PICV as On Off valve - FCU valve

[Vusal Quliyev]

Dear experts,
I was wondering about mechanical charecteristics (Q and deltaP) of picv valve at low deltaP situations (below min deltaP requirment of picv.) As you know at datasheets it is talking about deltaP over 10kPa only, however i was wonderful what will hapen if we provide 5kPa for example. What will be flow rate? Is it applicable for on/off control? Any recomendation letter about this?
Many thanks in advance for any recomendations.

 

[nuuvox000]

The factory tests their valves so I don't think anyone could tell you other than them. They'll most likely tell you it won't operate at that pressure and that's the end of the story.
I am curious what kind of system you have that could actually function at such a low pressure...

 

[HVAC-Novice]

If pressure is below the minimum dP, flow will be less than the valve is rated for, even if fully opened.

It doesn't matter if you have an on/off or modulating actuator. On/off are just the most extremes settings of a modulating actuator. The valve doesn't know the type of actuator.

If you mean Fan Coil Unit, I'm surprised you use an on/off control. We usually control DAT (in addition to fan speed). Too high DAT, and overhead diffusers won't heat the space properly. but that is kind of besides your original question, just an observation.

 

[Vusal Quliyev]

Dear Friends,
many thanks for information. Can i find any datasheet about exact DeltaP and Flow rate relationship at fully open position and below minimum DeltaP value?
Why I am looking for this is, we have less amount of deltaP available in the system and trying to understand outputs of each branchs.

 

[HVAC-Novice]

Look at the manufacturer spec sheet. Ask the rep if you can't find what you need. They also will be able to give better advice about THEIR products than we can. I use Belimo, FWIW.

 

[moideen]

Minimum differential pressure across the PICV which is required to keep the flow rate constant. Over the MINIMUM pressure, the PICV maintains the flow rate constant; under the MINIMUM pressure, the PICV works as a standard 2-way valve

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

 

[Vusal Quliyev]

Many Thanks.