navitron
 
Renewable Energy and Sustainability Forum
Welcome, Guest. Please login or register.

Login with username, password and session length
News: Anyone wishing to register as a new member on the forum is strongly recommended to use a "proper" email address. Following continuous spam/hack attempts on the forum, "disposable" email addresses like Gmail, Yahoo and Hotmail tend to be viewed with suspicion, and the application rejected if there is any doubt whatsoever
 
Recent Articles: Navitron Partners With Solax to Help Create A More Sustainable Future | Navitron Calls for Increased Carbon Footprint Reduction In Light of Earth Overshoot Day | A plea from The David School - Issue 18
   Home   Help Search Login Register  
Pages: 1 2 [3]   Go Down
  Print  
Author Topic: Heat pump CoP check, something seems off?  (Read 5698 times)
marshman
Hero Member
*****
Online Online

Posts: 1013


WWW
« Reply #30 on: October 24, 2019, 10:42:37 AM »

Did you ever go back to Kensa and query the figures with them??
Logged

3.15kWpk (15xSharp ND210)/SB3000. & 3.675kWpk (15 x Suntech 245WD)/SB4000TL, 10kW GSHP driving Wirsbo underfloor heating from 1200m ground loops. 10' x 7' solar wall (experimental). Clearview 650 Wood Burning Stove. MHRV - diy retrofit. Triple glazing.
geoheated
Newbie
*
Offline Offline

Posts: 39


« Reply #31 on: October 24, 2019, 10:50:32 AM »

The controller is built into the heatpump. It monitors the outside temperature and that is all. There is no temperature sensor in the house. The controller "simply" looks at the heat being taken by the system, I assume by the rate of decrease in temperature of the circulating water, and decides when it needs a "boost". There is a "heat curve" which you can adjust, nudge it down a bit if the house is too warm and up a bit if it is too cold. I spent the first heating season after the system was installed tweaking this and have not touched it since. Brilliant system as it just works.

Pretty sure the figures/timings I quoted are correct.  Heating is usually active from end of October through to end of April - give or take a week or so. Last heating season the heatpump (including all circulating pumps) used 1264 kWh for heating and DHW. This equates to approx 7kWh per day (1264kWh/180days).  Highest daily consumption recorded last year was 13kWh (inc. DHW).  House an old detached 5 bedroom Farmhouse in an exposed spot near the English Channel, approx 240 sqm. Living rooms sit at 20 degC 24/7, bedrooms a bit cooler. There are no zone valves in the UFH at all, I have just spent time balancing the flow round the loops to get the various room temps where I wanted them. There is one circulating pump for the whole house and this runs on its lowest setting consuming < 10W.

Roger

That sounds Very efficient for the size of your house, well done! I have a 3 bed and use more than you. Sounds like a nice setup.

I do recall now the optional outdoor sensor for the Kensa product. Makes sense and sounds like its doing a good job.
Logged
geoheated
Newbie
*
Offline Offline

Posts: 39


« Reply #32 on: October 24, 2019, 11:04:13 AM »

Did you ever go back to Kensa and query the figures with them??

I wanted to get some accurate logs of power-in and heat-out before i ask them what is up with their datasheet.

There is no way at this time of year with [>10 degC ground return and ~35 water out] it is achieving anywhere near the COP of 5.2 that these ideal conditions make on their datasheet.


Logged
nowty
Hero Member
*****
Offline Offline

Posts: 1027



« Reply #33 on: October 24, 2019, 11:37:51 AM »

When I put my GSHP in I measured its performance scientifically by running the output into a 35 litre builders bucket and measuring the temp with a thermometer over a timed period.

My heatpump is allegedly rated at 8kW output but my actual measurements showed the output was a near constant 5.7kW. So its a similar size to your 6kW Kensa unit, interesting to see the comparison on power consumption verses output temp.

There is a thread about it on here, https://www.navitron.org.uk/forum/index.php/topic,29762.0.html





Logged

12kW+ of PV installed and 60+ MWh's generated.
Home battery storage of 40+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage of 15+ kWh's.
6kW Ground source heatpump.
EV BMW i3 (another 30+ kWh's of storage).
290,000+ litres of water harvested from underground river.
geoheated
Newbie
*
Offline Offline

Posts: 39


« Reply #34 on: October 24, 2019, 12:22:57 PM »

When I put my GSHP in I measured its performance scientifically by running the output into a 35 litre builders bucket and measuring the temp with a thermometer over a timed period.

My heatpump is allegedly rated at 8kW output but my actual measurements showed the output was a near constant 5.7kW. So its a similar size to your 6kW Kensa unit, interesting to see the comparison on power consumption verses output temp.

There is a thread about it on here, https://www.navitron.org.uk/forum/index.php/topic,29762.0.html





Oh i do enjoy test like this!! Thanks for sharing.

Curious, how did you get the 5.7kW heat figure?

I did a quick calc and 35kg of water, raised 3K in 60 seconds is 7.5kW.

.............Update...............
Ignore that, just read your thread and or course its 40deg/17 mins = 5.7kW, obviously at the lower temperatures it will be putting out more kW than 5.7 and less at the high end, so infact the COP at the start will be higher!


« Last Edit: October 24, 2019, 12:49:37 PM by geoheated » Logged
nowty
Hero Member
*****
Offline Offline

Posts: 1027



« Reply #35 on: October 24, 2019, 02:40:58 PM »

Curious, how did you get the 5.7kW heat figure?

I did a quick calc and 35kg of water, raised 3K in 60 seconds is 7.5kW.

.............Update...............
Ignore that, just read your thread and or course its 40deg/17 mins = 5.7kW, obviously at the lower temperatures it will be putting out more kW than 5.7 and less at the high end, so infact the COP at the start will be higher!

I had omitted the decimal points to the temp table but I recall it really was a constant heating rate of approx 2 and a bit degrees / min. The other thing to note which you will find in my thread is that water flow rates and differing return temps (above zero) did not make much difference to the heat output or the COP.

Also the COP is higher at the low end because the power of the compressor is lower but I did not measure any particular increase in heat output. As the temperature increases so the gas pressure in the compressor increases so it takes more power to compress the gas, hence the COP decreases but again I did not find any reduction in heat output at the top end.

For what its worth, I do agree with you that there seems to be some inconsistencies in the Kensa data sheets you have issues with but that does not surprise me too much.
« Last Edit: October 24, 2019, 03:46:51 PM by nowty » Logged

12kW+ of PV installed and 60+ MWh's generated.
Home battery storage of 40+ kWh's.
Hot water storage of 15+ kWh's.
Heat storage of 15+ kWh's.
6kW Ground source heatpump.
EV BMW i3 (another 30+ kWh's of storage).
290,000+ litres of water harvested from underground river.
Pages: 1 2 [3]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.20 | SMF © 2013, Simple Machines
SMFAds for Free Forums
Simple Audio Video Embedder
Valid XHTML 1.0! Valid CSS!