minisplit evac & reweighing of liquid charge

[Thomas S.]

I maintain a couple office complexes with multiple fujitsu and mitsubishi minisplit systems in the southeast. One particular unit developed a leak due to building exterior wall (heat expansion on a 95F day) causing a stress on the suction lines, fastened through the wall inside a conduit that runs into the condensing unit outside.

Manufacturer rep stated that they recommend an unconditional evacuation and re-weighing of the factory charge (2 lbs 5 oz) every time a leak is corrected.

Sounds a little extreme but am planning on taking care of it this week. These are all 410a systems.

Tom

[KJPRO]

That's nice. Do you want my list of items to do this week or did you have a question?

[Thomas S.]

merely surprised at the recommendation so perhaps the question would be if the evac&reweigh is standard practise with any leaks on these units?

[Noon-Air]

Absolutely...especially with R410a

[Zyp]

You don't know why? - Maybe some re-schooling is in your future?

[Rod]

Most if not all mini split manufactures recommend this. R410A is a blend of 2 different refrigerants and depending on which camp you believe, one refrigerant may boil off or leak out quicker than the other and leave you with a compromised mixture of freon that isn't up to snuff (instead of the original 50/50 blend it may end up 60/40). Some 410A training I've taken has said this can happen and some has said it can't. Better safe than sorry I guess. Remember you have to add freon for any additional lineset over 25' for most of these systems.

[KJPRO]

Sure is, now get a trained technician to show you how and WHY it's needed.

[Thomas S.]

primarily I've worked on industrial chillers and retired after 30 years in the industry to the warmer southeast but have installed about 500 minisplits since starting to work again. I've found the factory support to be excellent and have taken some additional classes with the new refrigerant licensing.

[Thomas S.]

noticed the same sligthly contradictory messages in the classes I attended (have worked with chillers for 30 years) on the new refrigerants but I do admit that it's reassuring to have the factory reps always willing to assist when questions arise.

took care of the evac&recharge this morning, used nitrogen on the lines too just as they suggested.

[KJPRO]

Your point once again??? Other than to show EVERYONE that you are clueless, by posting the following quote... "I've found the factory support to be excellent and have taken some additional classes with the new refrigerant licensing." There is no NEW "refrigerant licensing", it's called manufacture's requirements to deal with R-410. There is a huge difference!

Now like I said before... "get a trained technician to show you how and WHY it's needed"

[KJPRO]

What was your micron reading?

[Thomas S.]

500

[KJPRO]

Held for how long?