how much hasn't escaped???

[robinsonr22]

when topping up a r410a system how much do you add at a time without going over the top? I've wondered this many times with other gases too, is there a rule of thumb or a pressure or temp you are looking for that tells you the charge is about right for the size of system and length of pipe run??

[monkey spanners]

If its air con, charge need taking out and weighing back in, any extra over standard manufacturers charge due to extended pipe runs needs calculating using the formula supplied with the unit or obtined from their technical representatives. When you find the additional charge, mark it on the unit for the next guy.

What sort of system are you asking about?

Jon :)

[JoeAT50A]

Normal room air conditoner wall mounted type multi split system 3 (3HP) model required 2.7kg of r410a and it will cope up to 40 meters as precharged. Additional refrigerant amount calculation rule of thumb should be 15 gram per meter.
Small sizes of air conditon is OKay to estimate.

[install monkey]

the system charge is on the nameplate.any additional charge must be calculated as per manufacturers literature.
this should be weighed in.
if a system has lost refrigerant then.
reclaim remaining refrigerant.
pressure test to locate leak.
repair leak and retest to proove integrity.
evacuate to less than 2 torr and ensure no backdrop.
reweigh gas into system-its upto you if you use the reclaimed gas.
label system of charge.
fill out f gas sheet if system contains over 3kg
retest system within 1 month to ensure all ok as per f gas recommendations.
DONT JUST SQUIRT A BIT IN! DO A PROPER JOB!

[robinsonr22]

many thanks for all the input guys, I'm just getting back into this after 4 years or so, I'm very rusty at the moment but with all the experience you guys have and my thirst for knowledge I'll get there eventually, by the way it's a toshiba multi, model number mcy-map040ht running 2 units in a theatre tech gallery, 7.2kg of 410a, I had 37.3 bar on the high side and 22.1 on the low, the unit shows no faults on the digital readout but was frosting up on the suction line, I dropped in 200g which seemed to make it a lot happier and the frost dropped back.
I found the unit had been pumped down for some reason but after checking found no leaks and no info inside the service panel, like you say it's only common courtesy to give the next guy the heads up on anything that's been done and why?
By the way Jon I'm not that far from you as I'm in north oxfordshire/south northants myself, maybe we've met in the climate centre botley before? who knows.

regards to all
Shaun