I’m going to apologize up front about the length of this post. Info from this forum has me concerned about my install (wiring/setup in particular). In May 2007, I had the following system installed:
XL16i Heat Pump 4TWX6036B1000AA
XV80 100k TUD100R9V3K
TCONT803 tstat w/Outdoor temp sensor
Aprilaire M-700 Power Humidifier
Aprilaire 2200 Media Filter
As I've been thinking of replacing my 803 t-stat with the IAQ, I've been reading this forum and trying to learn more about my system/watching how it performs in it's 1st cooler weather.
Everything seems to be working on the heat pump correctly (at least at moderate outdoor temps in the 40's and upper 30's) from my layman's perspective. It seems like it’s running the Comfort-R ramp profile. Heat pump kicks on, warms up for a minute, then the fan kicks on with warm air at registers. Fans kicks to higher speed after another 8 minutes or so.
Now as temps have dropped below freezing, I think I notice problems (like not getting to 2nd Stage with my gas furnace!!). Specifically, here’s what I’ve noticed:
1) When outdoor temps are below my compressor lockout, aux heat is called (shows up on t-stat) and gas furnace starts up. But it never gets to Stage 2. I stuck a thermometer in the supply vent (there's a 3-inch wide black fabric material between 2 pieces of duct just above the furnace burners and I had seen previous HVAC maintenance crew test temps there) and got supply temps around 108 last night with 67-68 degrees house temp. I’ve waited down there for 30 minutes and I never heard it kick to 2nd stage or saw any rise in supply temp.
2) When I change the t-stat to Em. Heat, the burners come on and I get about the same 1st stage supply temps (~108 w/67-68 inside temp). After about 10 minutes, the 2nd stage gas does kick on and I notice higher air flow and supply temps increase to 120-123 (w/same 67-68 inside temp).
3) The aux heat has come on even when the outside temps are above the compressor lockout setting (currently 30 degrees). I didn’t notice this until outside temps started getting down to the low 30’s. Is this because aux heat is coming on during a HP defrost?
I’m attaching some pics of the furnace board wiring and dip switches (install pics in separate post). From what I can tell here’s the settings:
1 – off , 2 – off, 3 – off, 4 – off, 5 – on, 6 – on, 7 – on, 8 – off
From what I can gather, this would make the settings: 3 ton unit, 400 cfm/ton, Comfort-R is on, and Normal heating airflow (950cfm/1300 cfm for 1st/2nd stage). I’m not sure what the difference is between 7 on, 8 off and the factory setting of 7 off , 8 on.
The wiring looks like it’s close to the wiring diagram on page 5 of the HP install guide (my contractor actually used the Figure 15 schematic from the TCONT803 install instructions after I noticed they were following the Figure 14 instructions which I think are for a multi-stage (non-scroll) heat pump like the XL-19i).
There are a couple of things that I have noticed (good and bad):
1) The R to BK jumper (W14 ) has been cut.
2) There is a wire connecting R to O on the furnace board.
3) YLo is isolated on the furnace board.
4) I don’t see any wire connecting W1 to W2 on the furnace control board.
5) W2 only has one wire connected and that heads to the T-stat. Figure 15 shows this connection is to the T-stat at X2 versus the W2 connection in Fig 5 of the HP install guide (that may not be a real distinction).
6) Notes in the HP install guide say “X2 must be connected to variable speed air handler terminal W3, as shown, for proper indoor air flow during the defrost cycle”. I don’t see a W3 terminal on the furnace board. Is that a problem?
1) Don’t W1 and W2 need a connection? Is this why I’m not seeing 2nd stage on gas furnace in regular aux heat?
2) What is different with Em. heat that allows it to get the 2nd stage call after 10 minutes?
3) The 1st stage temp rise (~40 degrees) seems a little low from what I can tell in the airflow/power tables in the furnace install guide (51 degrees). Is that a concern? With 2nd stage from Em. Heat the supply temps rise another 12-16 degrees (total temp rise ~52-56 degrees close to the furnace install tables of 56). Does that sound normal or is there some problem with the 1st stage supply temp rise? I’ve seen some variation in the 1st stage supply temps and maybe they are lower at times because of a defrosting, cooler coil that’s between the furnace and my supply vent thermometer? Would the supply temp of the furnace running during/just after a defrost cycle be lowered when compared to running in regular non-defrost times?
4) Are the times I’ve noticed the aux heat running at outdoor temps in the low 30’s (above the compressor lockout temp setting of 30) likely a result of a defrost cycle. Is it normal that aux heat (gas) comes on during the defrost cycle? What controls this process? Is the lack of me seeing a W3 terminal on the furnace board a problem? Is there a better way to setup what happens during a defrost cycle?
5) Is anything with my current wiring, etc causing harm to my system? Should I turn it off? Put it only in Em. Heat mode? Turn up the compressor lockout temp so as to more likely avoid the defrost cycle (I don’t understand the defrost process and controlling it at all). Does this situation warrant an immediate call to my HVAC installer?
Any other comments/suggestions/answers/advice on my setup/wiring is much appreciated. If I hadn’t been considering the IAQ replacement and reading this great forum, I likely would never have even noticed these issues.
Thanks for everyone’s help on this forum.