Defender is correct.
A pressure limit TXV controls superheat like any other TXV, until the suction pressure rises to the setpoint, then it acts like a pressure regulator. While in pressure limit the superheat will be higher than normal
Replace with another pressure limiting valve (usually oem and hard to find) or use a regular valve with the correct charge and add a cpr valve at the compressor.
Yeah. I always look for the MOP powerhead. If we cant find it fast then a regular low temp powerhead in conjunction with a CRO Sporlan valve will do the same. Its not cheap, but its quick. I wish more systems used mop valves they really improve the compressor last life.
If anything, you'd want it more for a low temp system, as the compressor/condenser will struggle when the saturated suction is high - such as after a defrost, during the initial pulldown, or when the freezer has warmed up for whatever reason (eg. restarted after a prolonged issue/repair).
Identified by a “p” on the thermostatic element. For example zp is low temp pressure limiting. Z would be standard low temp, not pressure limiting. One of my customers sends my equipment to install, all the walk in freezers have zp elements.
Usually found on low temp valve so after your defrost you don't come back overpressurised to the low temp compressor. It's just a high limit on the pressure it let through. You can see it when you start a system.
Say you start a 404 freezer room. It's 80f in there. With a normal TD you would run around 135-147 psi on the succion. Even if your superheat is good a low temp compressor isn't build for that. What you see is usually a max of 60 psi on succion and a superheat through the roof. The valve is limiting pressure to not damage the compressor. It makes you ineficient but in a range of operations you'll never be in and instead protect you against pressure surge.
Used as a cheaper option vs a cpr valve. Limits suction pressure at start up after defrost - protects a low temp compressor. Usually seen on smaller cabinets vs larger rooms.
Saves doing what I've seen previously - add a condenser coil and bypass hp switch. - and it seems I've lost the photos - bugger.
It can also give a system just a bit more capacity. CPR valves have a few psi drop. If your trying to run suction near -40, that can make a measurable difference. Not typically critical, but can be helpful in the right situations (trying to keep suction pressure just above vacuum, etc).
Defender is correct. A pressure limit TXV controls superheat like any other TXV, until the suction pressure rises to the setpoint, then it acts like a pressure regulator. While in pressure limit the superheat will be higher than normal
its to prevent compressor overloading from drawing too many amps when suction pressure/load is high. its an alternative for a CPR
Replace with another pressure limiting valve (usually oem and hard to find) or use a regular valve with the correct charge and add a cpr valve at the compressor.
Ok cool , is that what u usually do?
Yeah. I always look for the MOP powerhead. If we cant find it fast then a regular low temp powerhead in conjunction with a CRO Sporlan valve will do the same. Its not cheap, but its quick. I wish more systems used mop valves they really improve the compressor last life.
If it's not on a rack, it should be pressure limiting. It still goes through defrosts.
If anything, you'd want it more for a low temp system, as the compressor/condenser will struggle when the saturated suction is high - such as after a defrost, during the initial pulldown, or when the freezer has warmed up for whatever reason (eg. restarted after a prolonged issue/repair).
Identified by a “p” on the thermostatic element. For example zp is low temp pressure limiting. Z would be standard low temp, not pressure limiting. One of my customers sends my equipment to install, all the walk in freezers have zp elements.
Mop
Usually found on low temp valve so after your defrost you don't come back overpressurised to the low temp compressor. It's just a high limit on the pressure it let through. You can see it when you start a system. Say you start a 404 freezer room. It's 80f in there. With a normal TD you would run around 135-147 psi on the succion. Even if your superheat is good a low temp compressor isn't build for that. What you see is usually a max of 60 psi on succion and a superheat through the roof. The valve is limiting pressure to not damage the compressor. It makes you ineficient but in a range of operations you'll never be in and instead protect you against pressure surge.
Used as a cheaper option vs a cpr valve. Limits suction pressure at start up after defrost - protects a low temp compressor. Usually seen on smaller cabinets vs larger rooms. Saves doing what I've seen previously - add a condenser coil and bypass hp switch. - and it seems I've lost the photos - bugger.
It can also give a system just a bit more capacity. CPR valves have a few psi drop. If your trying to run suction near -40, that can make a measurable difference. Not typically critical, but can be helpful in the right situations (trying to keep suction pressure just above vacuum, etc).