4 way valves help

[maxcool]

Hi, I have just recieved a email from my boss explaining I have to attend a site tomorrow for fault finding purposes.

The site has a large chiller on roof so I am told and serves 80 plus ceiling suspended units ( vam style i believe )

What is the best way to test 4 way valves and actuators on each of the units? Anything else i should look out for when going through the units. I am told there are alot of problems.

[seanps1976]

water cooled units are usually fairly easy to test. find the thermostat for the individual rooms and test them in heating and cooling(assuming they do heating and cooling and not just cooling only), you should see the actuator motors move and open and close the valves you can also check the temp on the pipework either side of the actuators to make sure they are opening and you have flow, do this for both heating and cooling water pipes. also worth bleeding each individual coil to make sure you dont have air locked in there, should be a bleed point at the highest point on the coil somewhere. also check your fans and filters and thats about it.

if you find an actuator not working then remove the actuator of the valve and check that the valve spindle goes up down freely and again you should feel the pipe change temp after valve if working ok as you get the water flowing thro it, if this is fine then check you have voltage to actuator and the motor is moving up and down.
if you dont have voltage then check your thermostat out.

thats about it really that i can think of so i hope that helps ya matey,

sean

[Marc O'Brien]

Hi, I have just recieved a email from my boss explaining I have to attend a site tomorrow for fault finding purposes.

The site has a large chiller on roof so I am told and serves 80 plus ceiling suspended units ( vam style i believe )

What is the best way to test 4 way valves and actuators on each of the units? Anything else i should look out for when going through the units. I am told there are alot of problems.

Basic preliminary checks:


What has changed since there were no problems? Lack of maintenance? Rearranging of office partitioning without consideration to thermostat or ducting layouts? Time clocks not altered to new office layouts?
Then on the system the prior basic checks...

Chilled water is free of air. Flow is quiet.
Chilled water pressure on the pump suction side at the highest point of the immediate return is above 1barg.
Pressure rise through pump is per design. Often between 0.8 bar and 2 bar.
Flow through chiller results in design evaporator pressure drop normally between 0.25 bar and 0.8 bar (less than 0.5 bar is more common). Check strainers for fouling and piping for air ingress if pressure drops are less than commissioned.
Full load chiller operation causes a chilled water dT no greater than 6K just before leaving water reaches set point. If higher check for reasons causing poor flow volume - fouled strainer or air or commissioning or balancing valves incorrectly altered. If lower then check for excessive flow or poor chiller performance on refrigeration side. If you suspect poor chiller performance then report following temperatures: saturated suction and superheat then saturated condensing and subcool. Air on and off and water on and off. Check all fans run and all compressor load up.
Then go to the fan coils - provided they have available to them the right temperature and water pressure differences then the problems are local. Thermostat settings; sensor location and integrity; time-clock interlocks, filters; fans; water strainers; balance-valve settings; actuators; 2, 3 or 4 port valve spindle movement; duct and diffuser dampers and diffuser locations.
That should be a good start toward finding the first and most basic problems.

[maxcool]

Thanks alot guys. Will take on board all of your advice for tomorrow and future ref.

[nike123]

Hi Mark,
Your concise advice is always nice to see.
Welcome to RE!

Now I have one question. What is background of this advice:




Chilled water pressure on the pump suction side at the highest point of the immediate return is above 1barg.



I know that it must be some overpressure, but why 1 bar? In Reflex expansion vessel dimensioning software it is stated that that pressure must be above value indicated in manufacturer catalog for pressure needed for avoiding pump cavitation. Is this some universal safety margin?
For your information, automatically suggested pressure in software is also 1 bar.