condensate?

[Oz07]

Taking my MVHR ducts out through the roof and am going against couple of things.

 

Firstly it says ducting should fall away from the unit. you can't really manage this with a roof vent no matter how you go about routing the ducting, you would always end up with a bit of a puddle as the roof is pitched and you couldn't 'fall' a duct to a pitched roof.

 

At the minute i've set the ducting up with a slight fall back towards the unit. If any condensation does occur within these ducts and runs back to the unit will the condensate drain be effective or does it only work on the 'internal' ductwork?

 

Second thing is BPC told me my roof tile air vents were unsuitable, despite being expensive and made by the manufacturer specifically for property ventilation, not soil. They put this down to my vents having 12500mm2 and needing 20000mm2 or something. In the end they then said that the exhaust only needs 10000mm2 so that one could be left but the other needed changing. They have sent me one with a cowl over the top.

 

In the manufacturers instructions the unit says it only needs 10000mm2 clear vent for exhaust and intake so my tiles are ok. However no cowl on the intake. I've not had a drop of water come through even with that howling wind this week, the roof tile manufacturers have obviously built these to withstand weather. I would just have to clear any standing snow if that were to happen, although i'm sure snow would gather around a cowl too. Any thoughts?

 

Thanks

[JFDIY]

Go with the mfrs recommendations on the vent area needed, that should know best.

 

If there is a condensate drain on the unit then can't see an issue with s fall that goes either away from  or to the unit, or a combination, what you don't want is anywhere water can gather, so no U-bend scenarios.

[Oz07]

Yeh I thought it was good to see manufacturers manual and confirm tile vents in spec. 

 

Does the condensate drain work no matter where in the unit condensation forms then? Ie both sides of heat exhanger? Excuse my Neanderthal understanding of these units. 

 

Yes I've made sure ductwork has steady fall but all way back to unit at present

[Ed Davies]

53 minutes ago, Oz07 said:

Does the condensate drain work no matter where in the unit condensation forms then? Ie both sides of heat exhanger? Excuse my Neanderthal understanding of these units. 

 

I've no practical idea but it seems to me that it ought not to work for the inlet/supply path as the units are not supposed to mix the incoming and outgoing air.

[Mr Punter]

I understood that the condensate would form as soon as the exhaust air was passed through the heat exchanger and it would drip into the the condensate drain and be directed out.  There should not be enough moisture in the now cooler air for condensation to form on the remaining length of duct.

[Ed Davies]

3 hours ago, Mr Punter said:

There should not be enough moisture in the now cooler air for condensation to form on the remaining length of duct.

 

It takes time for droplets of water to fall out of the air; small heat exchangers won't be all that efficient at extracting latent heat. Also, there could be condensation in the inlet pipe if, e.g., it's been cold outside for a while so the pipe is cold then then weather changes to warmer damper air.