Jump to content

mvhr zones


Recommended Posts

Hi All and thanks for your experienced knowledge.

 

Could anyone please tell me how are the fans adjusted to accommodate the changes in air volume demand when zones are turned on and off ?

 

Best regards,

Ozpos

Edited by Ozpos
Link to comment
Share on other sites

Zones are not turned off or on. It's a continuous system. If a high rate is required, fan speeds adjust accordingly and ventilation rates at all outlets / extracts change proportionally. When commissioning, flow rates are set at each terminal at the standard fan setting to what the design requires. This is done by adjusting the aperture at each outlet 

Link to comment
Share on other sites

Hi @Conor, Thanks for your response.

 

I thought mvhr units run the fans in constant volume configuration such that the air flow is increased if the resistance to flow increases (e.g. due to filter contamination) ?

 

So if I have a zone that is not occupied for certain days in the week then that zone can be restricted with a motorised valve and the air flow reduced to a minimal.  At the same time as turning down the zone surely the fans need to be adjusted otherwise they will try harder to supply the constant volume.

 

Could you please explain more ?

Best regards,

Ozpos

Link to comment
Share on other sites

You're over thinking it. You don't want to reduce flow to rooms, the building needs to be continuously ventilated as a whole system. When you shut off a valve, the flow rate just increases at other valves, the fan speed stays the same (generally). You're just adding cost, complexity and work!

Link to comment
Share on other sites

Thanks but what about systems that have day time and night time zones ?

 

I do not expect to shut off a zone just reduce the flow to standby/holiday mode.  The valves I have seen are proportional.

 

I thought the whole point of zones was one of efficiency ?

Edited by Ozpos
Link to comment
Share on other sites

All zones are Preset according to design.  Night time turns the whole system fan down if you want it to!  If you boil a pan/have a shower and raise humidity levels the system boosts to bring levels back into range.  Absolutely no need to change each vent on the fly.  Once it's in, set, monitor, tweak, then forget about it.

Link to comment
Share on other sites

It sounds like you are talking about heating rather than ventilation? An MVHR doesn't have zones, air flows through the building from supply point to extract point. That's how they are designed to operate. View it as a flowing stream through your house. Water flowing from bedrooms to bathrooms etc.. if you shit off or reduce one of these points, you mess up the flow through the whole building.

 

You have different flow rate modes for different circumstances. Right now, ours is on a low rate eco mode, to reduce heat loss and drying effect.

Edited by Conor
Link to comment
Share on other sites

What about:https://www.duco.eu/uk/products/mechanical-ventilation/ventilation-units/ducobox-energy-comfort#multi-zone-valve

 

They say:

 

Compact external 2-zone control

With external 2-zone control, the house is divided into a day and night zone.

This zonal control is based on CO2 and humidity. It only provides ventilation where and when needed, in the right amount.

Zonal ventilation ensures maximum energy savings and increases acoustic and thermal comfort.

 

 

 

So I assume as the day zone time ends the zone valve reduces flow and at the same time backs off the fans to compensate.

 

Can anyone else shine a light on how this actually works ?

Link to comment
Share on other sites

Basically it's similar to their MEV system, the terminals respond to humidity and CO2 and open and close as a response to changes.  The fan speed ramps up and down as required to keep the pressure within system constant. Would assume extracts and supply terminals are linked so the response is, extract opens a suitable supply in the same zone also opens to keep the system balanced.

 

You would expect you just map the system to say terminal A and B are in zone 1 and C and D are in zone 2 etc. then operate a simple time clock or it just does based on where is sees CO2 or humidity. 

 

Reality of saving v cost?

Everyone watching TV in zone one, you go for a shower in zone 2. Both zones operating.

Link to comment
Share on other sites

Hi @JohnMo, thank you for your response.

 

I am an electronics engineer and always looking to use my knowledge to save cash. I can get hold of co2 and humidity sensors for a couple of quid.  In addition I have built a building control unit using a raspberry pi.

 

Do you know if many mvhr systems can be controlled by an external building management system ?

Link to comment
Share on other sites

1 hour ago, Ozpos said:

Hi @JohnMo, thank you for your response.

 

I am an electronics engineer and always looking to use my knowledge to save cash. I can get hold of co2 and humidity sensors for a couple of quid.  In addition I have built a building control unit using a raspberry pi.

 

Do you know if many mvhr systems can be controlled by an external building management system ?

If you want to go that route, I would suggest two small MVHR units, one for upstairs one for down.  Wouldn't bother with CO2 as there is supposed to be a strong enough link between humidity and CO2 in a household situation. But if cheap and available why not include.  But would use external sensors (in each room), not internal to the unit, then you can operate in four modes, off, on at minimum set back speed, normal speed, boost. Set threshold something like, humidity, below 41% off, above 41% on at min speed, 45% at normal speed, over 50% boost.

 

You don't need very complex units to do the above.

 

But not really convinced the effort is work it.

Edited by JohnMo
Link to comment
Share on other sites

1 hour ago, Ozpos said:

Hi @JohnMo, thank you for your honesty.  Could you tell me how long you have been involved with mvhr and at what level ?

 

Designed, installed and commissioned my own system. Have two units, partly to reduce duct lengths on a 25m long house, but also to reduce what boosts and when, I have used coanda effect supply terminals, to further reduce duct lengths.

 

Nothing complex about MVHR, just flows and pressure drops and trying not to overthink stuff that isn't important. Not easy when you read ill informed info everywhere.  Reality is you don't need to boost often, so why bother automating. If you have a shower in a cool bathroom and it's full of steam when you finish, hit the manual boost switch on the way out.  If your cooking smelly stuff, hit manual boost also. That's about the only time ours boosts.

 

My normal flows are now turned down well below (about half) building regs, and humidity floats around 42 to 45% over 24hrs.  CO2 - living room levels average (24 hrs) 521ppm, and max out 630ppm. Our bedroom CO2 levels average (24 hrs) 556ppm with a peak of 665ppm.

 

As I mentioned don't overthink it, keep it simple - let it get on with it. Check the filters every six months, give them a hoover, replace annually, have cone filters in the extract terminals, to keep duct clean.

  • Like 1
Link to comment
Share on other sites

  • 5 months later...

@Ozpos I'm also looking at the 2-zone system from Duco vs the 1-zone (Energy Premium 325-1ZH vs 2ZH).  Have you made any final decisions for your install?  I'd love to know where you landed. Thanks!

Link to comment
Share on other sites

@Ozpos

 

29 minutes ago, Dana said:

@Ozpos I'm also looking at the 2-zone system from Duco vs the 1-zone (Energy Premium 325-1ZH vs 2ZH).  Have you made any final decisions for your install?  I'd love to know where you landed. Thanks!

Hasn't visited since Nov 23. So don't hold your breath for a reply.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...