Electronic Expansion Valve

[Scramjetman]

The McQuay WHS series water chillers (made in Italy) use what appears to be a Carel controller mated up with a Danfoss Electronic Expansion Valve. The controller gets a signal from the Micro tech controller on where to position the valve.

Does anyone know what this signal is? Is it a high level interface or is it a 0-10V/ 4 - 20mA or similar?

[Paul J]

The driver sounds like it is being used as an analogue positioner which will be 0/10V or 4-20mA, check out the manual on page 21, sorry I'm not allowed to post a URL for some reason but the manual can be found on the carel website under EVD EVOLUTION Paul:cool:

[Super Fridgie]

Hi it is 0-10... Is the Carel Controller a PCO3?

[Scramjetman]

Thanks Paul. I wouldn't have found that in a pink fit. The Carel site is pretty cluttered and not easy to find your way around in. Looks like I can work that, Cheers -Richie.:)

[Scramjetman]

Hi Superfridgie - I think the main controller is a Mcquayized PCO3 or similar. They use it to signal the Carel EXV controller which is a separate device, which in turn positions the actual EXV. Some of these EXV controllers can be "talked" to at a high level via Modbus, or some other RS485 protocol and can exchange data with a DDC like the PCO3. I'm not sure whether McQuay do this or whether they use a conventional analog signal like 0-10V or 4-20mA from the DDC to the Carel EXV controller.

[Scramjetman]

A bit more info and a correction. The EXV is an ALCO EX8 and I did some on site investigation in the wiring and I've discovered the controller interface is high level using MS/TP connection or similar on IEE485. That solves that. Thanks for your input guys. I can fix the thing now. Cheers.

[raviperumal]

Hi , You can share the things, how u are going to solve the issue.

Cheers,
Ravi

[Spare Parts Man]

...if it is any help:-

Carel driver EVD0000000 Rev 2.022 is McQuay part number 129150142

Also there is the Carel driver EVD0000200 Rev 3.034 which is part no 129150138

Also please note that Alco have changed the EXV 8 EEV. The original one was Alco PCN 801964 with rotolock connections, they have replaced it with the EX8 PCN 800629, McQuay part no 131011432 which has soldered ports, this part comes with 135mm of pipe and an electrical connector. Details on service bulletin SPSB-08-003...

[Scramjetman]

I ended up installing an Emmerson (Alco) driver module which signals the EXV stepper motor. The driver module receives a 0 - 10V analogue signal signal from our chiller controller and sets the superheat temperature. The output from the driver module is a stepper motor drive signal which physically drives the valve open and shut over a period of seconds. This is positioned proportionally based on the analogue input signal.

I did consider using our own controller and driving the stepper motor directly with solid state relays but when the controller was loaded up with software, the scan times were reduced and valve speed dropped to open to shut in 90 seconds which was way too long. - especially when the Emmerson driver does it in less than 10 secs.

Thanks to everyone who contributed. We usually arrive at a solution when we do this sort of thing. Sometimes we explore all different paths to get there - discarding the options that won't work for us until it is down to a workable few. Then we pick what looks like the best and go for it. This forum is great for this process.