Trane System not Working
We recently had a 3 Ton Trane XL16i with VS air handler and 90% Efficiency gas furnace as back up installed.
Our house is 2200 square feet, 13 registers and basically a log cabin with insulation only in the ceiling and floor and lots of windows.
As the weather in the Northwest has cooled we have noticed several problems.
1) Vent temps of 75-80 degrees, sometimes higher, but not much.
2) The system constantly runs trying to maintain 65 degrees
3) If we ask for a 1 degree temp rise the system can do this incrementally to a point (approx 69 degrees) but if we ask for a 2 degree or more rise the temp in the house will FALL
This is with outdoor temps of around 40 degrees.
The first time the tech came out he thought an expansion valve at the compressor unit was bad and replaced it. Reasoning, the smaller line exiting the indoor coil was cold and the larger lineset was never really hot.
With this change the lineset is blazing hot, the small line still cold and the vent temps went up maybe a degree. He fiddled with the amount of charge and left again.
Came back and noted the coil (high efficiency) was very hot near the inlets but rapidly cooled. He thought something was wrong (plugged, etc) and replaced all the dryers, flushed the system and recharged. No change.
The ducts have been checked. Not intake leaks and no vent leaks.
I'm frustrated, they're frustrated and I'm looking for a fresh set of eyes to look into this. Not what I expect for the money spent.
Is this an issue with the system, the techs/installer or is the system undersized? All of the above?
How does the system do on gas heat? Have them make sure the wiring is correct per the OUTDOOR install specs, Is this a separate A/H or is the heat pump installed with the furnace? Little confused on that, as you shouldn't need 2 indoor units. The install guide for the furnace has 2 stage wiring diagram not 2 step. If they wired it with the indoor schematic it is wired wrong. the proper wiring diagram is on page 5 of the outdoor units install guide I believe.
You can't fix stupid
Was a load calculation done to determine proper sizing? You say your home is like a log cabin; I'm guessing that means a lot of heat loss. Trane is a bit weak on heat output. Do you have the model number of the furnace and coil so the BTU/H output can be checked? A "blazing hot" lineset does not mean the system is properly charged. Is the ductwork insulated? Is the ductwork in a crawlspace? A bit more info is needed.
The indoor unit is one large construct. Air filter, air handler and gas furnace portion and then coil.
The system is fine on the gas side of things. Just expensive.
Not sure about the indoor/outdoor thing you mention.
The duct work is insulated and no a heat calc wasn't done. No one offered or seemed to think it necessary when asked. Five estimates four wanted a 3 ton one wanted a 2.5.
Furnace number I can't find. Does TDY100r9V4W sound right?
Hope this helps
It looks like that match up (although it is a 3 ton system) doesn't even give 2.5 tons of heating when the heat pump is used. Might not be enough for the 2200 square foot "log cabin." ARI Ref. #797841
What is the ref # you refer to? I went to the ARI site but can't find the reference.
Why, if it's a 3 ton system would I get less than 2.5 tons of heat?
Even if the system is undersized can't I expect vent temps of greater than 75degrees?
Put that reference number in here where it asks for the reference number: http://aridirectory.org/ari/hp.php. The capacity for heating is 29,600 BTU/H (2.5 tons is 30,000 BTU/H). Trane has issues with getting the full heating capacity if you aren't careful matching the equipment up. You should be getting higher air temperatures, which is why it is possible that you may not have the correct refrigerant charge. You should have your pro back out to look at your system further.
Originally Posted by bkish
i think cmajerus may be onto the problem. the XL16i can be a bit confusing to wire becuase the indoor unit has one diagram the tstat another one and then the outdoor unit another. to get the heat pump operating right it has to be wired to diagram on outside. i made the same mistake when i first started using XL16i. however this is just a hunch as it is hard to say without being there. if they have been using this equipment combo for a whilethen they probably have it right and there may be another problem. One more thing is to check with company and see if it is in restricted mode, not allowing gas until certain temp, that can cause long cycles as well not really a prob but is not what many people are used to. When the system is wired right you should have a lower fan speed on first step of compressor and full speed on second. There are also dip switches in furnace to set heat pump size to match with air flow.
They are due out this week. At least I have a direction to point them.
I am curious why, if it were wired wrong, it would run but not put out a lot of heat. To me wiring is an on/off phenomenon. It works or it doesn't.
I think the system isn't correctly sized but the flip side is that I don't think this one is running right.
For instance, tonight it ran all night to maintain 65 degrees. The line set was warm, the vent temps 78 ish. If I bump the request up to 67 degrees the line set gets very hot (about 135 degrees) but the vent temps don't change.
Your data doesn't add up. You're probably assuming something that isn't so. There is no way for the line temp to rise, vent temp to remain the same, and the house temp to fall all at the same time, unless it was already falling before you bumped up the t-stat setting. Offhand it sounds like the unit is too small and/or the blower is moving too much air. Aside from that, the furnace should probably be kicking in at around 40º, which it apparently isn't set to do. In the upper NW, if the unit was sized for cooling, then 3 tons may be all that was called for. Unfortunately for you northerners, air source heat pumps are really worth crap because the heating end is too small when the cooling end is sized just right. Conversely, Floridians often have way more heat than they needed in winter, causing excessive short-cycling of their heat pumps. Here in the mid south the balance between cooling and heating is just about right. A two stage heat pump can be made to work well for you in the north, but in order to do so it must be oversized on the cooling end, running in low speed through much of the cooling season. Your system does not however appear to have been oversized any, let alone enough.
Originally Posted by bkish
I suggest you have them either work with you on upsizing the system, or else at least set the change-over temp higher, to the outside temp that is just a few degrees higher than the temp at which the heat pump begins to run continuously.
Last edited by hvacrmedic; 12-31-2007 at 03:08 AM.
I'm not sure why it would have more trouble keeping up (or lose temp) if I raise the temp, but it does. Too much air against a too cool coil, packing up, etc
Can someone answer some basic questions:
What is a good lineset temp on the second stage of the compressor? Is 135 in the ballpark?
What is a good vent temp for a heat pump system? A well installed, tyopical system.
Should the smaller line coming from the coil be warm, cold or room temp.
Should the coil in the airhandler be uniformly hot, cold at the middle? The bottom?
sounds like more wasted electricity. get that gas goin'. not sure what outdoor temp yer at but it sounds colder than 40. heat pumps cant keep up here in Chicago ( except maybe multi-unit bldg) we have some but always with elec heat strips or gas supplement
drywall or log interior- if drywall you can have insulation injected with little damage
The line temp is in the ballpark.
Originally Posted by bkish
The supply air temp will vary considerably and depends upon several factors. As the outdoor temp falls the heating capacity of the heat pump will drop. Corresponding to the reduction in capacity will be a lowering of supply air temperature. The supply air temperature also depends upon the volume of air flowing through the indoor coil, and upon the return air temp and to some extent on duct heat loss.
Because of the above factors, there is no lower limit to the supply air temp. It can even be lower than return air temp under extremely cold outdoor conditions, due to duct heat loss alone, though that would be an unusual situation.
The upper limit for supply air temp depends upon the type of system, air volume, and indoor and outdoor temps. I would consider a 50º rise to be a little too much rise, but it could be normal too. Without the performance data for the system I'd only be guessing.
The coil temp will not be uniform.