Heating and cooling options

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Re: Heating and cooling options

Postby Smurf1976 » Sun Dec 28, 2014 10:29 pm

Easiest way to get your mind around motors etc is to take it back to basic principles.

If there's 1, 2 or however many kW going in then it must also be coming out somewhere either as mechanical power or heat. If it wasn't coming out, the motor's speed would necessarily increase until the whole thing flies apart (the energy must go somewhere).

A 2HP free spinning motor under no load - so it's not producing much mechanical power. And it's not going to be putting out 1+ kW of heat either. Therefore it doesn't need 1.5kW to run it.

Obviously this is very heavily simplified as an explanation. But if there's energy going IN to a device then it must also be coming OUT in some (usually different) form be it mechanical power, sound, light, heat or whatever.
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Re: Heating and cooling options

Postby Cherokee Solar » Mon Dec 29, 2014 8:18 am

Hi James, Gordon and Smurf,

Many thanks for the explanations. That makes sense. I hadn't thought about it that way before.

Nice to hear about the low current draw on those AC units. That is actually remarkably low and would barely register 20A at about 25V here at night. Still, it does add up over a few hours.

I assume there is no massive start up current draw on those AC compressors? Do they connect into a standard mains house circuit or do they require their own circuit?

Gordon: I hope you received some of the recent heavy rains up your way?

James: The unit is a CC3300 chipper chopper which I picked up on eBay second hand for $55. Apparently it didn't work very well - but that was only because they didn't know that the blades had to be sharpened. Occasionally I'm embarrassed for my fellow humans. :lol: On a serious note, the trick with the unit - after much experimentation - is to feed the leaves in first followed by the branch. This is counter intuitive but feeding branches in first puts the blades under load which slows the unit and the leaves then possibly clog the blades. Feeding the branches in leaves first means that the woody material from the branches clears the blades just when they need to. Hope that makes sense. ;)

Smurf: How did your Christmas lights go this year?
Off grid solar + hot water. Heavily insulated + owner built flamezone house BAL-FZ. 300 mixed fruit trees + herbs + flowers + vegetables. Bees + heritage chickens. High up in the mountains north of Melbourne. http://ferngladefarm.blogspot.com.au/
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Re: Heating and cooling options

Postby Smurf1976 » Mon Dec 29, 2014 9:11 am

Cherokee Solar wrote:I assume there is no massive start up current draw on those AC compressors? Do they connect into a standard mains house circuit or do they require their own circuit?


Modern one (inverter driven) doesn't have the huge start up current that the old (non-inverter) units did. It basically just starts with a "normal" load electrically or very close to it.

In the case of grid power, it's fairly common to run a separate circuit for A/C (effectively a legal requirement in Tasmania for residential installations unless you don't want the 40% discount on power used, optional elsewhere) but in practice there's no technical reason why it couldn't simply be plugged in given the load. Obviously just plugging it in has some aesthetic issues compared to a hard wired install with no visible cables.

Smurf: How did your Christmas lights go this year?


Going nicely, chewing through the power and keeping people entertained. Only one mishap so far, wallaby ran into a stake and snapped it off at the base. :( Will have to glue it back together for next year. Wallaby seems unharmed.

I've already got more for next year and more to order. The new stuff is generally LED and uses a ridiculously small amount of power compared to the old incandescents. Replaced a long rope light (30m) this year due to failure. Old one drew over 420W at 240V, new one 12W running via a small plug pack transformer and it's just as bright. That said, a box of 60W incandescent blue bulbs arrived just before Christmas..... :D

Side note that the possum which goes along the back fence likes the red ones. Not sure why, but he/she seems rather fond of them. Often see it sitting next to one of the lights, always a red one.
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Re: Heating and cooling options

Postby mkitch » Mon Dec 29, 2014 8:07 pm

Presumably the possum knows that red light does not destroy your night vision :geek: Any comment Gordon?
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Re: Heating and cooling options

Postby Gordon-Loomberah » Mon Dec 29, 2014 8:15 pm

The story that you have to use a red light to preserve your night vision is a bit of a furphy, the reality is that dim lights of any colour work just as well.
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
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Re: Heating and cooling options

Postby Cherokee Solar » Wed Dec 31, 2014 8:17 am

Hi Smurf,

Many thanks for the information about A/C inverters. Certainly something to think about and the weather over Friday and Saturday is getting up into 38'C here.

Smurf1976 wrote:Only one mishap so far, wallaby ran into a stake and snapped it off at the base. :(


Pah, wallabies are nice to have around but mate, they are without doubt the biggest vandals! :lol:

Very occassionally I find them sitting in the raised vegetable beds here happily munching on the choicest selections and squashing the rest.

Great to here about the LED's and I would have liked to have seen that. They are really frugal. I run a whole lot of 12V G4 warm LED bollard garden lights here at night and they use so little energy that it is barely noticeable. The regulator turns them on at night when it senses that there is no energy at all coming from the solar panels (< 1V).

I don't get possums here because the owls consistently eat them. Possums could potentially eat the entire orchard in no time at all... :shock:
Off grid solar + hot water. Heavily insulated + owner built flamezone house BAL-FZ. 300 mixed fruit trees + herbs + flowers + vegetables. Bees + heritage chickens. High up in the mountains north of Melbourne. http://ferngladefarm.blogspot.com.au/
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