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Orlando, FL on Nov 13, 2011

I have a Carrier Heat Pump system with a FV4BNF005 air handler.

I just replaced the thermostat with a Carrier TP-PRH01-A. The previous model More thermostat was a Carrier TSTATCCPRH01-B. With the previous model thermostat the air handler's variable speed fan would run in high speed most of the time. With the new thermostat, the air handler's variable speed fan does not run at the higher speed, at least not yet. I have only had the thermostat installed for a few hours. I have checked and double-checked the wiring from the air handler to/from the new thermostat and I have compared the wiring to the way the old thermostat was wired. Everything appears to be wired correctly. What ideas and suggestions do you have? Any and all ideas would be greatly appreciated.

5 Comments

Woodbridge Environmental ... Colonia, NJ

you upgraded to a thermostat that provides better energy control of the system. With this your fan has not needed to operate on high speed as the lower speed appears to be doing its job correctly. As long as the system has been keeping up with the heat and cooling demands of the house I would not be to worried at this point. This is the whole idea of the variable speed system.
Also as long as the wires when to the same places on the base of the new as they were on the old. Everything should be fine.

on Nov 14, 2011 · Like 1
The Money Pit New York, NY

Well, a couple of possibilities come to mind. First, here is the (I think) install manual (http://www.docs.hvacpartners.com/idc/groups/public/documents/techlit/tp-prh-05si.pdf). I note that this is specifically designed to work with an outdoor temperature and humidity sensor. So, not sure if that has been installed but if not, that could be impacting behavior. Also, this thermostats has to be programmed to work with a heat pump. Heat pump thermostats are very different than ...»
traditional thermostats. So, be sure that you have it programmed for the heat pump mode. Hope this helps.

on Nov 14, 2011 · Like 2
Woodbridge Environmental ... Colonia, NJ

Very good pick up Money Pit. The switches must be set on the correct setting for the variable fan control Which should be on. Factory default is off.

on Nov 14, 2011 · Like 1
John Orlando, FL

There is an outdoor temperature sensor and a humidity sensor on the system and it appears I am getting proper temperature and humidity readings being displayed on the new thermidistat. This particular thermidistat has many, many configuration options. I have stepped through each one and set them with what seems to make sense. Just to be on the safe side, I have my HVAC servicer coming today to ensure everything is connected and configured properly. ...»

If the fan can run at a slower speed and the compressor unit does not have to run excessively because of it, that would be fine with me. The high speed that ran frequently with the old thermidistat was very noisy and annoying. I am just wanting to make sure the unit is being safe and efficient. I'll post the final outcome.
Thanks to all.

on Nov 14, 2011 · Like 0
John Orlando, FL

Here is the final outcome of the investigation on this issue. A jumper wire had to be added to the thermidistat connecting the R (Rc or Rh) terminal to the D1 terminal. Without the jumper wire, the thermidistat was making the air handler think it should run in dehumidify mode, thus causing the fan to run at slow speed. Once the jumper was added, the fan ran normally. The air handler has a variable speed fan, so the fan would start at a slower speed and then increase in speed to cool ...»
the house more efficiently.
I hope this post will assist others who may also experience this issue.

on Nov 14, 2011 · Like 1