Multiple fans off one isolator

[aj_london]

Hi folks,

Homeowner here. I'm in the planning stage of a project, seeking advice from professionals.

I need to upgrade the ventilation in my home following advice from a surveyor. The plan is to replace my one bathroom fan with two fans (one shower extractor and one MVHR unit). In addition, I need to add a MVHR fan to my dining room.

The isolator for the existing bathroom fan is just outside the bathroom. Would it be acceptable to have all three fans coming off this one isolator, despite the fact it would be controlling devices in different rooms?

This would be achieved by taking the existing bathroom fan feed (with switched and perm live) and splitting it into three with a junction box. Two of the split feeds would stay in the bathroom. The third one would go outside the house (via whiska boxes and conduit) and back into the dining room a few meters away.

The thinking here is to be minimally invasive in terms of messing up my freshly decorated interior, and take advantage of the fact that we are punching some big holes right through the wall anyway, so it's not that onerous to route cables via the outside.

Thanks in advance for your advice!

 

[Mike Johnson]

So the heat recovered would be vented straight back into the room the air was taken from, is this what you want?

Isolation switch's can be located in a bathroom if they are above 2.25M high, would seem preferable to running cables outside the building.

 

[aj_london]

So the heat recovered would be vented straight back into the room the air was taken from, is this what you want?

Isolation switch's can be located in a bathroom if they are above 2.25M high, would seem preferable to running cables outside the building.

Such is the way these single room MVHR units work. It's either that or just install an MEV. Some heat recovery seems like a decent idea, in order to keep the room warm and therefore keep the dew point as high as possible.

 

[brianmoooore]

Isolation switch's can be located in a bathroom if they are above 2.25M high

This only applies in the zones (1 and 2). Anywhere else in the bathroom they can be at any height, or they can be mounted immediately outside the door.

 

[Mike Johnson]

Europe is way ahead of us on this subject using multi ducted domestic systems of heat recovery, unfortunately not very viable in a flat without a false ceiling to accommodate the return ducting see this French system: https://www.leroymerlin.fr/v3/searc...pleted=true&keyword=vmc double flux connectée

 

[Mike Johnson]

This only applies in the zones (1 and 2). Anywhere else in the bathroom they can be at any height, or they can be mounted immediately outside the door.

If you want them at all, or put all the fans on one MCB in the CU, but being in the UK we tend to just join onto the lighting circuit (hence our wont for isolators) for the fan power and put in an inline fuse.

 

[aj_london]

This only applies in the zones (1 and 2). Anywhere else in the bathroom they can be at any height, or they can be mounted immediately outside the door.

Great to know. Per my previous question, is it a violation of any regulation to have the isolator in a different room? I realise it's unorthodox, but curious to understand if it's actually "wrong", if you see what I mean.

 

[Lucien Nunes]

There isn't a reg that specifically says you can't run three fans from one isolator, but there is a reg that says suitable isolation means shall be provided for maintenance. The problem with not having an isolator is that because many fans are installed in windowless bathrooms, people would be tempted to clean the fan while running (to keep the light on) or run a table lamp on an extension lead etc. The isolator allows the fan to be off for cleaning while the light is on. If your isolator is reasonably close to all the fans I would consider it acceptable to run all three from it, however as suggested by @brianmoooore I would put an additional isolator inline with the MVHR unit located directly adjacent to it, so that it can be serviced while the other two remain active.

 

[aj_london]

There isn't a reg that specifically says you can't run three fans from one isolator, but there is a reg that says suitable isolation means shall be provided for maintenance. The problem with not having an isolator is that because many fans are installed in windowless bathrooms, people would be tempted to clean the fan while running (to keep the light on) or run a table lamp on an extension lead etc. The isolator allows the fan to be off for cleaning while the light is on. If your isolator is reasonably close to all the fans I would consider it acceptable to run all three from it, however as suggested by @brianmoooore I would put an additional isolator inline with the MVHR unit located directly adjacent to it, so that it can be serviced while the other two remain active.

Understood.

Many thanks to all three of you for your help, it's much appreciated!