OK, that part I agree with. A 1500 watt electric heater
would give you 5100 BTU.
>The numbers for the heat pump came from the manufacturer's sheet
The numbers for what and from where? There are
multiple units listed with multiple specs for each.
It would be helpful if you could
specify what table entry you are using and for which
model. Let's look at the specs for the MSZ-GE09NA
which are on page 12 of the brochure:
At 17F it states:
Rated Capacity: 6600BTU
Rated Total Input: 700W
A 700W resistance heater would generate
700 x 3.41 = 2387 BTU
The heat pump is generating 6600 BTU
Meaning the heat pump is generating 2.7 times
more heat at 17F outside temp than you would get
with a resistance heater using the same amount
From the same specs, it gives the capacity at 47F as
10,900 BTU. The capacity at 17F is 6,600 which
means you're still getting 60% of the heat that you get
Now the part that I don't understand is the graph earlier in
the brochure that shows capacity staying constant all the
way down to 10F. I think we agree that sounds like marketing
BS of some kind, given that it does not have resistive heating.
On Sep 18, 11:14 am, " firstname.lastname@example.org"
There we have it folks. The usual KRW tactic. Try to now
change the discussion into something else. Art stated:
" But, it shows that you are almost getting the same amount
of heat as you would if it were a resistive heater. "
There was no qualification of temperature. Now, having been
wrong, just as I predicted, you try to weasel away by now
adding "at some low temperatures" into it.
Perhaps you should look at the data sheet for the Mitsubishi units
under discussion instead of embarrasing yourself further. Per the
analysis I showed in my last reply to Art,
at 17F, the MSZ-GE09NA is producing 2.7 times the heat that you
would get from a resistance heater. That's pretty impressive
performance in cold temps.
And it sure doesn't jive with:
"" But, it shows that you are almost getting the same amount
of heat as you would if it were a resistive heater. "
YOU are the one that agreed with the analysis that the
heat pump only generates about as much heat as an
equivalent resistance heater. YOU were agreeing that it
only moves the same amount of heat as it uses.
Now of course, you're trying to weasle away, by
adding "at some low temps" At 17F it's still generating
2.7 times the heat you'd get from a resistance heater.
Even at 5F it's still generating far more heat than a
And as predicted, instead of being a man and admitting
your error, you've quickly resorted to name calling.
On Sep 18, 3:47 pm, " email@example.com"
Show me where Art gave a temp that his statment applied to.
Typically YOU would be the one to jump all over something like
that, because it's open ended, generally not true, and
meaningless without specifying what temps you are talking about.
He now says it was at 17F that his analysis was done.
Well, per the Mitstubishi data sheet, which you obviously have
not even bothered to read,
page 12, at 17F you get 2.7 times the heat output that you would
with a resistance heater. That is not about the same amount of
heat as a resistance heater, it's 2.7 times greater. Art made a
YOU agreed with the analysis which is TOTALLY WRONG and
instead of admit it, as usual, you start the name calling.
Try reading the datasheet instead of embarrassing yourself.
YOU agreed with a faulty analysis that didn't even mention
what temperature it applied to. Now in my world when someone
> >" But, it shows that you are almost getting the same amount
It's a very broad indictment of heat pumps. And what that
faulty analysis was based on, I still don't know because Art
didn't say what numbers he was using. You obviously
have not done any analysis. I did. And per the Mistubishi data
sheet specs, at 17F your're getting 2.7 times the heat out of
their heat pump unit than you do with a resistance heater.
Now for most people, 17F is a pretty cold climate. And
per the Mitusbishi brochure, it's still nowhere near a resistance
heater all the way down to 5F.
Where is here?
More to the point than having once seen it, what are the averages?
Certainly a modern properly sized air-exchange HP will handle into the
lower 30's w/ no problems. The one thing is that they will tend to have
longer recovery time as the exit air temp's will not approach those of
conventional furnace (or even a geothermal unit).
They certainly have improved even air-exchange but in very cold climates
either they use geothermal (ground loop/well/deep reservoir all
possibilities) or have a conventional backup.
We replaced an early air-exchange in E TN w/ geothermal and it was
night/day...this is almost 20 yr ago now and the original HP wasn't but
a cheap contractor-supplied unit in the late 70s when even the good
weren't doing all that well, anyway. But, TVA power was cheap then so
the resistance heaters weren't a big deal--probably 70% of heating in
the area was electric at the time. By the early 90s the HP was on last
legs and power rates were much higher and NG wasn't yet available so
went w/ the higher installation cost of digging the trench and never
regretted it while were still there. AFAIK the system is still
functional w/ no problems--saw the new owner just a couple of years ago
and he's also quite pleased.
It has a thermistor in-line w/ the aux heat that keeps them from being
able to come on above about 18-20F so the 'Emer Heat' logic doesn't try
to kick on if, for example, the house has been turned down and then come
home and reset to normal so the dT is large and it thinks it can't catch
up. Newer t-'stats may also have better logic to know the difference
between chronic failure to keep up and change in demand.
A side benefit of the geothermal was essentially free hot water in
summer using reject heat from the cooling cycle...replacing electric
water heater inputs is _a_good_thing_ (tm) in most places given rates...
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