Recharging a 410a split

[damo567]

I have recently started a new job covering a mix of splits, VRVs and chillers. My background is Chillers and fridges, but thats why they employed me as the AC techs they have had in the past had little or no chiller experience.
As you can guess my learning curve has been pretty steep as most of the work is on the AC side. This website and forum has been a massive help (Cheers!)

On to the question, I have a Toshiba split using 410a, it has lost some of the gas and I'm currently finding the leak. On the bottle of r410a it states, this refrigerant must be charged in the liquid phase (I understand why) but on the split there is an access valve only on the LP side and if I charge liquid RF in there, when I flash it back up surely the compressor will draw in liquid (which we know is a bad thing).

I am possibly missing something obvious... but as they say there is no such thing as a stupid question...!

[taz24]

I have recently started a new job covering a mix of splits, VRVs and chillers. My background is Chillers and fridges, but thats why they employed me as the AC techs they have had in the past had little or no chiller experience.
As you can guess my learning curve has been pretty steep as most of the work is on the AC side. This website and forum has been a massive help (Cheers!)

On to the question, I have a Toshiba split using 410a, it has lost some of the gas and I'm currently finding the leak. On the bottle of r410a it states, this refrigerant must be charged in the liquid phase (I understand why) but on the split there is an access valve only on the LP side and if I charge liquid RF in there, when I flash it back up surely the compressor will draw in liquid (which we know is a bad thing).

I am possibly missing something obvious... but as they say there is no such thing as a stupid question...!


On 410a the pressure is high so they only put one access port on the low side (in cooling mode only) but you will need a 410a set of gauges.

You need to pull all the old refrigerant out, repair and prove gas tight and then charge with virgin 410a. Do not "just top up"..

You weigh in the full charge and if you can't get it in in one go then you will need to bleed liquid in as it is running. Do not charge with vapour, CHARGE ONLY LIQUID..

If you need to ask this are you ready to do the work??

All the best and be safe..
taz

.

[damo567]

I have all the right 410a equipment, just wasn't sure on the correct charging procedure. So basically you liquid charge with the LP valve closed, thus filling up the LP pipework with liquid, then thottle the refrigerant flow to the compressor using the LP valve so it is only getting vapour?

[El Padre]

Are you sure that there is not a port on the high side, inside the condenser?

There is only one port outside because even in cooling mode the expansion valve is in the outdoor unit, the pipes therefore are suction and expansion lines, and not liquid and suction, all splits are critically charged.

Its not easy working on chillers, VRV/F, splits close control, refrigeration etc. with all the different manufacturers controllers, logic, passwords to remember, but would we want it easy!

Cheers

[paul_h]

On a small split with only a suction access valve, you reclaim everything currently in the system, evacuate to a good vacuum, and then charge liquid r410a by weight while the unit is switched off.
It's safe to run the unit 10min later, but a good vacuum and warming the r410a cylinder if necessary to get all the weighed in charge while the unit is not running is the best way.

[back2space]

My engineer did not warm the bottle as he couldnt but the unit wouldnt take the last bit in so he had to turn the unit into cooling... could he have done damage for the last little bit?

[nike123]

My engineer did not warm the bottle as he couldnt but the unit wouldnt take the last bit in so he had to turn the unit into cooling... could he have done damage for the last little bit?

I done it lot of times without any damage. But charging should be done with short cylinder valve opening (2-3 sec) than waiting that sight glass in manifold is clear (and little more 20-30 sec.) and than repeating that procedure until all refrigerant is charged.

[back2space]

I done it lot of times without any damage. But charging should be done with short cylinder valve opening (2-3 sec) than waiting that sight glass in manifold is clear (and little more 20-30 sec.) and than repeating that procedure until all refrigerant is charged.

What kind of damage could it do? Or would it have happened by now I dont know if he checked manifold.

[monkey spanners]

What kind of damage could it do? Or would it have happened by now I dont know if he checked manifold.

It would have gone bang while he was charging it, i expect the system has an accumilator to catch any liquid so wouldn't worry.

Jon

[Brian_UK]

Although we charge into the suction line we normally do not actually charge full liquid into the pipework when the compressor is running.

The technique is to have the gas bottle liquid valve open but the manifold valve closed to start with.

You then crack open the manifold valve which acts as a control orifice and converts the liquid into either a vapour or two phase mixture.

Competent technicians do it all the time but do not expect to have to explain the procedure to whoever is looking over their shoulder at the time; it's just expected that it will be 'done right'.

[back2space]

Thanks... I will just have to assume it was done right because knowing my luck something will have happened!

[Brian_UK]

Sorry, should have posted this earlier but...

Why Compressors Fail - Liquid Slugging

A pdf from Danfoss
http://www.danfoss.com/NR/rdonlyres/CA85447B-C096-459F-B861-3BFD680DBC28/0/FSN008web.pdf

[back2space]

Sorry, should have posted this earlier but...

Why Compressors Fail - Liquid Slugging

A pdf from Danfoss
http://www.danfoss.com/NR/rdonlyres/CA85447B-C096-459F-B861-3BFD680DBC28/0/FSN008web.pdf

Seems pretty serious stuff. So I guess if nothing has happened now then all is good!

[cadillackid]

I charge about 90% in by a scale with unit off, wait about 10 minutes, start the unit and then SLOWLY crack the gauges off and on until last little bit of charge is in system.

also be sure when charging splits you take into account thye length of the pipework.. I find many in the field are pre-charged for 15 ft of pipe and the customer may have 25 or 30 ft of pipe installed so you have to account for that...

most heat pump splits have Accumulators on them to handle any Liquid that might still be present in the suction line.. this is because they require much different refrigerant capacities for cooling and for heating..

you would have to push a lot of liquid at it to slug the compressor out...
-Christopher

[nike123]

I charge about 90% in by a scale with unit off, wait about 10 minutes, start the unit and then SLOWLY crack the gauges off and on until last little bit of charge is in system.

also be sure when charging splits you take into account thye length of the pipework.. I find many in the field are pre-charged for 15 ft of pipe and the customer may have 25 or 30 ft of pipe installed so you have to account for that...

most heat pump splits have Accumulators on them to handle any Liquid that might still be present in the suction line.. this is because they require much different refrigerant capacities for cooling and for heating..

you would have to push a lot of liquid at it to slug the compressor out...
-Christopher

Accumulator is there for protection of rotary compressor from liquid because suction doesn't go in crankcase, it goes directly in cylinder.
Difference in charge stays in condenser. If liquid is present in accumulator all the time than that would be sign that superheat is insufficient.

[cadillackid]

doesnt flooding the condensor cause a reduction in capacity? or is that why the coils on these units seem to be larger than needbe for the rating of the unit?

plenty of capacity when partially flooded in cooling cycle yet plenty of coil area for heating cycle to proceed in colder ambient temps...??

-Christopher

[nike123]

doesnt flooding the condensor cause a reduction in capacity? or is that why the coils on these units seem to be larger than needbe for the rating of the unit?

plenty of capacity when partially flooded in cooling cycle yet plenty of coil area for heating cycle to proceed in colder ambient temps...??

-Christopher

In cooling, outdoor unit HE is not flooded. In heating indoor unit HE is partialy flooded which gives slightly higher condensation temperature which is desirable. Only drawback is increased strain on compressor and it should be designed for that, and expectations for his life is not as much as cooling only units.