MVHR Installation Issues

[MJNewton]

14 minutes ago, Nickw1982 said:

 

Appreciate your response and reading - I was also drawn to the same table, i believe they have used this document to highlight the associated Supplementary Information in this table 7.0 Section 5c. Where it states that a minimum of 300mm horizontal distance is required.

 

 ?

 

Ah, yes, that muddies the water a little! That said, I would expect manufacturer's installation instructions trump any other guidance/regulations, just like they do with gas appliances, electrical items etc and so there's still hope yet! 

[joth]

51 minutes ago, MJNewton said:

 

Ah, yes, that muddies the water a little! That said, I would expect manufacturer's installation instructions trump any other guidance/regulations, just like they do with gas appliances, electrical items etc and so there's still hope yet! 

I think you're finding a false dichotomy here. As the previous comment says, it's possible to comply with both minimums, but taking the larger of them as the limit. 

 

By analogy: my car has a maximum speed of 120mph but the road outside my house has 30mph max limit, which one should take precedence, MIs or 40 year old regulation?

 

 

[MJNewton]

43 minutes ago, joth said:

By analogy: my car has a maximum speed of 120mph but the road outside my house has 30mph max limit, which one should take precedence, MIs or 40 year old regulation?

 

*Now* who's presenting false dichotomies? ?

 

Only one of your variables is a requirement - the other is merely a capability. If the MIs said that you *should* drive at 120mph then you might have a point... Similarly if the MVHR MIs said the vents *can* (not *should*) be positioned upto 1500mm apart then the regs guidance of 300mm would be perfectly acceptable to comply with.

 

Regardless of how we get there though, it sounds like we are in agreement in what the ultimate requirement that must be satisfied is.

 

Edited November 12, 2021 by MJNewton

[joth]

2 hours ago, MJNewton said:

Only one of your variables is a requirement...

It's an analogy. Don't over think it!

 

2 hours ago, MJNewton said:

Similarly if the MVHR MIs said the vents *can* (not *should*) be positioned upto 1500mm apart

But that's not at all what the MIs say, they have a minimum not a maximum, so not sure why that's relevant.

 

2 hours ago, MJNewton said:

Regardless of how we get there though, it sounds like we are in agreement in what the ultimate requirement that must be satisfied is.

Agreed

 

[Nickfromwales]

23 hours ago, MJNewton said:

The location of the external discharge terminal should ensure that the potential for recirculation of extract air through the supply air inlet is minimised

Given that the holes are now made in the OP's nice stone faced wall, I feel I should cool the heels on this a little and offer reassurance that a lot of the 'big names' are happy with vents being as close together as 1000mm if they are subject to no opposing gables / obstructions etc. My PH design guru ( I hope he never reads this or II will have to pay him more ) states this is perfectly acceptable if the aforementioned observations are observed.

@Nickw1982

The supports ( lol ) holding the terminals eg the loose bits of wood are just a piss-take. Most competent DIY'ers would wipe the floor with that, much as they would with the scrapheap challenge cast-off that is used to "mount" the unit...... ALL of that needs completely re-doing afaic. Would be a few tenners of plywood / timber and a half day for one guy max.

 

The use of flexible ducting directly off the unit is not a big issue, and given the height you have available, lets face it, you're never going to get that resolved unless you take the roof off  I would, however, expect to see at least some rigid ducting off that unit, at least until the invert where the rigid exits away from the unit horizontally and the flexible gets adopted. That's just basic engineering where the weight of the flexible duct can clearly be seen collapsing under its own weight / lack of rigidity.

A section of flexible duct is often used on the output ( fresh ) side of MVHR units to attenuate noise, but usually a slightly different material makeup where a non-friable 'fabric' internal surface is purposefully employed, only usually 1000mm in length and in conjunction with the rigid / strategically used flexible stuff.

 

Bottom line, stand your ground and do not accept any wishy-washy resolutions. This needs a complete overhaul.

[Nickfromwales]

12 hours ago, joth said:

I think you're finding a false dichotomy here. As the previous comment says, it's possible to comply with both minimums, but taking the larger of them as the limit. 

 

By analogy: my car has a maximum speed of 120mph but the road outside my house has 30mph max limit, which one should take precedence, MIs or 40 year old regulation?

 

 

Manufacturers installation guidelines trump building regs in every instance.

[MJNewton]

11 minutes ago, Nickfromwales said:

Given that the holes are now made in the OP's nice stone faced wall, I feel I should cool the heels on this a little and offer reassurance that a lot of the 'big names' are happy with vents being as close together as 1000mm if they are subject to no opposing gables / obstructions etc.

 

And to be fair I seem to recall someone recently posting a picture of a *combined* inlet+exhaust terminal. Sure, it was fairly directional in its construction but even so - if that is in any way acceptable then one might argue that 900mm lateral separation is too.

 

Putting my Internet pitchfork away for a moment, it is perhaps the sort of thing that in theory having a 1500mm separation obviously matters but in practice it being less than this doesn't, particularly given we are where we are with this. It's a bit like the fall on my extension's flat roof - I won't open old wounds by dwelling on it too much but my builder didn't meet the minimum 1:80 guideline and whilst the roof seemingly works perfectly fine despite this it still haunts me to this day... but it probably shouldn't.

Edited November 12, 2021 by MJNewton

[Nickfromwales]

It's probably best to focus on what NEEDS to be achieved here, ( and not to terrify the OP with things that are not 'real world' issues  ). This probably needs a full day for 2 guys to rectify all of the internal stuff, plus whatever it takes to resolve the holes in the stone formed by the unsupervised use of TNT........... 

[Nickw1982]

Great discussion guys, please find below the sanitised response I received from the installer on Friday which also had a signed accompanying letter from Vent Axia. I have also sanitised and posted the letter wording below. Happy to hear your thoughts.....

 

----------------Email Start----------------

Good afternoon,

 

We acknowledge receipt of your emails dated 25 October and 11 November in which you set out your concerns. I have concluded my investigation into your allegations and will respond to each of those points in turn as follows:-

 

1.      Supply\Exhaust External Grille boxes

The installers have damaged my gable wall work whilst stitch drilling and chiselling the stone. The stone has been over chiselled above one box exposing the inner and creating an area that will hold water. This will accelerate weathering and the wall area will weaken over time. My builder has advised that this stone needs replacing as soon as possible. There is also cracking around both grille box areas and the silicone used to seal both grilles has collapsed allowing water to penetrate.

The grille boxes are not installed as per the manufacturer’s installation and commissioning manual which clearly stipulates on page 3, point 9 that the external grille boxes should be a minimum of 1500mm apart. I have measured mine and they are 900mm apart.

 

Installer Response: We acknowledge from the photographs that you forwarded to us that there appears to be superficial damage to your external wall at the site of the grille.  We have been liaising with several builders who have recommended that we approach a specialist masonry contractor and have we requested a price to repair and colour the stone to match the surrounding stonework, these will follow within the next few days.  We will be prepared pick up the cost of this repair.

 

 2.      MVHR System Unit Mounting

The MVHR unit has not been mounted as per the manufacturer’s installation and commissioning manual which clearly stipulates page 16, point 2 that there should be a minimum of at least 0.7m of straight pipe in line with the spigots. I have measured mine and there is 0.2m of straight pipe connected to the unit. There is also 0.6m space underneath the unit.

The unit has not been mounted as per our agreement using the plywood board. It still exists on the short wood with single screws.

 

Installer Response: We have consulted Vent-Axia on the two installation queries regarding the required distance between the two grilles and the straight run pipe in line with the spigots.  Please refer to the “installation clarification letter” attached from the XXXXXX Director for Vent-Axia who has given you clarity on those points.  I confirm that you do have an adequately sized plywood pattress which is the same size at the unit itself that in turn is secured to the two pieces of wood you can see in the photo which spread across the trusses. This was also discussed with Vent-Axia who concluded this was acceptable.

 

 3.      Ceiling plenum Installation

Most ceiling plenums have not been fixed at both sides in the loft space, loose bits of wood have been wedged underneath them adding weight on top my ceiling boards. The added weight has popped a screw and damaged my decorating in a bedroom.

 

Installer Response: I don’t have all the information I require to respond accurately to this issue but I will respond to you by the end of the business day on Monday 15 November.

 ----------------Email Finish----------------

 

LETTER FROM VENT AXIA:

 

Dear XXXXXXX,

Further to your email of 09 November 2021 regarding the site installation questions

raised by your customer we can confirm that from the information provided the units have

been installed to an acceptable standard and there will be no detrimental effect on the

performance of the unit or its service lifetime.

To answer the specific points raised:

1. The inlet and discharge grills must be a minimum of 300 mm apart to comply with

the Building Regulations. As an industry we would prefer to see greater separation

which has been achieved on this installation. We will be looking at our instructions

to soften the wording from ‘Must’ to ‘Recommend’ this larger dimension.

2. The 0.7m straight run does not apply to the standard Advance S, this requirement

applies only to the Constant Volume SX product variant which has pressure

sensors installed in the factory. Therefore the straight length of ducting of 200 mm

will not adversely affect the performance of the unit and is fully acceptable to Vent-Axia. We will look to clarify this in our instruction manuals moving forward.

I trust the above satisfies your concerns and reassures you that the installation that has

been carried out by yourselves is acceptable to Vent-Axia.

I would also like to thank you for pointing these issues out in our installation instructions.

Yours Sincerely

XXXXXXXXX

Vent Axia Director

[MJNewton]

Okay, that's not sounding too bad at all in my view!

 

The Vent Axia clarification regarding inlet-exhaust separation and the non-applicability of the straight exit pipe length are particularly helpful, and as I said I regard them as the expert witness in this case then you've got to go with that they say. Besides which, your 900mm separation is some way beyond the 300mm minimum and whilst it might not be all the way up to the supposed 'ideal' personally I'd be happy, and I'm a fussy bugger.

 

Picking up the repair costs for the stone spalling is fair enough too, assuming of course whoever does it does a decent enough job and I think you've got to give them that opportunity to do so. Ideally the damage wouldn't have been caused in the first place of course but that ship has sailed and you've got to accept the reality of the situation.

 

I am a little surprised about the ceiling plenum issue - I thought he was going to say he'd send someone out to improve the mountings as remedying that sounds fairly straightforward to me. Maybe the 'required information' is about who is going to come and do it?

 

All in all though, I think that's a very good response. Polite, well reasoned, considered. And what's more - an actual response which can't be taken for granted these days!