Pool heat pump - How many BTUs?

[Edward Reid]

that cold down here for that kind of thing, I would think.

The ground temperature in Florida is around 70F. That is the temperature of all those beautiful Florida springs. You want your pool quite a bit warmer than that. Water and concrete conduct heat well -- not like metal but well enough for insulation to make a big difference.

In the long run, the installation cost of solar (with virtually no operating cost) is tiny compared with the operating cost of a heat pump, so it's worth doing even if you do the heat pump also. Every bit of heat added by the sun doesn't have to be added by the heat pump. And you say tile -- if you have a concrete tile roof, then you should not be worrying about the weight of the solar heat system, which does not have much water in it at any given time. Just make sure to use a reputable installer so they don't damage the tile.

The larger unit will run less, but when you buy electricity, you pay for energy used. Energy = power times time. You have a power rat Edward

[Edward Reid]

If a 240V device is connected to a neutral, then there's an electrician whose license needs to be revoked. Retroactively.

What's usually called single phase is really two-phase -- two phases

180 degrees apart. Three-phase has the phases 120 degrees apart. Two phase is fine for balancing. You really only need three-phase for certain kinds of electric motors, which for obvious reasons aren't put in appliances destined for residential use.

With either 2-phase or 3-phase, appliances which need 120V are attached to one phase and a neutral. With 2-phase, appliances which need 240V are attached to both phases. With 3-phase, appliances which need 208V are attached to any two phases (dig out your trigonometry to figure out where the 208V comes from). Three-phase motors are more complicated ...

Edward

[trader4]

t get that cold down here for that kind of thing, I would think.

Agree with everything you say, except the power output/input ratio. No way you can get 20X the energy out of a heat pump that goes into it. Something like 4X is more like it. If you got anywhere near that amount of heat, everyone would be using one instead of gas, oil, etc.

[krw]

Are ovens and clothes dryers 240V? Every modern installation has a neutral.

Wrong. It's really a single split phase.

Completely wrong. Three phase isn't put in appliances for residential use because three phase isn't installed in residences in the US. In many places it's not even available at the street in residential neighborhoods.

Wrong. Don't give up your day job.

[Edward Reid]

The ratios I gave were BTUs/hour over watts. I didn't bother with the conversion factor to make it a real output/input ratio (for example watts out over watts in) because the only point was to compare the two units.

Thanks for reading carefully!

Edward

[trader4]

That is what it's called in terms of power distribution, but he is correct that it can be viewed as two phases. Graph the waveforms of the two hots and you clearly have two different voltage waveforms present, with one 180deg off from the other. Graph a 3 phase and you have 3 seperate waveforms, off by 120deg.

Sure 3 phase isn't available in homes. But even if it was, as he correctly points out, there is no need for it with small, cheap fractional horsepower motors like found in home appliances.

[Ralph Mowery]

Another US power pissing contest.

The normal home service of 240 volts is single phase with a center tap. There are actually some real 2 phase systems, but not in most of the homes.

I would like to see how one plans on hooking up a 3 phase 208 volt appliance to only two of the phases of a 3 phase system..

In areas that do have 3 phase 208 volt systems, it is easy to get 120 volts. That is from one of the phases to a center of a Y network. Same as you get

277 volts single phase from a 480 volt 3 phase system that is common in large plants.

[JoeBro]

[e-mail] wrote in news: [e-mail]:

Completely wrong. Stick to jerking off and leave the electrical to guys who know about it.

[Edward Reid]

Yes, they are 240V. (At least in the US. My comments apply to the US. All these can be built for 120V, or for 12V or for 1200V, but 240V is a good compromise for minimizing the wire diameter needed and minimizing the risk from high voltage in a residence.)

Most ovens and dryers will have a neutral run to them, but that's because they are multiple appliances in a single box. Specifically, they are a light bulb, a heating element, an electronic controller (in modern units), and in many cases a fan. The heating element is 240V and is not attached to the neutral. The light bulb is 120V and is attached to the neutral and one of the hot legs. Fans may vary but will be one of the two. The neutral is not used for the 240V part.

The compressor side of a split system A/C, or a package unit A/C or heat pump, may well have only the two hot legs and no neutral. It contains only the compressor and probably a heat exchanger fan, and these can both be 240V. It might contain electronics, but the electronics are fed through a step-down transformer within the unit anyway.

In all of these cases the major load -- the heating element for ovens and dryers, the compressor and probably the heat exchanger fan in A/C compressors -- uses the two hot legs and not the neutral, and thus is incapable of causing an imbalance, which was the comment I was responding to.

Edward

[gfretwell]

With a capacitor? In fact you can run a 3p motor on single phase with a capacitor.

[Edward Reid]

All true. However, based on the OP's posted numbers, the larger unit is slightly more efficient, roughly 6% more efficient. But that doesn't change what you say -- running for less time isn't a savings in and of itself.

Edward

[krw]

If you don't like facts, please don't confuse others with your bullshit.

Show me one.

Three phase? All three present. Easy, a rotary phase converter (AKA

3-phase motor).

Such are the shifting goal posts...

[krw]

Idiot. I am an EE.

[krw]

True but irrelevant.

True but irrelevant. They *are*.

True, but also irrelevant.

Did you have a point?

[Edward Reid]

A point? This is Usenet. Wash your mouth out with soap. ;-)

Edward

[JoeBro]

[e-mail] wrote in news: [e-mail]:

Well then, you are an idiot EE. There are lots of them in that field.