Heat pump problem, any ideas anyone?

[Contactor]

Hello

This is an old R22 Myson Copperad heat pump for a large pub. See wiring diagram, attached (sorry, not a great copy).

Running on heating:

LP holds steady at 3 bar
HP 10 bar start up, but then creeps up to 25 barg after 30 mins or so.

Compressor cycles on thermal protection at about 26/27 bar.

Superheat 5 c
Subcooling 3 c

Evaporator and condensors both have good flow of air.

Evaporator air on: 4 deg C off 0 deg C (cold weather).

Condenser air on 25 c off 43 c , this includes electric heating though.

Did not get round to running on cooling.

There's no receiver.

Any offers anyone?

Thanks

[Gary]

The heat is not transferring from the refrigerant to the air. Sounds like an airflow problem to me.

[lowcool]

outdoor valve restricting?

[fridge doctor]

LP at 3 bar on R22 seems a little on the low side, but it does of course depend on conditions. We know it's B cold in Scotland right now probably, but is it unusually so? Also how does the operation of the business have an effect? What are the opening hours and is the system left on during closed periods or expected to heat a cold building on a daily basis? Any more info you have may be helpful.

[Contactor]

The unit is in Oxfordshire ambient 4C. System is left off overnight and it is a stone structure.

They have it turned up to 35 degrees and it starts cutting out once the room starts coming up to temp, it usually holds room temp at about 23C.

I can only think this is a blocked TEV as we have a good airflow over both indoor and outdoor coil.

[Gary]

The unit is in Oxfordshire ambient 4C. System is left off overnight and it is a stone structure.

They have it turned up to 35 degrees and it starts cutting out once the room starts coming up to temp, it usually holds room temp at about 23C.

I can only think this is a blocked TEV as we have a good airflow over both indoor and outdoor coil.

Unfortunately we can't get an accurate dT across the indoor coil because the electric heaters were on while taking the air off measurements (I'm assuming the heaters are after the coil, not before), so... until proven otherwise (accurate measurements), the indoor airflow is NOT good.

[johnnychin]

This is something look like steam table in the chapter of Thermodynamics. Anyway, I have some links for you to make the reference
http://www.swep.net/index.php?tpl=page0&lang=en&id=165

http://www.takenice.netii.net

[lowcool]

open the valve up but be sure to count your turns and see if alters gauge pressures.it may not prove a blocked tx but at least you can get an idea were to start pulling the system to bits as gary said make sure airflows are not restricted especially if ceilings are high assuming thats where return air box is located
myself i prefer to work in psi and celsius as i find it more accurate than barr and my pressure temp charts are graded that way.
cheers and good luck

[multisync]

The unit is in Oxfordshire ambient 4C. System is left off overnight and it is a stone structure.

They have it turned up to 35 degrees and it starts cutting out once the room starts coming up to temp, it usually holds room temp at about 23C.

I can only think this is a blocked TEV as we have a good airflow over both indoor and outdoor coil.

I thought those units were capilary?

Is this the old all in one model like the one attached?

Did you ask Eaton Williams for tech info spares etc?

who looked at it?

[NoNickName]

It looks like a bad heat exchange on the high side. If off condition is 43°c, presumably the condensing temperature is 50°C or the like. That would correspond to 19 barg or 280psig. It looks like either a dirt coil or a high side obstruction.
Are the heaters before or after the condenser in regards of the air flow direction?

[Gary]

It looks like a bad heat exchange on the high side. If off condition is 43°c, presumably the condensing temperature is 50°C or the like. That would correspond to 19 barg or 280psig. It looks like either a dirt coil or a high side obstruction.
Are the heaters before or after the condenser in regards of the air flow direction?

Another possibility would be dirty fan blades.

[Contactor]

The heaters are after the coil. I will try turning them off for an accurate dT. Fan blades are a possibility, it's old, in a horrible pub and poorly maintained.

There is a TEV on each coil, no capillary. It looks similar to the picture but is ducted in a tiny loft so can't be sure if it's the same.

Condensing temp is creeps up to about 70 C before thermal cut out (about 27 barg 405psig).

Temperature was taken at the supply and return grilles, some distance from the AHU

[Contactor]

Can anyone explain why the LP is always 3 barg (-5c, 45psig) ?

[NoNickName]

It depends what is the ambient temperature.

For the high side, I fear incondensables in the system. By chance, was it OFN tested and not evacuated?

[Gary]

The heaters are after the coil. I will try turning them off for an accurate dT. Fan blades are a possibility, it's old, in a horrible pub and poorly maintained.

There is a TEV on each coil, no capillary. It looks similar to the picture but is ducted in a tiny loft so can't be sure if it's the same.

Condensing temp is creeps up to about 70 C before thermal cut out (about 27 barg 405psig).

Temperature was taken at the supply and return grilles, some distance from the AHU

The closer to the coil, the more accurate the dT.

[lowcool]

if your tx is over restricting that will give the low back pressure,if its a reasonable pipe run you can expect your head pressure to rise

[fixit]

Hello
Airflow, Have you checked the amps on the indoor fan, Does the fan motor feel hot,

[Contactor]

Returned to site today. Opened TEV by two full turns, just to see if restricted:

HP decreased and steady at 19 barg 274psig 51c
Subcoling minimal or 0k

LP increased and steady to 4 barg 57 psig 0c
Superheat 3k

Condenser on: 21c off 41c (excluding electric heaters)

Evaporator: on 6c off 5c

Fan is covered in crap but currently riveted and inacessible, unable to access heater battery which is also riveted with no access.

No unexpected or noticeable changes in temp across liquid line, drier or three way valve.

Condenser fan belt has got far too much play on it.

Against my better judgement I have left the TEV where it now is to keep the system running.

So it's looking like airflow after all. I also have my suspicions about it being overcharged.

Haven't checked the motor running amps.

[Gary]

Returned to site today. Opened TEV by two full turns, just to see if restricted:

HP decreased and steady at 19 barg 274psig 51c
Subcoling minimal or 0k

LP increased and steady to 4 barg 57 psig 0c
Superheat 3k

Condenser on: 21c off 41c (excluding electric heaters)

Evaporator: on 6c off 5c

Fan is covered in crap but currently riveted and inacessible, unable to access heater battery which is also riveted with no access.

No unexpected or noticeable changes in temp across liquid line, drier or three way valve.

Condenser fan belt has got far too much play on it.

Against my better judgement I have left the TEV where it now is to keep the system running.

So it's looking like airflow after all. I also have my suspicions about it being overcharged.

Haven't checked the motor running amps.

You won't be able to tell if the charge is right until the airflow is right.

I would drill out the rivets to remove and clean the fan assembly.

The belt probably has too much play because the drive pulley is worn. A 'U' shaped pulley cannot properly drive a 'V' shaped belt. You may need to replace both.

Lastly, return the TXV to its original setting, then check the charge.

[Gary]

You may want to point out to the pub owner that running high head pressure adds substantially to his operating costs and shortens the lifespan of his A/C system.

People tend to downplay the importance of good airflow. It is absolutely essential.

[Contactor]

Thanks Gary. Have explained the repairs vs running costs, fortunately this customer does have some concept which isn't always the case.

[lowcool]

if you open the valve further you will probably see more improvement in gauge pressures.sounds like the indoor unit is going to get some tlc,valve & belt change,maybe a pulley or two and a good scrub.
have fun contactor

[Contactor]

To be continued..............

[back2space]

I am looking fwd to you finding out exactly what the problem is.

Any chance of some pics?