Zone dampers in ducted system

[electronicsuk]

Following my previous thread a few months ago regarding the installation of A/C into my new home which is currently fitted with storage heaters, I have now bitten the bullet and decided to make the change.

I have (perhaps foolishly) decided to take on the task of installing the system myself. I've installed a couple of split systems before, but as I've mentioned before, I'm really an electrical engineer and ducted systems are entirely new to me. I'm willing to give anything a go and will put in the time and perspiration to make a good job of this, but I need to do my research beforehand.

I'm interested in zoning the system, but have been unable to find any suppliers in the UK of 200/250/300mm dampers + actuators for round ducting, or at least not any that list prices. Is zoning not common practice in the UK? There seem to be plenty of suppliers in the US and Oz. If anyone could provide me with details of a suitable supplier it would be much appreciated.

Would also be interested in hearing any advice/tips from the professionals that you've gathered with regard to this sort of installation. Upstairs will be via ceiling mounted ducts with the cooling/heating coil in the loft, and downstairs via floor mounted grilles (sigh!) with the coil and ducting in a 3ft void under the floor.

Kind regards

Matthew

[The Viking]

CCL Lindab Ltd

Unit 3b, Hill Court, Hillbottom Rd, Sands Industrial Estate, High Wycombe, Buckinghamshire HP12 4HJ
Tel: 01494 463490





What you want to ask for is Volume Control Dampers. If they can't supply the actuators then Control Center is a good place to look.

[Brian_UK]

One supplier of ductwork is Hotchkiss...

http://www.hotchkissairsupply.co.uk/prod_HFD.htm

Technical data from CCL Lindab

http://www.ccllindab.co.uk/uploads/d...uct_Damper.pdf

Also motorised here

http://www.bowcott.com/ces/damper.htm

If you use the circular butterfly type damper then you can normally convert them to actuator use without too much hassle using a Belimo type actuator..

http://www.belimo.co.uk/ch/en/index....TOKEN=52385642

Have fun....

[electronicsuk]

Wow! Loads of useful links there, thanks guys!

One more question if I might. I've read that it's necessary to have one outlet that is not connected to a zone control damper that will allow air to continue flowing through the fan coil when all dampers are closed. This makes perfect sense, as there would be no way for the A/C to measure the temperature of the return air without some flow.

It seems that this solution has some downsides, though. For example, if I want one room at 23 degrees, another at 21, and another at 18 (and assuming it's <18 degrees outside) then the main controller for the A/C must be set to at least 23 degrees. That means that my room without zoning will also be a constant 23 degrees whether I like it or not.

I assume that a possible solution would be to add an extra damper as a pass that would go straight from the outlet to the inlet and would be set to open when all other dampers are closed. This would allow air to continue flowing through the system and lead to the A/C quickly reaching the temperature set on the control panel and cutting out. Will I have to do this electronically, or is there a mechanical damper that will open past a certain static pressure?

What's more, will this be healthy for the air conditioner, or could it lead to rapid on/off cycling due to the low heat capacity of the short pipework run?

Best regards

Matthew

EDIT: A more sensible solution would be if there is some sort of electrical 'inhibit' that would allow the unit to be turned off when necessary, i.e. when all dampers are closed. Is this a standard thing, or am I asking too much?

[Brian_UK]

With 'zone control' in the commercial sense you would normally provide the air at the coolest required and then 'reheat' it at the branches or terminals.

I feel that perhaps you are trying to get too complicated or expecting too much from your systems.

The A/C unit will only provide air at one temperature it will not be able to give you different temperature in the different ducts.

If you want that type of control then you will have to have individual coils for cooling and heating in each branch duct.

Regarding having one branch open at all times, this is basic air balancing requirements.

Whatever the size of the system, be it two ducts or a twenty storey office block there must be one grille that is connected to the fan without any form of dampering between the two.

The reason being that if you have dampered every branch then you are wasting electricity by dampering the fan itself.

Sorry, lesson over, I'll go back to the corner now

[electronicsuk]

Thanks Brian. Guess I'll just have to have one open duct. My thinking re different temperatures in each zone was that by setting to the A/C to the highest temperature desired (for heating) I would be able to open/close each zone as necessary using a thermostat. As long as the air temperature out of the fan coil is at least as high as the highest temperature desired in the zones then surely this type of control is possible?

[Redhot]

Hey Electronisuk

The best solution for what you desire apart from a Direct Digital Controller Such as an Innotech Maxim III which you could program I and O as required however may not be able to replace or communicate with OME controller and would be exspensive the best solution would be IAS Smartzone controller (from oz not aware of any in the uk), a VAV (Variable Air Volume) system allows differant set points (temperatures) in differant zones and as you discribed a by-pass damper from supply to return there are some limitations but for what you describe/require vav is the best and does not require individual units.

Cant post url google, Innovative Air Systems Australia look at smartzone

Cheers redhot

[Redhot]

(The reason being that if you have dampered every branch then you are wasting electricity by dampering the fan itself.)

Hey Brain not sure what you mean by this!

There must be a Zone/Grills without damper contol, but if you where to block the supply the fan motor would actually pull less current as its doing less work!



Cheers Redhot

[electronicsuk]

(The reason being that if you have dampered every branch then you are wasting electricity by dampering the fan itself.)

Hey Brain not sure what you mean by this!

There must be a Zone/Grills without damper contol, but if you where to block the supply the fan motor would actually pull less current as its doing less work!t

Being from an electrical background, I would actually dispute that. The motor is working harder, as blocking the air path through the ductwork will cause an increase in pressure at the outlet of the fan coil unit. There wont physically be any air moving, but the fan is effectively fighting itself and this will in turn put extra torque on the motor, leading to increased load.

Either way, there's no dispute over whether or not its wasting electricity - if the motor is running but you're not shifting air then there's no point in it running at all.

[Redhot]

Thats what I originally thought until I was shown other wise, try it! the increased pressure causes the motor to do less work less current.

[Brian_UK]

If you have over dampered the whole system then the fan was selected for a higher duty than that required.

Better to reduce the fan speed down to provide the required, reduced, volume. This will reduce the power required and will also reduce the noise within the system.

[Redhot]

Brain ultimately that would the most efficient way however it would be very exspensive control wise to have communicating devises between dampers and fan speeds as it would be a OME controlling fan speed. Having a portion of the A/C dampered with a by-pass which opens as the zones close will give the reducing capacity and efficiency.

Cheers Redhot

[frank]

Thats what I originally thought until I was shown other wise, try it! the increased pressure causes the motor to do less work less current.

I agree.

If you allow a fan to run without any resistance (no ductwork) then it pulls more amps.

A fan must be selected though to operate within it's motor range. Fan curves are provided for this purpose.