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Thread: Digital Scrolls
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08-10-2011, 05:42 PM #1
Digital Scrolls
OK, I know some of this has been covered before but I can't find it (CM always seems to be able to) but can anyone think of a reason NOT to use a digital scroll on a heat pump with an appropriately sized storage tank?
Design info seems a bit lacking it seems as well.
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08-10-2011, 08:44 PM #2
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08-10-2011, 08:58 PM #3
Re: Digital Scrolls
Yes, but the "reported advantage" by Copeland (for heating) of a digital scroll (not an inverter) is better low ambient performance over a single stage unit, and they state this advantage for ASHPs with a water storage!!!!!
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08-10-2011, 09:19 PM #4
Re: Digital Scrolls
Argh I see
running at part load in low ambients will decrease mass flow through the outdoor evap
allowing more time for heat to be absorbed
made up figures for example
if at 0*c x amount of heat is added to refrigerant in evap at full load
and at full load you have 1kg of refrigerant passing through evap per minute
then at half load you have half kg of refrigerant passing through evap per minute
you add more heat to that half kg increasing suction pressure/temp
which in turn increases head pressure/temp
if suction pressure/temp remains too low
you will not gain enough head pressure/temp to heat the water to desired temp
R's chillermanIf the World did not Suck, We would all fall off !
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08-10-2011, 09:24 PM #5
Re: Digital Scrolls
Why digital scroll? ZB will do the job just as good and at a lower price.
Can you add HGB to keep the evaporator temp above 0C?
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08-10-2011, 09:58 PM #6
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08-10-2011, 10:47 PM #7
Re: Digital Scrolls
Just asking guys.....doesn't mean I believe them.
Isn't HGB a bit of an energy waster though?....Ambient to be concerned with is -15C
I think Mad would shoot me if i used HGB, may BigFreeze would too.
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08-10-2011, 10:58 PM #8
Re: Digital Scrolls
Argh you got me now Mike
if Mad would shoot you for using hgb, I'm not arguing
he could be bigger than me and may be bumping into him soon
and thinking about it
you transfer energy to heat and then dump it back into low side with out using it to make hot water
just to increase heat/mass hmmmm .... yeah does not sound economical when looking for efficient heat pump
God Mr mike - you getting me thinking tonight and Mad will probaly turn up soon and say I got it all wrong
R's chillermanIf the World did not Suck, We would all fall off !
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08-10-2011, 11:25 PM #9
Re: Digital Scrolls
He might tell me Chemi is spot on as well.....I must defer to my superiors on this and that is all you regulars...
Come on Mad, chime in.....
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09-10-2011, 12:12 AM #10
Re: Digital Scrolls
Mike
Gary has also shown me recently along with DesA
they all have an in depth understanding of heat/energy and efficient use
which is all based around
energy can niether be created or destroyed but transfered from one form to another
as the heat has to be transfered from energy and not transfered from ambient
when using hgb, it does appear your argument is justified with digital scrolls at -15
they probaly all on holiday for a week or two and we be left wondering till thenLast edited by chillerman2006; 09-10-2011 at 12:26 PM. Reason: created to transfered: Der
If the World did not Suck, We would all fall off !
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09-10-2011, 12:49 AM #11
Re: Digital Scrolls
we shall see if more of the jedi masters chime in.....I would like to have this discussion as i seldom hear anyone talk about them. Most of the talk is about inverters which I agree makes no sense in heating a big tank of water.
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09-10-2011, 06:49 AM #12
Re: Digital Scrolls
The simply question is "do you need close control of your water".
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09-10-2011, 12:06 PM #13
Re: Digital Scrolls
Nope, you don't need close control of your water.....but the question is " given components of the same size, will the digital actually have a lower running cost then the ZB at -15C" or is it just that they believe the comp size can be reduced giving a lower running cost"
Last edited by MikeHolm; 09-10-2011 at 12:09 PM.
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09-10-2011, 01:04 PM #14
Re: Digital Scrolls
Wouldn't using a bigger evap on a static control unit give you the same result except for 100% of the time?
An offloading digital scroll could be more than likely become undersized for the application when dropped to 75% load in winter running.
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09-10-2011, 03:25 PM #15
Re: Digital Scrolls
Hi BigFreeze
a larger evap would still give you the same heat transfer to a kg of refrigerant
you need to either control mass flow (reduce it to increase transfered heat per kg)
Or use another method such as hgb to increase mass/temp at compressor inlet at low ambients
R's chillermanIf the World did not Suck, We would all fall off !