Hi All. Live in eastern Ontario and just got installed a Greenspeed 25VNA048 heat pump w a 59MN7080 gas furnace to stop paying for oil. It was a learning curve for this system as it is an advanced heat pump system - expect the competition to ramp up their pumps HSPF to 13 also or lose the market. My coldest night so far was -15C and we got our 21C/70F indoor temp in our 2800 sq.ft house.My balance point is set for -17C/1F and I should be getting to -18C this wed/Thurs evening for a real test for the normal switch to gas furnace. Yes the system by default uses gas heat on defrost. Without it it would be blasting cold air in the ducts for 5 minutes. So the gas frnace heat modulates at 65% so to neutralize the cold air so air temp swings are minimum for comfort. Yes you can disable this on the touch screen interface in service/ setup/ heat source lockouts. Yes one can monitor electrical costs in $$$ or Kw and gas $$$ or therms on a per day/ per month and per year to date on the interface. I've experimented between the different options in choosing efficiency or comfort and there is a noticeable difference to the environment and a slight increase in costs of electricity between the two. I do prefer comfort. On an average cold day 0C/32F w -5C at night it costs me @ $5 per day in electricity and with heat on defrost w/ continuous low fan for only an additional cost of $1 every third day (.33cents per day). (yes the different areas of kw usage is separated in the readout) The only puzzle I have to resolve is last Saturday nite at 3 am the house felt cold - it was 15 F outside. Gas furnace came on for a couple of hours before pump came back ???. No codes or resetable fault codes registered on interface. The only way for the gas to go on at that temp way above the balance point is a 2 degree drop or a manual increase of temp of 2 degrees or more. So why did did happen.... stay tuned.... Gotta love saving money. Last year in October it cost me $425 in oil - this year for Oct gas+electrical $202 Included is a pic Update Jan 2014: had issues w furnace overiding heatpump prematurely and Carrier change my thermostat which had Version 9 to version 10 software - issue fixed. those who want to see what savings a heat pump can have over your specific system try this: http://sagoro.wrightsoft.com/Carrier/Default.aspx This post was edited by Cocobob on Mon, Jan 13, 14 at 23:22

I agree, With a 2 stage system, there won't be much difference between the 2. I would suggest the NATE dealer if for no other reason than they take the time to be educated and really, the installing dealer makes a big difference in the satisfactory outcome. They will have more resources to fall back on if they run into a question on your job, and they will also generally have a more thorough understanding of the little things about unit start up and such that can make a big difference in the long term performance of the system. This is not to say that the other sources you have mentioned may not be fine. It is just my opinion that dealers who care enough to take continuing classes and training will probably care enough to satisfy you better. As to heatpump vs AC. The advantage of a good heatpump with a low ambient control is that you can run it for heat when the outdoor temperature is around 30 or higher. A good Thermostat will automatically switch your system to furnace from heatpump based on the outdoor temperature. You are insightful enough to realize that is it usually either cool and mild, or really cold where you are. That is why the heatpump is such a good fit.

It is my understanding based on what I have read, the Infinity Controller can be programmed to have a furnace and heat pump lock out temperature. For example the heat pump lock out could be set to 30 degrees, and the furnance lock out could be set to 35 degrees. When the temperature is in the 30-35 degree range the heat pump would first come on (low stage, then high stage). If the temperature can be be achieved in a specified time, then the heat pump would shut down and the furnace would take over. The spread between the two lock out temperatures can be set from 5 to 55 degrees. The factory default is none.

Thanks for the update JB. Was the fan motor the only component you've had to replace on your system so far? I ask because I am having a similar issue with a 3-year old Carrier 24VNA0 AC unit wherein the condenser fan motor only runs for 5 seconds when the head pressure peaks. Then at some point during the cycle, the system throws the 56-OAT-OCT THERMISTOR OUT OF RANGE system event. I did the same testing that you did on your system and everything checks out good; even the thermistors. Nevertheless, I replaced the OAT-OCT thermistor assembly but this did not resolve error 56 nor did it resolve the issue with the fan motor turning on and off intermittently. This leads me to believe that the controller board cannot interpret the signals from the thermistors correctly. So, I suspect that either the controller board or the ECM fan motor needs to be replaced. I now have both parts on order and plan to replace the control board first, then if necessary the fan motor. I sure am glad Carrier gives a 10-year parts warranty because these systems apparently have issues...