How do you charge yours? step by step please

[SkyWalker]

hi guys, when you are charging a system for the first time, with a TEV and no reicever, what process do you take? on an air conditioning system

after reading garys 101 i beleive it be best to charge to 8k sub cooling max or full sight glass, depends which comes first? if its low ambiant temps this must have an effect on the condensor, lets say ambiant is 5C and design temp is 30C? do you block the condensor to increase head pressure (SCT) if the answer is yes, how much? when should the condensor blockage be removed and what effect will have, lets say we had 8k sub cooling the remove condensor blockage since its low ambiant wont this increase condensor capacity and increase sub cooling even more? cause liquid to back up and increase head pressure?

after we have correct high side (sub-cooling) do you then check low side and adjust tev once close to set point if needed? or maybe you monitor low side before this point?

since the compressor is suction cooled should i monitor superheat at evap outlet or compressor inlet? if its a large run the superheat may be different in these 2 places?

basically im after a basic step by step procedure for charging refrigerant.

i know many people who just charge to a full sight glass, never mind the cond air on temp, they may check superheat but they will check it when the room is no where near set point, i think some sort of step by step procedure to follow would greatly help me and im sure alot of others.

[SkyWalker]

also if the evap air on temp is very low we have no load, what can we do? i found this before on a air handler running full fresh air, with no load our superheat will be low but how low can we be comfortable with? if the air on is like 5C we are running system way out of design temps, but the system needs charging with refrigerant as the cliant wants there system signing over.

should we just concentrate on sub cooling? no more than 8k?

[RANGER1]

I think you can only do the best you can under the circumstances .
To hard to simulate .

[desA]

I have found the following sequence to be handy - others may differ:

1. Make sure all components set at standard factory setting e.g. TXV (nominally 7.5K SH)
2. Calculate initial charge estimate based on system piping & components volumes - allowing for 2-phase in condenser & evaporator;
3. Charge to calculated estimate;
4. Start system;
5. Observe that HP within reasonable upper limits i.e. does not run away;
6. Observe SH value exit evap - low/high?
7. Observe SC value @ condenser - small/large?
8. Begin tuning sequence, &/or charge addition depending on (6)/(7) above.

I typically install thermocouples all over the system in order to try & map the system properly.

I tend to be concerned, in the initial stages, more with the evap SH value, out of concern for feeding a wet feed into the evap. Once that is stabilised, I then begin focusing on the condenser SC value & total liquid line sub-cooling e.g SC,tot=(Tc,sat-Txv,inlet).

Things like evap flashing are also of interest.

In all, it becomes a round-about, of fine tuning & charge addition, once the system is initially stabilised.

[frank]

And a waiting game until the box comes down to set point.

[desA]

And a waiting game until the box comes down to set point.

And how... :D

Box exhibits its feminine nature - tuned parameter shows - initial correction, slight recovery, correction, stable (hopefully)... takes lots of TLC.

For heat-pumps, with an ever-moving cycle, it becomes a little more tricky... :p