DIYbanter - View Single Post

Art Todesco

On 9/18/2012 11:14 AM, zzzzzzzzzz wrote:
On Tue, 18 Sep 2012 06:26:59 -0700 (PDT), "
wrote:

On Sep 17, 1:28 pm, "
wrote:

Let's see. You get 3.413 BTU per watt hour of electricity for
resistance heat. For the outside unit, that comes to about 1630 watts
or 5570 BTUs if you put the power into a resistor instead of the
compressor and fan. Plus you have the add the indoor fan. And, I know,
I didn't add anything for power factor. But, it shows that you are
almost getting the same amount of heat as you would if it were a
resistive heater.- Hide quoted text -

- Show quoted text -

You didn't document the numbers you were using, but I
don't believe the analysis is correct. Any heat pump
system is going to give you a lot more heat out than
a resistive heater, 2 to 4 times as much depending on
the design, temps, etc.

His analysis is correct, as I understand the data.

His "analysis" doesn't make any sense. He doesn't
even make it clear which heat pump unit he's talking
about so we can see what numbers he's using.

His bottom line is that he is saying that with a heat pump
you get about the same amount of heat as you would with
a resistive heating element that consumes equal electricity.

At some low temperature, yes.

Why do you think people bother with heat pumps at all
if you get about the same amount of heat from a resistance
heater? Everyone would just use a cheaper resistance heater
where ALL the heat would go into the house.

Good Lord! Read!

Obviously What's missing here is
that not all of the heat is useful. Some of it is created by the outside unit
so doesn't contribute.

Obviously what is missing here is that you are wrong.

Nope, but it wouldn't be the first time you've been completely wrong.
Illiteracy will do that.

OK so according to the two of you,

I've noticed that whenever you say the above, you're lying.

the total heat generated by a heat pump is about the same as a resistance heater
that uses an equivalent amount of electricity.

Yep. You're lying again.

And according
to you, some of that heat doesn't make it into the house with
a heat pump because it's lost outside.

No, some of it is "generated" outside.

Therefore, a heat pump
system would produce LESS heat into the house than a
resistance heater?

If some is outside (it is), at some (low) temperature, certainly. As the
efficiency of the system goes down, at some point the gain from pumping is
offset by the energy dissipated (uselessly) outside. At that point the heat
pump costs exactly the same as resistive heat, to operate.

Not in my world of physics. Nor in the world where you see
heat pumps used because they deliver a lot more heat for
the same electricity usage as a resistance heater.

Idiot. As the temperature goes down, the efficiency goes down (at some point
it stops working altogether) and the energy hill gets higher. Somewhere along
the line the unit can no longer push heat up the hill. If there is heat lost
outside (there is), the unit is no longer putting out more heat than the
electricity it's consuming (total inside and out - both cost the same $$).

As noted (by everyone here) the efficiency of a heat
pump goes down with rising delta-T.

At some point the "heat pumped" = "wasted
heat", so resistive heat would be equally as efficient.

If they only produced heating
similar to resistive heating, you wouldn't see them used
and you wouldn't have folks bitching about the high
electric bill that occurs when they go to resistive heat
mode.

No, resistive heat is still 2-3x the cost of heat from a heat pump.

Now, why on earth would that be?

Are you really that stupid? If a heat pump moves twice as much heat as it
uses, it costs 1/2 to 1/3 as much as resistive heat (resistive heat costs 2-3x
more).

You agree

There's that lie tell, again.

with the
faulty analysis that says the heat pump only generates
heat about equivalent to a resistive heater.

Yep. At some point, resistive heat will be on par with a heat pump. Gotta
be.

And you say the
other issue is that with the heat pump, some of that heat is also
lost outside. So, how could resistive heat cost 2 -3X as
much?

You really are that stupid. Amazing.

Now go ahead, instead of admitting you made a mistake, double
down and as usual start with the name calling.

I made no mistake. You're simply too stupid to read. ...or think.

Ok, here's some explanation on my earlier post. The BTUs/KWHr (3.413)
came from the internet, which seems about right. The average 1500 watt
electric heater is usually in listed (if you can find it) at about 5K
BTUs. The numbers for the heat pump came from the manufacturer's sheet
posted earlier in this thread, for 17 degrees outdoor air temp. Sorry I
missed the part about "at 17 degrees." Now, if the outside air is 45
degrees, you'd see much bigger BTU numbers. And, of course, that's why
we use heat pumps. But at 17 degrees, the inside are will probably feel
cold, even though there is some heat being added.