model for that one, there is a significant price difference between heatpump and heat/cool thermostats.

It's a very simple job, you just have to be methodical and READ THE INSTRUCTIONS BEFORE YOU TAKE THE OLD T-STAT APART.

The instructions are generally pretty good, and usually come with adhesive markers so that you can label your wires (heat/ac control wire color coding is not a universal standard, sadly).

The round dial thermostats are interchangable with any other standard thermostat of a given type.

Finally, before you throw away the old thermostats, take a pair of wire cutters and cut the little mercury bulbs out of them. Take the mercury to your local hazardous waste people, keep the fish edible...

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