T O P
cansda7

Look in the O&Ms or call the factory to see what ambient temperatures it's rated for. You'd be surprised on some of these ambient rated loads, may need to order an oversized condenser


Kitemandoo

Manu. came in and tried to charge the system but now going off high head.. they should have over sized the condenser or used a receiver


f3ks

What’s your return air temp and is the compressor pulling FLA


Kitemandoo

Its a mua, 100% 100F fresh air, running close to fla.


Hvacmike199845

I’m going to say it’s low on charge but what I say may not be correct. You are pulling in 100 degree air so your evap is going to have a really really high load causing your suction pressure to be high. I would say your head pressure is low because of a possible leak. I would expect your head pressure to be up towards 475 psig when it’s running correctly. The compressor is running FLA because of the conditions. High suction pressure would drive up the head pressure. Does this makeup air unit have an energy recovery wheel? If so is it spinning? I ask this because we installed a makeup air unit this winter. The energy recovery wheel motor died on it. The energy recovery wheel will absorb the lack of heat from the exhaust and help temper the air coming into the unit.


Kitemandoo

no energy wheel, system held 500psi for 24hours and vacuum down to 91microns, decayed to 120 in 30 minutes. im expecting the same head pressures too..


Hvacmike199845

I’m going to say the startup dude knew something was going on but either didn’t know how to fix it or didn’t want to fix it.


f3ks

If that’s the case it sounds like you have too much load on the coil. Is the airflow correct? May need to slow down the fan.


Kitemandoo

Airflow is correct, this is a 50ton mua unit for a large facility, needs a ton of air.


f3ks

Ok, I’ve had this very similar issue with a 100% OA unit and the airflow was almost double what the unit called for. I slowed her down to proper cfm and my coil temp dropped and so did my space temp and RH. I would just be certain cfm is good. Either way, let me know what you find.


Kitemandoo

Alright, thanks for your input.


Napalmsoap

If you have a txv and 0 sub cooling with 30sh then yes you are undercharged.