Charging liquid 407 by LP ? Where goes liquid ? can it damage the compressor ?

I went through all the questions about the charge with R407 or R410 and I find no answer on my question.
On the outdoor unit, there is only one service valve.And thats why there is something I do not understand.
I know I need to charge in liquid, and the compressor must not run. If I have to charge liquid through the low-pressure valve, where goes the liquid? do I need to do something to control that ? Can I turn on the compressor without the risk of damage? Should I start in heating or cooling mode to avoid this risk?
thank you for your help!!

Sorry, in the title, I mean LP.

Hi pvl,

you can either use a quik charger which restricts the amount of refrigerant allowed through it or more likely use the valves on your gauges to restrict the amount of refrigerant allowed in to the service port.

i.e. Supply liquid to the manifold guage set and then use the valve on your manifold to control the flow into the hose connected to the system service port.

Charge it in cooling mode and if need be turn on the compressor to reduce the pressure to draw in the refrigerant.

Be careful which hose and gauge you have connected to the service port, if you are going to run the system in heating mode use the HP side of the manifold.

Thank you Tony,
So, if I understand correctly, when the gas is introduced as you suggest (without the kwik charger) I can start the compressor without risk. Yet there is a part of liquid refrigerant ?

Many smaller units only have a service port on the suction pipe. The other pipe isn't a high side pipe as the expansion valve is in the outdoor unit. It's on the suction side right after the expansion valve. It's more of a help when vaccing the system. It will be slightly higher pressure than the suction port but not at discharge pressure and full of liquid when unit is in cooling mode.
Many of these units will have a suction accumulator so the chance of getting liquid into the compresser is low unless you blast it in.

I've always cracked open the liquid valve on the refrigerant cylinder slightly and fully opened the manifold gauge valve to the suction pipe. This way the liquid has the longest distance to boil off. If you use the sight glass on the gauges then you can regulate the cylinder valve accordingly. I normally have it so you can see a few bits of liquid in it. This works with the compressor running or stationary.

In your question to Tonys post (hope you don't mind me barging in!) he is using the same principle but using the manifold valve to act as the restriction where as I was using the cylinder bottle - just as effective. Different strokes for different folks as they say.
A quick charger works the same way. A restriction device - liquid comes up to it, meets a small hole which causes a pressure drop which causes the refrigerant to boil at the other side. Difference is you (or the boss) have to pay for it.;)

Cheers,
Andy.

Most if not all ac compressors have a suction accumalator any way which give a little more protection from exessive liquid

It is simple as cake.
You have to recover every drop of refrigerant remained in system, then you should charge new fresh liquid refrigerant in system by weight to amount noted at nameplate and , if lines are longer than unit is pre-charged for, you should ad for that difference by amount noted in installation manual.
Then, you should start unit in test mode in heating mode. After some time (3-5 min.) stop test mode and start unit in normal operation.
That way you are charging liquid in high side and no damage can occur.

a big thank you to all of you to answer me

You are welcome