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I have just turned on the MVHR a couple of days ago and I keep getting smoke into the intake of the MVHR from on of my neighbours chimneys which is about 10m away. With the weather not being so good in the last couple of days, they have been using their log burner and I'm kind of forced to switch the unit off unit I come up with the solution. My unit has a summer bypass and I was thinking of switching this on when I can smell/detect smoke.

 

I'm trying to find a solution ESP based most likely to detect smoke in the intake and either switch the unit off or activate the bypass until no more smoke is detected.

 

I'm in the process of building a Wemos D1 mini with Tasmota loaded on it with 3 relay to control the 3 speeds on the unit + other temperature sensors attached. I have some spare GPIOs so I can attach some kind of sensor and control the unit based on the smoke readings.

 

If this fails I was thinking of making a prefilter box with some carbon granules and have the smell absorbed. But I think this way I will introduce more pressure into the system and I will have to speed up the unit and consume more power.

 

I'm looking for ideas on how to proceed, any help is appreciated!

 

PS: My neighbours are lovely, but this is a problem that I haven't foreseen :) and I need to find a solution quick so my wife stops complaining :)

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The bypass won't stop the smoke. That just stops the exhaust air from going through the heat exchanger.

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We have the same problem at times.  My solution is to turn the MVHR off when we smell smoke, but it's far from ideal.  In our case the problem arises whenever we have very still air, and seems to be related to the position of our MVHR intake.  The position of this intake isn't ideal, as it is high up in a gap between the house and the big retaining wall about 2m behind the house, and I think the smoke somehow gets funnelled into that area somehow.

 

I have noticed that the smell of smoke is a lot less pronounced lower down, so I keep meaning to see if I can find a way to reposition the intake.  This isn't at all easy, as it goes out through a wall, just above the first floor, so I've been looking at ways to try and run an external 150mm duct down the rear wall of the house, without it looking too untidy.  At the same time, I want to turn the intake around through 90 deg, as I think that may help, and I'd like to add a pre-filter, to help keep the F7 filter in the MVHR a bit cleaner. 

 

I've also been looking to see if it would be possible to fit an activated carbon filter at the newly positioned intake, as I'm hopeful that such a filter might help to remove smoke smells.  Not 100% sure how to do this, but I have some bags of activated carbon granules, sold for use in filters, and plan to see if I can pour a layer of these over some fine mesh, so that the intake air is pulled through it.

 

Finally, I've also been looking at whether or not it might be practical to use a combined UV-C/ozone lamp in the intake duct.  I've no evidence at all that this might reduce the smoke smells, but I do know that ozone is a very powerful oxidiser, that should, in theory, oxides the volatile organic compounds in smoke, but there are other hazards associated with using ozone in the treatment of the air supply into the house.  having said that, we have a small ozone generator in our fridge, and that works extremely well, and removes all smells in the fridge, even those from really smelly cheese.

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I've not used one, but a carbon filter (maybe in conjunction with an HEPA filter) should help.

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I was all set to install MVHR

A friend put us off for the same reason 

Dragging neighbours smoke in leads him to having it switch off most of the year

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Just to put our slight problem into perspective, the reason I've not done anything about it yet is that it only happens a handful of times a year.  It's not yet enough of a nuisance to have motivated me to get up a ladder and start playing around re-routing the intake with some additional ducting.

 

 

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Any chance you can move your air intake to a less vulnerable position?

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I wish I could move the intake somewere else, but my MVHR is in the loft it's not going to be easy. This has been designed in such a way that I keep bends and ducts to a minimum to reduce pressure in the system.

 

I have attached a photo of my room and the offending chimney in yellow together with the wind direction. :)

 

I'm going to do a bit more investigating in what sensor I need to pick so it can sense the smoke in low quantities.

I haven't yet ruled out the carbon pre filter. I would like this to be a last resort.

Thanks all for all your help so far.

2020-05-04_16_30_24.jpg

2020-05-02_17_02_24.jpg

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Can you swap the inlet and outlet pipes to atmosphere easily to see if that is better?

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Because of wind direction I'm a bit reluctant to do that. My exhaust is almost 3m away for the intake, to the right as you look at the roof. The wind usually blows from the west to east, this means from the intake towards the exhaust. I'm afraid I might get contaminated air back into the intake if I reverse them. 🙃

2020-03-31_17_22.54_-_Copy.jpg

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Unlikely to be a problem, it'll dispurse if the wind is that strong.

 

Got to be worth a try.

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54 minutes ago, Savage87 said:

Because of wind direction I'm a bit reluctant to do that. My exhaust is almost 3m away for the intake, to the right as you look at the roof. The wind usually blows from the west to east, this means from the intake towards the exhaust. I'm afraid I might get contaminated air back into the intake if I reverse them. 🙃

 

 

 

I very much doubt there will be the slightest risk of exhaust air being sucked into the intake with them that far apart.  Diffusion will be so rapid in any sort of a breeze that the exhaust air plume will be very diluted over a couple of metres or so. 

 

Got to be worth a try, as it's probably a fairly easy change to make.

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+1

 

Worth a try but will have to see how effective it is.

 

Is there any chance you can run a pipe around under the ridge to the extension? An inlet on the breeze block gable would be miles away.

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Posted (edited)

I will also likely have to tackle this same problem, a neighbour over the road has a wood burner, and when we have easterly winds, the smoke comes over, which also tends to coincide with the coolest temperatures, so almost a guarantee in winter months.

 

I have asked several MVHR suppliers, and all have said carbon filters, but none could guarantee they would work, and they can be quite expensive. There are cheaper versions online, high flow for hydroponics setups, so I may end up DIYing something out of one of these.

 

This is what i was originally looking into: https://www.ebay.co.uk/itm/Carbo-Air-50-Systemair-High-Quality-Carbon-Filters-Odour-Control-Hydroponics/152463760843?hash=item237f8c5dcb:m:my_06Dq0-ZHmaU_bAypD_Qg

 

Would just need an airtight box building round it, with a pipe going to the outside for the intake.

Edited by MikeGrahamT21

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I think that there needs to a very major change to the law on smoke, it is carcinogenic, antisocial and unpleasant 

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8 minutes ago, tonyshouse said:

I think that there needs to a very major change to the law on smoke, it is carcinogenic, antisocial and unpleasant 

 

I agree, but I can't see that happening any time soon, more the pity.

 

One thing I've noticed is that we can smell smoke coming in through the MVHR when we can't smell it standing on the path beneath the MVHR intake.  When I get around to adding an extension duct on ours, I plan to bring the intake lower, so that it's around chest height when standing at ground level.  As well as, I hope, reducing the probability of smoke getting drawn in, doing this will also make getting at the pre-filter I'm planning to fit.  Being able to just stand and change/clean a filter that will, I hope, catch most of the crud, should be easier than changing the filters in the MVHR unit itself.  I'm hoping that a large area pre-filter will make the MVHR F7 filter last a great deal longer between changes.

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Could you introduce an ozone generator at the MVHR intake?

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Run it in extract only mode*

 

 

 

 

*I'm really, really, not an expert I'm just repeating what my MVHR designer neighbour told me once. In theory it shouldn't work very well, but it does, apparently.

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21 minutes ago, Onoff said:

Could you introduce an ozone generator at the MVHR intake?

 

Yes, I think you could, with a bit of care.  The trick would be to get just enough ozone to neutralise the smoke.  As mentioned before, we have a small ozone generator in the fridge, that works really well at neutralising smells.  It's a small battery operated device, that works in a similar way to the ozone generators used in some public toilets, and emits a burst of ozone periodically (think it may be light triggered, when the door opens).

 

11 minutes ago, Conor said:

Run it in extract only mode*

 

 

 

 

*I'm really, really, not an expert I'm just repeating what my MVHR designer neighbour told me once. In theory it shouldn't work very well, but it does, apparently.

 

Not sure how many MVHR units have that as an option.  Ours has a pretty comprehensive control panel, but extract-only doesn't seem to be an option. For a pretty airtight house, it's hard to see how this would work, as there would only be a very tiny amount of air filtering in through leaks.   We turn our MVHR off whenever we get a "smoke event", and that works OK.  It takes a few hours before we start to notice the air quality getting a bit stuffy, but when we accidentally left it off overnight the stuffy air was very noticeable in the morning.

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Mine has no function to run on extract only either, plus any air that does come in through leaks will still smell of outside air!!!

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Mine would depressurise the house but not move any air 

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4 hours ago, tonyshouse said:

Mine would depressurise the house but not move any air 

Bad news if you had any gas appliances, one worth noting for anyone really that

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8 hours ago, Jeremy Harris said:

One thing I've noticed is that we can smell smoke coming in through the MVHR when we can't smell it standing on the path beneath the MVHR intake.

I guess it's continually being sucked into the house and concentrating there, whereas on the path it's diluted by the moving air.

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I can't believe that so many users have the same problem, but yet we don't have a simple (builtin) solution... I'm currently looking at some MQ-x sensors..

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