Does this mean that only compressor heat is being used for defrost? Pilko, are you wanting to make the tank storage as well?
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Does this mean that only compressor heat is being used for defrost? Pilko, are you wanting to make the tank storage as well?
mike ur dragging this post out arent u- just pop to pilko's and have a maul with his kit! or are u trying to get a sticky post haha
I'm dropping in at Xmas with a pint or two of cheer. Were are no where near a sticky anyway, haha.
@ Mike,
"Does this mean that only compressor heat is being used for defrost?" --- also the heat in the lines,the vapour in the "A" coil and the "A" coil itself."
are you wanting to make the tank storage as well?---only if the outdoor coil fails to defrost completely.
pilko
i guess you will have to see how it works without the extra heat source of the the room air. The other possible benefit of a tank (Mad, correct me if I am wrong) is that some of the tank heat could be used to do some floor heat if desired.
The coil is not defrosting using the compressor energy only (energy is still coming from the system)
Hot gas defrost, is more a compressor only defrost.
Using energy for more than one application, really means you study the applications to design the right system.
UPDATE,
Had 12 Defrosts with indoor fan stopped ---everything OK,
Writing some code to stop fan automatically at defrost start and restart fan when "A" coil temp >40*C.
pilko
Great news!
I am not normally into one up-man-ship, but in this case i think the "Pros" on HVAC TALK need to be told of your results.
In this industry things are very rarely black and white, so for one of the "pros" to say i was "wrong" was just pure arrogance and ignorance of the fundamentals.
Others gave opinions based upon what they know and seen, and that is fair comment.
@ mad fridgie,
If I respond to the other forum now, he will probably tell me that it is "OK for now but the compressor will
fail after a short time"---- so, I would prefer to give it more time and be able to tell them that it has been OK for a month for example.
pilko
I'm still unsure where the heat for defrost is coming from. I can't see enough heat from the local piping so there must be a high percentage of compressor heat going through.
Mad, I haven't see and "barbar" posts on the HVAC forum
Hi Mike,
good question.
What is the weight of the "A"coil and what temp is it, what is in the coil (hot refrigerant), you also have the interconnecting piping, and of course the mass around the all this. So you could work out the energy in all this. This energy is also is pumped (compressor uses energy) so the combination is rejected into the outside coil to melt the ice.
Reply on HVAC TALK, were removed and I got banned for a few weeks (Thats the rules, which I did break)
Pilko, fair comment
I'm back,
I am still defrosting without the indoor fan and everything is OK.
I just posted the following message on the other forum:-
"Update:-
I have been defrosting with the indoor fan shut down for the past 5 weeks . (approx. 120 defrost cycles). It works fine and I have had no problems.
pilko."
Good news
more comfort and less power
This a reply form HVAC-TALK
"Quote:
Originally Posted by pilko http://hvac-talk.com/vbb/images/buttons/viewpost.gif
Update:-
I have been defrosting with the indoor fan shut down for the past 5 weeks . (approx. 120 defrost cycles). It works fine and I have had no problems.
pilko.
I've been reading through this thread & though I haven't read it all it is a lot more interesting than I thought it would be. Any HP manufacturer or tech support would say as a fact that the indoor blower should always run during defrost & I would agree. You have evidently done significant research & found some conflicting data to support the alternate view which most anyone who works on HP's would disagree with. You have to remember HP's are designed for a variety of climates & yours may be such that a defrost is not needed very much so you mat be able to get away with stopping the blower while someone in another climate may not. There is no question that stopping the blower motor during defrost will lower the added cooling btu's entering the structure & also lower power consumption during that time but it also will make the defrost less efficient if it is really needed. Also compressor flooding should be a serious concern.
[FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]__________________[/FONT]
[FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]Gary[/FONT]
[FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]-----------"[/FONT]
[FONT=verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif]I wonder if you could forward this response.
Thanks Gary, for being a little more open on your thoughts.
It would seem that only North American heat pump systems continue to run the indoor fan on defrost, much of the rest of the world, turn off all the fans during defrost. These system are designed to run as low as -15C ambient. This is limited to refrigeration compression ratio limits, and not defrosting limitations.
Your concern on flood back is valid, in this case total charge and size of the suction accumulator was taken into consideration. Liquid flood back would not occur. How ever vapour at saturation may enter the compressor, but this is not really an issue, as the refrigerant passes over the comp motor, picking up sufficient superheat to ensure that oil dilution will not occur for the short defrost period.
Technically there is no reason why all systems in your neck of the wood s can not be converted, but there are practical limitations, such refrigerant distribution (primarily the out door coil), defrost sensor position and general control scenario. How do we determine defrost efficiency, defrost should be slower without a fan running (less energy picked up from the evap), so it would be fair to say efficiency is less, but if we include the energy to recover after defrost, then defrosting without a fan is more efficient.
cheers
mad fridgie (barbar)[/FONT]
Thanks Mad,
I have posted your / my response on the other site.
Regards
pilko
Quite a few rude answers on the other site.
It would be quite nice to know what sort of energy savings you are making.
Maybe you could be on to a winner converting systems. When you do, and make your millions, do not forget poor mad fridgie, at the bottom of the world.
I think you could install another external heat exchanger that will be replacing the internal one at the time of defrosting.