On Thursday, April 23, 2020 at 11:41:34 PM UTC-4, wrote:
On Thu, 23 Apr 2020 22:26:49 -0400, micky
wrote:

In alt.home.repair, on Thu, 23 Apr 2020 10:04:21 -0700 (PDT), trader_4
wrote:


On Thursday, April 23, 2020 at 11:29:34 AM UTC-4, micky wrote:
Another problem with getting a heat pump is that the wirign to the
thermostat is inadequate. no easy way to run a new wire to the same
location**.

1) I know they make wireless thermostats and wifi thermostats, but I
wonder if they made ones that are wired but can get by on only 4 wires,
maybe by modulating the signal or something, and demodulating it at the
furnace end.

https://www.ebay.com/itm/Nordic-Elec...-/303383890610

This looks like just what I need.

On this page there are mutilple models
https://www.fast-stat.com/
It says the 3000 only adds 2 control wires, while the
5000 adds 3 plus a C wire, and the
1000 adds 1 wire, and the
Common maker adds a C, and
7000 and 9000 extend the wiring.

Instructions are provided for each of them to figure out which to buy.
They sell them through Lennox stores, two of which are listed in
Baltimore, plus the installer can get them too, i'm sure.

They list a bunch of other suppliers including Home Depot. But Home
Depot just lists the Common Maker, at $41.

7000 and 9000 look pretty complicated, more than I need I'm sure.
if I only had 2 wires to begin with I'd need the 5000, but I already
have 4 or 5 wires, so the 3000 model is probably enough.


If you have 5 wires you are good to go without anything but a Mux will
work too if you really only have 4. That is pretty rare T stat wire,
make sure there is not another one in the jacket (cut off).


Yes, if it's just one stage eqpt, seems you could do an oil furnace and heat pump
on just 5. The one thing you'd be lacking would be a common wire so you
could have the thermostat powered off the AC transformer. That's nice so
you don't have to depend on batteries and you can have a backlit display
that's lit up all the time. But if it's too hard to run a new wire, you
can certainly live without it.

The bigger question for Micky is the economics of a heat pump vs oil furnace
in MD. Also with AC it's nice to have two stage, but when I was looking
ten years ago, those cost a couple thousand more. You did get higher efficiency
too, but there would have been nowhere enough payback on electric to make
the higher eff one worth the extra cost. And two stage is nice, but I don't
think worth a couple thousand extra. Two stages in a gas furnace was only
a few hundred bucks more, I got that.