The black smudge on the exhaust fan is where I've rubbed off whatever white mold adorns every part of its surface, to reveal the plastic beneath. Dare say I need to block out some time with the bleach this weekend and hope it's not ruined the fan; it was making a very odd thrashing noise when I first came to it; got the impression the condensate had backed up to the point where the blades were getting wet and flinging water around inside the polystyrene body..

Just the standard vent axia ones.. Most of that is black mold

When you say world side is that the world coming in or exhaust to the world? Your post prompted me to open up mine, been 4 months since last filter change , dry dust on the extract filter and a few dead insects and black dust/soot on the inlet, but internals pretty much as clean as day it was installed ( admittedly only 16 months ago) condensate drain looks clean and clear. But from your picture , i probably need to open it right up 6 monthly rather than annually.

"When you say world side is that the world coming in or exhaust to the world?"

Yes

On a VA Sentinel the world connections are on the same side of the box, fresh air from world at the top and exhaust air to world at the bottom in that pic. Most of the mold is on the exhaust so I'm not hugely concerned that the house has had volumes of spores actively pumped through it, but some of the HX vanes on the inlet side were starting to grow

The problem with the unit, and the reason why it sounded like someone throwing water round inside it when it was running was because the condensate drain hole had seemingly become blocked in the fan area and the fan housing had a pool of water in the bottom.. I'd already sucked the water out but you can see the tide mark in the bottom. Possibly been like this a while as the sides of the housing had "fling marks" in the dirt

"i probably need to open it right up 6 monthly rather than annually"


I'm planning on looking at mine annually; I've done the filters but I never pulled the HX in 8 years, which I plan to start doing and giving it a preventative spray with something to keep the mold in check, and also resolved to put the wet vac on the condensate drain and tip hot water in the other end just to give it a run of high speed stuff that should shift and accumulated goo

If there was space I would consider modifying the unit so it works like my modification of my dehumidifier in the garage does; the original continuous drain on it was a pipe plugged onto the spout of the drip tray but it was forever getting blocked with slime. I found it much more effectively to drill a hole slightly smaller than a drain tube outer diameter, 3/4 the way up the tank and lead the tube down to the bottom in a corner and have the output lower than the pickup. As the tank fills the tube does too and eventually it kicks off a siphon that rapidly empties the tank. The higher water velocity seems better at keeping the tube free of slime. There isn't enough space to do the same with the MVHR unless I do a lot of work. Its lasted 8 years so I'll make it a yearly job to flush it through and hopefully a stitch in time will save 9!

Yes, I did just use a normal P trap with an air gap and in summer it would go dry. Pouring a bit of veg oil into it seems to work; the oil sits on the surface and prevents evap but the condensate is still able to drip through it and away. Time over again I'd install a longer loop on the trap perhaps..

Dry traps are general plumbing parts. The best known is the HepVO but there are even cheaper clones nowadays.

I like the idea of vegetable oil in a U-trap I suppose it only works for low flow rates, otherwise the oil would be flushed away.

edit: thinking about the oil some more, if water later comes in then it will sink to the bottom (where it won't evaporate, yes?). So it will gradually fill up the trap from the bottom until it has pushed the downstream half of the oil into the drain. Then it can evaporate into the drain until it exposes the top of the bottom of the U. Rinse and repeat, gradually draining the oil until there isn't enough to fill the trap. Or have I missed something?

FWIW, there was a period when I was following the "if it's yellow let it mellow, if it's brown flush it down" mantra that the smell of the mellowing yellow became an issue. I used to float a thin layer of vegetable oil on top and that stopped the smell. I confess that nowadays between an MVHR and more regular half-flushes I've given up.

<blockquote><cite>Posted By: djh</cite>The best known is the HepVO but there are even cheaper clones nowadays.</blockquote>

I have had bad experiences with cheap plumbing particularly plastic stuff. My go to for a few years now are McAlpine British quality at its best. I note they do a dry trap called self closing waste trap for any one interested.

Won't ask why you don't use a washer for extended periods :)

Also found the time, when putting the MVHR back together, to fit the temp monitors I bought as an idle curio about 5 years ago

This shows how useful the temperature measurements are, every unit should have them. Loving this, and especially the case they're mounted in!

Need to know flowrates in/out in order to calculate efficiency (or at least, need to know flowrates are balanced).

The outgoing air here loses 7.6? of temperature and yet this heats the incoming air by 10.1? -> incoming air is ~30% lower flowrate than outgoing, system isn't balanced.


Approximately half the heat in the outgoing air is the latent heat of water vapour evaporated from the house, only a small amount of this is recovered by a MHRV as condensate. So MHRV suppliers ignore latent heat when quoting 'efficiency' as it looks bad for them. We could include it, if we know humidity in all 4 ducts.

Posted By: WillInAberdeenMHRV suppliers ignore latent heat when quoting 'efficiency' as it looks bad for them

But nevertheless PHI says that recovery, such as it is, is worth it - and worth the 24/7 electricity consumption? Vent gugu Peter Rickaby disputes it - the capex, the elect consumption, the likelihood of poor commissioning defeating the effectiveness; prefers 24/7 central lo-rate extract without recovery from wet rooms, trickle-vent-type mechanical-humidistat regulated inlets to inhabited rooms.

Posted By: WillInAberdeen7.6? should display as 7.6degrees - used to work on this forum but seems to have stopped working now, at least for my browser.

still works just the same 7.6 °C nothing has changed here or on the forum, I think. Whatever's broken it is on your device. FF 115.7.0esr (64-bit) works as well, which is the current FF ESR I believe.

>>>>> "still works just the same"
No, that's a different character. I normally use the 'superscript-formatted zero' character, which is available in one click from mobile keyboard, it used to display correctly on GBF but now doesn't. Neither do some other superscript characters.

The traditional 'degree' character that you used there, is still available, but I have to go down two levels of menus to get at that one on a phone keyboard. Not disastrous, just unexpected.

I'm using Gboard, which is the default keyboard service for Android and iOS, and I see is presently being used on more than 5 billion devices. I'd suggest that makes it the world's default keyboard now, so nowadays anyone using anything else would be weird!

But I don't think it's a keyboard or font problem - the 'add comments' form seems AFAICT to send the correct unicode characters off to the GBF server, but they are replaced by the ? unicode character in the html when the page gets served back.

Having replaced a Helios unit after 8 years due to the exhaust fan dying (twice), I can sympathise. If that is what it looks like at the unit, I wonder what the pipes look like!

I'd be interested to know how long folk have had theirs installed & running.

Personally, I think they have about a 10-year lifespan.