New MVHR Central Unit - Connections to existing Duct

[TimCx]

Hi now that I have decided on a new unit to replaced the old failed one, (as explained in my earlier 'Replacement MVHR central Unit - Confused !' thread in this forum.) I am looking at how to connect the new unit as it is a lot bigger than the old one. The new unit is a 'Vent Axia Kinetic Advance S'

 

I have attached some photos of my ducting where it joins the MVHR in the garage. These show the old failed unit which is approx. (WHD) 560x500x260 the new unit will be approx. 660x760x443.

 

I am planning to put the new unit on the wall and slightly to the right of the where the old one was. The 2 ducts on the right are the to/from outside, and the others are to/from dwelling.

 

Previously the ducting was connected to the spigots using the thing aluminium flexible ducting and it sat below the ducting. It may not be clear from the photos but the to/from dwelling ducting comes through the wall just above the old unit and the from dwelling (marked III) is a 'T' joined to the leftmost of the Square ducting which drops down from the top. 

 

I have a couple of questions about terminating the new unit:

1. Is it OK to use the thin aluminium flexible duct to connect to the spigots? or is there a better way I will need probably some flexibilty to line up with the new unit.
2. I am planning to shorten the vertical rectangular duct and re-join it to the round but to give more room to wall mount the new unit. 
3. Can anyone advice how best to join the to/from dwelling to the new unit causing as little airflow restriction as possible The From Dwelling will have to be a take 2 bits of ducting into a single spigot.
4. The ducting above the old unit was all boxed in, if I re-box it for the new unit should it be insulated? 
5. I understand that there is (or was) a loan balancing tool available from this site, can someone tell me what the process is to borrow/rent it?

 

Thanks

 

 

 

 

 

 

 

 

 

Edited September 29, 2022 by TimCx

[jack]

That aluminium flex tubing is far from ideal as it has quite high internal resistance.

It's also uninsulated, which isn't great given the system is in a garage (presumably not within the thermal envelope of the house). 

If you can, you're better off replacing the ducting that's outside the thermal envelope with proper insulated ducts like these. 

 

Ideally you'd also insulate the unit itself to reduce heat loss and condensation. Is there room to add rigid insulation as part of the boxing-in?

And is there a condensation drain underneath the existing unit?

[TimCx]

33 minutes ago, jack said:

That aluminium flex tubing is far from ideal as it has quite high internal resistance.

It's also uninsulated, which isn't great given the system is in a garage (presumably not within the thermal envelope of the house). 

If you can, you're better off replacing the ducting that's outside the thermal envelope with proper insulated ducts like these. 

 

Ideally you'd also insulate the unit itself to reduce heat loss and condensation. Is there room to add rigid insulation as part of the boxing-in?

And is there a condensation drain underneath the existing unit?

Thanks Jack, I was suspicious that the ali flex stuff wasn't great.  Interesting that you picked up on the condensation drain, the old unit did not have one and I think that has a lot to do with it failing as its electronics were flooded, the new one will have one.

 

These is some scope for limited insulation and boxing but although its in the garage (which is outside the thermal envelope) the garage rarely gets very cold normally 10C or more even on a cold winters day, this probably due to heat from 2 freezers a fridge and a load of solar equipment.