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Inlet and exhaust location near to gas flue


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We are going to have a ground floor plant room (1900 wide x 2150 deep) in which we will put the MVHR unit. We are also installing a gas boiler for DHW but I'm not sure where to install it - either in the plant room with the MVHR unit or in the utility room. My concern is around the necessary separation of the MVHR inlet and the flue for the gas boiler. Does anyone know what the regulations state and what is actually required in practise? I have a feeling that any regulation, should one exist, might not be good enough rather than too much!

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The same diagram is in the building regs that you can download for free. I could point you to the Scottish version, but probably best if you look it up on your local council website (It is almost certainly the same diagram)

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We have a similar arrangement  - the MVHR intake / extract is on the south wall of the utility, 1.5m apart and about 4-500mm above ground from the outside.

The gas flue is on the west wall and from memory needed to be 300mm away from the door opening to meet regs and 2000mm above the external finished ground level to avoid an ugly cage around it.

The gas flue was quite tricky to locate as the MBC studs kept getting in the way.

Big tip - get your MVHR penetrations and flue sleeve (we used 150mm PVC duct) in the wall ahead of blowing the insulation and any external wall finish such as render etc. as it makes life much easier.

Darren from MBC did ours in return for a bacon sandwich - I find this this is the preferred MBC currency for doing 'favours' :)

It's also good practice to get your electrical penetrations (usually short sections of 22mm PVC ducting) in at this stage too  so they can be taped for the airtightness and nicely rendered from outside.

We left the gas main penetration until after the gas was re-connected as it needed to be close to where the meter box was.

Be warned, the MBC erection stage will go very quickly so you need to have your sparky geared up and have made all of these decisions in advance! Also ask for a few left over rolls of Sika tape to airtight any follow on penetrations and repair any rips to the yellow paper or holes in the green board - i.e. if you remove a piece of batten. 

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Thanks Hugh.

The table for BS5440 is just for the position of the gas flue isn't it and doesn't take into consideration the requirements of MVHR? So, on my 1900mm wall I could put the MVHR inlet and exhaust far enough apart from each other but I'm still not 100% sure on the gas flue. I think if I read it correctly I could put the MVHR inlet and exhaust approx 1500mm apart and the gas flue another 300mm further away, although I'm not sure why the two exhausts would really need that separation

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10 hours ago, Bitpipe said:

We left the gas main penetration until after the gas was re-connected as it needed to be close to where the meter box was.

Could you not dictate the position of the gas meter at all? You wouldn't be able to post a photo up of your meter and its location would you? :) 

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13 minutes ago, worldwidewebs said:

Could you not dictate the position of the gas meter at all? You wouldn't be able to post a photo up of your meter and its location would you? :) 

Ish, we laid the perforated yellow duct to the utility wall and then refined the position of the box when it was being installed. Plumbers advised to wait until the box was in place before drilling holes in the wall.

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Just now, Bitpipe said:

Ish, we laid the perforated yellow duct to the utility wall and then refined the position of the box when it was being installed. Plumbers advised to wait until the box was in place before drilling holes in the wall.

When I started planning for this build, I had in my mind a vision where I would have no ugly boxes, pipes etc stuck onto it and I'd have full control over everything. It would appear I was very much mistaken! :(

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You can see the box next to the utility door in the pics I uploaded to the soffit / fascia thread.

Gas would appear to be one of those services where the meter needs to be very close to the house, lots of restrictions on the ducting also  - worth a read of the national grid website.

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2 minutes ago, Bitpipe said:

You can see the box next to the utility door in the pics I uploaded to the soffit / fascia thread.

Gas would appear to be one of those services where the meter needs to be very close to the house, lots of restrictions on the ducting also  - worth a read of the national grid website.

Ah, many thanks :)

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