Txv question

[fr420]

When should you use a "ZP" thermostatic charge on txv head versus "Z" charge?

[mspanky]

When the valve is being run by a single compressor with no crankcase pressure regulator.

[fr420]

When the valve is being run by a single compressor with no crankcase pressure regulator.

So with a single compressor and no cpr, I should use a "ZP" correct

[jpsmith1cm]

So with a single compressor and no cpr, I should use a "ZP" correct

It would help you more to understand WHY you need a CPR or a ZP power element.

A CPR or a ZP power element limits pull down load on the compressor.

A CPR does this by setting a maximum pressure that will feed through the valve.

A ZP TXV does this by shutting down when the suction pressure exceeds a set value.

[fr420]

I'm more confused now........ What's the set value?? Here is my situation. I use to do a lot of refrigeration work. When I say refrigeration I am talking about refrigerated warehouses and the such. I got away from refrigeration and haven't done it in about 10 years, but by default I inherited a mess. I arrived at this job on Monday. It's a walk in freezer with 2 units, I found both compressors flooding after changing some valves and valve plates, I restarted one of the units and found txv bad called supply house to get a new one and they told me the wrong power heads were on there. I had kt-183-fc heads on both txv's. I was told they were for medium temp, which I agree with. They proceeded to tell me I need a head for low temp which is a Z charge, and since I didn't have a cpr I should use a head with "zp" charge. This is a 0 to -10 box that was originally r-12 and now has Hot shot in it. I just want to make sure I am getting good info from my supplier.

[jpsmith1cm]

Well, the "set value" will vary with refrigerant.

ZP isn't the only Pressure limiting TXV made.

http://sporlanonline.com/10-9_32011.pdf There's a list of pressure limiting power elements on page 8 and what pressures they are limited to.


Since this sounds like a fairly good sized freezer, I wouldn't be afraid to install straight Z elements. That said, ZP elements won't HURT anything in your application.

C charge elements are generally referred to as medium temp elements, but are rated by Sporlan for evaporator temps from -10 to +50 degrees, so they aren't technically WRONG. Z charge elements are rated for 0 to -40 degrees evap, so wind up being a better match for low temp work.

[mspanky]

If the freezer is a pump down setup using a liquid line solenoid for temperature control, then I would use a Z power element. I agree with jpsmith that a ZP won't hurt anything and the only instances I run into them is on fractional or small HP compressors that are easily overloaded (and single phase). A ZP element may add a little more time to pulling the temps down after a defrost, if anything at all.

[2sac]

If the freezer is a pump down setup using a liquid line solenoid for temperature control, then I would use a Z power element. I agree with jpsmith that a ZP won't hurt anything and the only instances I run into them is on fractional or small HP compressors that are easily overloaded (and single phase).

+ short runs and lack of an accumulator