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11-06-2012, 12:49 AM #1
Water Source HP condenser flow issues
I have a new 2 ton mcquay wshp that has an air delta T of 10 deg. and a condenser water delta T of 25 deg:
return air 72 supply 62
supply water 75 return 100
r410a low 130~45 deg high 350~106deg.
My first thought is to flush the condenser loop in the unit, there are no strainers or flow-raters around the unit and it is on a closed loop system. Beyond that, I was advised by a trusted supervisor to switch the 1/2" steel braid hoses (which is the standard for the unit, per the product literature) to 3/4", leaving the 1/2" piping from the main supply line to the unit. If a gummed-up condenser coil is not the issue, will the increased hose diameter increase the water flow, even if the unit is designed for 1/2" and the piping is 1/2" as well?
11-06-2012, 05:38 AM #2
Is there multiple units on this condenser loop? What head pressure are they running?
11-06-2012, 05:40 AM #3
I don't think the 3/4" hoses will help.
11-06-2012, 09:27 AM #4
there are about 60 similar hp's on the system. no problems with HP over the summer in any units in occupied suites. The one in question is in a vacant suite. When I originally looked at it for the management who want to lease the space it was off on a HP fault. resetting the unit didn't erase the fault. checked the HP switch, it was closed. Replaced the circuit board and the unit ran. I will check the pressures on some of the nearby units. I'm hoping the flush will produce something. If not maybe a booster pump is necessary.
11-06-2012, 08:01 PM #5
flushed condenser, cleared some crud from it, water split went down a few degrees
changed hoses, water went down a few more degrees, now the split is 17 deg. 75/92 deg
pressures went down a little but they seem to be normal 125/320 psi (43/100)
air split is still low 67/59 in cooling, but higher 83/99 in heating. also, the pressures don't change in heating mode.
the two units just upstream in the loop, one has a normal water split 8 deg., one is a little high 14 deg.
another unit next door on another branch (same loop) has a normal water split as well (10 deg)
11-06-2012, 08:09 PM #6Professional Member*
- Join Date
- Jan 2008
- Dallas ,Texas
Your condenser delta should average 10 degrees I think you water flow is low a gummed up condenser should show a lower delta T.
11-06-2012, 08:15 PM #7
ANYBODY who installs a closed loop condenser system and does not install local strainers on the inlets is "Cheating" and this is the end result.
How was the system ever balanced without circuit controllers? This blows my mind....
IMHO you should have flow devices and strainers on every unit you touch. Otherwise you will just be chasing the problem around like a Super ball in a gymnasium.
GTIf a day goes by and you have learned nothing, I hope you got a lot of sleep.
11-06-2012, 08:35 PM #8
Do you have IOM for this unit? It should state the minimum gpm required. You could disconnect waterline and see how long it takes to fill a 55 gal drum. Then calculate gpm.
11-06-2012, 10:04 PM #9
Look in the IOM for the unit, there should be a chart to show pressure drop on the heat exchanger so you can calculate GPM..
11-06-2012, 10:53 PM #10
i would love a wye-strainer and a pressure tap on the shutoff. unfortunately, this is a 30 yr old system with PVC piping and leaky gate valves. at least this one has ball valves (PVC ones). First thing i did was look up the manual (installer was nice enough NOT to leave it) and found the GPM is 6.4. I like the fill the drum idea, maybe 2 5 gallon buckets would be more practical?
also, don't these pressures seem correct for the system? I was told 10-12 degree above condensing water temp for the head pressure in water cooled system. i am wondering if there are air flow problems. i did find that the IBM was wired for the wrong speed, but i corrected that first.
11-06-2012, 11:00 PM #11
oops I was using the return water temp. when i was thinking the head pressure was correct instead of the supply. the supply temp is 75 deg so i guess the head pressure should be 256
11-07-2012, 11:08 PM #12
Is your water line big enough to feed all of the heat pumps in the loop. By the way they all need strainers and h2o circuit flow control.
What is the GPM for the unit you are working on, it may be more than the other units already in the systemWaddya mean don't thaw out the frig with a knive?
11-08-2012, 12:32 AM #13