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<font face="Helvetica, Arial, sans-serif">Switching to a standard
north american recirculating system changes everything. and makes
choices more complex.<br>
Now one can use a wide range of ERVs (that might have appropriate
flow, say 60 cfm continuous, or 120 cfm run half the time) and
wide range of standard split HP products.<br>
Just because it is not standard does not make it better.<br>
For example, Fujitsu, LG, Mitsubishi and Daikan all have "slim
duct' type systems where they have an small air handler. The
problem is, their fan efficiency is so low, it begins to really
impact system efficiency. The COP of all of those products in the
under 2 ton range during normal heating weather (say 20F or -7) is
worse than mid-range standard split products. They are intended
for very short runs (like 20 ft) with one or at most two fittings,
not a whole duct system. With care in duct/fitting design you can
do more, but the electric draw is still high.<br>
Standard products can also provide heating output at low
temperatures. I have a Carrier SEER16 heat pump that provides 12
000 Btu/hr at -20C. Most brands with R410 have the same
performance. But they are not modulating. Using an ECM motor and
a large blower reduces the fan power but reasonable duct sizes are
needed to keep things quiet and efficient. <br>
<br>
Larger ducts (8" or more diameter) should be sized to keep
velocity at between 500 and 750 feet per minute, and smaller ducts
at 400 to 500 fpm. This means, if you are moving 1000 cfm, you
need a duct with about 1000/750 =1.25 sq ft of cross sectional
area. A duct of 6"x6" is 1/4 sq ft so should not have more than
500*0.25=125 cfm for low pressure drop and quiet performance. <br>
<br>
I attach a couple files: one is a drawing of one of about 20 in
the Ventilation Guide (see our website) that shows how to hook up
an ERV/HRV into a standard recirculation system. You do not need
a special balancing HRV if the pressure differences are small,
which they should be in a right-sized duct system.<br>
<br>
the second is the best I could find on fan power vs flow and
pressure. For low energy systems, we design the ducts to have a
static pressure of less than 0.5" w.c. (125 Pa) when
heating/cooling, so that when just used to circulate fresh air the
pressure drop will usually be approaching 0.1" or lower (25 Pa).
Under these conditions, an ECM fan in a standard AHU will draw
less than 0.33 W per cfm of air flow. During ventilation mode, my
own off-the-shelf AHU draws 32 W to move around 300-340 cfm.<br>
<br>
The recuperator is an odd choice as it seems to draw a lot of
power (200W!) during high flow. I have not measured one though. I
attach a standard HRV that under continuous flow mode draws 24 W
to provide over 50 cfm of air, enough for most homes. The boost
mode allows for parties and baths etc.<br>
<br>
I guess in general the IDEA of a good HRV ducted into the return
of a modulating heat pump is excellent, exactly what many people
want and need. But the actual products we have available are far
less than perfect and hence other arrangements are usually less
expensive and high performing.<br>
<br>
<br>
</font>
<div class="moz-signature">Dr John Straube, P.Eng. <br>
<a class="moz-txt-link-abbreviated" href="http://www.BuildingScience.com">www.BuildingScience.com</a></div>
<br>
On 12-03-22 4:16 PM, Gennaro Brooks-Church - Eco Brooklyn wrote:
<blockquote
cite="mid:CAPV9BxN2eUg0SB1TFoxNogO3M7GEiOq4=WA2Zv95zByBnMvqaA@mail.gmail.com"
type="cite">I've installed both systems and from my experience it
wouldn't be crazy to even go to a 12" trunk. But with those
numbers you could get away with a 10". You definitely want to
insulate the duct for sound reasons, especially if you are
increasing the cfm with the inline mini-split. The one drawback
out of the RecoupAerator's many benefits is that they are noisy
(compared to say a Zhender) , so you want to design accordingly.
<div><br clear="all">
Gennaro Brooks-Church<br>
Director, Eco Brooklyn Inc.<br>
Cell: 1 347 244 3016 USA<br>
<a moz-do-not-send="true" href="http://www.EcoBrooklyn.com"
target="_blank">www.EcoBrooklyn.com</a><br>
22 2nd St; Brooklyn, NY 11231<br>
<br>
<br>
<br>
<div class="gmail_quote">On Thu, Mar 22, 2012 at 4:06 PM, Alan
Abrams <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:alan@abramsdesignbuild.com">alan@abramsdesignbuild.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Stuart and John--how do you think Mr Slim and the
RecoupAerator would handle some fairly long duct runs? <br>
longest would be 12' vertical and 20' horizontal, with at
least four 90d elbows-<br>
<br>
-AA<br>
<br>
<br>
<div class="gmail_quote">
<div class="im">On Thu, Mar 22, 2012 at 3:54 PM, Stuart
Fix <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:sfix@renubuildings.com" target="_blank">sfix@renubuildings.com</a>></span>
wrote:<br>
</div>
<div>
<div class="h5">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Alan,<br>
<br>
Check out the Mitsubishi Mr. Slim series. They go
down to 9000 Btu/h, and<br>
can operate to -20C. We've built a prototype that
uses their ducted<br>
fancoil unit inline with the ERV supply, with the
addition of a return air<br>
duct to feed the extra CFM.<br>
<br>
So in operation:<br>
<br>
- ERV operates continuously, 100-200CFM, blowing
through the fancoil (must<br>
use extremely efficient ERV for this to make sense,
try UltimateAir<br>
RecoupAerator)<br>
<br>
- Fancoil kicks on as heating or cooling requires,
using the 100-200CFM of<br>
the ERV and sucks an additional 300-500 CFM through
the return air duct.<br>
Using the RecoupAerator makes this easy, as its ECM
motors are self<br>
balancing, so it'll compensate as the Fancoil
depressurizes the system.<br>
<br>
In addition, if your climate is cold enough to
require it, the Mitsubishi<br>
makes a PAC controller that lets you use the fancoil
with an inline<br>
electric heater even when the condensing unit
outside has locked out due<br>
to cold weather.<br>
<br>
You'll end up upsizing the supply trunk to around
10", but that's still<br>
small enough for the ERV to handle by itself.<br>
<br>
This may not have made sense, drop me a line if
you'd like more info or a<br>
sketch.<br>
<br>
Cheers,<br>
<br>
Stuart Fix, P.Eng., LEED® AP<br>
PHI Certified Passive House Designer<br>
MASc. Building Science<br>
Mechanical Engineer<br>
ReNü Building Science Inc.<br>
<br>
#206, 506B St. Albert Trail | St. Albert, Alberta |
T8N 5Z1 | C.<br>
<a moz-do-not-send="true" href="tel:780.554.8192"
value="+17805548192" target="_blank">780.554.8192</a> | <a
moz-do-not-send="true"
href="mailto:sfix@renubuildings.com"
target="_blank">sfix@renubuildings.com</a><br>
<br>
<br>
Message: 1<br>
Date: Thu, 22 Mar 2012 11:43:26 -0400<br>
From: Alan Abrams <<a moz-do-not-send="true"
href="mailto:alan@abramsdesignbuild.com"
target="_blank">alan@abramsdesignbuild.com</a>><br>
To: listserv Green Building new<br>
<<a moz-do-not-send="true"
href="mailto:greenbuilding@lists.bioenergylists.org"
target="_blank">greenbuilding@lists.bioenergylists.org</a>>,<br>
<a moz-do-not-send="true"
href="mailto:healthyhomebuilding@yahoogroups.com"
target="_blank">healthyhomebuilding@yahoogroups.com</a><br>
Subject: [Greenbuilding] small in line heat pump<br>
Message-ID:<br>
<br>
<CADj3_s6M8kN0nE_T-N=<a moz-do-not-send="true"
href="mailto:mha3KQhVh-0f%2B1dwdaKG_2myfrC87gg@mail.gmail.com"
target="_blank">mha3KQhVh-0f+1dwdaKG_2myfrC87gg@mail.gmail.com</a>><br>
Content-Type: text/plain; charset="iso-8859-1"<br>
<div><br>
anyone know of a small capacity (12K - 18KBtu)
heatpump, suitable for<br>
installation in line with an ERV?<br>
<br>
-a<br>
<br>
<br>
*Alan Abrams**<br>
Abrams Design Build LLC*<br>
</div>
*A sustainable approach to beautiful space*<br>
<div><br>
6411 Orchard Avenue Suite 102<br>
Takoma Park, MD 20912<br>
office 301-270-NET- ZERO <a
moz-do-not-send="true"
href="tel:%28301-270-6380" value="+13012706380"
target="_blank">(301-270-6380</a>)<br>
fax <a moz-do-not-send="true"
href="tel:301-270-1466" value="+13012701466"
target="_blank">301-270-1466</a><br>
cell <a moz-do-not-send="true"
href="tel:202-437-8583" value="+12024378583"
target="_blank">202-437-8583</a><br>
<a moz-do-not-send="true"
href="mailto:alan@abramsdesignbuild.com"
target="_blank">alan@abramsdesignbuild.com</a><br>
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Message: 2<br>
Date: Thu, 22 Mar 2012 14:25:37 -0400<br>
From: John Straube <<a moz-do-not-send="true"
href="mailto:jfstraube@uwaterloo.ca"
target="_blank">jfstraube@uwaterloo.ca</a>><br>
To: Green Building <<a moz-do-not-send="true"
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<div>Cc: <a moz-do-not-send="true"
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Subject: Re: [Greenbuilding] small in line heat
pump<br>
</div>
Message-ID: <<a moz-do-not-send="true"
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<div><br>
Thats a tough one Mr Abrams<br>
To deliver 12 KBtu you need about 400,
preferably 450 cfm. So what kind<br>
of ERV is it? most residential scale ERVs are
like 50 to 150 cfm to serve<br>
normal size homes. 400 cfm ERV must be for a
commercial use?<br>
If you are talking water source HP, Trane and
Florida Heat Pump (now<br>
bosch) makes a line of water to water heat pumps
that small, and you use a<br>
stadard coil in the air stream.<br>
For air to air, all of the standard split units
(meaning you can put the<br>
coil in a duct airstream) start at 18 kBtu/hr.
Which requires a lot more<br>
airflow yet again. But Goodman Trane Carrier all
make units at 1.5 tons,<br>
they are just not that efficient.<br>
<br>
On 12-03-22 11:43 AM, Alan Abrams wrote:<br>
> anyone know of a small capacity (12K -
18KBtu) heatpump, suitable for<br>
installation in line with an ERV?<br>
><br>
> -a<br>
><br>
><br>
> *Alan Abrams**<br>
> Abrams Design Build LLC*<br>
> /A sustainable approach to beautiful space/<br>
><br>
> 6411 Orchard Avenue Suite 102<br>
> Takoma Park, MD 20912<br>
> office 301-270-NET- ZERO <a
moz-do-not-send="true"
href="tel:%28301-270-6380"
value="+13012706380" target="_blank">(301-270-6380</a>)
fax <a moz-do-not-send="true"
href="tel:301-270-1466" value="+13012701466"
target="_blank">301-270-1466</a> cell<br>
> <a moz-do-not-send="true"
href="tel:202-437-8583" value="+12024378583"
target="_blank">202-437-8583</a> <a
moz-do-not-send="true"
href="mailto:alan@abramsdesignbuild.com"
target="_blank">alan@abramsdesignbuild.com</a><br>
> <mailto:<a moz-do-not-send="true"
href="mailto:alan@abramsdesignbuild.com"
target="_blank">alan@abramsdesignbuild.com</a>><br>
> <a moz-do-not-send="true"
href="http://www.abramsdesignbuild.com"
target="_blank">www.abramsdesignbuild.com</a>
<<a moz-do-not-send="true"
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><br>
><br>
><br>
>
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