My Installer advised the Setbacks should only be 3 or 4 °F so the Heat Pump can handle it. I've got mine 3°F cooler (70°F to 67°F at night -11 pm to 6 am => and when were are away most days 8am to 4 pm).
Does anyone have any thoughts on the furnace fan on ciculating the air at slow speed 24/7?
I was over at my Brother in Laws yesterday (he's acouple miles away and has a 2 ton Lennox XPG15 with Electric supplimental heating) and it was a degree or two below 0°C (32°F) => and his unit was still running.
I asked him what his set point was, and he advised he thought it was -5°C (23°F). So now I'm more confused as I would have thought there would be a Lennox standard setting for this.
Balance point is determined by the homes heat loss to the heat pumps BTU output.
So it is different for each home that has a different heat loss.
Ask your contractor for the BTU specs.
Or go to the AHRI website. And look at the heat ratings for 47 and 17 degrees.
And plot a graph.
TDR, time delay relay.
Yeah, you can draw a straight line for the heat pump's heat output.
If your heat loss at 15° is 50,801, then your heat pump won't handle the load by itself. Which is normal. The heat pump is sized to the cooling load, not the heating load.
Thats why you have the furnace to take over when the heat pump can't handle the load any more.
I need to figure out the second point for the Heat Loss portion of the graph.
By the way, does anyone know if there are any published coefficient of performance (COP) at various operating temperatures for the XPG15 heat pump?
Here is a graph that might be easier to use. You don't have to convert KW to BTU.
Put a dot at the BTU/heat loss for your design temp using the left side of the graph. Then draw a line to 0 BTU loss at 65°(the outdoor temp heat is not needed anymore).
Then plot your heat pumps BTU output at 47 and 17, and draw a line from each dot.
Where the 2 lines intersect is your heat pumps thermal balance point.
Thanks for the tip
I knew there was a point where the House Losses became zero BTUs. I used the 65 °F suggested in the attached, but I may tweak it as my Misses has actually put the heat on many times when it's not 70°F in the house. So the Heat Pump would have to come on in these cases. That would affect the graph, and push out the balance point to the right.
Is 65°F Industry Standard?
I also put on a green line representing the case if (when?) I insulate about 50 feet of concrete support wall in the storage area of the basement. I never realised the impact of leaving this area as built (by our general contreactor 21+ years ago) until the Energy Audit I had done October 29th. If it's insulated, the Energy Cost Saving$ wlll be ~$265 Canadian. There is also a one time Federal grant or $343. Sounds like a decent project for the winter...
It seems the "arbitrary" cut off point set by the Contractor for the Heat Pump - 1.5 °C /34.5 °F - is very close to the Balance point on the graph (2 °C /35.5 °F) without the Reno, and a bit too high with the Reno 0 °C /32 °F.
Please advise if I interpreting all of this correctly? Thanks for the assist.
Looks like you pretty much got it.
Don't increase to 70 for plotting. It will give you a false balance point.
Your wife may still use the heat. But the building should be gaining enough heat at 65 that the house doesn't cool below 70 over night. So you should use 65.
I'll leave the graph as is then. Thanks.
I noticed my System acting strange in the last couple of days. The Official high temperature recorded at a nearby small airport has been about 2 °C /35.5 °F, but the outside temperature indicated by the Thermostat has been swinging up to 4.5 °C /40 °F in the day time, and then quickly retreating 4 or 5 degrees F (in a minute or two) and then repeating the cycle.
During these excursions the System sometimes calls for Heat - but the Heat Pump never turns on. To my knowledge it hasn't been on in days, and probably rightly so, as it's been hovering around freezing for about a week. (Official recorded High 2 °C /35.5 °F and low about -9.5 °C /14.9 °F in the last 5 days. That's pretty cold for Vancouver. We have usually have less than 40 days per year at or below freezing.)
I typically don't pay this much attention to a Thermostat, but as I'm still learning / understanding this System, I pay far more attention to it than normal, and will continue to do so until I'm comfortable it is operating correctly.
I figure the ComfortSense 5000 or the Probe must be defective, or there is a loose connection somewhere.