Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: gnarly on March 03, 2018, 11:58:06 AM



Title: Heat pumps in the cold snap
Post by: gnarly on March 03, 2018, 11:58:06 AM
How have people's heat pumps been handling the 'beast from the east' over the last few days?

I currently just have a small Daikin split ac unit in my living room, it is great most of the time, but can't really cope with extended low temperatures.  The main problems are:
- outdoor unit noticeably louder, I think it's because the outdoor unit is mounted on the house and it just seems to vibrate more (which conducts through the cavity wall)
- drain freezes and drain pan starts to fill up with ice; if the temperature stays below freezing the whole day then the ice just builds up
- more defrost cycles which means a lot less heat

(so the main mottos are: don't mount the outdoor unit on the house; and you do need back-up heat)


Title: Re: Heat pumps in the cold snap
Post by: linesrg on March 03, 2018, 01:08:38 PM
gnarly,

As you've asked here's the view from Courtiestown.

The ground loop temperature has obviously been going down throughout the winter not helped by the fact that we have had precious little rain to assist in 'recharging' the ground so the heat pump must be doing progressively more work as the winter pweriod goes on.

I've been running the heat pump on an inclination setting of 42o degrees C since I started adjusting it in early October. As the outside temperatures (and the wind) caused the house temperature from the target 18.3o C set point (sensor in Hall) I started cranking up the Inclination setting to 45o C. Somewhat obviously this did cause the heat pump to crank up the compressor with a commensurate increase in hum/ vibration.

The heat pump is located in the Utility Room and you can hear it in the kitchen but is isn't intrusive and doesn't make any more noise than the old condensing LPG boiler that preceded it.

Has it coped? I would say yes but as I've posted elsewhere the system is confused currently as it is being fed a misleading figure for the outside air temperature. When it was getting an accurate external temperature it was obviously determining that the inclination limit was limiting and was heating the radiator circuit to 49o at one point.

I would say it has coped but I would like to see the external temperature issue resolved.

Regards

Richard


Title: Re: Heat pumps in the cold snap
Post by: donegal on March 03, 2018, 01:12:31 PM
Gnarly,
I was considering starting a similar thread, ive a geothermal heatpump and so far it holding up well,  the ground loop temperature is down to -1
deg, which is good for my system compared to the first few years.  I have to run it for a few hours extra per day, so currently running the heatpump for approx 11 hours per day, seven of those at night rate. Managing to keep the living areas At 20-22 deg.
This cold snap has left me determined to upgrade the insulation and airtightness, as the draughts are the real problem in one or two areas, particulalry my sheltered East facing hardwood front door.
We havent had the worst of the cold, but its been below freezing for most of the last week, with a biting east wind and the ground is frozen solid.
I am wary of the ability of air source heatpumps in cold snaps, but everyone tells me im wrong, i'll be interested to see what feedback you get.
Tony



Title: Re: Heat pumps in the cold snap
Post by: djs63 on March 03, 2018, 02:46:05 PM
We have a gshp and it copes very well (touch wood). We have gone through the insulate, insulate and insulate process as per Martinís advice. We donít use any supplementary heat except twice a week  lighting a log stove.

It has been -5C for 5 days, now zero, bitter strong east wind and we are about 2 miles from the North Sea across low lying fields.... Ground rock hard. :snow


Heat pump does what it says on the tin for us. More heat energy out than electricity used.

Neighbour just cleared the road outside where it was 2 foot deep in snow. The A1 has been closed for 3 days with a convoy system running occasionally, now open. Snowblower did an excellent job.



Title: Re: Heat pumps in the cold snap
Post by: titan on March 03, 2018, 03:10:31 PM

I've been running the heat pump on an inclination setting of 42o degrees C since I started adjusting it in early October. As the outside temperatures (and the wind) caused the house temperature from the target 18.3o C set point (sensor in Hall) I started cranking up the Inclination setting to 45o C. Somewhat obviously this did cause the heat pump to crank up the compressor with a commensurate increase in hum/ vibration.

I assume inclination temp is the flow temp ? unless your unit has a variable speed compressor ( not normal)  then the hotter temperature is achieved by running the pump longer so it should not sound any different just run a little longer. I know you have mentioned your problems with your outside temperature sensor, there is a lot of debate whether weather compensation is the best way to run a HP system because it just does't have the rapid response of a gas boiler. I did not commission mine and just use zone valves, I like the KISS principal


Title: Re: Heat pumps in the cold snap
Post by: DonL on March 03, 2018, 03:22:14 PM
ASHP has handled the beast without any problem, maintaining the desired inside temperature and without significant use of the back up resistance heater.
Don


Title: Re: Heat pumps in the cold snap
Post by: linesrg on March 03, 2018, 03:28:40 PM
titan,

The Inclination temperature is, in theory, the level at which the house can be maintained at the set temperature with the external temperature at either -1 or -5o C.

The compressor is modulating.

I'd agree with you that with a heat pump you aren't going to see the speed of response like we did with the old LPG condensing boiler but even that had to overcome the system/ building hysteresis.

Like djs63 I am still chasing down draughts.

The big sources of lost heat in the property remain the Hall, downstairs bathroom and (to a degree) the  Living Room which still need upgrading i.e. ripping out and replacing with insulated walls, UFH etc.

One day.

Regards

Richard  



Title: Re: Heat pumps in the cold snap
Post by: camillitech on March 03, 2018, 09:26:48 PM
Our's is coping just fine but is certainly working harder. Only uses 810W for an alleged 3kW output and is normally perfectly matched to our 800W hydro, but that's been frozen for two days. Wind turbine filled by the 'Beast from the east' and plenty of sunshine for the PV have been picking up the hydro slack. House toasty at 22.4 degrees but the water has been off for a couple of days too, so we've not had a wash for long enough either. To be honest I think we'd have been struggling had we needed DHW too. Having said that Scottish Water have been tankering over articulated lorry loads of water to the rest of the island 'on the mains' so I'm not feeling too bad about our spring supply and hydro freezing up. I'm really not a fan of heat pumps but have been pleasantly surprised with our little Eccocent unit which is actually designed to be fitted inside the house. Our's is in 'The Bunker' a well insulated 'lean too' plant room on the gable end where the freezer, 1500lt TS batteries and a heat dump live. All in all, it's far from perfect but I'm pretty chuffed. 


Title: Re: Heat pumps in the cold snap
Post by: davec on March 04, 2018, 11:12:43 AM
Quote
How have people's heat pumps been handling the 'beast from the east' over the last few days?


TBH Gnarly, I hadn't thought about it till I saw your question... just checked and the borehole return temp is 8degC so our GSHP seems well in scope. The house is at its regular temperature and the children are still taking massive showers. The outside temp has been sub-zero since last Tuesday but hasn't gone much lower than -5; we've been shovelling a lot though!

Dave.


Title: Re: Heat pumps in the cold snap
Post by: Bodidly on March 04, 2018, 11:39:52 AM
Our GSHP has been fine. Only run the house at around 17C and use a wood burner to top up if need be. Ground loop is running cold coming in at -1 and going out at -5 probably due to rather short ground loop. UFH only having to run at max of 29C even when -6 outside with gale force wind. It must be 7 or 8 years old now and as good as the day it went in.


Title: Re: Heat pumps in the cold snap
Post by: NoahsDad on March 25, 2018, 07:01:17 PM
My 12kW Dimplex ASHP coped well with the 2 cold snaps this winter. Only thing worth mentioning is that during the Beast from The East spell the LCD screen on the control box displayed an error on one occasion which stops the HP operating. A quick trip and reset saw it working fine straight away again.


Title: Re: Heat pumps in the cold snap
Post by: geoheated on April 02, 2018, 01:14:02 PM
Happy with my ground loop temps over the winter!

6kW Kensa Installed last year by myself. Set approx 37 deg output temp during cold spell.

(https://s7.postimg.org/6vt6k5duv/Capture_1.jpg) (https://postimg.org/image/6vt6k5duv/)