Micro Channel Condenser and High Head

[refer madness]

Just completed a warranty compressor change out on a York Sunline 3 ton RTU. After weighing in factory charge and running the unit in cooling to verify proper operation we found the head pressure fairly quickly (less than 2 mins) elevating to above 500 psi and trip out on high head. I was testing in a relatively low ambient (approx 40F). Coil is clear, OFM running in the right direction.

After consulting with the local York rep, he figures this is due to a lack of internal area in the condenser for a surplus of liquid refrigerant to stack up, as is possible with a traditional tube style condenser. He said he`s encountered this with the Micro Channel coils and low load/low ambient in the past.

Does this explanation sound legit? Anyone else encountered this?

[JWB]

Don't know what your metering device is , but sounds restricted. Local guys whose co. uses York hate those coils. Just what they whine about at the supply house. What did the suction side do?

[Dallas Duster]

Sounds about right to me.

[lions_lair]

I wanted to post here so I can follow this thread. I have had evap. Coils slugged with oil do this. And like the other guy said,what did the suction do? What metering device u using?

[refer madness]

The unit has a txv and suction pressure was around 120 psig.

[Dallas Duster]

The unit has a txv and suction pressure was around 120 psig.

As far as the discharge line piping goes is there a "trap" in between the compressor and the inlet of the condenser? Is it a hard shut off TXV or does it bleed somewhat?

[servicetrane]

is r-22? r 410-a?

[just_opinion]

Just completed a warranty compressor change out on a York Sunline 3 ton RTU. After weighing in factory charge and running the unit in cooling to verify proper operation we found the head pressure fairly quickly (less than 2 mins) elevating to above 500 psi and trip out on high head. I was testing in a relatively low ambient (approx 40F). Coil is clear, OFM running in the right direction.

After consulting with the local York rep, he figures this is due to a lack of internal area in the condenser for a surplus of liquid refrigerant to stack up, as is possible with a traditional tube style condenser. He said he`s encountered this with the Micro Channel coils and low load/low ambient in the past.

Does this explanation sound legit? Anyone else encountered this?

From the number, my guess is 410A freon.

I think the York rep's explaination is BS.
I think the scale you used was probably inaccurated. Please read the total charge and weight it in again with a different scale. It does not take much to over cahrge this micro-channel condenser coil system.

[VTP99]

:ditto: On checking your charge.
Is there any fan cycling with that unit ?
120 psi looks like 41*

What's next coil heaters ? :toetap:

[flange]

I have been on the phone with factory guys and can tell you some things they have told me. Example: hey factory guy, your nameplate charge isnt right." Well, yeah, we havent quite gotten these new refrigerants down yet, we were pretty good with r22, but still experimenting with r410. set it up for eight to ten subcooling, and fifteen superheat, and go from there......."

Look at actuall conditions and charge accordingly. if no restriction, take some juice out lad.

[refer madness]

I think you guys are right about this being an overcharge. I'll be back at site tomorrow morning and will adjust the charge as needed. Really appreciate all the quick feedback.

To answer a couple of other questions:

* Not sure whether the TXV is hard shut off or bleed type, but will try to find out.
* No fan cycling installed
* This is indeed R-410A

[Dallas Duster]

I think you guys are right about this being an overcharge. I'll be back at site tomorrow morning and will adjust the charge as needed. Really appreciate all the quick feedback.

To answer a couple of other questions:

* Not sure whether the TXV is hard shut off or bleed type, but will try to find out.
* No fan cycling installed
* This is indeed R-410A

Take 1% of the charge out and see what happens. 410a is a weird animal.

[DavyB]

I think you guys are right about this being an overcharge. I'll be back at site tomorrow morning and will adjust the charge as needed. Really appreciate all the quick feedback.

To answer a couple of other questions:

* Not sure whether the TXV is hard shut off or bleed type, but will try to find out.
* No fan cycling installed
* This is indeed R-410A
I think you're on the right track. I've seen this on a microchannel York 5t with a partially clogged strainer as well. You should be able to pump it all down as it is nameplate. If you can't you know they gave wrong data. If you can, check the txv strainer as well.

[slugger1]

just a couple of thoughts not famillar with sunline rtus. electric heat or gas? with compressor change non condensables? did you change the drier? i'm assuming blower is running and filters are clean. if you can keep unit running long enough maybe with a jumper check superheat and subcooling will help you get an idea whats going on.

[servicetrane]

remember that the 410A is 75% more pressure, install a machine trane to 410A and is discharge pressure and suction 450psig of 100psig.using the correct gauges?

[Dallas Duster]

Take 1% of the charge out and see what happens. 410a is a weird animal.

Sorry meant to say 10% but for some reason it won't let me edit my post.

[VTP99]

Sorry meant to say 10% but for some reason it won't let me edit my post.

They cut the edit time way down.:(

[lions_lair]

If the head pressure is 500 or more,trippin high head p/s. And only 120 suction,that's low for that h/press. I'm thinkin restriction. Find the restriction

[refer madness]

Returned to site this morning and slowly removed gas while monitoring pressures/temperatures. 6-8 oz of gas made a huge difference in pressures, and I'm no longer seeing the spikes in head pressure. Had a hard time getting reliable SH/SC readings because of low ambient but hopefully will be able to get back later in spring for some more reliable readings.

Thanks again for the input guys.

[DavyB]

Returned to site this morning and slowly removed gas while monitoring pressures/temperatures. 6-8 oz of gas made a huge difference in pressures, and I'm no longer seeing the spikes in head pressure. Had a hard time getting reliable SH/SC readings because of low ambient but hopefully will be able to get back later in spring for some more reliable readings.

Thanks again for the input guys.

You don't seem convinced that you figured it out.

[behappy]

You should be able to pump it all down as it is nameplate. If you can't you know they gave wrong data.

Our experience is that the microchanel coil is too small to pump it down (into the condenser coil). Recover.

[DavyB]

Our experience is that the microchanel coil is too small to pump it down (into the condenser coil). Recover.

How can you not be able to pump down what was initially charged into the unit?

[DavyB]

Our experience is that the microchanel coil is too small to pump it down (into the condenser coil). Recover.

In your experience, are the condensers cleaned before you attempt a pumpdown??

[Dallas Duster]

Lack of volume in condenser coil to pump down . There is no room for much storage of refrigerant.

[DavyB]

Lack of volume in condenser coil to pump down . There is no room for much storage of refrigerant.

Makes sense, but how was the system holding charge initially charged into the unit? Seems to me, if it can hold it, it can be pumped back into it.

[refer madness]

You don't seem convinced that you figured it out.

I'm confident I've figured it out. But I prefer to take SC/SH readings under design conditions, and to get the outdoor coil anywhere near 100F SDT was going to be very difficult with such a low ambient. After removing the 6 oz's, operating pressures/temps looked normal, but I prefer to take readings under conditions that are closer to design. That's all I'm saying.

In terms of the condenser capacity, if the unit is charged at the factory and allowed to equalize, it makes sense to me that a full charge could fit into the entire system but not necessarily the condenser. It seems like these condensers are less forgiving to overcharge though, as was the case with me.

[Dallas Duster]

Makes sense, but how was the system holding charge initially charged into the unit? Seems to me, if it can hold it, it can be pumped back into it.

I'm sure it doesn't hold much.

[behappy]

In your experience, are the condensers cleaned before you attempt a pumpdown??

Years ago we got one of the first one's York put out. 4 ton new install and Ooopps, I forgot to put in the scrader cores (don't ask). Well let just pump er down and pop them it. No way Jose! It hit critical pressure in no time.As far as factory charge, most are a holding charge, not a charge for line set and inside coil. See the other post on name plate charge.:whistle:

[BaldLoonie]

Nope, you don't pump down to a MC coil!

[refer madness]

I think I may have been unclear in my original post that this was a package unit. I was wondering why some of your were talking about pumping the system down, and whether or not it could take a holding charge.

So on the split MC condensing units is there enough refrigerant typically to supply a short pipe run and indoor unit with sufficient refrigerant, or do you always need to add some? I mean if they can't be pumped down that makes me wonder how there could be enough charge for the whole system even with a short pipe run.

[Dallas Duster]

Just completed a warranty compressor change out on a York Sunline 3 ton RTU. After weighing in factory charge and running the unit in cooling to verify proper operation we found the head pressure fairly quickly (less than 2 mins) elevating to above 500 psi and trip out on high head. I was testing in a relatively low ambient (approx 40F). Coil is clear, OFM running in the right direction.

After consulting with the local York rep, he figures this is due to a lack of internal area in the condenser for a surplus of liquid refrigerant to stack up, as is possible with a traditional tube style condenser. He said he`s encountered this with the Micro Channel coils and low load/low ambient in the past.

Does this explanation sound legit? Anyone else encountered this?

What exactly was the name plate charge?

[dave sulz]

Did you check subc
ooling

[refer madness]

What exactly was the name plate charge?

5 lb 10 oz.

I think it's possible there were issues with the scale we used initially, so more than the above may have been added when we first charged.