City Multi...PUHY-P300YHM-A

[ronaldo9]

Hey guys,

Hope someone can help.
I have 2x PUHY-P300YHM-A piped together, with four indoors (havent checked models yet). No BC .The problem is no cooling performance at indoors. Its an open plan retail area with another system identical to this one,the two outdoors on this other system are running flat out all day so the demand is there.

On the system im working on one outdoor will run at about 40Hz for about 10 mins then the second one will kick in and run at the same for about 5-10 mins and then stop. The first unit will continue running after this. Some points to mention;

-Frost coming back on suction, and on receiver.
-Liquid line cold.
-No heat in condenser coil.
-Tc of -13
-Discharge temp can hover around 50 and get as high as 70
-HP between 18- 30 bar (was at 35 at one stage)
-LP around 5 bar ,,,,SOG???? Maybe not
-Very important,,,the indoor units are doing nothing, no temp difference between inlet and outlet on any of the units
I thought maybe one of the units was passing gas with LEV stuck open, this would account for frosting suction. But surely the unit that was passing would show some cooling performance while starving the other units. And yet with a cold liquid line and frosting suction line its as if the indoor units arnt connected to anything. (the pipes are connected and to the right outdoor).

When i got to this site at first i thought poor performance, inverters not ramping up, SOG, had no recovery machine with me to verify the charge so i decide to add a kg to see if it made a difference, none , i added another 4 kg to see and still nothing. I believe these units can take up to 5kg overcharge without effecting system. However then i got a 1500 fault, excellent, making things difficult for myself as usual. Im going back to site in morning and the first thing im gonna do is verify the charge by weight and get that out of the way.I was wondering if anyone had any other ideas on what the underlying issue is, whats stopping the comp running above 40Hz, why is there no temp difference at indoors?
I did read a post by Pie Man regarding the same 1500 fault and got some helpful tips on Discharge superheat and its effect on comp.
I did check actual and real readings for HP and Discharge temp on one unit but not the other.

Any readings ive got are from SW-1, i was meant to organise a site visit with ME for maintenance tool a while ago but with 16 hour days becoming the norm ive let it slip.

I look forward to the time when i can offer advice instead of receiving it.

Regards

[multisync]

Thermatech is you're man -and probaby a darn sight cheaper than M.E !

[marc5180]

Hi Ronaldo, not worked on the heat pump only models that much but i work on the R2 heat recovery quite a lot and know them pretty well.

Not as good as Thermatech.....yet:D but i'll try and help

Do you have a service manual for this? That way you could trace through the outdoor refrigeration circuit and check what solonoids and LEV's should be open.

Have you checked operation of the 4 way valves? do they switch over if you remove the coils?

Check Target condensing temp and actual condensing temp on the SW1 settings to see if this is having an effect on the inverter not ramping up.

You say discharge temp can hover between 50-70C and Discharge pressure up to 35 bar, if that is the case surely the condensor coil must be hot/warm....check thermister values on the oudoor unit TH2, TH3, TH5, TH6, TH7 and also LEV 1 and 2 to try and follow the hot gas/warm liquid.

Firstly need to find where the hot gas is going and if it is going to the indoors then using SW1 check the indoor LEV opening, liquid and gas thermisters and superheat readings across the coil.


BTW another way of checking for undercharge is if the compressor shell bottom temperature is high. (The difference between the compressor shell
bottom temperature and low pressure saturation temperature is greater than 60°C)

[Thermatech]

Outdoor unit target evaporating at 7.1 bar = 0 deg C.
Frosted suction back from indoor units makes lower than target & so compressors ramp down.
Max comp speed on size 300 = 74 hz.

The comp will ramp up again if the pressure & temp rise above target. But in this case suction pressure / temp below target so comp tends to stay at low speed.

So why suction frosted coming back from indoor units if high temp in occupied space ?

Prime suspect as you considered is indoor unit LEV locked wide open making liquid to suction bypass & frosted suction.
Or could be indoor unit fan motor not running so liquid flushing through indoor unit & dumping into suction line.
Or ducted indoor units with closed supply duct dampers or even long supply ducts & units set on low static fan setting making poor air flow.
Maintenance engineer forgot to clean air filters on indoor units making poor air flow.

With some liquid return accumulator will be full & the extra refrigerant charge made accumulator overflow & then less than 10 deg C DSH & 1500 fault.

As this is relatively new system you could check for installation mistakes like crossed pipes & control cable.

Monitor outdoor unit with two sets of gauges connected to HP / LP service ports & HP / LP service valves & use SW1 to confirm correct data from pressure sensors & confirm correct refrigerant flow / pressure through the outdoor unit.
If you have good refrigerant pressure & subcooled liquid at liquid line service valve but frosted suction back from indoor units then liquid flooding into suction at 1 or more indoor units has to be suspect.

I know in retail site its sometimes difficult to get up to high level indoor units so try remote monitor of indoor units by looking at the indoor unit coil temp & SH for all the indoor units using SW1 at the outdoor unit this might show which indoor unit is the problem.

[ronaldo9]

Hey Guys,

Only just getting the chance to reply, thanks marc5180 and Thermatech, this was a real tricky one. I was reassured to read your posts and see that i had been checking the right things. However it was all in vain.

"As this is relatively new system you could check for installation mistakes like crossed pipes & control cable."

And so it was, crossed communication cable, system is in over a year and it was never picked up on when commissioned. The system it was mixed up with had gone out on a drain pump fault and so wasnt running. Those extra few kgs i put in were the worst thing i could have done. System is running and hopefully there is no lasting damage done.

Anyway thanks lads for the help. For those us barely scratching the surface on this game all the help is really appreciated.

Once last thing im glad im working these long hours, cause the World Cup sucks balls!!!