Strange Heating Issue (Reversing Valve?)

Hey Guys,

I don't normally post on the forum but enjoy searching through it. Though I am unable to find any information to help with this issue. I only have some of the specific information that I may need, but let me know if I need any more that will help.

Unit: 15-20 yr old R22 Ducted unit - Has had a reversing valve change about a year ago.

Issue: Our tech that visited the job says the air conditioner ran on cooling, pressures were about 60-70PSI suction, 250PSI Discharge on a 30 degree (celcius day). The issue shows when the unit is switched to heating, and the discharge pressure rises very quickly until the unit cuts out due to the high pressure safety. You can hear the reversing valve swoshing when changing between heating and cooling, the coil is fine.

I'm honestly at a lose at what would cause this issue, so any nudge in the right direction would be very appreciated!

Cheers,
- Cory

A blocked check (non-return) valve perhaps?

This is normal when ambient is 30C.

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Originally Posted by Brian_UK

A blocked check (non-return) valve perhaps?

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Could be possible, I'll have to have a look if this unit is fitted with one.

Thanks!

Quote:

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Originally Posted by chemi-cool

This is normal when ambient is 30C.

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I can't say that I've ever tested a unit of this age on heating when it's hot outside. Though the pressure raised and cut out within minutes after starting. Surely if it was working as normal, it would gradually rise in pressure until it cut out?

It seems like when the unit is switched to heating, there is a blockage in the discharge line. but on cooling it's fine. There is a lot of pipe work done inside of the unit into the new reversing valve, so I'm guessing it's been changed from the old coke can style to the new style of valve. I'm wondering if this diagnoses would be possible if the previous techs who changed the reversing valve accidently swapped two of the pipes around that go onto the reversing valve (although I'm doubtful that anyone would do that).

Quote:

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I'm wondering if this diagnoses would be possible if the previous techs who changed the reversing valve accidently swapped two of the pipes around that go onto the reversing valve

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In that case cooling cycle wouldn't work as well.

Seems to me the unit is ok.

I'd say just leave it be & wait 'till the cooler months to test heating..

Potentially there is nothing wrong with it, just that the indoor unit isn't capable of rejecting the sort of heat being absorbed from a +30°C outdoor coil.

Thanks everyone for the advise. I'll wait until we get some cooler weather and retest. Fingers crossed that the unit is fine!

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Originally Posted by CoryH

Thanks everyone for the advise. I'll wait until we get some cooler weather and retest. Fingers crossed that the unit is fine!

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Disconnect the outdoor unit fan motor(s) this will reduce the duty so the Hp should be a lot slower to rise.

Just thinking out loud here but could it have anything to do with the fact that the reversing valve becomes energised when on heating. Is the valve moving correct when switched to heating, causing a blockage. And unit works correct on cooling because valve isnt energised.

I have had the 4-way valve not cycling over fully in the heating mode causing a partial blockage and then the valve cycles back for full flow in cooling. There could either be a small piece of debris or some distortion of the valve and slider.
If this is the case, then the probable only cure would be a new 4-way valve.