Rudd A/C with piston

[sean88]

Does anyone know about Rudd A/C's with piston metering devices.

I'm doing a PM on a 4 ton Rudd A/C 10 SEER, all I could get off the name plate was 048.

I checked the charge and got 225 psi head and 68 psi suction with 5 degrees superheat. 85 F Outdoor ambient and 74 indoor db. The charging chart on the inside cover showed with an outdoor ambient of 85 and 4 tons I should have 228 psi head, so far so good. Well, I checked the suction chart and it said with 85 outdoor and 68 psi suction I should have 54 F suction temp, I had 40 F. I didn't add refrigerant since the head pressure looked ok.

Am I missing something here? Should those charts be somewhere close to each other?

[karsthuntr]

The liquid line pressure chart is for when inside conditions are not ideal. When conditions are good you need to use the SH chart. With the pressures you posted I would say you have no airflow across the coil (low suction, low SH, and normal LLP). Check the coil and see if it is dirty. Check the duct and see if it's undersized.

[karsthuntr]

On second thought the SP maybe normal and it is overcharged. Check airflow before removing charge.

[sean88]

thanks karst. I've got 8 more of these units to do on Monday. I'm so excited to go up into that attic!

[t1tech]

i've been working on a ruud with that kind of pressures that you are describing and i put a time delay out side and needed to put evaperator 35 deg t-stat on the indoor coil but no ones ever home, so put device outside and works fine

[bb]

Originally posted by t1tech
i've been working on a ruud with that kind of pressures that you are describing and i put a time delay out side and needed to put evaperator 35 deg t-stat on the indoor coil but no ones ever home, so put device outside and works fine

Huh ?

[websy]

I think he means he put the evaporator anti-freeze control on the condensing unit.


Sean,

5 degrees of SH is a little dangerous and could lead to some problems. I definitely would not add any refrigerant to this system as it probably has more than enough. I would double check that your airflow is okay although considering your system pressures it is probably not an issue. System sounds overcharged to me.


-websy