Compressor false load for De-humidifier

Hi

I make a de-humidifier using a simple condensing unit and evaporator coil, TEV, R134A etc approx 800w cooling. The load on the machine can vary a lot and at present I fit a hot gas bypass valve (ALCO ACP3) from the discharge gas side to suction side after the TEV but before the evaporator to maintain the suction pressure above zero at low loads.
my question is could I do this with a solenoid valve I.e. Danfoss, operated via a pressure switch? my concern is as soon as the valve opens would it let too much gas in too quickly with the pressure going up and down to quickly, I assume I could fit capillary tubing but it's knowing what size to use and would this cause any other problems?
Any one else done this?
My reasons are that the Alco valves are very difficult to get hold of, having to wait up to 8 weeks, so looking at an alternative.

Regards
CB

Could try Sporlan.
Ideally I think you need modulation type valve, not on/off, as would not be as smooth.

https://sporlanonline.com/literature/90/90-40.pdf

Add a crankcase pressure regulator to prevent overloading it.

Use either a Danfoss KVC or CPCE valve , the CPCE valve is the far superior modulating hot gas valve and allows the Tev to keep the suction superheat stable

Thanks guys !!
re Danfoss valve it’s only a small system with 1/4” discharge pipe, smallest Danfoss valve I could see is 1/2” obviously I can add reducers but just wondering if it’ll still work ok?

Would recirculating some of the warm air off the condenser back onto the evaporator during low load create an artificial load? removing the need for the hot gas bypass valve.

Would reversing the air flow during low load be any use? Heat the intake air with the condenser then pass it through the evap, any heat rejected by the condenser could be picked up by the evap.

If your only using the evaporator to remove moisture, and not using the condenser to then heat the dryed air. Would reducing the speed or stopping the condenser fan reduce the cooling capacity enough during low load?

If you were to use a solenoid and pressure switch to dump hot gas into the evap, maybe a hand reg valve or needle valve could be used instead of a capiliary?

Danfoss AKV valve or an EVRP can be used for hot gas .these have small capacity and can be pulse operated over millions of cycles whereas the standard EVR solenoid valves are only rated for half a million cycles and consequently the armature and tube wears and fails very quickly if it is pulsed

Not usually my type of thing.
However I had a System I built years ago with Eutectic plates. They present a challenge as the load falls off dramatically before the plates are solidly frozen. This would lead to rapidly cycling the Compressor and slow down the cooling time.
I used a Sporlan Hot Gas Bypass valve and it worked perfectly.
Glenn is the one who can speak about using the larger valve of course. Hunting might be an issue.

Quote:

---

Originally Posted by Glenn Moore

Danfoss AKV valve or an EVRP can be used for hot gas .these have small capacity and can be pulse operated over millions of cycles whereas the standard EVR solenoid valves are only rated for half a million cycles and consequently the armature and tube wears and fails very quickly if it is pulsed

---

that sounds a good idea, would I need a controller to control it ?

Thanks, I normally use an alco one but can’t get hold of them

Quote:

---

Originally Posted by seanf

Would recirculating some of the warm air off the condenser back onto the evaporator during low load create an artificial load? removing the need for the hot gas bypass valve.

Would reversing the air flow during low load be any use? Heat the intake air with the condenser then pass it through the evap, any heat rejected by the condenser could be picked up by the evap.

If your only using the evaporator to remove moisture, and not using the condenser to then heat the dryed air. Would reducing the speed or stopping the condenser fan reduce the cooling capacity enough during low load?

If you were to use a solenoid and pressure switch to dump hot gas into the evap, maybe a hand reg valve or needle valve could be used instead of a capiliary?

---

hi , thanks valve or needle valve may be a good option ����