Author Topic: How to add a remote temperature sensor  (Read 1883 times)

Offline Furf

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How to add a remote temperature sensor
« on: November 07, 2015, 03:43:38 PM »

Hello. I'm really hoping someone here can point me in the right direction. I just want to be aware of my options for controlling my hvac system before committing to having my hvac contractor and/or electrician install the system (I'm not looking to "DIY" the installation)

Here's the system in a nutshell:
-3 story house, with upper floor partially open to main floor below.
-excellent winter solar heat gain
-wood heat on main floor.
-Broan 10 kw electric furnace with ecm fan motor (sort of... It's the 13x)
-heating climate only, no cooling required.

The idea is that we know the stratification will occur, as the peak of the roof is quite high up. What I want to achieve is this:

A sensor up high will monitor air temperature at this level. A cold - air return duct is located at this height also. When the main floor thermostat calls for heat, the temperature of the air up high is used to determine weather heat is supplied by furnace, or if the fan only comes on, recirculating heat from up high throughout the house.

The high sensor is in place, wired to an empty box in the wall. From this box, a standard red 5-strand thermostat wire runs to the furnace (not currently connected).
The main floor thermostat (Zen thermostat)
Is connected to furnace with same type of red 5-wire, and also has a red 2-strand wire coming from the furnace in place but not connected.

Electrician says he thinks I will need a second "cooling thermostat" between the sensor and the furnace to make this work.
Is this the best way, or should I be looking into a PLC or HVAC-Controller? I just want to keep it as simple/inexpensive as I can given the system requirements. The logic seems straightforward, but how to best implement it?

Offline scarey8

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Re: How to add a remote temperature sensor
« Reply #1 on: November 10, 2015, 06:40:46 AM »
Look into the Honeywell IAQ Products and they provide a wireless remote indoor sensor.  The challenge will be either to sense the air space temp in this upper floor area which will inherently make for a wider swing in temperature in your living space, if the ceiling are is 25 degrees all the times persay  and temperature is sensed there, the rest of your home will droop in temperature as the temp sensed will satisfy the thermostat.  Its a bit over the top what your trying to do with the controls in my opinion, why not have your furnace fan run all the time and just return that warm air. 

its possible to do what you want to do, but you will have to decide how much you want to spend

you most likely will have to change out your thermostat to something with remote sense capabilities, and something with multi staging, treat the first stage of heat in the control profile as you are trying and if heat is still required the electric heat will be brought on.