Reply to Thread

Originally Posted by DreamCar

Right you are, I should have checked before posting. It was late & I wasn't at my work laptop. Just lazy!

This is however an open forum for discussion, and I for one would rather know the poster's level of confidance in their answer than assume they're 100% sure.

We're on the same page.

Originally Posted by NINAX

There seems to be a around trend here, more and more "I don't know, but" and "I've never used one, but"....

Not specifically directed at anyone, just a general observation.

Right you are, I should have checked before posting. It was late & I wasn't at my work laptop. Just lazy!

This is however an open forum for discussion, and I for one would rather know the poster's level of confidance in their answer than assume they're 100% sure.

There seems to be a around trend here, more and more "I don't know, but" and "I've never used one, but"....

Not specifically directed at anyone, just a general observation.

Originally Posted by NINAX

Yes, it doesn't..........and?

If my recollection is sound (a big if...) you can't download a pressure dependant sequence into a VMA-1420.

Originally Posted by DreamCar

I didn't think the CZA supported pressure independant control. Haven't used it in a while though, so I'm not really sure.

Yes, it doesn't..........and?

I didn't think the CZA supported pressure independant control. Haven't used it in a while though, so I'm not really sure.

Try it config'd as CZA.

Assuming the VMA is pressure Independant you can get it to do what you want...sort of.

You need to write JCB/GPL so that when the AHU goes into "Heat" you command the VMA first to Unoccupied then to "Warmup", the warm up is a Box Mode function. Make the warm up CFM setpoints about 1/2 of cooling setpoints to start with. The key is in the Supervisory controller logic so you don't over heat the space.

HVACpro asks a question (Initiate warmup mode if supply air is much warmer than zone temperature?) that is the answer to yours. If the VMA is not on a network you'll need to add a supply air sensor.

Another possible option is to configure the VMA with Commercial Zoning Applicatons/Damper Assembly(VMA) in HVACpro.

VMA1420

Good-day,

We have a VMA1420 that is setup for cooling only. This worked fine until modications were done to the AHU which now controls supply air based on OAT.

Basically, in summer mode the VMA damper will open to cool and close to heat.

In winter mode, the damper should open to heat and close to cool. But since the VMA is in cooling only, the damper closes when we need to heat up the room.

Since the VMA doesn't work in this manor (winter mode) how can I change the VMA to open (moduate) the damper in winter to proivde heating.

In the Q&A no heating is selected.

Thanks