Carrier VVVT System

[Electrocoolman]

Hi Guys, has anyone experience of one of these systems. I'm trying to sort out the 'whole system' , not just the Carrier side.

On the Carrier side, we basically have a load of Slave control units and possibly one (or two) Masters (covers two floors). Each slave controls its own air damper box which is fed from a single common duct which can deliver EITHER warm air OR cool air, but not both at the same time.

As I understand it, the Master polls the slaves to see what their demand is (ie. either Heat or Cool) and this then itself demands (presumably on the majority) either warm air or cool air from the AHU.

The AHU is controlled on the building TREND system, the duct pressure being maintained via a pressure sensor and VSDs controlling the supply and extract fans.
The Trend has x4 temperature set points. x2 Heat and x2 Cool.

What would the typical duct pressure be on such a system?

Does anyone know what signals the Carrier Master outputs? Is it 0 -10v for heating and a separate 0 -10v for cooling ? Are there any other outputs (eg fan speed)?

The other open question is what is the minimum recomended deadband for the room controllers? (ie difference between heating and cooling setpoints).

As this is in a people training enviroment, the small rooms can get 'stuffy' very quickly, so the input of air on a regular basis is relatively important, which if the deadband is too wide, and the damper box remains shut can happen.

Your help and advice would be much appreciated.

As I understand, not many of these systems were installed!

Regards, Adrian.

[Brian_UK]

Hi Adrian, I worked on one of those beasties some years back, I wish you well.

Various documents are available here...
http://www.commercial.carrier.com/co...ID4396,00.html

Can't remember enough about the VVT to be able to help further, sorry.

[Electrocoolman]

Thanks Brian,

Adrian

[sedgy]

hi, electrocoolman , carrier vvt, you should test each area controler to see if one or more motorised duct vaves are working < in round ducts the valve is egg shapped so it seals correctly<
when this is proven, you could test the return air, is there a fire shutter that has brocken and the spring return has made it shut? best of luck
they are not the easyest job to work on .

[Electrocoolman]

Hi Sedgy,
Thanks for the advice.
The main reason for getting 'to the bottom' of this system is due to a major energy saving drive around our site.

It was the fact that despite the supply and extract fans being VSD driven, they were running full speed all the time!
We've discovered that some zone controllers were in full demand due to broken / stuck buttons on the covers, so the system could never ever satisfy their demand and full air flow in these zones.

Since releasing these, the zones have quietened down, but will check each zone in turn.

Haven't looked for fire dampers on the system but that's a good point.

Adrian

[sedgy]

adrian, this systemis not run of the mill, without the manual, any eng , wood strugle, if it was me < again < I would get carrier in<expencive but essential <I worked on a site with 2 of these systems in manchester < bea< put the onous on the manufactorer on paper, there are times to pass the parcel- this is the time