MVHR unit floor installation - pipework support

[phatboy]

Hi all,

 

I am ready finally to install my MHRV unit - all of the plenums, 75mm pipe and manifolds are in, and loft covered with 200mm of top-up insulation and a new deck above.

 

I have a hipped roof, and so don't have a wall on which to mount the unit in the loft.  I am struggling with how I will get the pipes to the top of the unit, and supported due to the need for a flexible section of pipe on the in/outlets.

 

It's a Vent Axia Sentinel Kinetic BH.

 

Any advice or pictures of installs much appreciated!

 

Tim

[joe90]

I also have a hipped roof (warm) and hung my unit from the roof timbers on triangular ply panels then used flexible 6” pipes from unit to manifold (home made) and unit to wall vents. Main reason for hanging from the roof was to stop any noise transference through the floor to the bedrooms, it’s also on rubber mounts.

[phatboy]

Thanks @joe90, I probably should mount it from the roof timbers really, but as the wiring is from below just float it 1" above the floor.

 

Your unit looks to be horizontal, where as mine is vertical.

 

I think I also have an idea now for supporting the pipes, and will move the flexible section to where the vertical from the unit, meets the almost-horizontal to outside and to manifolds.

 

Cheers

[oranjeboom]

On 10/05/2019 at 11:40, phatboy said:

I am struggling with how I will get the pipes to the top of the unit

 

Just installing my Kinetic and in a similar situation as yours. You say 'top' of the unit...you probably have a reason for connecting the flexi up there, but if not, then you could also swap the spigots round to the side (instead of top), which may make connections easier/shorter.

 

[phatboy]

36 minutes ago, oranjeboom said:

 

Just installing my Kinetic and in a similar situation as yours. You say 'top' of the unit...you probably have a reason for connecting the flexi up there, but if not, then you could also swap the spigots round to the side (instead of top), which may make connections easier/shorter.

 

 

Hi, by top I meant top-sides - I'll definitely be using the side vents to avoid an extra 90degree bend.

 

I think ill use rigid from the unit, and a short length of flexi where the pipe goes horizontal.

 

Just need a nice cool day to go in the loft and get on with it!

[oranjeboom]

28 minutes ago, phatboy said:

 

 

Just need a nice cool day to go in the loft and get on with it!

Yes,  just come out of the loft myself, sweating like a pig. Was cool in the house so was a welcome thing to go into loft to warm up!

 

By flexi, do you mean this:

 

 

Only asking as the install guide states flexi duct:

 

 

Ideally I don't want to use that as I can imagine the air resistance will be so much more (but it's used there to 1) make install easier, rather than having to cut pipework 100% correct 2) reduce vibration from the unit itself to the rest of the duct work).

 

[phatboy]

11 minutes ago, oranjeboom said:

Yes,  just come out of the loft myself, sweating like a pig. Was cool in the house so was a welcome thing to go into loft to warm up!

 

By flexi, do you mean this:

 

 

Only asking as the install guide states flexi duct:

 

 

Ideally I don't want to use that as I can imagine the air resistance will be so much more (but it's used there to 1) make install easier, rather than having to cut pipework 100% correct 2) reduce vibration from the unit itself to the rest of the duct work).

 

 

Yes that's the stuff I am going to use, as BPC sent me a 10m length of it.  So it's flexible, but inside seems reasonable smooth and strong once it's stretched out.

[oranjeboom]

9 minutes ago, phatboy said:

Yes that's the stuff I am going to use, as BPC sent me a 10m length of it.  So it's flexible, but inside seems reasonable smooth and strong once it's stretched out.

 

Okay, thanks! Guess that's why it's best to stretch it out. 

 

Looks as though I will have to delay my install once again as there's a birds nest in the eaves and I'm missing a part from BPC, so that will give you some time to install yours and then for me to pick your brains later on! : )

[MJNewton]

I always assumed the recommended 'flexible duct' connections to mean something more like this 'semi rigid'¹ ducting:

 

 

 

Relatively stiff compared to the 'soft' flexible ducting (it retains whatever form you shape it) but still unlikely to transmit vibrations and being much smoother inside (particularly when stretched out).

 

¹ Not to be confused with the 75mm/90mm semi-rigid ducting used for radial distribution! *sigh* I've never known a subject have so many ambiguous terms. Please nobody mention plenums, manifolds, vents, valves, terminals or grilles!

Edited May 16, 2019 by MJNewton

[dpmiller]

I think they've recently moved to a short flex-coupling option, at least that's what they sent me- it's a ~ 6" length of what seems like a silicone coated fabric tube.

[phatboy]

9 hours ago, dpmiller said:

I think they've recently moved to a short flex-coupling option, at least that's what they sent me- it's a ~ 6" length of what seems like a silicone coated fabric tube.

 

Ah, these?  https://www.bpcventilation.com/flexible-rubber-circular-connector

 

Not cheap though when you need 4 at least!

[dpmiller]

Not cheap, true; but the tool for the job. It's made to flex and is smooth bore. Convoluted tube is remarkably restrictive, and if it's flexible enough for isolation tends to degrade over time in my experience.

[phatboy]

I've contacted BPC to check if it is a new product, and will likely purchase 4 of them - will ask for a good deal as a very recent customer!.  Also saves faffing with the metal insulated stuff and the risks of cutting myself!

[phatboy]

BPC aren't quick responding to me (I need to contact them as we don't pay VAT in Jersey)

 

Does anyone know of any other suppliers of these new flexible pipes?  Google isn't much help!

[PeterW]

You could make those ..! They are PU coated fabric, which to anyone else is just wipe clean tablecloth material from a hardware shop. 

 

Cut it to length and then make a mandrel from another piece of hose, make sure you’ve got a good overlap and then glue the join with something like clear CT1. 

 

 

[phatboy]

1 hour ago, PeterW said:

You could make those ..! They are PU coated fabric, which to anyone else is just wipe clean tablecloth material from a hardware shop. 

 

Cut it to length and then make a mandrel from another piece of hose, make sure you’ve got a good overlap and then glue the join with something like clear CT1. 

 

 

 

Hmmm, I thought they looked thicker?  Maybe I can make up some nice floral ones!!! https://www.ebay.co.uk/itm/PVC-TABLE-CLOTH-TREES-VINTAGE-BIRDS-DAISY-FLOWERS-LEAF-BLUE-PINK-YELLOW-WIPEABLE/292177301611?hash=item44071fd06b:m:mR9buH5OfLHYRMemZ2jR5uA

[dpmiller]

they're a lot thicker.

[phatboy]

Progress update from today!

 

Took @joe90 's sensible suggestion and roof mounted the unit, and included a generous piece of rubber:

 

And then cracked on with the pipework.  Will insulate it all next week.

 

I did in the end buy the flexible rubber adapters, and they were less hassle than the metal flexipipe, and look to cause less restriction (BPC have now removed them from their site!)

 

 

It won't look as pretty as some others have managed as I don't have a nice wall behind to run everything on, but it will be done right (I hope!) and work

 

Tim

[mathraki]

@phatboy thanks for the pictures.

 

The Flexible Silencer on the domestic supply side - did you consider rigid v flex silencers when planning ? is one more effective than the other ( they seem similar in price).

 

[phatboy]

1 hour ago, mathraki said:

@phatboy thanks for the pictures.

 

The Flexible Silencer on the domestic supply side - did you consider rigid v flex silencers when planning ? is one more effective than the other ( they seem similar in price).

 

 

Sort of, but quickly decided a flexible one would probably help me with funny angles a bit better... and it did.

 

Since then, I added a silencer to the domestic side extract too, and it was worthwhile.  Also, the way I fixed the unit to the roof wasn't good.... I used screws, and over time them moved and the unit tipped a little.  I had to re-do it with some M8 bolts.

 

Can't believe I did this 2 years ago!