Tue, 19 Dec 2023 08:23:40 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297696#Comment_297696 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297696#Comment_297696 Tue, 20 Sep 2022 21:27:23 +0100 quinnj3
I hope someone here can help me. First some background on my system.

I DIY installed my MHRV about 13 years ago using a Vent Axia Air Minder plus ventilation unit. The pipes are all solid (apart from direct connections to HRV unit) and are either within the insulated layer of the building or wrapped with 40mm fibreglass foil wrap and taped up to avoid cold air pockets. There are a couple of condensate drains tied to the overflow of the house to carry away condensate that may build up in the extract pipework as it leaves the insulated layer to the uninsulated layer. In theory the unit is perfectly sized. In practice I believe it to be oversized as a draft can be felt at times when standing near the inlets. It's also quite noisy and I never need boost mode. It's permanently on low vent mode.

I have to admit I've somewhat neglected the system as it's always just worked. I wash and clean the filters at least once a year but they are always filthy. I should be doing it 4 times per year. I've only previously opened the unit up and cleaned the heat exchanger once about 5 or 6 years ago. At that time there was no mold present except for a small bit around the condensate drain; the unit was very clean otherwise.

We dry our clothes in the house and due to the effectiveness of the MHRV a clothes horse dries in less than a day. Over the past year or two we have noticed it is taking a couple of days to dry clothes. Up until recently (the last few months) we have had zero mold in the house; now we have noticed a small amount developing in our main bathroom.

Over the past few weeks the unit has been getting quite noisy to the point I've switched it off a couple of times at night. This evening I split the unit to find the extract fan appears to have a failed / failing bearing. Of more of a concern was the dirt and mold on the H.E. The extract blower is caked in what appears to be dust and mold also. The inside of the unit is largely dry except for a small damp spot at the condensate drain. The unit is exceptionally dirty also. Fortunately the air inlet fan and ducting is pristine so the filtration appears to be working there.

Obviously I'm really concerned with the mold issue and would like to get to the bottom of it. I can't tell 100% just yet but I believe the HE may have blocked with dust (even though it is filtered), reduced the air flow through it allowing the damp extract air to mix with the dust and facilitate mold growth. Is this a likely scenario?

Comments and opinions welcome.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297699#Comment_297699 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297699#Comment_297699 Wed, 21 Sep 2022 08:15:50 +0100 Peter_in_Hungary
Having said that when you previously opened up the unit it was clean now it is dirty. What has changed in the system?

I would clean the unit and then repair the extract fan and monitor the unit.

Would it be possible that the failing extract fan is causing an imbalance which allows or promotes the build-up of dirt and moisture which then allows mould growth]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297704#Comment_297704 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297704#Comment_297704 Wed, 21 Sep 2022 11:36:10 +0100 djh
You say you wash the filters at least once a year, but when did you last replace them? Do so at least every few years.

You clearly need to replace a failing fan, or the whole unit if that makes more economic or practical sense.

If the extract fan is not working properly then all the air that is being pumped in by the intake fan must be escaping through cracks etc as well as through the ductwork, so you may have problems elsewhere as well. The humidity will likely have increased, as demonstrated by the mould and the increased drying times. I would suggest opening windows regularly and not drying clothes inside until you have repaired or replaced the MVHR unit. i.e. treat the house as a 'normal' unventilated house.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297706#Comment_297706 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297706#Comment_297706 Wed, 21 Sep 2022 11:51:39 +0100 Mike1
To reduce dust on the extract side of the system, you could also consider fitting filter fabric to the room extract vents - or at least to the kitchen & bathroom, if they don't already have them.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297713#Comment_297713 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297713#Comment_297713 Thu, 22 Sep 2022 08:15:08 +0100 quinnj3
I contacted Vent Axia about a replacement fan however the model of MHRV unit I have has been discontinued for over 10 years. They have no spares available.

I decided to strip the motor to see if it could be repaired. Long story short I have the old bearings removed (which have considerable play in them) and will order replacements for about £2 each. I think I'll do the fresh air fan when I'm at it.

I also took to cleaning the unit. There was mold on the HE unit but not nearly as bad as I'd thought. What I assumed was mold on the fan turns out to be polystyrene being cut / melted away with the fan movement with some mold growth on top. As usual I jumped the gun without a proper investigation. One thing to note is the fan is quite rusted. Should I clean and paint this or will that upset the balance?

The exhaust air duct into the heat exchanger has some fluff on it but it's not bad and crucially it's bone dry. After cleaning the HE there is only a small amount of residual mold on the outside of the fins at the cold exhaust side. I cleaned with a mild caustic solution (G101 from Autosmart) and left the solution on for 10 minutes or so. Hopefully all growth will have been killed off now.

Some pictures for you all attached.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297714#Comment_297714 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297714#Comment_297714 Thu, 22 Sep 2022 08:16:20 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297715#Comment_297715 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297715#Comment_297715 Thu, 22 Sep 2022 08:16:44 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297716#Comment_297716 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297716#Comment_297716 Thu, 22 Sep 2022 08:17:18 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297717#Comment_297717 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297717#Comment_297717 Thu, 22 Sep 2022 08:18:36 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297718#Comment_297718 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297718#Comment_297718 Thu, 22 Sep 2022 08:19:26 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297719#Comment_297719 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297719#Comment_297719 Thu, 22 Sep 2022 08:20:07 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297720#Comment_297720 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297720#Comment_297720 Thu, 22 Sep 2022 08:20:50 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297721#Comment_297721 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297721#Comment_297721 Thu, 22 Sep 2022 08:24:31 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297722#Comment_297722 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297722#Comment_297722 Thu, 22 Sep 2022 08:24:50 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297723#Comment_297723 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297723#Comment_297723 Thu, 22 Sep 2022 08:25:11 +0100 quinnj3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297724#Comment_297724 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297724#Comment_297724 Thu, 22 Sep 2022 09:55:24 +0100 revor http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297725#Comment_297725 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297725#Comment_297725 Thu, 22 Sep 2022 09:57:48 +0100 Peter_in_Hungary
For the rust you could (gently) clean off the rust and then spray with a can of spray paint suitable for the fan material. Spray just enough to cover the material. I would not brush the paint on.

Whilst Vent Axia may not have spares (at their inflated prices) often manufactures will use off the shelf industry standard units rather than design and manufacture their own (makes sense from a cost/profit view point) and the components will often have a part number or 2 that can be tracked down on the internet and ordered separately. Otherwise fans (and other mechanical bits) often come in generic sizes so searching for fan type by size and wattage can produce results.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297734#Comment_297734 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297734#Comment_297734 Thu, 22 Sep 2022 21:18:43 +0100 quinnj3
I didn’t paint the fans as I wanted to get it running again however I spent a bit of time isolating the piping and unit from the timber floor it sits in. Over the years it has been quite noisy with transmitted noise through into the room below.

The fans are running almost silently, I actually believe it’s quieter than new however they may be slightly out of balance as there is vibration I can feel when touching the motors. I was careful to mark the position they were in previously but I suppose cleaning them down has removed some old rust. This may have led to an almost imperceptible pulsing. I’ll keep an eye on it over the next weeks. I’m going to have to budget for a new unit as I can only assume it would be more refined.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297735#Comment_297735 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297735#Comment_297735 Thu, 22 Sep 2022 21:57:09 +0100 borpin
Measure, measure, measure. Data is absolutely invaluable. Find a way to record the temperature and humidity of the exhaust air - this really is vital to know what is going on.

I'm convinced that I have been overventilating my house for years. I now measure the CO2 in the exhaust air (plus a couple of rooms) and that has resulted in me reducing the ventilation rate massively. I should have fitted a smaller unit, but didn't really start gathering the data until after I'd replaced it. However, when one of the kids come home, I need to increase the ventilation to maintain the right CO2 level.

Re your mould, my suspicion would be that the Heat Exchanger is not working correctly and so the RH is not being reduced.

As DJH says, get some sensors to measure the RH and Temperature in the house. I bought these recently and read the data using HomeAssistant https://www.amazon.co.uk/dp/B08XQD8MFZ

Final thought, when replacing the unit, I fitted an inline filter box on the inlet side and that significantly reduces the amount of crap that gets as far as the MVHR unit!]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297736#Comment_297736 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17575&Focus=297736#Comment_297736 Thu, 22 Sep 2022 22:17:09 +0100 quinnj3
In terms of measuring I think I’ll look into that Borpin. In winter I’m convinced the mhrv is cooling the house due to air flow. Now is the time to take the readings before I plump for an new unit. My house isn’t air tight in terms of an airtight barrier. At the time of install all I wanted was controlled ventilation so my house is traditional construction with thermal blocks on inside cavity and heavier than specified loft and void insulation. I do notice a draft through the key hole of my living room doors as well as the split between my patio doors. They are pvc but were also cheap to fit budget at the time of building.]]>