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R410A Puron

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I hope that Ted will chime in on this one.

I came across a Puron unit today it's a suck pump and it's just about a year old.The customer states that it worked fine for the winter heating but the past few times they needed it for cooling,it wasn't supportive enough,

they also commented that as the day went on it just couldn't keep up & it only got warmer.

 

Today the temps where in the high eighty's & the occupied space was 84 degrees I turned the unit on and within a few minutes the supply air temp was 49 degrees,seems cool but it should be a little cooler.I went out side and put the guages on and under the load my pressures where high as expected,my suc pressure was @ 165 and my high side was 260.

 

One more pice to the puzzle my my return air temp was 76.6 degrees and my supply temp was 49.8 so the Delta T was 26.8 my sub cooling should be @10 degrees but under the load it will be higher untill it levels out.

 

My thoughts where,my suction pressure should be 105-115 and my high side should be in the ball park of 315-350,no?

Could there be a restriction?

 

Any advice would be nice.

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Heat works cooling doesn't? Only 2 places in a heat pump that cause that.

 

Your info is odd, a 26 degree split and you mention sub cooling changing under load.

 

Sub cooling should be 12 to 15 degrees after unit has stabilized (run for 20 minutes) and should not change under load. If you have high sub cooling you're over charged and the stacking liquid in the outdoor coil will give you higher than expected sub cooling values.

 

 

If you mean super heat, 10 degrees is a tad low or can point to low air flow.

 

Just going by the pressures you listed, it sounds like compressor valves, or a check valve on the indoor coil is leaking or a reversing valve issue.

 

Need to confirm air flow first, then give us super heat and sub cooling readings + supply and return dry and wet bulb readings will help. Indoor coil has a TEV right?

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I should have been more specific,26 degrees was my current Delta T & the Sub cooling design is 10 degrees and I wasn't there,the CFM's is great this unit is a VSD.

 

 

You had mentioned VVVVVVVV

Sub cooling should be 12 to 15 degrees after unit has stabilized (run for 20 minutes) and should not change under load. If you have high sub cooling you're over charged and the stacking liquid in the outdoor coil will give you higher than expected sub cooling values.

 

End quote.^^^^^^^^^^^^^^^^

 

Is this why my pressures seem high?

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High suction and low head = high side getting to low side and not going through the metering device.

 

Large evap split + inadequate cooling makes no sense if air flow is right.

 

Some of your symptoms sound like a 2 speed unit with the fan set up wrong.

 

No way to tell whats wrong with current info you have given.

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something wrong with your #s, at 165 suction you would have evap temp around 58 deg. hows that making 49 deg air???cwm13.gif

 

not into to many heat pumps here but it sounds like an issue with indoor check valve to me.headscratch.gif

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Ted I agree with what your saying with my evap temp/pressure reading thats why Im in a bind on this one.My suction side should be lower and my high side needs to be higher,the temp/ pressure tells me my liquid line temp is @ 85 degrees when I should be @ 105.......

I dunno,I had to put this account on the back burner today but I will have the pleasure to hit it first thing in the Am.

I had another joyful call,I had three RTU package units down on a Hospital,one unit,the condenser fan blade came off the shaft and severed the closest liquid line,thank God that was it easy fix.Another had a filthy C coil, unit kept tripping on high head and the other POS was just low on gas.

On the plus side Am getting a good tanwink.gif

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With 410 a your design subcool is normally on the nameplate. Most units I run across are 10 or 11. What was your LL temp? Did u calculate subcooling? Your LL press is low and your suction press is high. Did you check amperage? cwm40.gif I am leaning toward a TXV issue. Is the sensing bulb in the correct position? the TXV could be stuck open. and you would have very little subcooling, I would think.

 

There is a screen in the TXV and it could be clogged with anything....solder possibly ( I always braze 410a linesets) ...copper from reaming...anything. I have seen this before. I also think the pressures would be opposite in this case.

 

 

I am not an expert by any means! I did stay at a holiday inn express last night. biggrin.gif Take my advice with a grain of salt please, just trying to help!

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spent most of the morning on a 2 week old white rubber roof on a dialysis center, filters, belts and 5 new touch screen stats.

 

pretty much snow blind by the time i got done....cwm31.gif

 

one unit would not fire up the compressor but the indoor blower was running.

 

ended up the friggin roofers cut the thermostat wire and r-g was shorted.......mad.gifmad.gif

 

i was not a happy boy today.frown.gif

 

 

as for your problem i don't think i would be looking for a restriction at the pressures your running, i'm sticking with a check valve bypassing or maybe a bad reversing valve.

 

try switching it back and forth between heat and cool and see what happens....cwm40.gif

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personally beings that its only a year old i would lean heavily towards the TXV sensing bulb was not removed when brazing in coil and damaged the sensing bulb. i had an installer create daily service calls for me almost the whole summer two years ago with that issue

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The plot thickens,I did an evac on the refrigerant and re charged it and still the same(Negative on the TXV, I took it apart when the system was empty)but thanks for the input.

 

Check this out,I took amp reads on the compressor and they were less than half they were in the low 3's when it should be around 7-8 so theres another one for the mess.I'm thinking the revesing valve isn't closing fully.

 

I spoke with our distributor and they told me they'll give us a new condenser so I guess I'll change out the POS.

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if it has a combination txv/checkvalve in the indoor coil you might want to change that at the same time just to cover all bases.wink.gif

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Why are you changing out the condenser? I guess this was a service call. The complaint was, insufficient cooling. Heat pump about a year old.

As has been mentioned by Ed J and ted527, how and where are you getting your readings? subcooling - 10 degrees. suction press. 165 psig/ high side is 260 psig. Are you taking temp readings as well for your superheat.

 

So you evacuated the system. Did you perform a deep vacuum test to check for leaks/moisture? Did you use the old refrigerant to recharge the system? Did you use measure/weigh how much 410 you recovered?

 

How did you check the txv? Did you disassemble it when the system was off. When the system was still running did you check to see if there was a pressure/temp. change. Does this txv have a sensing bulb?

 

Reversing valve. Did you check for internal leak? Sometimes, I find that if the 4 way valve is leaking I confuse it for a compressor that is not pumping to capacity. If I suspect that I have a reversing valve that is leaking from the high side to the low side, I attach a temp. sensor to check the temp. of the low side line from the evap. and the permanent suction line between the 4 way valve and the compressor. If I get a reading of more that 3 degrees difference, I know my reversing valve is leaking.

 

Compressor. You mentioned your getting half RLA. Did you also check the comp. windings? With compressors, I block the airflow of the condenser to simulate a 95 degree day to get my head pressure up to 275 psig. and suction press. is 70 psig. The compressor should be pretty close to running at fla. If the suction pressure is high and the discharge pressure is low, the amps will be low. This shows me that the comp. is not pumping to capacity.

and if I turn off the unit and I hear like a whistling noise and if I touch the suction line to see if it gets warm immediately right after I shut off the unit. then I would think that the compressor has an internal leak from the high side to the low side. Just my .02.

 

Any more info would be good. Good luck with the repairs.

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Thanks for the hit you seem to know your stuffcwm15.gif

Yes it was a service call for not enough cooling,I don't want to change it out but it seems thats the road I'll be taking,it's been going on long enough.I feel bad for the customer.

When I did a evac I didn't measure for weight,I was to focused on getting to the bottom of this so it went into a reclaim bottle that I didn't weigh first.after that I ran a nitro pressure check @ 250 PSI for 24 hrs. it held so then I ran a vacuum for 40 min VS 30 (1.5Ton) and recharged the system in liquid form.

 

After all this the pressures seemed close to where I need to be coil was close to 50 degrees but after fifteen mins of operation the pressures went back to where they were beforekooky.gif now keep in mind I took apart the TXV and found no obstructions or debris bulb is OK(I installed this unit back in July 0f 09.

My amp draw was still the same,under half,see this is the weird part,if my suction side is high that means my comp is saturated which means I should be drawing some amperage,but I'm not.....***?!?!

 

I didn't check the four way for a temp diff,but like I mentioned earlier I'm leaning toward a valve failure.

Truth is I don't have one of them fancy temp probes you can lay on an object and monitor,I'll be buying one this summer.

 

So Im still back at square one....That is unless you see something.

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View Post .

 

My amp draw was still the same,under half,see this is the weird part,if my suction side is high that means my comp is saturated which means I should be drawing some amperage,but I'm not.....***?!?!

 

 

So Im still back at square one....That is unless you see something.

 

High suction and low head = a comp that is not doing much work. A compressor that is not doing much work will draw low amps, not high.

 

 

You have liquid going from the highside to the low side and by-passing the TEV.

 

 

If it is a combo TEV / check valve you need to replace the entire assembly, if you have a separate check-valve change it, it is your problem. Based on the info you provided it was either the 4-way valve or the check, you already eliminated one of them, good luck smile.gif .

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View Post it held so then I ran a vacuum for 40 min

 

 

 

cwm31.gifcwm31.gifcwm31.gif sounds like you need a micron gage more than a fancy temperature sensor.biggrin.gif

 

 

with 410 refrigerant and the new oil a vacuum under 500 microns is more important than ever before.

 

like said before, if you are going to change the whole unit change the indoor valve at the same time.wink.gif

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