Setting up a training system

[Aronsx]

I wanted to set up a training system in our shop. I got a old trance Xr1000 condenser furnace and coil. I wanted to install a system like I have at my community college. I had this system up and running but it seemed out of wack. It was only about 80 in the shop. The suction was 65 psi and head was about 275. I had 50 degree of SH, I had about 35 degree OF SC. I pulled both the condenser and evaporator and cleaned them. I have to braze it back together To get it up and running. I’m thinking that it may have a liquid line restriction in the filter drier causing higher SC.

[fridg]

Put ball valves in so you can have multiple components ,, just shut the ball valves for the Fault scenario you want to replicate.

[Aronsx]

Great idea, I like that.

[Aronsx]

I checked the piston orfice to see if it was clogged but it was clear. The only other place a restriction could be it the filter drier. The one installed by trane on inside of unit. The condenser coil was dirty. That’s why I cleaned it. I did charge the system up to 310 head and 80 suction but it didn’t change the SH. How close is to close to have these units together.

[garyed]

If you're reading high head at the outside service port connection then the dryer inside the unit would have nothing to do with it.

[Aronsx]

I would see a temp drop across the drier too, right Gary?
How far apart should I set these units. I’m thinking 18 inches is enough.
I’m a little confused on why the SH and SC was so high. And suggestions on why?

[garyed]

I would see a temp drop across the drier too, right Gary?
How far apart should I set these units. I’m thinking 18 inches is enough.
I’m a little confused on why the SH and SC was so high. And suggestions on why?

Not necessarily on the temp drop & I would guess a few feet apart would be OK. Are you sure the coil is reasonably matched with the condenser & that the gas has not been mixed with anything? You could remove the piston completely just to see what happens too.

[Aronsx]

I’m not sure if the units were match I would have to see if the model is still readable. The system was a old system that one of the other techs had replaced. They look like they should be matched, both 1.5 ton. I only put in more refrigerant to see if I could lower the SH but I didn’t want to go over 310 head pressure. I didn’t see much improvement in SH. I took the r22 out Checked the piston and cleaned both coils. I’m gonna put it back together soon. A dirty condenser will show high head pressure. What happens to SC? SC would lower, right? High SC tells me condenser is full correct? I was thinking a liquid restriction? But I don’t see anything else in condenser that could be a restriction.

[garyed]

SC doesn't get very high with a dirty condenser, it usually looks relatively normal. That's why you can usually tell a dirty condenser or not enough heat transfer off the condenser by just feeling the heat of liquid line when the head pressure gets high.

[Saturatedpsi]

It was only about 80 in the shop. The suction was 65 psi and head was about 275. I had 50 degree of SH, I had about 35 degree OF SC. I pulled both the condenser and evaporator and cleaned them. I’m thinking that it may have a liquid line restriction in the filter drier causing higher SC.

I checked the piston orfice to see if it was clogged but it was clear. The only other place a restriction could be it the filter drier. The one installed by trane on inside of unit. The condenser coil was dirty. That’s why I cleaned it. I did charge the system up to 310 head and 80 suction but it didn’t change the SH. How close is to close to have these units together.

Strange...I would have expected the SH to drop at 80 psi suction. One thought...I'm assuming there's no ductwork, which would eliminate a lot of external static and the blower would move more air. If the furnace tonnage drive is way more than the coil tonnage, that might explain the high superheat. You might try slowing the blower or choking down the return some.

The numbers definitely indicate a restriction downstream of the head pressure measurement...either a restriction, undersized piston or plugged distributor line(s) feeding the coil. I've seen that once in near 40 years but it can happen. You can expose the front of the coil, run the condenser with the blower disabled and see what kind of frosting occurs.

Other than that, increase the piston size or install a TXV.

The "proximity" between the units is irrelevant to the operating numbers when all the "flows" are correct.

[Aronsx]

Wow, I didn’t think of that. I will slow the blower motor down to medium or low. Thanks for the advice. I would like the system to run correctly so we can get some good training on it. Thanks

[beenthere]

Strange...I would have expected the SH to drop at 80 psi suction. One thought...I'm assuming there's no ductwork, which would eliminate a lot of external static and the blower would move more air. If the furnace tonnage drive is way more than the coil tonnage, that might explain the high superheat. You might try slowing the blower or choking down the return some.

The numbers definitely indicate a restriction downstream of the head pressure measurement...either a restriction, undersized piston or plugged distributor line(s) feeding the coil. I've seen that once in near 40 years but it can happen. You can expose the front of the coil, run the condenser with the blower disabled and see what kind of frosting occurs.

Other than that, increase the piston size or install a TXV.

The "proximity" between the units is irrelevant to the operating numbers when all the "flows" are correct.

If the line set is less than 15', then the factory data plate charge is too much. So proximity counts a little.

I'd look to see if there is a strainer in the piston holder fitting.

[Aronsx]

I took out the piston and blew out evap with nitrogen. Th episton was clear. I think Saturatedpsi is onto something with the lack of static pressure. Ill let you know when i get back in shop and put it together. I had planned on it today but i had a install to do, 3 ton Heat pump

[Saturatedpsi]

I had this system up and running but it seemed out of wack. It was only about 80 in the shop. The suction was 65 psi and head was about 275. I had 50 degree of SH, I had about 35 degree OF SC.

I checked the piston orfice to see if it was clogged but it was clear. I did charge the system up to 310 head and 80 suction but it didn’t change the SH.

I took out the piston and blew out evap with nitrogen. The piston was clear. I think Saturatedpsi is onto something with the lack of static pressure. Ill let you know when i get back in shop and put it together. I had planned on it today but i had a install to do, 3 ton Heat pump

Reduced airflow may improve the superheat but the head pressure and subcooling numbers are still high...you had already checked and cleaned the orifice. Good possibility the numbers will still be screwy unless you fix the metering/restriction issue.

[Aronsx]

I could try and install the TXv i took off another syatem today. todays TXV was off a 3 ton, that will be way to big for this 1.5 wont it?

[Aronsx]

I only raised the pressure to 80 on suction to see if I could get super heat down. I am excited to see if your idea works.

[Saturatedpsi]

I could try and install the TXv i took off another syatem today. todays TXV was off a 3 ton, that will be way to big for this 1.5 wont it?

For experimental/trial and error purposes, it should work well enough...may "hunt" a little. But it'll eliminate a possibility.

[knave]

A training system? Good to hear of someone who trains.
Though it would take some extra work, you could install both metering devices in parallel, with ball valves, to train how to charge with either device.

[Wiggipop1]

Adding more refrigerants is only goin to throw your pressure off more already high sc tells the horror stories of over charge or restriction, check your braze joints about 4 inches on both sides for a temp difference, sometimes the rods create that restriction if the conditions are right, also any patched areas, adjust your sc properly and run sh again, check the blower drive for cooling capcity, if you drive is too big the air flow will never be right.... if your air flow is off, then nothing is right.... could also check temp / pressure chart, add 30 to ambtemp for 10 seer to the ambient temp going into condensor and you should be close as a gross charge on head pressure example
80 ambient +30 on r22 = about 238 psig on head for a piston unit. Hope that helps some ..