View Full Version : ???confused
06-25-2005, 06:22 PM
I am looking for some help and suggestions....
I have a seven year old 5 ton BPD condencer heat pump matched to a Bryant air handler.. I have 77 degree return air 65 supply air. Have 250 discharge psi 95 SUCTION pressure..? 67 degree
suction line 112 degee liquid line.. 100 degree day.
pulled out only 6lbs r-22 thinking it might be over charged and weighed in the 10lbs data plates calls for. no change in stats. while systems opened i checked the piston...no problem there....brand new air filters
clean coil...duct work looks straight and clean
while systems running front seeded suction to a vacuum.no leakage thru revesing value.
06-25-2005, 07:55 PM
Measuring the return right at the unit? Otherwise sounds like some hot air getting to the coil with that suction.
06-25-2005, 07:59 PM
Check return air ductwork...you might be picking up heat in the return air stream that's driving your suction pressure up. Superheat indicates you're pushing a lot of vapor through the evap...common with pistons on hot days.
Also check aux heat strips to see if they're stuck on. Quick check with amp clamp on sequencers or contactors will tell the story (if you can't see the contacts pulled in).
Piston not fully seating might also explain higher evap pressure. Liquid is bypassing orifice and flooding evap.
What's your subcooling like?
06-25-2005, 08:27 PM
Here are two other possible causes of higher than normal suction pressure and lower than normal liquid pressure, they are a bad compressor such as valves or internal pressure relief is open or an oversized or bypassing metering device.
06-25-2005, 09:31 PM
I agree with Shogun8.
With 77* return air, 95 psi suction and a 12* delta sounds like high side valve leakage back to low side of the compressor.
A weak bypass will show on your gauges, high side will rise as low side drops then suddenly high side drops as low side rises accompanied by a hissing sound at the time of relief.
Hope this helps.
06-26-2005, 07:02 AM
if it has electric strip heaters in air handler i would check those(as mentioned above)I had that problem a few weeks ago. One of the 5kilowatt heaters was stuck on. it would only affect suction pressure if coil is downstream of heaters though.
06-26-2005, 09:24 AM
See if the unit will pump down. If not, oh well........
06-26-2005, 10:24 AM
thanks for the suggestions ...
the system is a straight heat pump no aux. heat
I`ve closed the suction service value during operation and it pump down to a vaccum. that should tell me my values are good..??? duct works in good condition no tears....I can`t figure out why the high suction..I pulled the piston.it was a .96 and that`s what the unit calls for....I would hate to condem the unit and change to find the problem is still there...any more suggestion....
06-26-2005, 07:25 PM
Heat pump reversing valve failures can be easily confused with compressor failures. Defective reversing valves can sometimes be hard to detect because weak compressor valves and bleeding reversing valves are usually characterized by higher-than-normal back pressure and lower-than-normal high-side pressure, as well as low system capacity. Another malfunction that can also give similar symptoms is a liquid bypass. This is a bypass from the liquid system to the low side and will also cause high back and low head pressures. A liquid bypass could be caused by a stuck- open expansion valve, , leaky check valve, or an oversized or poorly seated fixed orifice so donít assume that the compressor is at fault. If all of this is good then you have to ck out the reversing valve next.
07-02-2005, 07:01 PM
check the Rev valve..check the center tube and the suction tube the temp should not be even close..if they are. replace the reversing valve. I am betting it is not the compressor..it's pumping it's little butt off. All your systoms are pointing toward the rv allowing hot gas to go directly into the suction line, thus, causing the higher then normal suction
07-03-2005, 11:57 AM
high suction, low superheat, low subcooling looks like orfice is to large. bad compressor valves will give you a lower subcooling and a higher superheat so i dont think you have a compresssor problem.
07-03-2005, 11:26 PM
I agree with those saying rev valve. Although this is not the most fun repair in the business. It sounds likely that will be the one that will fix your problem. Just be sure to check for temp gain from the suction gas entering into the valve then leaving the valve. If you have no sensible change in temp then continue troubleshooting, it will not be the valve.
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