Two x Small, or One x Large

[Andehh]

Due to the nature of our 240sqm bungalow, and all ceiling heights being average of around 3.5m+ and it being ''H'' shaped with kitchen, lounge etc on one ''wing'' and bedrooms & bathrooms on the other ''wing''  our builder's initial thoughts are for two MVHR system. He is out seeking quotes, with a request from me to try and make it work as a single unit.

 

Has anyone else gone through a similar challenge? Did you go for 2 x smaller or 1 x bigger unit? Anything worth being aware of in making the decision (other then 2 x energy costs and 2 x filters)?

 

Ducting looks to be 75mm semi rigid pipes, what is a good safe ducting to look out for in the returned quotes to ensure best performance?

 

Thanks,

[JohnMo]

We have a larger and smaller one.  193m2 and tall ceilings.

 

One unit does the two guest bedrooms, and bedroom two en-suite and our bedroom en-suite.  We shower in our en-suite, so only the small unit goes into boost, instead of the whole house.  The other unit serves the rest of the house.  Small reduction in electric, but less air changes in the winter, which should mean slightly less ventilation heat loss.

 

Running cost for electricity should be pretty much the same for one big one or two smaller ones as the total flow rate is the same.  They could be slightly lower with 2, as your duct runs should be shorter, so less resistance to flow and fan runs lower on its curve requiring less less power to the fans.

 

Filters X2 costs.

[Thorfun]

our house is 420m²-ish in total. our M&E consultants wanted to give us 2 x units but I fought against it as didn't want double the running costs, double the maintenance etc. in the end they designed a system that worked with a single Q600 and 90mm semi-rigid ducting.

 

it's not commissioned yet though but they promise me the flow rates will work.

[Seren161]

We have circa 350 m2 over 3 floors ..eventually went with one large unit instead of two units.. and 90 mm semi rigid ducting for similar reasons.. A couple of earlier quotations suggested 2….we do have some longer than ideal runs but not too bad as over 3 floors as opposed to a single floor area ..not yet commissioned so don’t know yet how optimal our set up is..

[Andehh]

Thanks for the feedback guys!