I have a new bathroom extractor fan, its timer is set by default to continue to run for 35min when turned off. This feels long and it’s a small bathroom, is there a way to calculate how long an extractor fan should run based on the room size?
How long for extractor fan timer?
- Thread starter mxo
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Size of bathroom and bath or shower migt help the boys.
15minutes tops.
This assumes there is adequate spaces for air to enter the room, or the d as n will not extract efficiently.
This assumes there is adequate spaces for air to enter the room, or the d as n will not extract efficiently.
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I seem to remember it is in one of the parts of the building regulations, seem to remember 15 minutes.
Much will depend upon how much air the fan actually shifts when it's running.
Your room is 2m x 2m x 2.5m = 10m3.
An extractor fan rated at 90m3/hour would change the air in the room 9 times an hour. Personally I aim for 3 to 4 changes of air which in your case works out at approx. 25 minutes.
An extractor fan rated at 120m3/hour would change the air in the room 12 times an hour, which works out at approx. 20 minutes.
This assumes that the location of the fan is correct though. It needs to establish a flow of air across the room, so ideally the fan should be located diagonally opposite to source of the replacement air; usually the door. [make sure the door doesn't fit too tightly to restrict air flow] If the fan is located directly at the side of the door the majority of the room won't benefit from a direct flow of air, so it would need to run for longer.
You may also want to consider:
1. How much steam is produced: Showers produce more steam than a bath & some people shower for 2 minutes others for 10.
2. If you have towels drying on a towel warmer, that moist air will continue to be produced after the room is vacated and so you might want to leave the fan running for longer.
3. If the bathroom is heated. Warm air carries more moisture than cool air. Meaning that more moisture will be extracted in less time when the air is warmer. Also there will be more condensation to get rid of, if the fabric of the room is cooler and allows more condensation to form.
Your room is 2m x 2m x 2.5m = 10m3.
An extractor fan rated at 90m3/hour would change the air in the room 9 times an hour. Personally I aim for 3 to 4 changes of air which in your case works out at approx. 25 minutes.
An extractor fan rated at 120m3/hour would change the air in the room 12 times an hour, which works out at approx. 20 minutes.
This assumes that the location of the fan is correct though. It needs to establish a flow of air across the room, so ideally the fan should be located diagonally opposite to source of the replacement air; usually the door. [make sure the door doesn't fit too tightly to restrict air flow] If the fan is located directly at the side of the door the majority of the room won't benefit from a direct flow of air, so it would need to run for longer.
You may also want to consider:
1. How much steam is produced: Showers produce more steam than a bath & some people shower for 2 minutes others for 10.
2. If you have towels drying on a towel warmer, that moist air will continue to be produced after the room is vacated and so you might want to leave the fan running for longer.
3. If the bathroom is heated. Warm air carries more moisture than cool air. Meaning that more moisture will be extracted in less time when the air is warmer. Also there will be more condensation to get rid of, if the fabric of the room is cooler and allows more condensation to form.
You could try a shorter time [he says wearing his energy saving hat 
] and see what happens. If you aren't left with a fresh dry bathroom you could always put it back. Assuming your fan has an adjustment facility.
] and see what happens. If you aren't left with a fresh dry bathroom you could always put it back. Assuming your fan has an adjustment facility.some fans have an adjustable run time. there might be a small circuit board inside with an adjuster on it
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I had thought the bit about working with light switch had been removed, seems I was wrong, so if natural light must be able to switch on without the lights, I remember @ban-all-sheds saying about use of double pole switches so a push switch could be included as well, but thought dropped when we went onto LED lighting.The merged approved documents England Page 22 ventilation said:
as a rule of thumb. you might try 20 mins and see how it goes. it is only a rule of thumb though
If you have a modern fan with a ball-bearing motor and rubber mounts, that is practically inaudible, I would leave it running long enough to clear a steamy bathroom on a cold frosty night.
If you have a noisy old fan that is an annoying nuisance, throw it away and buy one as above.
If you have a noisy old fan that is an annoying nuisance, throw it away and buy one as above.
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