Energy – calculation

[Speedy Builder5Participant @speedybuilder5]

If I install a Trickle flow bathroom fan which consumes the following:-

Wattage: 1W at lowest trickle speed – 8.3W at highest extraction speed

Ignoring when the fan is working at full power, how many kilowatts will it consume per year in trickle mode.

Is it just 1000/ 365 x 24= 0.12Kwh

Bob

[Clive Brown 1Participant @clivebrown1]

1 year (non-leap) = 8760 hrs. Therefore annual energy consumption @ 1 watt continuous is 8.76 kWh.

[Michael GilliganParticipant @michaelgilligan61133]

I would express it as

… but I’m very tired at the moment, so might have done something daft.

MichaelG.

.

Edit: __ <phew> Clive got the same answer.

[John HaineParticipant @johnhaine32865]

The clue is that the fan consumes 1 watt, which is power, or 1/1000 kW.  Energy consumption is then the integral of this, so the fan consumes 1/1000 kilowatt-hour, multiply by hours/year to get annual consumption.

[Speedy Builder5Participant @speedybuilder5]

Thank you.  1 Kwh has an average price of £0.25 or about £2.25 per year.  That doesn’t seem too much to fork out.

Background to my request is that I have a tenanted flat where the bathroom has been allowed to develop mould. That has been treated with “Mould stop” to little effect.

The bathroom window is left open ajar as confirmed by the letting agent but still the mould has returned. I think the problem is that there is no through draft. There is an extractor fan that comes on when the light is on plus a delay after but that has not solved the problem. I guess the tenant is resistant to leaving the bathroom door open especially in winter!

The suggestion is to install a fan with humidity control and Trickle mode for constant air movement, but I needed to show the tenant that having the fan on Trickle would not significantly be a burden on the electricity bill.

Bob

[duncan webster 1Participant @duncanwebster1]

Put a vent in the door to allow some flow, then hope the tenant doesn’t block it off

[not done it yetParticipant @notdoneityet]

I doubt 1W will solve your problem.  The room needs to be dried out as well as kept ventilated.  A cold and damp room is more likely your problem.

[JasonBModerator @jasonb]

That is why the fan has a humidistat. It will run faster to remove moisture above a certain level and then revert to trickle mode the rest of the time.

Bear in mind that the low wattage fans quoted flow figures are with zero restriction. So keep any ducting to a minimum, don’t use the flap type back draft shutters and ideally have some way for fresh air to enter so they are not pulling a vacuum. If it is the one I think it is then the constant flow metering will increase the wattage to meed that flow if there are restrictions so you may not be running at 1w

[not done it yet]

On not done it yet Said:

I doubt 1W will solve your problem.  The room needs to be dried out as well as kept ventilated.  A cold and damp room is more likely your problem.

Always best to identify root-cause if possible, but it may not help!   A friend and wife lived in a house for 25 years without any problem in the bathroom before emigrating.   Not sure he wouldn’t be coming back to the UK, he decided to let the house for 3 years. Went well abroad, so he returned to the UK to sell the house.  In good order throughout, except the bathroom was very mouldy and damp-damaged.   Seems the tenants, a husband and wife of his age, both enjoyed two long hot showers a day, hated cold, and never opened a window!

Tenant behaviour was the problem.  I shower as quickly as needed to get the worst off.   My children luxuriate under under the shower, generating far more steamy damp than I do.

The easiest way to dry out a bathroom is to ventilate it.   Keeping it warm is expensive and, unless the wet air is ejected, it will still cause condensation.  Jason’s advice makes a lot of sense to me:  a trickle fan with a free-flowing vent, that runs fast whenever it detects high-humidity.

Dave

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