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VMCs
Jan 2, 2023 9:50:31 GMT 1
Post by jardiniere on Jan 2, 2023 9:50:31 GMT 1
The house I moved into a year ago has a VMC. I know nothing about it other than the owner said it needed to be used less in summer when the windows are open. It has 2 speeds and is permanently on 1 unless I switch it to 2. How often and how should it be maintained? Are they expensive to run? Haven't had the annual electricity bill yet.
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curtis
Member
Charente Maritime
Posts: 516
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VMCs
Jan 2, 2023 10:35:04 GMT 1
Post by curtis on Jan 2, 2023 10:35:04 GMT 1
I have to say I turn mine off in summer. Perhaps I shouldn't? When it is so hot it doesn't seem necessary. I always have it on the slower setting otherwise the noise is a little intrusive.
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Post by norfolk on Jan 2, 2023 10:35:55 GMT 1
If you live there permanently does it need to be on continuously ? I don’t have any VMC in this place and there’s no dampness whether I’m there or absent for a few weeks.Each property is different I supppose.
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VMCs
Jan 2, 2023 10:37:05 GMT 1
Post by annabellespapa on Jan 2, 2023 10:37:05 GMT 1
It is an air circulation system sucking air from the house and hopefully putting fresh air in, they are normally in the loft, they use little electricity but check that nothing is touching it or blocking it, e.g insulation as they can overheat and catch fire, I normally suspend the unit from a beam by some straps or rope so there is no chance of it touching it making it over heat. It is a simple thing to do, when I am not there for a period of time I switch off on the fuse board just in case.
edit- Having just read JonnyD's post I agree that they should be left on low for the situation he is dealing with now, we have owned the house for 14 years so have learnt it nuances, each house is different but if he buys a dehumidifier as I described he could have that on a timer system in addition to his VMC, I hate the things as even on low I can hear it.
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exile
Member
Massif Central
Posts: 2,765
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Post by exile on Jan 2, 2023 10:37:13 GMT 1
You may find hat switching from 1 to 2 just changes the speed of the inbuilt fan. They should be installed so that they cannot be turned off - except by cutting power at the electricity circuit board (tableau).
AS for maintenance, ours is installed in a place that is completely inaccessible so has received no maintenance in 15 years.
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exile
Member
Massif Central
Posts: 2,765
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VMCs
Jan 2, 2023 10:42:49 GMT 1
Post by exile on Jan 2, 2023 10:42:49 GMT 1
Just to add, if you have a fuel burning system in the house - oil/gas heating; Wood burner; even a gas hob (though perhaps less necessary) etc. - a VCM is an essential since it ensures the feed of fresh (and partially heated) air and reduces the risk of a build up of carbon monoxide.
Note though it is not a replacement for a CO monitor.
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Post by Polarengineer on Jan 2, 2023 11:08:14 GMT 1
there seems to be a lot of conflicting advice here about the VCM. The units available from the brico are mostly only extraction fans, they have 3, 4 or more 80mm dia connections for toilets and bathrooms and one 125mm connection for the kitchen. they usually have two speeds. These units hang in the loft on a nylon string suspension to avoid any noise transmission made through the more firmer fixed bracket type of fixture. having them on permanently seems pointless and can best be started by a proximity sensor in the space to be vented (toilet, bathroom etc.). Replacement fresh air is allowed into the spaces by vent grills or fanlight windows etc. In really modern houses, a VCM also includes a heat exchanger and ducting to bring in fresh air to replace the air exhausted. The heat exchanger removes the heat from the outgoing air and transfers it to the incoming fresh air. These are complicated systems with ducts to and from the rooms that are being vented. These systems may even have a humidity sensor or some other control system to operate automatically. Old stone houses have always been built to allow the walls to breath and if the house gets refurbished with modern insulation and placo everywhere, then one should take into account the requirement to have air spaces between the insulation and the wall that allows air to circulate, forced ventilation is not normally required for this. There you go. That's my pennothworth, pick the bones out of that.
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suein56
Member
Southern Morbihan 56 Brittany
Posts: 7,963
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Post by suein56 on Jan 2, 2023 12:10:10 GMT 1
You may find that switching from 1 to 2 just changes the speed of the inbuilt fan. They should be installed so that they cannot be turned off - except by cutting power at the electricity circuit board (tableau). As for maintenance, ours is installed in a place that is completely inaccessible so has received no maintenance in 15 years.Ditto here .. we can see (and hear) our vmc unit in the loft but there is no way we can get to it. We've been here 10 years - it was the previous owners who had the house built in 2003 .. no idea if they ever had it 'serviced', we haven't.
In the house we rented when we first arrived in this area we also had a vmc - it worked fine. That house had been built in 1995 and I am fairly sure that no-one had looked at the vmc since. It was on permanently - summer and winter.
Can only agree with exile that the only way to switch off either of our vmcs was to completely cut the power at the tableau.
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VMCs
Jan 2, 2023 12:56:25 GMT 1
Post by annabellespapa on Jan 2, 2023 12:56:25 GMT 1
I was told almost 20 years ago by an Estate Agent that VMC's were intoduced as most French houses have larger windows on the front of the house and historically south facing to gain maximum light and heat through the glass, on the rear of the property would be smaller windows if any and that is where the stale air gathers and causes infections, VMC's were introduced to move the air in the property to take out stale, maybe infected air.
In Brittany where it was mainly farming back in the day, peasants would literally put themselves to bed after all the crops were in around Autumn and come out of their houses in early spring, it is believed their metabolism would naturally slow down and they could survive the winter on minimal food, very similar to the mediterranean diet but the problem was that whole families would share a bed and any illness would spread quickly. We had a house with a barn but it was actually the peasant quarters on the farm, it had a chimney plus either side of the chimney were window like holes in the wall were the animals were next door and the heat from the animals would contribute to heating the house, from that you can see that animal illness and human illness went back and forth.
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Aardvark
Non-gamer
Living in soggy 22 and still wondering what's going on.
Posts: 2,173
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VMCs
Jan 2, 2023 13:05:48 GMT 1
Post by Aardvark on Jan 2, 2023 13:05:48 GMT 1
Our Breton palace only has two medium sized windows, both facing East. I often wonder about the intelligence of the original builders.
When I renovated began to renovate this place the logical area to build a shower room had no window so some sort of ventilation was imperative. I bought a unit from Screwfix that combined a shower extraction fan with a halogen downlighter. Mounted above the shower space it provides good light and sucks most of the damp air up and out. The tiled areas and walls never get damp, only the mirrors occasionally. It is manually switched on when using the shower or toilet and when switched off it continues to run for anything up to half an hour (adjustable). It's also useful for extracting odours after using the toilet. A full VMC system would have been a nightmare to install and costly but tempting if it was the type that senses humidity and switches off once below a certain level.
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VMCs
Jan 2, 2023 13:28:59 GMT 1
Post by woolybanana on Jan 2, 2023 13:28:59 GMT 1
The problem with VMCs is that they suck warm air out of the house and replace it with cold, thus increasing your heating bills. My policy is to run the VMC part time and definitely not when the weather is very cold.
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VMCs
Jan 2, 2023 16:19:42 GMT 1
Post by houpla on Jan 2, 2023 16:19:42 GMT 1
Not all VMCs, as mentioned above. The 'double' versions extract heat from the stale air and it's recycled to warm the incoming fresh air. As per sue and exile, ours was fitted 15 years ago and has run ever since without any problem. We were specifically told by the electrician to leave it running 24/7/12
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Aardvark
Non-gamer
Living in soggy 22 and still wondering what's going on.
Posts: 2,173
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VMCs
Jan 2, 2023 17:06:51 GMT 1
Post by Aardvark on Jan 2, 2023 17:06:51 GMT 1
The problem with VMCs is that they suck warm air out of the house and replace it with cold, thus increasing your heating bills. My policy is to run the VMC part time and definitely not when the weather is very cold. Understandable but that is exactlly the time it is most needed.
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VMCs
Jan 2, 2023 19:25:50 GMT 1
Post by pcpa on Jan 2, 2023 19:25:50 GMT 1
check that nothing is touching it or blocking it, e.g insulation as they can overheat and catch fire, That simply is not true, did the Estate agent tell you that? You can stall the fan and the windings will not even overheat, thats exactly what happened to all of mine after 18 months because of the crappy motor run capacitors that were fitted, all replaced at a cost of €1.50 each, I was unlucky with the cheapest Brico-depot ones 15 years ago, for most other people they just go on working reliably for ever as people have attested. You could bury the thing inside a roll of 20cm insulation and block the inlets and outlets and it would barely be warm to the touch, these things use between 12 and 20 watts on the slow speed and unlike an LED light produce precious little heat, the energy goes into rotating the fan.
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VMCs
Jan 2, 2023 19:34:05 GMT 1
Post by pcpa on Jan 2, 2023 19:34:05 GMT 1
The units available from the brico are mostly only extraction fans, having them on permanently seems pointless and can best be started by a proximity sensor in the space to be vented (toilet, bathroom etc.). Absolutely not, they must be left on the low speed 24/7, they consume a fraction of the power that an extractor fan does and your advice regarding switching them would be valid for a noisy powerful traditional extractor fan but not a VMC, VMC's move a much smaller volume of air for a given time. The hygroreglable ones (2nd speed switches on detecting an adjustable humidity threshold) seem like a good idea in principle but if you set them low enough to be triggered by a shower etc then they will switch on to the high speed for hours on end on a day that is apparently humid but seems quite dry and sunny to me, I have my VMC switching to the higher speed for a timed period after I have switched off the bathroom light, others may prefer it to go on on entry so the noise will mask any percussion
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