heat pump supply air not warm enough

homermandy

I have a 7 year old Trane xl16i heat pump 3 ton with electric strips backup. Auxillary strips have been disconnected to try and find my problem.

My problem is that in outdoor temps of 45 or so my air supply at the handler never gets above 75. Return air is 63.

I hooked up gauges and here are the readings.
outdoor temp is 35
Suction pressure is 110psi
liquid pressure is 280psi.
both are within the spec curve called out in the manual for that temp.

the suction line temp at the outside condensor as it leaves is around 140deg.

suction line temp entering air handler is about 115deg.

Liquid line temp entering air handler is 72deg.

Any thoughts? I lowered the blower speed to 350cfm per ton, was 400.

clean indoor and outdoor coil as well as air filter. I know on service calls in the past my unit would put out 90deg plus easily

thoughts?

Thanks

GW

Did you check sub cool? You may be low on juice

GW

Fixed or tx? I'd look at sc and sh

homermandy

Tx. It gets up to 65 tomorrow so i can run in cool mode to check subcool and superheat. I am concerned about the loss of 25deg in vapor line. Vapor line is insulated and runs about 12 feet insulated.

EBEBRATT-Ed

Your #s don't look right. Is this r-22 or R-410? Your running this in heating I assume. If 22 and you have a 110 suction press your killing the compressor. Get an amp draw on the compressor and see what it's doing. You say suction line temp leaving condenser is 140? you mean discharge temp correct? Need more info and clarification

homermandy

Ok. R410a. Schrader valves are hi port right before the switchover 4way valve and low pressure schrader valve right after switchover valve for the large suction/vapor line. Those pressures are right on the curves from trane for the ambient temp.

now there is an expansion valve on the return line at the condensor that has scrader valves there. I just took some pressures and they are both 275psi high and low. That is right at the expansion valve.

The temp of 140 is the large suction tube at the bottom of the 4 way valve that travels to the air handler.

hope this helps.

homermandy

<img src="https://us.v-cdn.net/5021738/uploads/FileUpload/df/ea72553a901b626136a493d74becec.jpg" />

homermandy

Ok correction. That is not the txv valve. It is the service ports. Low is 250 and high is 275. Tja earlier readings were right before the 4way valve at 275psi. The other port is on the suctionline that must be the return. It is the middle line. Not the line going to the air handler.

Soooooo.....looks like 250 is very high low pressure. Ideas?

homermandy

Could this be a bad switchover valve? Possibly bleeding highr pressure into the low pressure line?

don_9

I am confuse.at 35 odt your hp should be giving you about a 20 degree delta t.however if i was to believe your first reading with 410 i would say you were low on refrigerant/blend.Now reading your second readings i would say your compressor not pumping.you need to put your high side guage on the big line n your low side guage on the true suction port that is tied in behind the reversing valve in heat mode.ok with that said I am going to go with the reading you first posted bc they look more beliveable with 410 blend on a 35 degree day.The reason is your sst are 40 degrees n your discharge temp headed to the airhandler is 140 degrees.So where i set now is i am thinking maybe just a tad low on refrigerant.then my other concern is the 140 temp at the hp, n then at the ah you only have 115.either you have no insulation on the suction line or you have a kink in the line.it is a pain in the butt however,you can get a sensor on the suction line would be your best bet n give us a superheat reading.As for the reversing valve bleeding over to me that like hitting the lottery, very rare, but possible.I had a old timer tell me many moons ago that the evaporator is the boss and it dictate what goes on in the rest of the system.so superheat at the evaporator is key here even in heat mode.

EBEBRATT-Ed

Measure suction line temp and pressure at compressor, same with discharge line at compressor. Also take temp and pressure in and out of the outdoor coil if you can. Take compressor amps.

Then we can diagnose

Techman

Yea, I'm confused too. On a 35* day, you are cooling off the OA, so the discharge air is colder. Now what is the low side/evap press w/ 35* air? r410a.A HP w/ 63* RATemp is fighting a loosing battle, and what is the design "balance point" of this system? Its gotta be near/above that 35*OA temp.Bring on 1 stage of e-heat and recheck.Also,most of what everyone else said.

Techman

I believe those charging charts are for above 65*f

wogpa67

Are you sure the second stage has pulled in?

unclejohn

I'm glad too see Trane is using a "charge robber " what ever the heck that is. You are using the wrong chart to check the charge. There should be a heat cycle chart some where on the unit. A 12* rise is not bad if you are in low heat. It could take 15 mins or more to switch to hi heat unless you know how to force it in. Where you having a issue with the unit not maintaining temp? If not forgetaboutit.