Trane guys I have a question

[teckster]

Ok here it goes I have a Trane mod. SEHFC754N167A8AD9C01A0W00G0K000RT008000 ser. C02c01857
Let me first explain I am not a apprentice and I have a Trane unit as mentioned above that is having issues on above 95 degree days. We which is one of my top teck and I have looked at this unit and found that the condenser is under sized at the design load conditions. I will give the details we are seeing. first I live in Denver and we don't have near the air you guys do at sea leavel so here are the readings. Trying to maintain a discharge air of 55 degrees and the oat is 95 with a 30% humidity level on the day we are seeing this. Pressures are at 70 suction with a 20 degree superheat as we removed freon to confirm what we were seeing and the discharge pressure was at 410 plus and rising and it tripps at 420psi. We removed enough Freon R-22 to get as low as 4 degrees subcooling and it still tripps if all three compressors are runing. I cleaned the condenser coil for circuit #2 just to see what would happen and the unit would stablelize at 410 psi but we did notice the fan blades have been changed with 5 blade fans and they are at rated amps and this was done by trane after the oringinal install.
so here we are trying to figure this out. We disconnected one compresor on both circuits and the unit will cool the space and stay running. So I am wondering if the condenser is under sized as we removed enough freon to where the superheat will continue to rise. Any thoughts :gah:

[GREGHVACGUY]

Did you pull the condensor coils apart to clean them.

[KB Cool]

I know what's wrong it! The model numbers too long! Throw it in the garbage! :grin2:

[Southern Mech]

Did you pull the condensor coils apart to clean them.

I pack is not a split coil

[Southern Mech]

have you pulled charge an weighed?

[lynn comstock]

Ok here it goes I have a Trane mod. SEHFC754N167A8AD9C01A0W00G0K000RT008000 ser. C02c01857 Packaged unit, commercial with 3 (or 4??) compressors, 2 separate circuits. Let me first explain I am not a apprentice and I have a Trane unit as mentioned above that is having issues on above 95 degree days. We which is one of my top teck and I have looked at this unit and found that the condenser is under sized at the design load conditions. I will give the details we are seeing. first I live in Denver and we don't have near the air you guys do at sea leavel so here are the readings. Trying to maintain a discharge air of 55 degrees and the oat is 95 with a 30% humidity level on the day we are seeing this. Pressures are at 70 suction with a 20 degree superheat as we removed freon to confirm what we were seeing and the discharge pressure was at 410 plus and rising and it tripps at 420psi. We removed enough Freon R-22 to get as low as 4 degrees subcooling and it still tripps if all three compressors are runing. I cleaned the condenser coil for circuit #2 just to see what would happen and the unit would stablelize at 410 psi but we did notice the fan blades have been changed with 5 blade fans and they are at rated amps and this was done by trane after the oringinal install. Are all of the blades' rotation correct? so here we are trying to figure this out. We disconnected one compresor on both circuits and the unit will cool the space and stay running. So I am wondering if the condenser is under sized No way. as we removed enough freon to where the superheat will continue to rise. Any thoughts :gah: Previous techs may have left air or nitrogen in the systems. Even R410A is possible. In any event the purity of the refrigerant must be checked against a PT chart. Recover the refrigerant, test the purity, recharge with pure R22 by weight and see what happens. Restricted driers ahead of the SC temperature reading point could be hiding an overcharge.There is no reason why the discharge pressure should exceed 340 psig on a 100°F ambient. Recirculation of condenser discharge air or wind may contribute to your problem but I doubt that this would be a major factor.

[jasonjoseph1975]

I agree with the above statement. must pull apart coil. with multi circiuts there is more then one coil on top of each other and from the outside coil may look clean but when pulled apart there will be a thick layer of dust. If still a problem and is believed to be first statement, then remove all refrigerant, purge, evacuate and recharge with factory amount of refrigerant. Also never hurts to call Trane tech support they are very helpfull.

[Allen]

Hi Teckster,
The IntelliPak unit does NOT have a split coil like the Voyager II units. The IntelliPak has a single coil as Southern Mech stated.
Do the procedures that Lynn Comstock has recommended. Pay close attention to the liquid line drier, if it is stopped up and the unit was running low suction, someone may have thought the unit is low on refrigerant, and added some refrigerant. Now the unit is overcharged and running high head pressure.
The condenser is not undersized. Your unit was built in March of 2002, the temperatures have certainly been at 95 degrees or higher since then. That sort of problem would have been found before now.
Good Luck,
Allen

[R123]

You can also check the purity of the refrigerant by pumping down the unit, then manually run the condenser fans (no compressor), and see if the saturated refrigerant temp in the condenser matches the outside ambient temp.

[chillerout1]

I would pull charge replace driers w/ shell driers with valves on both sides and weigh charge in. I had some units a little older than that driers were stopped up and someone had overcharged unit

[vanillaIce84]

Sorry to get off subject, i have a unit with a bad baysensorsomthing19b. Can I switch to a conventional stat by switching from the numbers to the y r g w terminals. Or is there another control ill need.

[redcell09]

If you have the UPC board with the #'s and the letters. Yes you can switch to a conventional stat. If you have the UPC board with no connections on it, then you would need the C.T.I board. (Conventional Thermostat Interface)

[vanillaIce84]

Thanks a lot. I have seen that cti but never knew what was for.

[redcell09]

It reconfigures the L.T.B for conventional thermostats. The pain in the neck is to see if your unit is pre 93 or after 93. They change where the wires land on the LTB

[vanillaIce84]

Ok, ill check. It is a reliatel board. It is cool all the things u can do it just cost to much to replace.

[redcell09]

Yeah. I like working on Trans units. They are usually pretty easy. I hate Yorks, no field experience by anyone in the factory, the electrical panel is way to small.

[vanillaIce84]

I'm new to commerical. So I have a lot to learn about walkins and econimizers. I don't understand yorks compressor lockouts. Is it only lock if low voltage amp draw is to high to it ? I don't understand how it sence the amps.

[CommtechinVA]

I'm new to commerical. So I have a lot to learn about walkins and econimizers. I don't understand yorks compressor lockouts. Is it only lock if low voltage amp draw is to high to it ? I don't understand how it sence the amps.

With all due respect, you hijacked the thread. Why not start a new thread and talk all you want about cti boards and York compressor lockouts.:whistle:

PS. Welcome to the forum.:cheers:

[vanillaIce84]

I can do that if it bothers you

[R123]

I can do that if it bothers you

Hello my friend and welcome to the forum!
It's not that it bothers him, but the person who started this thread is looking for help with his Trane unit and when you hijack a thread and change the subject, it takes away from the original person looking for help. Its no big deal, we've all done it (including me).

[freonr22]

Instead of the expense of ball valve and shell driers, recover, reinstall the relatively inexpensive factory recommended driers, and recharge?

[Tech Rob]

Could be:

Dirty coils
Wrong fan blades
Low load
Overcharge
Non-condensibles
Undercharge
Restricted driers

Or any combination of any number of the above.

I hope this is helpful. If it's not, post the following, and maybe I can offer more assistance.

constant volume or vfd? fan speed/static press.?
low ambient dampers?
return temp.
supply temp.
mixed air temp.
outside ambient temp.
suction press.
disch. press.
liquid press.
how many compressors running and which circuits?
how many fans running?
subcooling
superheat (all 3 of them)
press. drop across driers
clear sight glass?

[Phisher]

Make sure all of the condenser fans are rotating the right direction. You will bypass a lot of the coil if one of the fans is running backward. There should be a noticeable temperature drop across the drier if it's restricted.

[controldude]

Teckster, I don't remember the part # but there is a 5 blade cond. fan that needs to be on your unit due to the low airflow here.

[Youngbeechnut78]

Hello, just thought I'd put my two cents worth if it helps. If both condenser coils are clean and match the unit, make sure that the motors and blades are original and match as well. Now if other people have messed with it, I personally would start from scratch and recover, remove old driers flush system with nitrogen make sure that there are no " Restrictions ", including in the metering device. Pull a good vacuum of 700 microns or lower if possible and charge with virgin refrigerant. After all you don't know what might be in the existing refrigerant. Well hope that helps and don't give up I'm sure you'll figure it out. It sounds like a restriction of some sort. Might be within the system, or circulation of air through the condensers. Check for distinctions or irregularity in the line sizes compare circuits. Good Luck!

[controldude]

Teckster, I don't remember the part # but there is a 5 blade cond. fan that needs to be on your unit due to the low airflow here.

Now I know who you are just call me when you get back from vacation!!!

[teckster]

Thx control dude I did check the unit and it does have the 5 blade fans and the amprage is actually a little over the full load amps of the condenser fans. I did check the pressure on the R-22 freon and there is no air in the system and I did remove the charge and weight it in to the name plate specks. I did however disable the smallest compressor and the machine runs and discharges the 55 degree air as needed by the building. I checked the coil at night to confirm that I could see light through the coil and it is clean (as I cleaned it myself) I have not had any issues once I disabled the compressor. I did however find out if the oat temps are over 95 degrees the unit has has problems for years. I also took a pressure drop across the condenser and I have a 25psi differance from the compressor discharge to the tap on the liquid line at the service valve.
Thx Guys for all the responses

[GOVHVAC]

Does this unit have low ambient dampers? If so are they open? Also make sure all fans are running the right way by climbing on top of unit. I have seen these run backwards because of a bad run cap you can't tell by looking at the fan it looks like its going the right direction. You must feel the air flow coming out to make sure its turning the right way.

[Williamsma]

You say that the condensers are clean, is the discharge air off the condenser fans straight up or hitting you in the face?

I agree with Lynn Comstock about the refrigerant purity and weight. If I don't know if it is correct, recover, change driers and weigh in the correct charge. When you check the charge by subcooling or superheat, the manufacturer says that the charge has to be close to begin with before using those methods to check and adjust the charge.

Have you verified with Trane that the fan blades are correct, the fans are turning in right direction and the fan blades are in the proper position in the opening?

[a.desisto]

Is it possible someone has swapped out a compressor on this unit? The unit has 2 different size compressors in it now, maybe it was suppose to have more smaller compressors? Seen it before, and causes the unit to act like condenser is too small.

[lynn comstock]

Is it possible someone has swapped out a compressor on this unit? The unit has 2 different size compressors in it now, maybe it was suppose to have more smaller compressors? Seen it before, and causes the unit to act like condenser is too small.Good suggestion. Welcome to HVAC-talk. Go pro when you get more posts up.