Charging a heat pump

 
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Old 01-18-2012, 09:02 PM   #1
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Charging a heat pump


More specifically, the discharge superheat method; Ambient temp added to discharge temp. This method has served me well but doesn't work AT ALL in 410A systems. Anyone else use this method or know why that it doesn't jive with 410A?

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Old 01-18-2012, 09:11 PM   #2
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Re: Charging a heat pump


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Originally Posted by triple rectifier View Post
More specifically, the discharge superheat method; Ambient temp added to discharge temp. This method has served me well but doesn't work AT ALL in 410A systems. Anyone else use this method or know why that it doesn't jive with 410A?
In what mode of operation....

In heating the only way to be absolutely sure on a heat pump is to weigh the charge in.
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Old 01-18-2012, 09:15 PM   #3
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Re: Charging a heat pump


In heat pump mode...If it's a new install it's a no brainer. What I'm talking about is a unit you are not familiar with and need to get running.
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Old 01-18-2012, 09:18 PM   #4
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Re: Charging a heat pump


Just to clarify, I've installed heat pumps when the ambient is in the upper 30s/low 40s. When i know the factory charge and what needs to be added per 15' of lineset etc. But I've checked this method (discharge SH) and it's dead accurate with 22 systems...410A, not so much.
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Old 01-18-2012, 09:25 PM   #5
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Re: Charging a heat pump


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In heat pump mode...If it's a new install it's a no brainer. What I'm talking about is a unit you are not familiar with and need to get running.
Right...same principle triple.
Use the calculators provided by the manufacturer for "ball park" but still manufacturer's require that system charge be weighed in on heat pumps during the heating season.

Keep in mind that R410,while it has minimum fractionation, it is still a zeotrope refrigerant which means it has more than one saturation temperature for each pressure. Those old methods once used with R22, a pure refrigerant, will not work the same with R410.

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Old 01-18-2012, 09:33 PM   #6
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Re: Charging a heat pump


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Those old methods once used with R22, a azeotrope, will not work the same with R410.
Thanks for the reply. My 410 experience is limited. My tried and true methods of verifying charge (on HPs in HP weather) aren't adding up with the 410 splits. Roof tops, obviously, not an issue.
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Old 01-18-2012, 09:46 PM   #7
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Re: Charging a heat pump


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Thanks for the reply. My 410 experience is limited. My tried and true methods of verifying charge (on HPs in HP weather) aren't adding up with the 410 splits. Roof tops, obviously, not an issue.

No worries mate....next time you're at the supply house pick up a newer PT chart that has the bubble and dew points for zeotropic blends.
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Old 01-22-2012, 07:58 PM   #8
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Re: Charging a heat pump


weight in charge in the heat pump mode per data plates, and then fine tune if needed. If around 60* you can artificially build heat in the condenser to simulate a 95* outside ambient temp and charge in the cooling mode with subcooling(if TXV) or evaporator superheat if fixed type orifice. Personally, I have not seen a problem between R22 or R410A The 410 fractionates so minutely that is is a trick to actually see any variation in the outdoor or indoor coil due to fractionation of the refrigerants.
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Old 01-23-2012, 09:45 AM   #9
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Re: Charging a heat pump


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weight in charge in the heat pump mode per data plates, and then fine tune if needed. If around 60* you can artificially build heat in the condenser to simulate a 95* outside ambient temp and charge in the cooling mode with subcooling(if TXV) or evaporator superheat if fixed type orifice. Personally, I have not seen a problem between R22 or R410A The 410 fractionates so minutely that is is a trick to actually see any variation in the outdoor or indoor coil due to fractionation of the refrigerants.
Admittedly.....410a is classified as a "near" azeotrope refrigerant directly because there is little slide or glide between the blends but the fact remains that it can seperate. In fact there are many cases where it has which it turn will cause irractic pressures and operation of the equipment....this is why all zeotrope refrigerants, including 410, must be charged as a liquid.

410a, despite its good qualities, is a very poor refrigerant when compared to some others. Equipment components are more expensive due to a need for greater design & build to be able with stand the extreme differences. That being said 410 is here for now so we all have to deal with it.

Do not be surprised however to see 407c in the near future. It has a closer characteristics to R22 and a lower GWP than both R22 or R410.
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Old 07-22-2013, 10:48 AM   #10
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Re: Charging a heat pump


yes I agree.. weigh in the charge for heating on a heat pump. simple as that.
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Old 05-05-2014, 09:22 PM   #11
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Re: Charging a heat pump


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In heat pump mode...If it's a new install it's a no brainer. What I'm talking about is a unit you are not familiar with and need to get running.

What is "heat pump mode"?
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