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-----Original Message-----
From: Bill Dube via EV <>
To: ev <>
Cc: Bill Dube <>
Sent: Thu, Nov 30, 2017 01:16 PM
Subject: Re: [EVDL] Heat pump vs resistive Heater (never buy another AC unit)

The "mini split" type heat pumps and AC units that I have installed in 
my house have a single outside unit and multiple (2) inside units.

The inside units have a finned coil and a fan. The outside units have a 
finned coil, fan, compressor, and the control electronics. (They have 
variable frequency drives running _everything_.) The inside units 
typically mount near the ceiling on the wall.

Here is a link with pictures of a typical installation:
<a href=""; 

The ones with a high SEER rating are _unbelievably_ quiet. Less noise 
that a refrigerator. We often completely forget that they are on. Maybe 
45 dB with the fan set to maximum.

Typically, we set the fan speed to "automatic" so the fan speed varies 
with the demand on the system. The system slowly ramps up and down to 
meet the demand. All fans and the compressor are controlled by VFD's so 
nothing cycles on and off. You set the temperature on the remote and the 
system heats or cools to maintain that temperature in that room. The 
units each have there own remote and you can set the temperature of each 
room independently. (You can't set one room to heat and another to cool 
if the inside units share an outside unit.)

On the particular model we have, you can chose to set the temperature 
sensor on the remote, or on the wall unit, to control the wall unit. 
Thus, if you are working at your desk that is some distance from the 
wall unit, you set the remote to sense the temperature, and place the 
remote near you.

The high SEER demands that the temperature difference between the room 
and the finned coil be as low as practical. There is no reason to have 
120 F air coming out of the inside unit, unless you have set the desired 
room temperature that high. (I think the maximum room temperature set 
point is maybe 90 F.) The air coming out of the unit is maybe 5 or 10 
degrees different than the desired room temperature.

Folks that have these modern units absolutely love them. We bought one 
at first for the master bedroom and the office. After a year, we bought 
one for the other side of the house, and then bought one for the garage.

Bill D.

On 11/29/2017 10:13 PM, EVDL Administrator via EV wrote:
> On 29 Nov 2017 at 18:14, ROBERT via EV wrote:
>> A heat pump outputs a register temperature of approximately 90 F.  This
>> low a temperature blowing across your skin is not comfortable to a lot
>> a people.
> I think this is less true of recent heat pumps.
> I'd like to hear from someone who owns an EV with a heat pump -- how warm
> does the air from the vents feel in the winter?
> I think that many or most older heat pumps did have this annoyance.  It's
> not an EV, but I knew someone who had a late-1990s GSHP (Waterfurnace brand)
> at home.  The heating air from the vents always felt cool to me, meaning
> that it was below body temperature. Ninety deg F would be quite believeable.
> That's definitely not the case with my Mitsubishi mini-split from 2013.
> Although I haven't measured its outlet temperature in heating mode, most of
> the heating seasons it feels quite warm, almost hot.  So it has to be well
> above body temperature.  As the outdoor temperature falls, its outlet
> temperature declines too.  However, it stays noticeably above body
> temperature down to an outdoor temperature of around -15 deg C.
> Thus I see no reason that an EV heat pump would have to produce air that
> feels cool under most conditions.  For the times that it did, I'd expect it
> to have auxiliary resistive heat.
> David Roden - Akron, Ohio, USA
> EVDL Administrator
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