Trane XL16C Dual Fuel Heat Pump - Variable Speed / Stage Questions
Just had a reputable company come out and install a new Trane XL16C Dual Fuel Heat Pump (3 ton) w/ Honeywell IAQ today and haul away my dying contractor grade Carrier 48gs gas pack (3.5 ton). The installers did a very good job made every effort to answer any questions I had. Now that I have had time to coexist with my system for a few hours I have some questions.
1) The installer showed me the dip switches where the CFM can be adjust. I believe that the settings are 350, 400 (default), and 450. Is this cfm setting for when the blower is at 100%? I believe the installer said, yes. If so seeing that my previous unit was a 3.5 ton should I bump the switch to run at 450?
2) What are the variable speed rules for the blower on heat mode? cool mode? i.e. x% for y time. How can I tell when the blower is running at 100%?
3) Since this unit has a 2 stage compressor, what are the rules for when the compressor engages stage 2? Can this be driven by or displayed on thermostat?
Thank you for your help.
Don't mess with the dip switches for best humidity removal in summer 350 is good, otherwise 400 is standard and yes it's for 100%. The % of blower speed depends on manufacturer maybe a trane guy can come along and answer the 2nd ?.The tstat should say 2nd stage when the ac kicks into high speed, you will also probably notice a change it airflow between the speeds
2nd stage usually kicks in when the inside temp gets above/below set temp by 2 degrees F
Good deal. Thanks. The unit has had no problem keeping within 1 degree of the set temp. I have noticed some long times, however, I could just be paying way more attention to it since it is new and fresh on my mind.
Originally Posted by jtrammel
Long run times is good it creates more even temps throughout your home and is actually cheaper to run than starting and stopping.
Thanks for the great info. I did notice that the my entire downstairs was more comfortable over all this evening as compared to before when the jet engine would fire, run for 15 minutes than shut off only to be cold 20 minutes later...
Originally Posted by jtrammel
Hopefully a Trane expert will chime in with some info on the variable speed blower.
Any suggestions on how to best program my thermostat for good efficiency while still keeping warm? In the past I would allow a 2 degree step down at during work hours and at night.
Is this suitable for a new high efficiency system like the XL16C Heat Pump?
Example Winter Program:
It's better to find a temp that you're comfortable and leave it alone with a heat pump, but a couple of degrees won't be a problem. If you set it back <2F it would bring the gas furnace on until it reached the set temp then use the heat pump to maintain set temp. Did they set a lock out temp for the gas furnace so it will only bring on furnace during defrost above a certain temp (~30F)
Yes, the furnace lockout is set to 35F.
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Last edited by jpsmith1cm; 11-17-2012 at 09:33 PM.
Reason: non AOP member
Last night was our first night with the XL16C keeping us warm. I have to say that despite being .5 ton smaller than my previous system it kept my main floor relatively comfortable. Especially our Master BR which would usually turn into a sauna for the first 5 minutes of each gas cycle.
That said I noticed that throughout most of the night if not the entire night the unit was running in some form or another. While I never bumped out of stage 1 and low on the blower it did run for hours on end. I got up to take a look at the thermostat a few times and it never swayed from the setpoint which was 68, the gas lockout is set to 35. The outside temp bottomed out at 39.
Is this normal? Should the unit be running non stop for hours on end without a break? I am so used to my gas furnace cycling on and off a few times an hour so any insight into what I should expect as a new heat pump owner would be much appreciated.
Good deal with the XL16. The heat pump will definitely run longer than your previous gas pack but that is good. Think about it. Your old gas pack probably had a BTU rating of approximately 75,000 to 110,000 or more. So every time the beast would come on it would dump 75,000 + Btu's in your home regardless of your homes heat loss. This would lead to short cycling and premature failure of equipment.
Imagine cooking a steak with a propane torch, yeah, you could get the outside of it done quickly but what does the inside look like? Probably still raw meat. It cannot cook it evenly without the proper amount of time for heat transfer. Same way with your home. You do not need 100,000 Btu's all the time, it will not keep the rooms conditioned evenly. It is not economically efficient to run your car 100 miles per hour every where you go, it is better to go 50 miles per hour without a break than to start and stop, start and stop constantly 0 to 100 miles per hour. If you had to run everywhere you went instead of walking you would be worn out. lol
With your new Heat pump it is 3 ton capacity. Each ton is equal to 12,000 Btu's so the total for your heat pump is 36,000 Btu's + you have additional gas heat in case the heat pump is not enough. Additionally, your heat pumps 1st stage is approximately 70% capacity so 70% of 36,000 is 25,200 which is actually close to 2 tons. Not as many Btu's as your gas pack but the idea of the matter is to meet your homes heat loss at a constant rate. if its 50 degrees outside you may only need 25,200 Btu's to keep it conditioned. At 0 degrees outside you will need that 75,000 + Btu's of gas heat to accommodate your homes heat loss.
if you have natural gas I would leave it at 35 if you have propane I would drop the lock out to 20 or 25 degrees and see if it can keep up with the heat pump ,400 cfm per ton will give a little more btus in heat and cool .
My gas backup is NG, which is fairly cheap in NC but likely nowhere near as cheap as it is to run the XL16C I bet. I will know next month when my bills come in. I am used to my gas bill creeping into the $225+ range in the peak months of Jan & Feb.
Originally Posted by catmanacman
Right now the unit is set to 400CFM and on stage two it flows plenty of air.