Warning about MVHR cleaning/maintenance

[jack]

We had a leak from underneath our MVHR unit a few days ago.

I took apart the u-bend underneath and was horrified to find it 95% clogged with some sort of bio-jelly. The leak was caused by water backing up above this in the cold weather (lots of condensation) and then finding its way out around where the threaded outlet is connected to the unit (loose screw, now tightened).

 

I cleared the u-bend out then decided to check the rest of the internals.

 

For context, until about a year ago I checked the inside of the MVHR unit pretty regularly - virtually every time I changed the filters (so maybe once every three months on average). It was always spotless. I then got a bit slack and probably haven't checked it since last winter.

 

This time, however, it was pretty disgusting. There was a patch on the heat exchanger where some mould was starting to build up. There was also some pretty disgusting biological buildup on the drainage surface under the heat exchanger and around the drain.

 

Worryingly, there was also a pool of standing water underneath the filter for the incoming cold air. There's a pocket there that doesn't drain but could potentially hold quite a lot of water before it would start overflowing into the drain.

 

I cleaned it all out and sprayed it with bleach.

 

I'll be keeping a much closer eye on this in the future, but I thought I'd share this with others as a warning.

[RandAbuild]

Very timely warning Jack.

I've just noticed that the uninsulated plastic adapter on the incoming supply pipe from the ductwork to the MVHR unit (a Vent Axia Kinetic Plus) is producing a lot of condensation on its surface, which is running down the side of the unit. I will have to devise a means of insulating this adapter.

I measured the temerature of this incoming pipe and it was 13deg (it must pick up some pre-heating through the house). The outgoing pipe was at 16deg, whilst the supply to the house was 21deg and the exhaust from the house was 23.5 deg. So it's pretty efficient.

Anyone else had this problem?

[TerryE]

@RandAbuild, (we can chat about this this PM ) We also have a Vent Axia Kinetic Plus, and vacuum out the filters every 3 months and did our first annual service about 3 months ago.  It was all pretty clean inside. But I can see Jack's point.  Give the bacteria some standing water and warmth and somehow they'll fine a way to make a living out of the air particulates. 

 

@jack, thanks for the warning.  This all reminds me of a report on a set of MVHR installed in a build of community housing.  Over half were incorrectly installed (IIRC, half were installed back-to-front) and only one in the entire community was being regularly maintained and used correctly. 

[jack]

23 minutes ago, TerryE said:

 

@jack, thanks for the warning.  This all reminds me of a report on a set of MVHR installed in a build of community housing.  Over half were incorrectly installed (IIRC, half were installed back-to-front) and only one in the entire community was being regularly maintained and used correctly. 

 

I remember reading about that or something similar. It's absolutely critical that these things are maintained.

 

I was surprised to find that the heat exchanger on our Brink unit is riveted to together, so can't be taken apart for cleaning. I'm sure I remember reading about at least one person (@Bitpipe maybe) who was able to take theirs apart and wash all the individual plates. I may look into whether it's possible to do this by drilling out the rivets and replacing them with some other form of fastener.

[Big Neil]

Obviously dependant on pipe location but for insulating the pipes, some sort of spray foam, if only for relatively inaccessible areas?

[jack]

Just now, Big Neil said:

Obviously dependant on pipe location but for insulating the pipes, some sort of spray foam, if only for relatively inaccessible areas?

Whatever you use, it needs to be closed cell.

[Big Neil]

righteeeo.

[Cpd]

2 hours ago, jack said:

clogged with some sort of bio-jelly.

......I have also had this problem in the past but it was from a bath / shower pipe. The pipe sagged and water must have been sitting in it and the bio jelly had virtually filled the whole pipe from the bath to the main waste pipe about 2.5m ...... what a horrible experience. It takes a lot to gross me out but that was one experience I am not looking forward to repeating. I wonder how wide spread this problem is and what one does to avoid it beyond just using a lot of bleach.  

[Bitpipe]

1 hour ago, jack said:

 

I remember reading about that or something similar. It's absolutely critical that these things are maintained.

 

I was surprised to find that the heat exchanger on our Brink unit is riveted to together, so can't be taken apart for cleaning. I'm sure I remember reading about at least one person (@Bitpipe maybe) who was able to take theirs apart and wash all the individual plates. I may look into whether it's possible to do this by drilling out the rivets and replacing them with some other form of fastener.

 

Yes, our Vent Axia Sentinel (standard BPC issue) allows you to unscrew the front cover, remove the heat exchanger and wash it out.

 

That said - the exchanger unit is solid - a six sided cell with solid top and bottom - you can get water into it but you can't take it apart itself. I usually clean it in the bath with a shower attachment.

 

I normally do that just after autumn when I replace the filters and give the whole inside a good clean, including the fan blades, summer bypass vanes etc.

 

Just gave the filters a good hoover just now - I should do that every month but usually forget - try and change them every 3/4 months.

 

Not seen any issues with condensate building up though - will double check that. Ours runs straight down to a condensate pump (no u bends) where it mixes with boiler condensate and both are pumped up to the utility room drain from the basement plant room. 

Edited January 22, 2019 by Bitpipe

[jack]

1 hour ago, Bitpipe said:

That said - the exchanger unit is solid - a six sided cell with solid top and bottom - you can get water into it but you can't take it apart itself. I usually clean it in the bath with a shower attachment. 

 

Ah, same as ours then (I seem to recall reading once that the heat exchanger is common across a lot of these units).

 

I did give it the once over, but I suspect it could do with a more aggressive clean at some point.

[J-P]

I also have a leak from a Vent Axia Kinetic Plus, water trickles out from the front and sometimes from the back of the case. Drain pipe and trap appear to be clear. 

The problem seems to stem from the poor design of the the cell/unit in respect of condensed water; it just has to find its way out of the cell, past the summer bypass and down the drain. There is a slight fall on the foam insulation that the bypass mechanism sits on but nowhere near enough to ensure water runs into the centre of the unit and then down the drain. With high levels of moisture and cold weather I e. winter, water just spills out in all directions! 

I think a proper solution would require modifications to the cell and the summer bypass to provide a decent route for water, in the meantime removing the summer bypass unit in winter solves the problem (making sure to insulate the 2 power connectors).