Home Automation Technique

I was assuming the space was a cellar and the air had to be lifted out. Less work done by the fan shifting air sideways from an under-croft, but the principle is the same: how much air will be shifted in a given time by a motor of a certain power. I don't think fresh air coming in alters the sums because the replacement air does no work.

An equivalent way of ventilating the space is with a fire.

The fire and chimney are a heat engine that lifts damp air up the chimney which is replaced by fresh-air at the undercroft's entrance. As the heat engine obeys the same physical laws as the electric fan it's possible to calculate how much fuel (energy) is needed to remove a volume of air in a given time. Incoming fresh air doesn't alter the amount of work done by the fire either. I hope!

Dave

Edited By SillyOldDuffer on 11/10/2020 13:37:34

Dave, the incoming air does work against atmospheric pressure, which is in balance, so the outgoing air floats in the in-coming. Its more like moving a counter-weighted lift than moving the load on its own.

Its really a viscous flow problem, not a potential energy one. It would be interesting to know if your answer is anywhere near correct, it could make a good rule of thumb.

Great point Speedy Builder 5. The problem of moisture-laden air entering cold properties is a common one in historic monuments and can cause mould. The solution of drying incoming air (Air conditioning) is getting popular where budgets allow.

The solution?

My son assures me that the Samsung SmartThings Hub will let me program my needs with user defined variables and loops and if thens so that's the way I'm going with wifi sensors and a wifi power switch.

When I get into the new house and have this automatic fan running I'll try to remember to post an addendum here. (If it's not running then it's a lot less likely that I'll post.)

Cheers, Colin

Glad you're sorted out Colin. I'm still in disarray due to Roger's comments. Yesterday I proved conclusively to myself that Roger is wrong, only to realise my counter-argument was fallacious. Too many things making my brain hurt at the moment!

Dave