What was I doing wrong

[lees8110]

Hi all,

I am still very new to the trade and still have alot to learn.

I am just after a bit of advice.

I replaced a compressor the other day on a heat pump unit, the system is on R22 and requires a charge of 5.44kg.

I decided to way the charge in as its a package unit, I trickle charged it into the suction as a liquid not exceeding 2.5 bar.

I noticed the compressor was getting very hot although the the suction was nicely frosted. As though it wasnt getting enough cooling from the charge in. and then it went out on thermal.

Now fully charged the system seems to be running fine and am getting all the corrrect temps/pressures.

Could this of been down to the change over valve in the wrong position. Ie not in cooling mode???

Thanks in advance for any advice given.

[desA]

I trickle charged it into the suction as a liquid not exceeding 2.5 bar.

I noticed the compressor was getting very hot although the the suction was nicely frosted. As though it wasnt getting enough cooling from the charge in. and then it went out on thermal.

I feel a little sorry for the poor compressor.

Why did you not vapour charge into the suction line of an operating system?

[lees8110]

I have just been used to doing it this way from charging zeotropes.

Charging at such a low pressure will cause it to boil off into the manifold/sytem before it reaches the compressor would it not?

[desA]

Point taken. Would it not have been better to charge into the liquid line - as liquid - with the system offline?

There are adapters which can be used to ensure that the liquid has really & truly vapourised, if you are going to charge that way.

[lees8110]

O right I havent heard of these, what are these called?

O and I always charge first as a liquid into the liquid line until the pressures equalise. But in this case it took about 50 grams as the ambient was about 4 degrees c.

[monkey spanners]

I think that it might have taken too long for the refrigerant to go in and the compressor overheated in the process, your gauges will only tell you whats in the line and not what the compressor is seeing when charging like that.

When the weather is cold it can be helpfull to warm the bottle with some warm water in a bucket or a special heater blanket and then dump as much liquid in before you run it.

[hyperion]

In cold conditions, you could with care, use your reclaim pump to pump most of the weight of the liquid into the liquid line before turning the unit on. The remaining trim charge could then be carefully added as vapour once the unit is running.

[lees8110]

Cheers Guys,

Advice appreciated:)

I will try using my reclaimer next time I think.

[lowcool]

dont recovery units require lubrication?

[thebigcheese]

was it reclaimed r22 you where using

[El Padre]

You can normally find a warm place to put the refrigerant cylinder before you commence the repairs, will save you loads of time.

Cheers

[kkeithd2]

Only 50 grams of liquid at 4 degrees r u sure you pulled a good vac on the system ?

[frosty74]

always ensure you pull a good vac
as previously mensioned warm the bottle tub of hot water you can also get heater jackets.
you can also charge liquid does your manifold have a sight glass?
if so you can liquid charge very carefully flashing off through your manifold that can be a faster method also

[tradybrad]

yes to everything frosty74 has written with your ambient conditions if good vaccum is achieved scaling in refrigerant (vapour) with assistance with warm water or heater blanket charging of unit would be easy via suction shroeder port of compressor

[lees8110]

was it reclaimed r22 you where using

Yes, Dont worry.


You can normally find a warm place to put the refrigerant cylinder before you commence the repairs, will save you loads of time.

Cheers

Yes I warmed the bottle in the site workshop with a heater prior to charging.


Only 50 grams of liquid at 4 degrees r u sure you pulled a good vac on the system ?

Yes I vaccd it twice and broke with ofn in between to below 2 torr both times to ensure no moisture present.


always ensure you pull a good vac
as previously mensioned warm the bottle tub of hot water you can also get heater jackets.

I will have to try this.

you can also charge liquid does your manifold have a sight glass?
if so you can liquid charge very carefully flashing off through your manifold that can be a faster method also

Sorry I didnt explain correctly, I did charge as a liquid boiling off in my manifold into the suction shroeder just before the comp inlet at around 2 bar.

[chillin out]

Hi all,

I am still very new to the trade and still have alot to learn.

I am just after a bit of advice.

I replaced a compressor the other day on a heat pump unit, the system is on R22 and requires a charge of 5.44kg.

I decided to way the charge in as its a package unit, I trickle charged it into the suction as a liquid not exceeding 2.5 bar.

I noticed the compressor was getting very hot although the the suction was nicely frosted. As though it wasnt getting enough cooling from the charge in. and then it went out on thermal.

Now fully charged the system seems to be running fine and am getting all the correct temps/pressures.

Could this of been down to the change over valve in the wrong position. Ie not in cooling mode???

Thanks in advance for any advice given.
Getting back to your question....it sounds like there is nothing wrong, except you might have taken a little too long putting the gas in the system.

Chillin:):)

[Tayters]

Yes, Dont worry.



Yes I warmed the bottle in the site workshop with a heater prior to charging.


:off topic:

Also when reclaiming it helps to use a cool bottle. I saw a bloke leave one in a freezer cold room on site before using it.
Some recovery units have a diagram on the side with different ways of recovering refrigerant.

[cadillackid]

my reclaimer has a sub cool function.. on larger systems i reclaim for a while then hit the subcool function and that will make a bottle frosty for recovering if i want it to, but if im going to re-use the gas I dont get my bottle too cold...

I also never re-use refrigerant from a fried compressor replacement, esp if it was an electrical failure.. I like to flush a system after compressor failure and use fresh gas.. might cost the customer a few more bucks but increases the longevity of the system.
-Christopher