Help with Heat pump diagnostics


  #1  
Old 03-04-15, 01:27 PM
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Help with Heat pump diagnostics

Ok, I have a heat pump that I installed about 1 month ago. It has not been performing properly since installation. By not performing properly, I mean I cant keep the house over 60F even when the outside temps are 15F.

This is an 18,000btu Senville Aura mini split. I am heating one open space of 900sqft. Thermopane windows, R24 in the walls, R40 in the attic.

What I have done so far....

HVAC contractor came and recovered the unit, verified no leaks, and weighed in the label charge (67oz r410a)

- I have checked all the sensors, and all are reading proper resistance.

- I have checked the compressor windings for proper resistance.

- I have verified no bulging capacitors, burn marks or other defects on the circuit boards.

- I have verified proper communication between indoor and outdoor unit.


What I have observed....

This is where things are really making me scratch my head.

Right now, the outdoor temp is 40F and sunny, and indoor temp is 64F.

If I put my heat pump on max temp (86F) and run the indoor fan at HIGH, I get a discharge air temp from the head unit of 95F, and a draw of 6.25 amps.

If I put my heat pump on max temp (86F) and run the indoor fan at LOW, I get a discharge air temp from the head unit of 118F, and a draw of 7.6 amps.

My question is, shouldn't the compressor be ramping up when the indoor fan is on high, and slowing down when it is on low to keep a steady discharge temp?

I am wondering if this could be a TXV issue. I had the heat pump apart and took a look and noticed it does not seem very well insulated to begin with.

I also notice when the fan is on low, and the head unit heats up past a certain amount, there is a very slight whistling from the lineset. Maybe a pinch somewhere?

Can anyone point me in the direction of what the issue might be? I know this is a cheaper unit, but I had a 12,000btu of the same model that heats better than this one, so I cant believe it is just the way it is supposed to perform.

I have a gauge set a detailed service manual (not the one on their wensite, it is garbage) if there are any other checks that might help.

A pic of my TXV http://i984.photobucket.com/albums/a...304_152354.jpg

Spec sheet for the compressor
http://www.areacooling.co.uk/files/d...131917_18_.pdf
http://www.areacooling.co.uk/files/d...064939_82_.jpg
 
  #2  
Old 03-05-15, 07:54 AM
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Here's some TXV troubleshooting info that I cobbled together from searching on the issue a few years ago, maybe it'll help.


http://www.doityourself.com/forum/he...heat-pump.html
 

Last edited by Houston204; 03-05-15 at 06:32 PM. Reason: Giving charging instructions is not allowed
  #3  
Old 03-05-15, 01:01 PM
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Thanks for that info. I will do some more investigating to see if I can narrow this down.

Are there any HVAC techs here that are willing to at least weigh in on whether or not this system is even working normal? So far my experiance with geting advice on mini splits from the internet has been worse than pulling teeth.
 
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Old 03-05-15, 01:16 PM
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What should the compressor discharge temp be on a typical mini split in heat mode? Right now I am reading 95F with an outdoor temp of 23F. Isnt that extreamely low?
 
  #5  
Old 03-06-15, 05:56 AM
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Houston204:
I apologize if the TXV tips I offered went over to the realm of charging ... I can't see where, but hey, it's your forum.
It's ironic that with your no-charging rules you prominently display advertising for TXVs and charging related tools and apparatus.
 
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Old 03-06-15, 04:08 PM
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No worries, i think I have found the problem. Perhaps Houston would care to weigh in on this?

I checked out the model number of the compressor in this 18,000btu heat pump, and it is only rated for 13,000btu. Is there any HVAC tech here that can tell me how a 13,000btu compressor can output 18,000btu of heat? Is this why it is not heating like I would expect an 18,000 btu to heat?
 
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Old 03-07-15, 08:28 AM
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One would think so ... but a few years ago, I was having similar issues of what I considered inadequate heating performance with my new 42000 btu/hr (3.5 ton) rated heat pump, so I checked the compressor only to find that its manufacture, Danfoss, described it as 36,000 btu/hr (3 ton) .
When I complained to the heat pump manufacturer, York, they declared that because of their clever engineering and advanced TXV technology, they were able to meet the ARI certified performance requirements... sigh.
 
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Old 03-07-15, 08:47 AM
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Given this unit is considered a "cheap Chinese POS" by HVAC techs, I have my doubts there is much clever engineering going on here. Looking at their 12k model, it has an 11k compressor. Their 24k model has a 26k compressor. it is only their 18k model that seems why out of whack. Also this unit does not have any ARI cerification label on it, only ETL.

Did you ever find out what was causing the inadequate heating performance? Or did they just tell you that's just the way it is?
 
  #9  
Old 03-08-15, 10:05 AM
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It's a rare manufacturer / distributor / dealer that is concerned with customer satisfaction or capable of providing it... that's why we civilians fritter away our time on forums like this trying to get lemonades from these pesky lemons. I guess if you have primitive designs, use cheap components, with the lowest cost labor, ... , the results shouldn't surprise: "that's just the way it is".

After a few leak repairs, proper weighing in of refrigerant (at considerable expense) the performance has improved - but the manufacturer's claims are, well, just claims .
I still suspect the TXV, but have yet to find a tech who knows enough to diagnose, let alone replace.
 
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Old 03-08-15, 10:42 AM
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I had a 12k unit from the same manufacturer before this 18k. The 12k was not quite keeping up on colder days, so I figured I would upgrade. That 12k could put out more than 120F at the head on a 32F day. My 18k can only put out 90F on the same day. There is definitely something wrong with this unit, and I can't accept it is just the way it is. I had great performance with the smaller unit, and this one can't come close to matching it. There is a problem somewhere, but no one can seem to find it. The company claims they have not had other complaints about poor performance, despite the undersized compressor. They are supposed to call me next week. We will see how this plays out.
 
 

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