EcoRenovator - View Single Post - Ductless Failure (Mitsubishi mini-split)

Xringer · 12-30-16, 01:46 PM

I'm somewhat familiar with Sanyo MS and they have over-pressure sensors,
that are suppose to kick in, and shut down the system if the pressure goes too high..
However, I once had a brand new system that popped a hole in the copper tube
coming from the compressor, resulting in the loss of all the R410a.
I assume it had the required amount of R410a refrigerant from the factory. But, I could be wrong..

If someone added more refrigerant than was required by the system,
that could cause serious over-pressure, resulting in a leakage problem.

Because most MS systems only have a single service port, it's not easy to
accurately add R410a to these type of systems.

The standard procedure that many techs use, is to recover all the R410a,
weigh it to see if the right amount was in the system..
Then, charge the system with the correct amount of R410a.

The outdoor unit tag has the amount if R410a listed in pounds..
The length of line-set is a factor. If the line-set is longer than about 25 feet,
then more R410a is added per-foot, per the install manual.
If the line set is under 15 feet, the manual might recommend recovering a small amount of R410a. To avoid over-pressure.

It's a well known fact that some HVAC techs do not have much experience
working on mini-splits.. While some are experts, many are not..

I have a very basic EPA certificate. (So I can work on my own stuff).
But, I'm not an expert by a long shot..

12-30-16, 01:46 PM	#2
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	I'm somewhat familiar with Sanyo MS and they have over-pressure sensors, that are suppose to kick in, and shut down the system if the pressure goes too high.. However, I once had a brand new system that popped a hole in the copper tube coming from the compressor, resulting in the loss of all the R410a. I assume it had the required amount of R410a refrigerant from the factory. But, I could be wrong.. If someone added more refrigerant than was required by the system, that could cause serious over-pressure, resulting in a leakage problem. Because most MS systems only have a single service port, it's not easy to accurately add R410a to these type of systems. The standard procedure that many techs use, is to recover all the R410a, weigh it to see if the right amount was in the system.. Then, charge the system with the correct amount of R410a. The outdoor unit tag has the amount if R410a listed in pounds.. The length of line-set is a factor. If the line-set is longer than about 25 feet, then more R410a is added per-foot, per the install manual. If the line set is under 15 feet, the manual might recommend recovering a small amount of R410a. To avoid over-pressure. It's a well known fact that some HVAC techs do not have much experience working on mini-splits.. While some are experts, many are not.. I have a very basic EPA certificate. (So I can work on my own stuff). But, I'm not an expert by a long shot.. __________________ My hobby is installing & trying to repair mini-splits EPA 608 Type 1 Technician Certification ~ 5 lbs or less..