Robert, your method of putting fans near a radiator is something I had wanted to try. Really getting OT, here, so if people prefer, reply privately.

A couple years ago I had to replace my gas furnace. I looked into getting a heat pump system but it was not possible with the various constraints and payback period so I bought a new gas furnace :(


Anyway, one of the options I studied was to put in radiators instead of forced air. I would have run pex through the ducts to each register. One of the advantages of this kind of unit would have been space - no blowers, and I could have reclaimed return air duct space.

I didn't want surface mount radiators because of the space they take. It might have been possible, but not easy. Instead I wanted to find some recessed radiators with a small fan to waft the air over the fins and into the room - gently, not with a breeze. Couldn't find any such product. Also, the fans would have to be very high quality in order to last and operate extremely quietly.

Has anyone considered this?

Peri

------ Original Message ------
From: "Robert Bruninga via EV" <ev@lists.evdl.org>
To: "Electric Vehicle Discussion List" <ev@lists.evdl.org>
Cc: "Robert Bruninga" <bruni...@usna.edu>
Sent: 30-Nov-17 4:54:49 AM
Subject: Re: [EVDL] Heat pump vs resistive Heater (with radiators)

Yep, 90F is just fine for heating since it is continuous and low velocity. Sure, people love to stand over a blast of 140F furnace air, for the few minutes the furnace is on, because they get so cold with no warm air when
it cycles off.  I prefer the consistent warming of my heatpump and
cast-iron radiators.

PLUS it reduced our $3000/yr oil costs down to only $1000 electric which was easily made up with another solar array to keep us 100% carbon and oil
free.  See http://aprs.org/geothermal.html

The water in the heatpump and old cast iron radiators rarely gets above
about 105F and yet heats the house in Maryland just fine*.  Of course,
being a hacker, I keep the hot water that low (higher efficiency for the heatpump) by having some convenient fans by some of the radiators where we
can hide the fans.  This doubles convection and heat flow while keeping
the water temp lower. The heatpump can go to 126F, but the efficiency is
-much- lower than when it is running at only 105F.

PLUS it is free "zone" heat in every room, simply by which fans are on.

I even wired an outlet on the floor near every radiator where we can hide
a fan, so that the fans only come on while the compressor is running.

Our church went from $4000/yr for Propane down to $1100 added electric
with an air-source heatpump. And again, we are reducing that to zero with
another solar array.

* When temps get below about 20F, then the radiator water temp does get to
about 115F and the house can barely maintain 65F.  At lower temps, I
finally turn on the AUX heat.

The three HVAC companies all wanted to design an 8 TON heatpump and all
were leery that the water temp would not be high enough for COMFORT
because "radiators are designed for 140F". I argued, that the house was built with no insulation and with blown in insulation a few decades ago, that the radiators are now oversized, AND that if I needed more heat, I'd
do the fan thing.

Two of the three companies refused to do the job because they clearly had
rarely done a heatpump-to-hot water system and only were following
"typical" guidelines without any actual "engineering" to match my needs.
The winning contractor, agreed to do it MY way and his was the lowest
price too.  He got $28k, the others wanted $38k and $48k.  Half of that
was the HEATPUMP cost.  The other half was for the Geothermal wells.  A
lot, but reducing my family's $6000/yr energy costs down to only about
$300/yr very qickly has made it up.

If we had gone for air-source instead of ground-source, the cost would
have been half but not quite as efficient. Besides, the wife wanted a new driveway, and since that is where the wells had to go, then she got a new driveway (costing more than the entire HVAC system in the first place) yet that was all part of the job which also qualified for the 30% energy tax
credits.


Bob

-----Original Message-----
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of ROBERT via EV
Sent: Thursday, November 30, 2017 12:22 AM
To: Electric Vehicle Discussion List
Cc: ROBERT
Subject: Re: [EVDL] Heat pump vs resistive Heater (never buy another AC
unit)

Anyone who has a home heat pump can check the register temperature with a
thermometer.  You will find if the heat strips are not energized the
maximum temperature is about 90 F with an outside air temperature of about
68 F.  Give it a try.  Then tell me I am incorrect.  In addition, the
current building codes require a 15% fresh air intake to the return air. The old codes allowed a closed recirculating system. This does not help
the efficiency but improves the air quality in the structure.


________________________________
From: EV <ev-boun...@lists.evdl.org> on behalf of EVDL Administrator via
EV <ev@lists.evdl.org>
Sent: Wednesday, November 29, 2017 10:13 PM
To: Electric Vehicle Discussion List
Cc: EVDL Administrator
Subject: Re: [EVDL] Heat pump vs resistive Heater (never buy another AC
unit)

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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