Is there anything wrong with our MVHR plan?

[Mr Blobby]

We have an MVHR plan originally from our M and E guys which I think is OK, like this:

 

 

The unit is in the loft under a warm roof, in the centre-ish of the house.  The external vents are through a North facing gable end wall.

The first floor heat exchanger will probably be replaced with a bit of UFH upstairs, but apart from that, is there anything fundamentally wrong with the layout and ducting plan?

The third diagrm shows more extract than supply vents.  Is that an issue for balancing?

 

I ask because a leading MVHR supplier refuses to engage with us and give us a quote until after we pay them a fee to (ostensibly) rewrite the ducting plan. 

 

 

 

 

Edited June 14, 2023 by Mr Blobby

[Shaun McD]

Hey John, 

 

I am by no means an expert in this field, I did the design and installation in current house and planning the same for the next one. Couple of small points maybe worth considering;

• Loft location is convenient in one way, but is also a torture in another. You need to access the machine to change filters (twice a year for us), and when my machine played up a few months back, it was less than fun getting it down the attic stairs to have a full inspection. If possible, I would look into placing the unit in a closet or wardrobe on the first floor. 
• I wouldn't be greatly concerned with the balancing between floors since the overall balance is correct, but, I would also possibly have a look at having two machines, one upstairs, one downstairs. As you can opt for smaller units, the price may be very similar, but gives you more overhead if you want to run higher rates than those listed without much stress on the units.

[JohnMo]

The flow rates look massive, these should/need to be trimmed back.

 

[Mr Blobby]

On 11/07/2023 at 11:51, JohnMo said:

The flow rates look massive, these should/need to be trimmed back.

 

 

Holy crap, our flow rates are more than double part F recommendation.

Thanks for this, I'd not looked at that document before, just assumed the flow rates from the M and E guys must be about right.

Yes, they will be dialled down 👍

Edited July 22, 2023 by Mr Blobby

[andy500]

I fitted ours about 15 years ago. One of the best things we’ve done - minimal mould to date - but it was never professionally set up or balanced or anything clever like that. Fully variable fan speed is very useful so you can dial it down if you want, and fine tune with screw in/screw out duct outlets.
Access to as many ductwork fluff-storage dead spots as possible would be useful- we have a shower room extract line that I now know I can’t get to if I needed to without replastering. I extended the ribbon cabling on our Stork main unit control panel and fitted the display to the landing wall so I can see the fan speed, whether it’s in boost etc - useful as we have pull switches for time delay boost mode next to the two showers.