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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8252
Experience:  Furnace, A/C and heat pump specialist.
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Hvac problem

Customer Question

Hvac problem
Submitted: 2 years ago.
Category: HVAC
Expert:  airheatman replied 2 years ago.
Tell me a bit about your problem.
Customer: replied 2 years ago.
I have a package unit which is not cooling enough , its 80 degress inside, i change filters, check pressure, low side 115 psi and high side 390 psi, i tighten the fan belt , everything looks like working fine but the temp inside is not going down, can you help me with some idea please
Customer: replied 2 years ago.
I wish you can be able to help me before tomorow so i can go ahead and get it running , my boss is getting mad on me for that
Expert:  airheatman replied 2 years ago.
What is model on unit. R22 or R410 refrigerant?
Customer: replied 2 years ago.
It is 410a
Customer: replied 2 years ago.
Trane model TSC060E40A1C
Expert:  airheatman replied 2 years ago.
The pressures are not bad, See below:
http://i.imgur.com/fW6E59d.png
What is the delta T (Temp difference across evaporator. In other words what is return and supply temp?
Customer: replied 2 years ago.
Air coming to the room is at 70, and at the filter it is 81
Customer: replied 2 years ago.
Temperature at the TXV in is 70 and out is 56
Customer: replied 2 years ago.
I am guessing it might have a bad txv but i am not sure because i never replace one
Customer: replied 2 years ago.
How do you know when a txv is acting differently?
Customer: replied 2 years ago.
I measured the evap coil with infra red sensor and it is between 65 and 56
Expert:  airheatman replied 2 years ago.
I might try giving it a small amount of refrigerant and see if we can get the pressures up to about 125 to 130 and low 420s and see if we can get delta t up. I am thinking if txv, we would be lower on suction pressure. The 115 is a tad low for 80 degree return
Customer: replied 2 years ago.
Is it like if you add more refrigirant the temp increase at the evaporator? If i am not wrong because i always charge r 22 at 68 psi at 40 deg, i am not sure if it is the same for 410 a
Expert:  airheatman replied 2 years ago.
Adding refrigerant should lower the temp of evaporator coil.Normally a 40 degree coil would be about 118 to 120 with R410A.
Customer: replied 2 years ago.
I can go there again tomorow and add some more refrigirant and see what happen
Customer: replied 2 years ago.
115 i believe is not that bad
Expert:  airheatman replied 2 years ago.
Don't give it a lot and remember R410 will suck into the system a lot quicker that 22 so we don't want to overcharge. I would say give it less than a lb and lets see which direction we go. We can pick this up after you try this.
Expert:  airheatman replied 2 years ago.
I agree that the 115 is not bad. If we can get the delta t up to at least 17 from 11, we should be good.
Customer: replied 2 years ago.
Alright, thank you , let me do that and get back to you, have a good one
Expert:  airheatman replied 2 years ago.
Sounds good.Look forward to hearing back
Customer: replied 2 years ago.
Good afternoon boss, i did charge it to 130at the low pressure, i am getting 70 deg coming out of the vent and 80 at the filter, ambient temp inside building is at 95 and hot air coming out from condensor fan is 110 deg, suction line temp close to compressor is 82, see what you can tell me about it
Customer: replied 2 years ago.
There is an emerson txv model X15111287070 in the unit, in case i have to change it will you please see a match for it, may be i will not find the right one
Expert:  airheatman replied 2 years ago.
Only a degree better drop than we had yesterday.What is head running?
Customer: replied 2 years ago.
Its close to 420
Customer: replied 2 years ago.
The pressure went down to 360 and 125 on the low side
Expert:  airheatman replied 2 years ago.
I don't think I would go any higher.If air flow is good I am like you in thinking maybe the txv is nor allowing refrigerant to flash at correct location in the coil. Finding the replacement may be a bit tricky unless you are or know a Trane dealer. Most of these valves are imported from China(another reason we have so many issues with them ) and they are hard to cross reference. Trane is sort of protective of their part numbers and info as they want their "Dealers" getting the work on their units.
Customer: replied 2 years ago.
I had a problem with a pressure switch and they did not want to sell to me so i replaced it with a universal one
Customer: replied 2 years ago.
I am getting 86 deg at the txv inlet and 60 out
Expert:  airheatman replied 2 years ago.
One thing I haven't asked is about location of the bulb on the txv. Is it positoned between 1 and 3 oclock on the suction line?
Customer: replied 2 years ago.
It is at 12 oclock, but the pipe look like a 3/4 inch pipe
Expert:  airheatman replied 2 years ago.
I might suggest moving the bulb around slightly towards 3 oclock as well as completely removing from the pipe just see if the superheat and sub cooling change.
Customer: replied 2 years ago.
I moved it from side to side, pull it out and hold it tight in my habd, put it in a glass of water but both pressure remain the same
Customer: replied 2 years ago.
Sorry i mean my hand
Expert:  airheatman replied 2 years ago.
At this point, I believe we may be on to something as flow should change when bulb is moved or temp changed.I don't think it is properly metering causing flash too late in coil.Just not sure of a source for getting correct txv unless you ca get a supplier to help you cross reference
Customer: replied 2 years ago.
Yeah thats what i am going to do now, let me ser when can i get that and let you know, thanks a lot, it was nice having you as a guide especially when it get to this point
Expert:  airheatman replied 2 years ago.
PLease follow up and let me know how it goes.
Customer: replied 2 years ago.
Good evening, i did change the txv and replace it with another exactly the same , same part number, now i am getting air inlet to evap 85 and air outlet from evap 71, thats 14 deg difference, pressure is at 400psi and 125 psi, high side gauge needle is shaking a lot i dont know why
Expert:  airheatman replied 2 years ago.
Did you pull a vacuum on system when replacing txv. Usually high fluxuating head is non condensibles in system.
Customer: replied 2 years ago.
Yeah i did for about 30 mins, i talked to a friend who got hiw own ac company and i was told to charge it up to 160 on the low side and 425 high side due to the heat, after that i was getting air coming out of the evap at 66 deg and inlet was 83, i let it to run a d left as it was too late and the office door was closed , may be on monday i will check again and to see, but i have been checking everywhere to see about the low side being that high to make it wifk and i could not find any, if you have any idea ease help me understand this , thank you
Expert:  airheatman replied 2 years ago.
THis seems awfully high. If you are having to get pressures that high to get a 17 degree drop, I am wondering if possible we are drawing hot air in return somewhere.

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