<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman,new york,times,serif;font-size:10pt"><div>Eddie:<br><br>I never heard of a heat-pump that uses a electric resistance heater to warm the air over the outdoor coil. I am working on a Citi-Multi project now and looked up the wiring diagrams in their 676 page engineering manual. They do not indicate an outdoor auxiliary heater besides the crankcase heater for the compressor.<br><br>Some heat pumps have an auxiliary heater for the indoor units to warm the air when the heat pump is in reverse mode for outdoor coil defrost and as supplemental heat.<br><br>The Citi-Multi has a COP of 2.4 at 17 degrees F, which of course is 2.4 times more efficient than electric resistance heat.<br><br>Paul Diglio<br></div><div style="font-family: times new roman,new york,times,serif; font-size: 10pt;"><br><div style="font-family: times new
roman,new york,times,serif; font-size: 12pt;"><font face="Tahoma" size="2"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Eddie Corwin <ecorwin@altanova-energy.com><br><b><span style="font-weight: bold;">To:</span></b> deepika khowal <deepika.khowal@gmail.com>; equest-users@lists.onebuilding.org<br><b><span style="font-weight: bold;">Sent:</span></b> Thu, November 4, 2010 3:16:51 PM<br><b><span style="font-weight: bold;">Subject:</span></b> Re: [Equest-users] PTAC and PTHP<br></font><br>
<div style="font-family: arial,helvetica,sans-serif; font-size: 10pt;"><div style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;"></div><div><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="4"><span class="Apple-style-span" style="font-size: 10pt;">A heat pump are a MUCH more </span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="3"><span class="Apple-style-span" style="font-size: 13px;">efficiency</span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="4"><span class="Apple-style-span" style="font-size: 10pt;"> way of heating. The only issue with heat pumps are that they do not work well in cold weather (<40*F) below this temperature, they are pretty much electric resistance heaters. A lot of improvements have been made, for
example, the Mitsubishi Citi M</span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="3"><span class="Apple-style-span" style="font-size: 13px;">ulti-Split</span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="4"><span class="Apple-style-span" style="font-size: 10pt;"> systems can operate at temperatures as low as 13*F. For these types of systems, they </span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="3"><span class="Apple-style-span" style="font-size: 13px;">operate</span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="4"><span class="Apple-style-span" style="font-size: 10pt;"> as Heat pumps at 40*F and above. At 40*F and below, they use electric resistance heat to warm the air flowing over the outdoor unit (</span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif"
size="3"><span class="Apple-style-span" style="font-size: 13px;">allowing</span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="4"><span class="Apple-style-span" style="font-size: 10pt;"> for heat transfer between the air and the </span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="3"><span class="Apple-style-span" style="font-size: 13px;">refrigerant</span></font><font class="Apple-style-span" face="arial, helvetica, sans-serif" size="4"><span class="Apple-style-span" style="font-size: 10pt;">). So once you get down to 13*F they start to use a lot of electric resistance heating. Still much better that pure electric resistance heating!</span></font></div><div style="color: black; font-family: arial,helvetica,sans-serif; font-size: 10pt;"><div><br></div><div>-Eddie</div><div style="font-family: arial,helvetica,sans-serif; font-size: 10pt;"><br><div style="font-family:
times new roman,new york,times,serif; font-size: 12pt;"><font face="Tahoma" size="2"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> deepika khowal <deepika.khowal@gmail.com><br><b><span style="font-weight: bold;">To:</span></b> equest-users@lists.onebuilding.org<br><b><span style="font-weight: bold;">Sent:</span></b> Thu, November 4, 2010 2:52:38 PM<br><b><span style="font-weight: bold;">Subject:</span></b> [Equest-users] PTAC and PTHP<br></font><br>
<div>HI </div>
<div>I am trying to model a room with 80% glazing which has a wall unit air conditioner.</div>
<div>what will be the difference PTAC using electric heat / heat pump for heating ?</div>
<div>which one is advisable in terms of efficiency and energy savings?</div>
<div>does anyone has any thought on this?</div>
<div>Thanks</div>
<div>Regards</div>
<div>Deepika</div>
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