ok, help me fix my heat pumps

[1201]

The numbers are specific to each individual unit.
Was a heating load calculation ever done? If not start with that.
You should choose equipment based on that data. It's not likely that you can "fix" the current equipment if it was not correctly designed to begin with.

I did a load calculation and slightly oversized the overall system over what the calc said.


I know the numbers are different for different units. I just posted that because it looks like 45 is indoor air temp and 70/59 is outdoor dry bulb/ wet bulb

 

[S Davis]

I did a load calculation and slightly oversized the overall system over what the calc said.


I know the numbers are different for different units. I just posted that because it looks like 45 is indoor air temp and 70/59 is outdoor dry bulb/ wet bulb

So the current system that doesn’t cut it was sized above the heat loss of the structure? What was used for the calculations?

 

[1201]

So the current system that doesn’t cut it was sized above the heat loss of the structure? What was used for the calculations?

I used energyplus , and coolcalc.com for manual j

 

[S Davis]

Ok well if the calculations were correct then the equipment wasn’t sized properly, what is the rated equipment output at your design temperature? This is assuming the equipment is installed properly with correct refrigerant charges.

 

[RCinFLA]

When you say vacuum micron gauge is calibrated for nitrogen- I thought you only use that under vacuum and not under pressure?

Micron gauge is displaying microns level of vacuum by the rate of heat loss from a thermistor to any surrounding/remaining gas. Different gases have different heat transfer rates. The micron gauge vacuum displayed represents amount of heat loss from thermistor into nitrogen gas.

At same level of vacuum, if remaining gas is refrigerant gas the micron gauge micron gauge actual readout will be different than if remaining gas is nitrogen. It is not really important to know this as when you get to less than 500 microns range there is not much heat loss from thermistor regardless of type of surrounding gas as the gas density is so low.

It is more important that the thermistor be kept clean. Getting it coated with high density POE oil contamination is very common issue when you let micron gauge get subjected to refrigerant from system. The POE oil becomes an insulating blanket around the thermistor greatly reducing the heat transfer rate and slowing down the micron gauge response time to showing actual vacuum. The POE oil also sucks up moisture very well and if the oil coated thermistor has moisture bubbles popping out of the oil coating the micron gauge reading will jump around.

 

[1201]

Ok well if the calculations were correct then the equipment wasn’t sized properly, what is the rated equipment output at your design temperature? This is assuming the equipment is installed properly with correct refrigerant charges.

My assumption is that the refrigerant charges are incorrect so I need to test the systems.

The equipment is properly sized. One system is blowing room temperature air so that can't be a sizing issue.

 

[Partimewages]

You don't need to open up the refrigerat system to balance the charge. Find the correct manual and adjust from it with gauges and a scale. If you need to take some out you will need an empty recovery tank.

 

[1201]

You don't need to open up the refrigerat system to balance the charge. Find the correct manual and adjust from it with gauges and a scale. If you need to take some out you will need an empty recovery tank.

Thanks! Ok so if I have the correct manual I can charge using pressure? In that scenario what's the scale for?

 

[AntronX]

You should study up on how to service mini splits. I like this guy's channel.

 

[1201]

You should study up on how to service mini splits. I like this guy's channel.

I really dislike that guy's videos. He spent 12 minutes saying a lot of words to end up saying you can't check the charge via superheat or sub cooling you have to weigh it in. I don't watch YouTubers who don't know how to be concise .

But, do you know what gauge he had on the service port? I want to buy that

 

[Partimewages]

Thanks! Ok so if I have the correct manual I can charge using pressure? In that scenario what's the scale for?

If the charge is incorrect you will need to add or recover. Sometimes it's just easier to pull the whole charge out and start over.
Unless you have a bad refrigerant component don't open the system to the atmosphere.

 

[1201]

If the charge is incorrect you will need to add or recover. Sometimes it's just easier to pull the whole charge out and start over.
Unless you have a bad refrigerant component don't open the system to the atmosphere.

Ok I think I understand now. So check the pressure and if it's off then I know I'm low or high on charge. Then , remove all the old refrigerant and weigh new refrigerant back in? Thanks

 

[Partimewages]

Yes, it doesn't seem like that is the best but anytime you can avoid opening up the system to atmosphere is a good thing.
If you know you don't have leaks.
If leaks are a concern. If you suspect a leak check with the bubble method first before pulling the charge back to the compressor section and valving off. Then introduce your dry gas pressure and check again.

 

[MajicDiver]

If you know you don't have leaks.

It’s been many years since I’ve done any work on a/c, but isn’t high discharge pressure a potential sign of air?

 

[Partimewages]

It’s been many years since I’ve done any work on a/c, but isn’t high discharge pressure a potential sign of air?

Yes, but it could be some other things. If air/atmosphere is a real concern the only good solution is to pull the charge and recycle it. Then check for leaks with dry nitrogen repair and pull a vacuum. Then weigh in the correct charge for the equipment/lineset.

 

[S Davis]

You need to figure out where you are starting from, the system that doesn’t work could have been started with air in the system and could have burned out the compressor (need to do an acid test)and might need total replacement.

The two working units could have a refrigerant leak or not have been evacuated and charged properly, if they were not evacuated and have moisture in the system that needs addressed.

I am just guessing and I am probably wrong, there are a number of things that could be wrong. You either need some in person help or find some learning on the subject first.

It is impossible to walk someone through with such little knowledge on such a complex subject. We don’t even know what brand or type of equipment we are talking about. And please be careful you are working with high pressures, I have seen a refrigerant line give up at 600psi during pressure test and it isn’t something you want to be close to.

 

[shopman]

I'll give you the best advice of anyone out here. Just pay someone who knows what they're doing to check out your systems for you. In the long run it will save you money along with give you the peace of mind that the work was done correctly.

 

[1201]

You need to figure out where you are starting from, the system that doesn’t work could have been started with air in the system and could have burned out the compressor (need to do an acid test)and might need total replacement.

Thanks. I will be putting the pressure gauge on it today. It's possible there is sure in it but I doubt it. I did a soap bubble test today and found no leaks but I did see a little oil around the air handler fittings so maybe it is leaking who knows. I'll find out when I pressure test with nitrogen. I have the nitrogen and regularly now so I'm set there.

The two working units could have a refrigerant leak or not have been evacuated and charged properly, if they were not evacuated and have moisture in the system that needs addressed.

They supposedly came with enough charge for 25ff of lines from the factory. I vacuumed them out and made sure they held vacuum for at least an hour, but I didn't triple evac or remove the Schrader valve so maybe it wasn't done correctly.

I am just guessing and I am probably wrong, there are a number of things that could be wrong. You either need some in person help or find some learning on the subject first.

Learning on the subject speaks to me. Is like to find a course on Hvac so I can be empowered going forward. Finding someone knowledgeable on mini splits on my area is tough

It is impossible to walk someone through with such little knowledge on such a complex subject. We don’t even know what brand or type of equipment we are talking about. And please be careful you are working with high pressures, I have seen a refrigerant line give up at 600psi during pressure test and it isn’t something you want to be close to.

Thanks for the warning

 

[1201]

Ok big update:

I got the pressure gauge in today. Thanks to @AntronX for posting that vid. I saw what he was using for a gauge and ordered it.i didn't want to use my regular manifold because I would lose too much refrigerant. Thank you Amazon next day delivery.

I tested the worst one. it looks like I'm extremely low on refrigerant and don't know why. It worked all summer. So now I have to pump down any remaining refrigerant and pressure test with nitrogen and hopefully find the leak and fix it. I suspect it's at the air handler connections(found some oil at those connections) but I'll find it sometime this week.

I need to get my 608 quickly so I can buy 410a

Standing pressure, unit off. Every thing I've read says this should be around 300 psi?







Turned it to cool mode 62 degrees, high fan. Thermostat temp indoor was 76 degrees. This looks low


Hmm
This looks suspect. I took off the insulation btw. It was insulated until this morning.

 

[S Davis]

I do a 600 psi test for a min of 24 hours.