ok, help me fix my heat pumps

[1201]

update. pressure tested the bad unit's lines. found a very very tiny leak. tightened fitting and leak is gone. I pressure tested the lines at 450psi and it didnt move for the first three hours. I left it overnight and it had dropped by about 1 psi. should I be concerned about this?

also, I spent 5 evenings studying for and passing my 608 type 2, and then when I went to order r410a, they didn't even ask for the cert. WTH ???!!!

 

[Partimewages]

Great! Now you have the certificate for the future and no one can take that.
I would not be concerned about the 1 psi.
My assumption is you will vacuum down and recharge.

 

[1201]

Great! Now you have the certificate for the future and no one can take that.
I would not be concerned about the 1 psi.
My assumption is you will vacuum down and recharge.

Thanks! I won't worry about it.

Yeah I need to order a bunch of stuff to recover the old refrigerant and weigh new refrigerant back in. I will vacuum the lines before I do all that .

It's still cheaper than the $750/unit a local tech wanted

 

[MajicDiver]

and then when I went to order r410a, they didn't even ask for the cert. WTH ???!!!

You don’t need it to buy, you are just supposed to be cert’d to actually put it in a system.

 

[MajicDiver]

left it overnight and it had dropped by about 1 psi. should I be concerned about this?

Overnight I’m sure this time of year the temperature dropped. Unless the start/stop temperature is about the same the pressure will change due to that. Someone out there probably has a chart/equation for calculating the pressure change due to temperature with that type refrigerant, if you know the actual volume of the system you are testing.

 

[1201]

You don’t need it to buy, you are just supposed to be cert’d to actually put it in a system.

That just seems open to a lot of illegal handling lol. If an uncertified person can purchase then nothing is stopping them from handling lol.

Anyhow it is what it is. I'm glad I got the cert and I learned a lot from the training

 

[1201]

Overnight I’m sure this time of year the temperature dropped. Unless the start/stop temperature is about the same the pressure will change due to that. Someone out there probably has a chart/equation for calculating the pressure change due to temperature with that type refrigerant, if you know the actual volume of the system you are testing.

I thought it may be this bit I wasn't sure.

 

[MajicDiver]

I thought it may be this bit I wasn't sure.

And I’m not suggesting that someone actually correct such a test for temperature, it’s just something to be aware of. In large systems where it is difficult to bubble check everywhere very quickly- such as hydrogen cooled utility sized generators- you have to because you got to know when to stop looking.

 

[Supervstech]

Im impressed you are learning all this to get your systems setup properly.
I have been doing this 40 years, trained by my father and his father who started the company in 46...

There is a LOT to learn in order to properly service a system.

Mostly good advice here.
Critical info in green grass states is to KNOW thw infiltration number for the structure, have an accurate list of all doors and windows including direcrection facing.
All overhangs and attic ventilitaon status.
Then an ACCURATE manual J8 load calc, then an ACCURATE manual D ductwork layout.
Soooo many homes put too large equipment on too small ductwork wasting sooo much energy.

Right sized, makes the best function.

 

[1201]

Im impressed you are learning all this to get your systems setup properly.
I have been doing this 40 years, trained by my father and his father who started the company in 46...

There is a LOT to learn in order to properly service a system.

Mostly good advice here.
Critical info in green grass states is to KNOW thw infiltration number for the structure, have an accurate list of all doors and windows including direcrection facing.
All overhangs and attic ventilitaon status.
Then an ACCURATE manual J8 load calc, then an ACCURATE manual D ductwork layout.
Soooo many homes put too large equipment on too small ductwork wasting sooo much energy.

Right sized, makes the best function.

Thanks. I appreciate that. I did a lot of homework before sizing and I knew I would have some challenges and honestly didnt do enough to mitigate them this winter.

the good thing I did :duct work is within the conditioned envelope. I dont have an uncoditioned attic so no duct leaks, or any duct leaks leak back into the conditioned envelope.

the bad thing- too many -leaky- windows. if the sun if out this is a positive as the windows face south and are net heat gainers, but when its cold and the sun is not out, oh boy- the house gets cold. I was supposed to mitigate this by having window insulation for these "storms" but my lazy behind was too busy focused on solar and didnt get to it. hard lesson learned

 

[1201]

Update, and a question:

Preface- worst unit got fixed. Had a tech come out and recover and weigh new r410a in
I watched and learned. He didn't weigh the amount he was recovering so I have no way of knowing how low it was.

Anyhow, today I fixed on of the half working units. I pressure tested at 400psi for one hour, it held. I vacuumed it to 260 microns and after one hour it had risen to 270 microns so the lines were nice and tight and dry.

Yet, when I removed the refrigerant it was 1 lb low. Spec is 5.73lbs and it was 4.70lbs.

How? How can it be low if the lines are not leaking?

 

[Partimewages]

How do you know what it had in it to begin with?
Maybe the factory under charged.

 

[1201]

How do you know what it had in it to begin with?
Maybe the factory under charged.

It says it on the unit itself and also in the manual. It supposedly ships with enough refrigerant for 25ft of line and .33lbs per foot additional.

I hope it's a factory undercharge. Im worries it could be something else in the system leaking? When you pressure test the lines you close the valves to the rest of the system and only test the lines

 

[Partimewages]

You can always pull the charge and test the whole system.

 

[1201]

You can always pull the charge and test the whole system.

Oh! I didn't know that was an option. Thanks! If this happens again that's what I'm going to do.

I assume that pulls all the oil out as well and I would need to add fresh oil? No way midea is going to tell me what oil out how much is needed. I tried to call to find out why the point check function was not working and they said I should go and hire a tech to call for me

 

[Supervstech]

Refrigerant recovery rarely pulls out oil.

 

[Supervstech]

Update, and a question:

Preface- worst unit got fixed. Had a tech come out and recover and weigh new r410a in
I watched and learned. He didn't weigh the amount he was recovering so I have no way of knowing how low it was.

Anyhow, today I fixed on of the half working units. I pressure tested at 400psi for one hour, it held. I vacuumed it to 260 microns and after one hour it had risen to 270 microns so the lines were nice and tight and dry.

Yet, when I removed the refrigerant it was 1 lb low. Spec is 5.73lbs and it was 4.70lbs.

How? How can it be low if the lines are not leaking?

Depending on the refrigerant manifold and hoses, they can hold 6 oz or more, and the recovery machine also holds a bit of refrigerant.

 

[1201]

Depending on the refrigerant manifold and hoses, they can hold 6 oz or more, and the recovery machine also holds a bit of refrigerant.

Ah! Ok that makes sense and explains part of it. Thanks. The machine has very little charge after the purge.

Let's say I was 8oz low. Is that enough to have it not work below say 40 degrees?

 

[RCinFLA]

Recovery does pull out a little POE oil but it is not a significant loss.

Normal cooling run cycle the output of compressor refrigerant gas volume spits out about 1-2% of the flow mass as oil compared to refrigerant mass.

Variable speed compressor systems need to keep track of how long they run at lower speed. To get oil back to compressor you need reasonable vapor mass flow in the suction line. At less than about 50% normal full run speed the compressor loses oil to system distribution, mostly collects in indoor evaporator.

If run at slower speed for a few hours the computer will speed up the compressor for about 10 minutes to recirculate the oil that got stuck in system distribution. The length of time it can run at slow speed depends on oil sump reserve in base of compressor.

This is also why you should not vertically coil up excess refrigerant lines on pre-charged lines like used on Mr. Cool mini-splits. The vertical coil becomes an oil trap retarding oil return to compressor and collecting oil in the bottom of the tubing loops. Coil excess lines and place them horizontally flat, like under the outside unit bracket if mounted above ground level.

Most reverse cycle, heat/cool units have an accumulator before compressor suction input because heat mode has a higher probability of liquid refrigerant flood back to compressor which is damaging to compressor. Some oil collects in accumulator and they have a dip loop tube to suck the oil off the bottom of accumulator.

Reason why it is important to weigh in refrigerant for mini-splits is primarily due to the accumulator. Overcharging refrigerant can just cause accumulator to fill up with cooled liquid refrigerant without a significant pressure readings indication. A flooded accumulator defeats the liquid refrigerant flood back prevention to compressor provided by accumulator.

 

[MajicDiver]

The vertical coil becomes an oil trap retarding oil return to compressor and collecting oil in the bottom of the tubing loops.

I left the coils vertical on one of mine. I’m curious your thoughts on how big a deal it is? What you say makes total sense, could kick myself…….