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R32 Mini split/heatpump lineset leak detection.

The expansion valve is inside the indoor unit right where the evaporator is that is where it goes from liquid to vapor? The lines on the indoor unit are not removeable so how do you braze and flow nitrogen through the expansion valve which is inside the indoor unit?
We are talking mini split right, they don’t usually have thermostatic expansion valves in the indoor units, if other equipment adding service ports comes to mind. If you are connecting it anyway, you don’t have to flow nitrogen through the expansion valve just the point you are brazing.
 
Just to add... If I was brazing. I'd definitely test at full pressure, but these are screwed on fittings
 
The expansion valve is inside the indoor unit right where the evaporator is that is where it goes from liquid to vapor? The lines on the indoor unit are not removeable so how do you braze and flow nitrogen through the expansion valve which is inside the indoor unit?
On a traditional US split system, you're right the expansion valve is right before the evaporator. When using a TXV, it has to be because the temperature sensing bulb has to be attached right near the evaporator. On minisplits, they use an electronic expansion valve (EEV). It doesn't have a temperature bulb attached to it. So they put it inside the outside unit to keep the head units simpler and cheaper to make. That's why on a minisplit, all the copper lines have to be fully insulated. On a traditional US split system, the liquid line doesn't have to insulated due to the expansion valve being in the air handler.
 
On a traditional US split system, you're right the expansion valve is right before the evaporator. When using a TXV, it has to be because the temperature sensing bulb has to be attached right near the evaporator. On minisplits, they use an electronic expansion valve (EEV). It doesn't have a temperature bulb attached to it. So they put it inside the outside unit to keep the head units simpler and cheaper to make. That's why on a minisplit, all the copper lines have to be fully insulated. On a traditional US split system, the liquid line doesn't have to insulated due to the expansion valve being in the air handler.
This is also why you don't use sub-cooling to determine refrigerant charge level in a minisplit like you do in a traditional US split system. And therefore why they don't put high and low pressure service ports on minisplit systems.
 
In terms of the pressure used for nitrogen pressure testing, you should use the design pressure rating for the lowest rated component in the system.
 
There is no brazing involved at all. This is a flare screw fittings unit. It is pre-charged with 1.6kg of r32 and the refrigerant is locked inside until manual release valves are opened.

This pressure leak testing is done by connecting to the service ports (with refrigerant valves closed). Pressurising it, then going with a bubbling liquid around the fittings.
Yes I understand that I was replying to someone else who said brazing a mini split was a good way to avoid flare joint leaking. The one I installed I used nylog on the joints seemed to work okay I don't have a nitrogen bottle to pressure test it. Did hold a vacuum for 24 hours I used a torque wrench on the fittings. Unfortunately do to the E0 error not able to even turn it on yet waiting on Chinese support still about 6am Monday maybe in a few hours they will reply.
 
Yes I understand that I was replying to someone else who said brazing a mini split was a good way to avoid flare joint leaking. The
I must have missed it.
one I installed I used nylog on the joints seemed to work okay I don't have a nitrogen bottle to pressure test it. Did hold a vacuum for 24 hours I used a torque wrench on the fittings.
I used a poor man's torque wrench in a form of spring scale (one you weight stuff by hanging). I "calibrated" my scale with a real torque wrench (I just don't have the ends that fit HVAC fittings) and I "torqued" it like that...

Unfortunately do to the E0 error not able to even turn it on yet waiting on Chinese support still about 6am Monday maybe in a few hours they will reply.
Wow, that's a bummer. I'm sorry to hear that. Here I wouldn't get any warranty by doing a DIY install. But I'm getting a personal HVAC certificate hopefully next month so I'll be able to sign my own paperwork and get warranty etc.
 
I must have missed it.

I used a poor man's torque wrench in a form of spring scale (one you weight stuff by hanging). I "calibrated" my scale with a real torque wrench (I just don't have the ends that fit HVAC fittings) and I "torqued" it like that...


Wow, that's a bummer. I'm sorry to hear that. Here I wouldn't get any warranty by doing a DIY install. But I'm getting a personal HVAC certificate hopefully next month so I'll be able to sign my own paperwork and get warranty etc.
Here state contractors license boards require 2 years of verifiable experience working under someone else's license number before your allowed to even take the contractors test to get a license. I noticed on Diakin registration form they want the contractors license number.
 
I must have missed it.

I used a poor man's torque wrench in a form of spring scale (one you weight stuff by hanging). I "calibrated" my scale with a real torque wrench (I just don't have the ends that fit HVAC fittings) and I "torqued" it like that...


Wow, that's a bummer. I'm sorry to hear that. Here I wouldn't get any warranty by doing a DIY install. But I'm getting a personal HVAC certificate hopefully next month so I'll be able to sign my own paperwork and get warranty etc.
Things have changed I had to have years worth of hours on the job and the test was no piece of cake either, but that was over 25 years ago. We used to have good service technicians as well, now they just rely on error codes and have absolutely no idea how to troubleshoot without a computer telling them what’s wrong and how to fix it.
 
Here state contractors license boards require 2 years of verifiable experience working under someone else's license number before your allowed to even take the contractors test to get a license. I noticed on Diakin registration form they want the contractors license number.
I'm in Europe (Poland). Here there are two kinds of "entry level" licenses. One is a so called personal license. No experience necessary, but you can't have a conviction for "crimes against the environment" (as funny as it sounds). You just do a days course and pass a theory followed by a practical exam. I'm told its not difficult if you prepare. They even do them on weekends. This gives you ability to buy refrigerant gasses as well as to do installs/servicing for yourself or an employer. If you want to do it for others you need a business license which is a similar procedure (a course followed by a theory+practical exam). You also need to have various equipment for a business license (recovery machine, recovery bottles, leak detection stuff etc). Someone with a personal cert can just hire the kit.

I was very (positively) surprised you don't need industry experience. This is very different for electricians certs for example for which you need to have worked in the field or have relevant school.

However, mind there are many industry certifications people do in addition. This is the bare minimum. These certs just give you ability to buy and use refridgerant gasses and equipment containing them legally.

Edit: Just to point out some idiotic laws we have here... You can't buy firefighting gases like HFC277EA without the same license for refrigerant gases. Yes, a firefighting gas that gets released to the atmosphere anyway during proper activation of the device. You still need a license to buy it. Insanity. You can buy oxygen depletion fire fighting devices that are very deadly for humans without any license. But for HFC277ea you do, because they class it in the same table as freons.

This is another reason for me doing that cert. So I can buy a 3kg self activating bottle of hfc277ea for my "power house".
 
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Is R32 available in the US I see lot of complaints on Amazon about people with R32 mini-splits saying HVAC contractors tell them they can't get R32.
 
Is R32 available in the US I see lot of complaints on Amazon about people with R32 mini-splits saying HVAC contractors tell them they can't get R32.
I can have 22 cylinders of R32 delivered tomorrow, so it is available in the PNW.
 
The expansion valve is inside the indoor unit right where the evaporator is that is where it goes from liquid to vapor? The lines on the indoor unit are not removeable so how do you braze and flow nitrogen through the expansion valve which is inside the indoor unit?
The expansion valve in a mini split is in the outside unit, and 90% of the time it’s an eev.
 
F-gas course here in the UK is five days, doesn’t expire, and you can take it with no prior experience. If you’re doing r290 mini-splits then you don’t need this course obviously.
 
Is R32 available in the US I see lot of complaints on Amazon about people with R32 mini-splits saying HVAC contractors tell them they can't get R32.

Yes, it's available but not commonly used so most HVAC contractors don't keep it on their trucks. In the US, R410A is being replaced with R454B which has less environmental impact than R32.

Fyi, since it seems like a lot of people don't realize that R32 is one of the component refrigerants that make up R410A. R410A is a blended refrigerant made up of 50% R32 and 50% R125. That's why you have to charge R410A as a liquid. If you charge it as a gas, you'll first draw out the R32, then once that gone, you'll get the R125. But you'll screw up the ratio of the remaining R410A in the cylinder.
 
Ok. I need to top up a new r410 system where the charge is not enough for the line set length.
So I'll turn the bottle upside down and feather the liquid in very gently.
 
Issue for charging is the vapor phase 'glide' difference of R410a. It is less than 1 deg F but near ambient temp (60-85°F) the R32 vapor will boil off a little before the R125 vapor as refrigerant gas vapor is removed from jug.

That is why system charging with R410a is done as a liquid. You have to do it in small increments allowing some time to vaporize the liquid once injected in system to avoid excessive liquid from entering the vapor suction line input of compressor which can be damaging to compressor.

Most reverse cycle cooling/heating heat pumps have an accumulator on suction line before compressor input to help prevent liquid refrigerant return to compressor. When you have an accumulator you pretty much have to charge by weighing in the refrigerant as the accumulator may collect liquid refrigerant during refrigerant charging giving the appearance the system is still low on refrigerant charge.

In common residential air conditioner, the whole load of refrigerant mass circulates around the system is one to three minutes near full running capacity of compressor. This mixes up R32 and R125 vapor components and ensures refrigerant POE oil is 'blown' back to compressor in vapor suction line.

Typically, below about 50% run speed on a variable speed compressor there is not enough suction line refrigerant vapor mass flow rate to 'blow' back all the oil droplets and there is a net loss of oil from compressor oil sump reservoir to system distribution (copper tubing and evaporator). The system computer must manage the time spent at slower running speeds and increase the compressor speed periodically to ensure oil is brought back to compressor. About 5-10 minutes at full speed is enough time to ensure most of oil is flushed back to compressor. System can run at slowest speed for 30 to 100 minutes on oil sump reserve before a speed up cycle is initiated to flush back the system distributed oil. Evaporator is usually where most of the oil collects.

Vertical coiling excess lines on Mr Cool units creates oil traps that makes it more difficult to push oil back to compressor.

On original question, when a system has been used with distributed oil throughout system, refrigerant and moisture can get trapped in oil that when system is vacuumed will cause bubbles to slowly get pulled out of distributed oil. This gives a degradation in vacuum level and the false appearance there is a system leak when doing a vacuum holding test. A new virgin system will be clean and dry in the tubing and evaporator so there will be no oil to trap refrigerant or moisture.
 
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Vertical coiling excess lines on Mr Cool units creates oil traps that makes it more difficult to push oil back to compressor.

This is one of the main reasons I don't recommend the type system with pre-charged line sets. Line sets should never have excess tubing. They should always be trimmed to fit. Care should be taken to not have up and downs in the lines sets that'll create oil traps, except where they are explicitly recommended by the manufacture's installation manuals. That's typically only when the line set is installed in a multi-story building when a large vertical drop cannot be avoided.
 
This is one of the main reasons I don't recommend the type system with pre-charged line sets. Line sets should never have excess tubing. They should always be trimmed to fit. Care should be taken to not have up and downs in the lines sets that'll create oil traps, except where they are explicitly recommended by the manufacture's installation manuals. That's typically only when the line set is installed in a multi-story building when a large vertical drop cannot be avoided.
Somewhere I heard the hole that goes trough the wall (indoor to outdoor) should be at a downward angle. Is this only because of the condensate tube or other ones too?
 
Somewhere I heard the hole that goes trough the wall (indoor to outdoor) should be at a downward angle. Is this only because of the condensate tube or other ones too?
It's for the wire dumb dumb, so that the electrons slide the right way 🤣
 
In all seriousness, thanks for the high technical involvement in this thread, heating and cooling seems like a very simple thing to do until you're really getting into it and the math and physics involved, quite amazing.
I'm just an electro mechanical engineer that has installed a few split and mini split systems and finally decided to get a digital gauge set to do it properly.
 
Somewhere I heard the hole that goes trough the wall (indoor to outdoor) should be at a downward angle. Is this only because of the condensate tube or other ones too?
I guess in a lot of situations that would make sense. Especially if going through a thick wall. But it would be as much for the condensate flow as you point out.
 

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