Mini split pressure test

[jjrbus]

Daikin mini split calls for 625 psi nitrogen leak test when new. That is with the service valves closed, so only testing lines and evaporator.

I will need to nitrogen test the condensor after getting the unit evacuated so the service valves will have to be open. The high side design pressure is 604 psi and the low side is 391 psi. So it seems that I should use less than 391 psi, is that correct?? I do not want to put the system on heat to raise pressure as I have no idea how much refrigerant is in the system and do not want to risk damaging unit.

 

[American Locomotive]

You do not need to nitrogen test the condenser, because the factory has already done that and charged it. The only things you are pressure testing are your flare fittings, line set, and indoor unit. You do not open the service valves until you are ready to put the system into operation:

- Pull a quick vacuum on your piping (~1500-2000 micron is probably enough)
- Pressure test with nitrogen at whatever your desired pressure and duration
- Vent nitrogen charge
- Do full vacuum (below 500 microns)
- Close valves on your manifold gauge set (do not disconnect any hoses while under vacuum)
- Open service valves on system to release charge
- Disconnect hoses/gauges

 

[jjrbus]

You do not need to nitrogen test the condenser, because the factory has already done that and charged it. The only things you are pressure testing are your flare fittings, line set, and indoor unit. You do not open the service valves until you are ready to put the system into operation:

- Pull a quick vacuum on your piping (~1500-2000 micron is probably enough)
- Pressure test with nitrogen at whatever your desired pressure and duration
- Vent nitrogen charge
- Do full vacuum (below 500 microns)
- Close valves on your manifold gauge set (do not disconnect any hoses while under vacuum)
- Open service valves on system to release charge
- Disconnect hoses/gauges

Thanks for the response, 3 year old unit with a leak I can't find.

 

[American Locomotive]

Oh, you're the guy from the other thread. You should keep it all together in one thread, because now it's going to get confusing.

"High side" and "low side" is a little ambiguous when it comes to heat pumps. When in heating mode, the compressor, indoor unit, reversing valve and expansion valve will all be "feeling" that 600 PSI (potentially). In otherwords, the majority of the components. Even in cooling mode, on a very hot day, condensing pressures could get up to 450-500 PSI.

400 PSI would be definitely be a "safe" pressure to test everything, and would probably be enough to find a leak in the out door unit.

 

[jjrbus]

Thanks again. I pressurized the lines and evaporator to 400 psi and suspect I have a minuscule leak in the evaporator coil, showed nothing at 260 psi. My cheap halogen detector does not pick it up. Bubbles show nothing, that I can see. This is the only area on the coil that the ultrasonic detector reacts to and only when I spray it with distilled water. It is a double coil, inner and outer so would guess the leak is on the inside coil.

 

[jjrbus]

Leak confirmed, at least one I believe there is another one. Hours looking for this, unlikely I would have found it without the
ultrasonic detector.

 

[fitter30]

I've had good luck with Retorseal leak freeze for small leaks. Travels with the oil used on a 3 head mini system total lines 180'. Used the 1.5 oz don't want more than 10% of compressor oil capacity.

 

[jjrbus]

Daikin 15 series has been discontinued so no new heads available. Kudos to Budget HVAC in Tampa. They found a new evaporator coil for $180. Now need to decide if I should order and replace coil or buy new system and relocate to a better location? Or tempt fate and try a leak sealer.

 

[metlmunchr]

Kudos to Budget HVAC in Tampa. They found a new evaporator coil for $180.

Budget is a good company to deal with. A few years ago the out of warranty Copeland scroll in my 3 ton R22 heat pump quit pumping. My preference was to change the compressor rather than the entire system if the cost of the compressor made sense.

I have a license and an account at Ferguson locally and they were about $850 for the compressor. Checked with Budget and they were the same price, but the man there then told me there was another compressor model that was much more widely used, physically identical, and 1000 btu less capacity for $550. It also came with POE oil rather than mineral, so it could be used with either R438 or R407c while the original came with mineral which limited me to R438. At that time, a drum of 407c was $100 less than a drum of 438. Shipping the compressor from FL to NC was $40, so overall they saved me $360 on compressor and refrigerant. That's the kind of product knowledge that makes customers return in the future.

Once the new compressor was installed and the system recharged, it cooled so much better than it ever had before that I suspect the original compressor likely had a pumping capacity problem from day one.