410 low ambient control

[hvacnut1]

Just wondering, what the common practice is for controlling 410 in low ambient conditions. Is temperature or pressure better, and if the answer is pressure, what should the cut in-cut out be? Thanks.

[bob_scheel]

Just wondering, what the common practice is for controlling 410 in low ambient conditions. Is temperature or pressure better, and if the answer is pressure, what should the cut in-cut out be? Thanks.

420 cut in, 300-350 cut out. I prefer the fan speed controls that run off of temp. I like to install the probe on an intermediate manifold on the coil or about 1/3rd down from top on a U tube. A pressure switch works fine on TXV systems, not so good on capillary systems.

[al o]

johnson controls makes a p-66 for 410

[just_opinion]

Just wondering, what the common practice is for controlling 410 in low ambient conditions. Is temperature or pressure better, and if the answer is pressure, what should the cut in-cut out be? Thanks.

It is no different from R-22 when you look at the temperature on the T/P chart.

[DaveG]

Be careful if you use the Johnson P-66. The P-66 varies voltage not frequency, and this isn't acceptable to all universal duty motors. Check with the condenser fan motor manufacturer to see if yours is approved for the P-66.

[drunkenkoala]

I.C.M makes a control, that is for fan cycling, and it seems to work pretty good, it has a temp sensor that sits on the liquid line, similar to what was said in the previous post. Putting a fan cycling or reverse acting pressure control, does not work tho if you have really low ambient with high wind. I am up in Calgary, and we have installed some of these, but still seem to get a a problem when they run in -40, with liquid slugging back to the compressor.

[mrllyonsden]

Just wondering, what the common practice is for controlling 410 in low ambient conditions. Is temperature or pressure better, and if the answer is pressure, what should the cut in-cut out be? Thanks.

Search the entire area for an R-22 system and junk the R-410, just like heatpumps they should never have come above the Mason Dixon line. Just a comment from Maine.

[bob_scheel]

Search the entire area for an R-22 system and junk the R-410, just like heatpumps they should never have come above the Mason Dixon line. Just a comment from Maine.

R-410 is really better than R-22 efficiency wise. From the owners perspective it is great. (I installed a R410 heat pump in my own home last year)

From the service/installers point of view you can no longer be lazy and careless about nitrogen purge, good vacuum, and moisture contamination.
R22 will let you get by with some sloppy technique. 410 won't.

[flip2cho]

420 cut in, 300-350 cut out. I prefer the fan speed controls that run off of temp. I like to install the probe on an intermediate manifold on the coil or about 1/3rd down from top on a U tube. A pressure switch works fine on TXV systems, not so good on capillary systems.

Why not pressure? In a cap tube system it is the pressure you want to maintain because it is the pressure difference that regulates how much refrigerant flows through you cap tube.

[flip2cho]

I.C.M makes a control, that is for fan cycling, and it seems to work pretty good, it has a temp sensor that sits on the liquid line, similar to what was said in the previous post. Putting a fan cycling or reverse acting pressure control, does not work tho if you have really low ambient with high wind. I am up in Calgary, and we have installed some of these, but still seem to get a a problem when they run in -40, with liquid slugging back to the compressor.

How would Low Ambient cause liquid slugging back to your compressor? It would just cause over efficiency of your condenser causing it to hold more liquid thus starving your evap and that wouldnt cause liquid slugging...

If your temps get to low you can use the fan cut out in addition to a receiver and condenser flooding

[Murphcoair]

I think Johnson discontinued the P66.
Now they offer the P266

http://cgproducts.johnsoncontrols.com/MET_PDF/12011534.pdf

[bob_scheel]

How would Low Ambient cause liquid slugging back to your compressor? It would just cause over efficiency of your condenser causing it to hold more liquid thus starving your evap and that wouldnt cause liquid slugging...

If your temps get to low you can use the fan cut out in addition to a receiver and condenser flooding

You are not taking in to account what happens when the unit shuts off in low ambient conditions. The coldest part of the system is the outdoor portion of the suction line. That is where the liquid refrigerant starts to condense/migrate. Then when the compressor turns on it sucks a solid plug of liquid and wham no more valves. Crankcase heaters can help but if its cold enough or you have a long enough exterior suction line you need to install a suction accumulator to trap the liquid.

[flip2cho]

You are not taking in to account what happens when the unit shuts off in low ambient conditions. The coldest part of the system is the outdoor portion of the suction line. That is where the liquid refrigerant starts to condense/migrate. Then when the compressor turns on it sucks a solid plug of liquid and wham no more valves. Crankcase heaters can help but if its cold enough or you have a long enough exterior suction line you need to install a suction accumulator to trap the liquid.

But I am taking into account. Ofcourse the unit should be equiped with a suction accumulator you are absolutly correct. I was never talking about a unit without one. In those climates it's common sense. But you are incorrect about where the majority of ref will stay. In the coldest part it correct always. At any given time where is the majority of your refrigerant? It isn't the suction line it's the condenser. In extream low temps on off cycle the suction line and condenser will quickly be the same temp. At that point why would the majority of your ref leave your condenser, travel through the evaporator which will be warmer due to low ambient temps and settle in the suction line? Any ref left in the suction line will safley be stored I the suction accumulator.

My original statement was how in the world would a low ambient cutout failing or not being "good enough" ever ever cause liquid slugging??