Chiller problem....please help!

Hi guys, i wonder if anyone could help with an issue i have with a Carrier water chiller R22 (model 30ran055 i think!). The unit has two circuits with two compressors on each circuit.

Now, the problem i have is that on start up, suction pressure on both circuits go straight down to a negative pressure. I know for a fact it is not short of refrigerant and it doesnt seem like there is a blockage as the discharge pressure doesn't go too high (180psi).

Also, both liquid line sight glasses seem to be full of oil.

Any advise would be greatly received, thank you :cool:

This is unusual, I think you have a damaged evaporator cooler, water has already contaminated your compressor and worse the whole refrigerant line system.,but check your pressure gauges if they are working correctly?.

As the unit has two circuits and both have simillar low pressure conditions then the problem would appear to have a common source.

you must confirm that you do have water flow. There should be a flow switch installed in the water circuit, but this may be stuck in a flow condition, even if there is no flow. It is therefore essential that you establish whether or not there is water flow through the shell and tube evaporator.

You didn't state if the chiller was air or water cooled. However, you need to confirm that adequate cooling medium is available at the condenser.

Are you sure there is a refrigerant charge in both circuits?

Does the unit have liquid line solenoid valves and if so are they being energised at start up? Has the unit pumped down and locked itself into an lp lockout. You may need to force the llsv open to confirm there is no liquid held back in the line.

Quote:

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Originally Posted by syd

Hi guys, i wonder if anyone could help with an issue i have with a Carrier water chiller R22 (model 30ran055 i think!). The unit has two circuits with two compressors on each circuit.

Now, the problem i have is that on start up, suction pressure on both circuits go straight down to a negative pressure. I know for a fact it is not short of refrigerant and it doesnt seem like there is a blockage as the discharge pressure doesn't go too high (180psi).

Also, both liquid line sight glasses seem to be full of oil.

Any advise would be greatly received, thank you :cool:

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Hi check exv operation ,if fitted,
!;)!

nevgee is right, troubleshoot all means you have before concluding anything else.,check also your filter-drier,maybe partially clooged-up..
We'll wait for your reply..

The chiller is air cooled.

I agree that the problem must be from a common source. To start with i thought i must have a leak on both circuits, but after pressure testing, and re-charging etc, i still have the same problems.

I know my gauges work as i have a set on each circuit and also i get a read out on the display.

The chiller does not have solinoid valves.

I have tried fully opening the expansion valves and it has no affect.

It does seem like a blockage but my HP does not rise excessively. :confused:

I will go back to it on Monday to check but i think the water flow is good as the water circuit has another chiller on it that seems to be running fine. Also there is a pump in the unit which runs.

I'm not sure i have seen so much oil in the liquid line sight glass before??

Thanks for the input, guys.

Quote:

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Originally Posted by syd

Now, the problem i have is that on start up, suction pressure on both circuits go straight down to a negative pressure.

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What does the pressure do after startup?

Quote:

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Originally Posted by syd

I know for a fact it is not short of refrigerant and it doesnt seem like there is a blockage as the discharge pressure doesn't go too high (180psi).

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A liquid line restriction does NOT cause the discharge pressure to rise.

[quote=Gary;184334]What does the pressure do after startup?




The suction pressure goes down fairly quickly onto a vac and the discharge pressure goes up to around 180psi, then it cuts out on LP. Both circuits do exactly the same.

I cant see there being a blockage on both circuits.

[QUOTE=syd;184343]

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Originally Posted by Gary

What does the pressure do after startup?




The suction pressure goes down fairly quickly onto a vac and the discharge pressure goes up to around 180psi, then it cuts out on LP. Both circuits do exactly the same.

I cant see there being a blockage on both circuits.

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Why not? Stranger things have happened.

But I'm guessing that you just haven't found the liquid line solenoids, yet.

Hi Syd,

Once you have checked the water flow etc. You could try swapping the controller with the chiller that works as that is something else common to both circuits.

Although the problem as previously stated sounds like a blocked drier, you could braze in a section of pipe to replace the drier just to prove it either way, the drier on one circuit might have been blocked for years and now the other one is blocked it seems like they both failed together which is I agree sounds unlikely.

Cheers

hi after trying to run comps and they are stopped by lp ,what happens to the low side pressure?

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Originally Posted by goshen

hi after trying to run comps and they are stopped by lp ,what happens to the low side pressure?

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The pressure takes a very long time to build up again.

Thanks for all the advise, i have a few things to try when i go back.

Hi Syd.
Has there been flow issue with the water circuit what is happening to the water temp whilst the systems are pumping down?
Some of these units have a evap pump.
Is this relevant on this unit?
Using a temperature comparator could you tell us which comes first the unit LP cutout or LWT setting?
Cheers Grizzly

Quote:

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Originally Posted by syd

The pressure takes a very long time to build up again.

Thanks for all the advise, i have a few things to try when i go back.

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Hi think u found your problem -liquid solonoied valve not opening!!!:)

Some questions that come to mind are ...

what type of chiller is it? Air cooled / water cooled/ packaged or remote condenser

2 circuit reciprocal or scroll compressors?

What number of off loading / capacity control is there?

are the expansion valves thermostatic or electronic?

Has this chiller got a microprocesor controller?

As previously suggested, is the controller working correctly and why would this machine run into a vacuum? Surely the lp switch / transducer should trip the compressors before vacuum is reached?

Quote:

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Originally Posted by goshen

Hi check exv operation ,if fitted,

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Goshen might have the right idea ;) .... if there is a control fault the electronic expansion valves may be held closed by the microprocessor.

Go to Basics please measure the standing pressure and the ambient temperature. If the refrigerant standing pressure is not close to the pressure for the refrigerant corresponding to the ambient then there may be leak of tubes or some issues.
Apparently it appears there is leak as your suction is low and discharge also seems to be low. This also can be verified if we know the ambient dry bulb and wet bulb. The condensing pressure in temperature shall be around 10 degree more than ambient dry bulb for water cooled and 15 dgree F more than ambient DB for air cooled.

Is this the first time you've worked on this system?

Ok, so i went back to the job this morning and have come to the conclusion that both the TXV are faulty and not allowing any refrigerant though.

After speaking to another technician who has worked on a number of these models it appears that vibration, over time, causes the bulb to leak.

It seems like a good theory to me. Also there are no solenoid valves on this unit.

The full model number of this unit is:
AquaSnap 30RA010-055

way to go ,thats the way to do it,
And yes i have seen similar units with txv do this,but never together
Good luck

Great start, but relating to a previous comment, if there is water in the refrigerant it can simulate a "bad" expansion valve as well. I'd do a water analysis (oil or refrigerant sample) and a really thorough pressure test! Good luck!

Good to hear .... thing to do is to try one circuit first and confirm your diagnosis. let us know what the out come is.

It is also possible that the TXV inlet screens are plugged. You may want to check these before replacing the TXV's.

Ok guys, thanks for all the advise. I feel much happier with the situation now :-)

I shall let you know how i get on.

Does this chiller have suction line filters?

Hello again,

I just thought i would let you know that the chiller is up and running :). It would appear that both the expansion valves had lost the charge, causing them to close shut. After removing and installing the new valves it works fine.

Sorry for the late reply and thanks again for all the help.