[Tfug] *Way* OT: Swamp coolers, ACbrrs, etc.

[Adrian]

On Wednesday 20 June 2007 17:28, Bexley Hall wrote:
> 
> --- Adrian <choprboy at dakotacom.net> wrote:
> 
> > Well now.... I would go out on a limb and say that,
> > until the humidity exceeds 
> > ~75% (WAG), a swamp cooler will ALWAYS be more
> > efficient than an AC unit. Now 
> > notice... I said more efficient, not more
> > comfortable...
> 
> *assuming* the cooler can actually *get* to the
> desired "indoor temperature"...
>

Bah.... silly details....


> > The power used by the circulation fan in both cases
> > is approximately the same. 
> 
> In our case, the cooler fan draws considerably
> more power than the ACbrrr... it moves two or three
> times the volume of air that the furnace does
> (air conditioning is designed for low velocity
> delivery of air).  E.g., cooler motor is 1HP.
> I suspect the furnace is 1/3 or smaller (I will
> check tonight -- I took some power readings earlier
> and will run all the math later)
>

Both furnaces and swamp coolers typically have multiple fan speeds. Furnaces 
(modern ones at least) will use a variable speed drive or VFD. Swamp cooler 
motor typically have 2 sets of coils, connected in series for low speed, 
connected in parallel for high speed. I assumed the former as i always run 
mine on low speed, seems to cool better.

> > Swamp -
> >   Fan 120V*2.5A = 300W
> >   Pump 120V*0.25A = 30W
> >   40% duty cycle == 3.2kWh/day
> 
> I'd disagree with the duty cycle assessment -- esp.
> at this time of year.  Ours runs full out to maintain
> an indoor temperature of ~78-80.  Note that swamp
> cooler can't "coast" as long as the ACbrrr -- because
> the windows are open

Well... I based my calc of current temperatures and my units performance. 
Currently it is running about 35min per hour during daylight and 15min per 
hour at night to maintain temperature. (I put in a digital thermostat which 
automatically turns the swamp cooler on and off, pre-wetting the pads). I 
only keep 1 bathroom window up high open... so hot air blowing in isn;t a 
problem.

Adrian