Having a go at fitting my mvhr system tomorrow any tips

[janedevon]

As above me and the sparky are installing first fix tomorrow, any tips appreciated all supplied from BCP should be a fun day 

[Declan52]

Leave extra in length so its easier to join both ends up. 

Have it sitting on a stand like the spark would have a reel of cable so it's easy to pull.

Make sure where the ducts are going they will fit, no toliet pipes etc in the way, before you start.

Have you checked that the actual main unit will fit where you want it to go and have enough room to get at it for changing the filters.

[janedevon]

Thanks Declan, i didnt realise every vent needed 2 runs to it wow a lot of space needed!!

[TerryE]

4 minutes ago, janedevon said:

Thanks Declan, i didnt realise every vent needed 2 runs to it wow a lot of space needed!!

 

No, they don't; only the higher flow ones, typically.  You have to plan out the runs carefully because the pipes running into manifolds end up like Clapham Junction, and you want to order them whenever practical to avoid cross-overs.

[janedevon]

Ah ok thanks, the diagram from bcp isnt easy to make sense of especially for me lol i see now that some have 2 still with 13 extract/intake plenums there is going to be a lot of pipe, may have to adjust as we go as imdont think bcp have taken into account limited roof space due to us using it as rooms. 

[Declan52]

31 minutes ago, janedevon said:

Thanks Declan, i didnt realise every vent needed 2 runs to it wow a lot of space needed!!

I didn't mean two ducts just two ends of the duct needs enough slack to be able to connect it to the plenum and the ceiling plate. Very easy to leave a length short.

[readiescards]

Keep us posted of how you get on. My BPC kit lying here ready for installing...

[Stones]

I've recently fitted my MVHR ductwork (another BPC customer!).  It's the first time I've used a radial system.  Previous builds have used a mix of rigid and flexible main duct runs with individual rooms Tee'd off.  I found the radial ductwork much, much easier to work with.  

 

I think the best tip is to having a cutting list.  Work out / measure how long each of your duct runs is going to be so you can maximise the amount of usable duct from each roll.  Case in point, BPC wanted to supply me with 4 rolls of duct.  I worked out a cutting list at the point of order and reduced the number of rolls required down to 3.  All I'm left with is a 1.4m length and 5 offcucts ranging between 300mm and 600mm.

[jack]

1 hour ago, Stones said:

I think the best tip is to having a cutting list.  Work out / measure how long each of your duct runs is going to be so you can maximise the amount of usable duct from each roll.  Case in point, BPC wanted to supply me with 4 rolls of duct.  I worked out a cutting list at the point of order and reduced the number of rolls required down to 3.  All I'm left with is a 1.4m length and 5 offcucts ranging between 300mm and 600mm.

 

+1 on the above.  I did exactly the same.  With that and a couple of minor tweaks to manifold positioning, I managed to get down from 4 rolls to 3 as well, which was a non-trivial saving (we stupidly went a more expensive route).  

[PeterW]

There are easy little tools online to work out cutting lists that maximize usage of stuff like timber that can be used to work this out 

[jack]

Yep, although the difficult bit may be working out the individual run lengths to start with.  There'll be bends, perhaps not of constant radius, plus the map is not the territory and you may find yourself losing/gaining when you actually go to install the stuff.  I had real psychological difficulty committing to the first few cuts!

[Declan52]

Same here I made a slight boob on my first length so added a good ft on each run from then and it made it easier to connect at both ends instead of pulling it tight to get it to fit.

[DeeJunFan]

BPC seem to be of the opinion that its easier to over supply than to rush some extras out.

 

The duct etc isn't that expensive so id rather be looking at it than looking for it.

 

Again, just a bit of pre-planning on your duct runs and also how you will install the main unit.  Think avoiding vibration noise. We installed my brothers on a floating platform hung from chains.  Means its not actually in contact with the attic floor.

[Declan52]

I used the roll I had left over as a French drain behind my retaining wall. A couple of mins drilling and it's working fine. Saved a few quid.

[Bitpipe]

I did a longish post in ebuild on this after my first fix with BPC kit - must go look for it and re post.

 

Agree with everything above. My strategy was to have the coil near where the distribution boxes were and pull it from there to the plenum location - essential that you mount it on something otherwise it will kink and tangle - i put it in a doorway on a length of CLS timber and that worked well enough.

 

If possible, get a mate to help as once the pipe goes round a few bends its impossible to pull from the coil and the coil needs to be slackened off and duct occasionally pushed from that end as well as pulled - i make a lasso from poly rope to help pull the duct and also put slips of cardboard over any ridges where the pipe kept catching to help it slide more easily.

 

Would advise locating all your plenums first  (good to liase with your electrician to see if they'll be in line with lights etc) and bring the duct to each one. Use WD40 silicone spray ( a big can with a nozzle) to get the duct into the plenum - it is too tight otherwise when the O ring has been fitted.

 

Then leave a generous amount at the distribution box end because, as Terry says, you'll likely be moving them around a bit to get them to sit flat.

 

Last thing I did was cut the ends to the distribution box - I did have to go back and trim a few inches off each one before plaster boarding as they were pushing the box at an angle.

 

It's not a technically difficult job and you'll soon get the hang of it.

 

+1 on the BPC over supply - I have 4off 2m lenghts of 180mm steel radial ducting as we ended up with the distribution boxes much closer to the unit than originally planned as it was the only place they would fit and accept the multitude of ducts (each one is 14 port, every one used!).

 

[TerryE]

Are you using eco / PosiJoists?  You will find it a lot easier to do your main runs along and at 90° to the joist lines.  Think about where you are going to duct between floors and how you are going to fire-break these.  I positioned my plenums in the loft under the eaves on the landing with the pipes snaking down into the floor void.  I have a floorboard box arrangement which sits over the lot apart from cut-outs for the two main in/out pipes going to the MVHR unit itself. 

 

Avoid cross-overs but you will find some are inevitable, but space them so that you don't end up triple stacking pipe and have a Spagetti Junction rather than a Clapham Junction.

[janedevon]

Thanks all

 

11 hours we have all,plenums in place and most of duct runs in ans oddly we have run out of duct none left at all maybe need another 20meters used up 200 i think the problem was our house is open plan and living in roof space, so a lot had to go through rafters both sides using up more duct than the plans said i think they asumed a normal flat roof.

 

left all ducting near position of manifolds to be connected after the weekend fun day, just got to work out best way of insulating duct in rafters as its stealing my insulation space.

 

l

[ProDave]

10 hours ago, Stones said:

I

 

I think the best tip is to having a cutting list.  Work out / measure how long each of your duct runs is going to be so you can maximise the amount of usable duct from each roll.   .

 

 

 

Okay, coming at this from a novice point of view, having never (yet) ducted an mvhr system.

 

I would have assumed one could get (or make) an in line coupler to join two lengths of ducting together. then no need to work it out, just pull through until the roll runs out, insert coupler, start next roll, no waste.

 

No I know why we don't do that with UFH as in line water connections that you can never get at are a bad idea. But an in line connection in an air pipe, that in many cases will be in a loft space etc where you can get at it does not sound like a bad idea at all.

 

If in line couplers are not available I think I have just found a gap in the market.

 

[janedevon]

We manually unwound each roll on floor space then fed through a run pulled to location of manifold left a little slack and cut and fixed to plenum then moved to next hole until roll ran out. All 20 ports on manifold will be used when we get a few more meters of duct.

[readiescards]

17 hours ago, TerryE said:

Are you using eco / PosiJoists?  You will find it a lot easier to do your main runs along and at 90° to the joist lines.  Think about where you are going to duct between floors and how you are going to fire-break these.

Fire break?

 

Edited August 26, 2016 by readiescards
trouble with editor

[TerryE]

@readiescards, you just need to remember that you will need to comply with the BRegs Part B when dealing with your Building Inspector.  You also need to take sensible precautions to satisfy yourself.  We've had some other discussions about this on other topics.  In my view, the main issue that you need to consider here is compartmentalisation: for example if you have a kitchen fire, you don't want the smoke or  fire quickly spreading into the rest of the house through your ducting. Here I am mainly talking about any boxed-in channels where you hide your pipe runs.

 

In England for the most part, a single detached family dwelling can be regarded as a single fire compartment, but you don't want to get into a dispute over the advisory aspects. Take an example in our case. We have a warm roof so three storeys and our manifold plenums in the loft level. We have two double vents in the kitchen/dining room on the ground floor, so there is a duct carrying the 4 pipes from the loft void through our second bedroom down to the kitchen.  I don't want this to act as an internal chimney if I have a hob fire. I have deliberately positioned  the duct well away from the cooking end, and sealed around the entrance and exit to the duct with fire break packing. 

 

My advice is to think about the fire risks and address them sensibly and discuss what you are proposing with you inspector.

Edited August 26, 2016 by TerryE

[Bitpipe]

Good point Terry - in our house (effectively 4 floors as we have basement and room in roof) we also have more stringent fire regs - FD30 doors on every room that opens onto the hall and separate means of escape from basement (external stairs) plus - and this has bemused everyone - dedicated smoke alarms in every hall cupboard.

 

I digress.

 

Our MVHR distribution boxes are in the basement with the individual ducts rising to the first floor via the utility (now completely boxed in and plastered over) and on to the upper floor in a similar fashion. Our BC inspector did not raise any fire issues with this approach.

 

Our of interest, how is it any different to boxed in soil pipes that rise through a building?

 

 

[TerryE]

9 hours ago, Bitpipe said:

Our of interest, how is it any different to boxed in soil pipes that rise through a building?

 

IMO, I don't think that is it.  We've discussed the use of intumescent rings, and I personally think that these are totally OTT within a single dwelling even with FD30-style ratings: by the time that they have activated then you've pretty much written off the dwelling if it has a timber frame or eco-joints. The issue is more one of safely evacuating the occupants. 

 

However, again I consider the case of a kitchen fire -- say a fat fire because someone leaves a pan on the stove.  Such fires account for ~50% of reported fires in the UK. (Most of the rest are smoker-related, so if you don't smoke and don't have open fires, then kitchen fires are by far the biggest risk.)  Here if the fire is contained in the kitchen then the evacuation risk to the occupants is low and the risk to the whole building is mitigated.  But you don't want a smoke or hot gas chimney from the kitchen up through the fabric of the house, so any service voids or boxed in vertical risers should be properly air (smoke) tight top and bottom with some some of cavity barrier.

 

Anyway, that's my view but I would be interested in any other comment.

Edited August 26, 2016 by TerryE

[Nickfromwales]

On 25 August 2016 at 19:15, ProDave said:

 

 

 

Okay, coming at this from a novice point of view, having never (yet) ducted an mvhr system.

 

I would have assumed one could get (or make) an in line coupler to join two lengths of ducting together. then no need to work it out, just pull through until the roll runs out, insert coupler, start next roll, no waste.

 

No I know why we don't do that with UFH as in line water connections that you can never get at are a bad idea. But an in line connection in an air pipe, that in many cases will be in a loft space etc where you can get at it does not sound like a bad idea at all.

 

If in line couplers are not available I think I have just found a gap in the market.

 

Yup. A coupler and a generous bead of CT1 will seal just about anything tbh. 

[TerryE]

On 25/08/2016 at 19:15, ProDave said:

I would have assumed one could get (or make) an in line coupler to join two lengths of ducting together. then no need to work it out, just pull through until the roll runs out, insert coupler, start next roll, no waste.

 

Nah,  do the longer runs first, and just think through the length mixes.  There's no point in joining when you don't have to.  One less thing to do wrong.  We had 200m of pipe and we got a full 50m roll over plus a couple of bits 3 and 5m everything else was <1m trimmings.

Edited August 27, 2016 by TerryE