Weather dependency and buffer tank
I have an ASHP with a buffer tank. It has been set to run a weather depent system, so normally it runs at 40 degrees C, when it's cold outside it runs at 43 degrees C. Does this mean I am wasting money heating the buffer tank by 3 degrees C when it's cold outside, and should I turn of the weather dependency>
Hi Simon, the reason it is a good thing to run the heat pump with weather dependency is for exactly the situation you describe. When it is cold outside the water is heated more so that you still feel toasty in your house.
A better way to think about it is that if you turned off the weather dependency then you would have to have a set water temperature of 43 degrees C all the time to account for those days which are cold, then you really would be wasting the energy in the extra 3 degrees on the warmer days.
I dont think 3 degrees sounds like a large differential, some HPs allow the weather dependency curve (line really) to be adjusted in its gradient giving more or less of a differential. If yours does you could try a bit or trial and error to find the right setting for you. For instance if your current setting is 43 degrees at -2 outside and 40 degrees at 15 outside, you might be able to adjust that to 43/-2 and 35/15 and see if that is warm enough on the warmer days.
Hope that makes sense 🙂
House-2 bed partial stone bungalow, 5kW Samsung Gen 6 ASHP (Self install)
6.9 kWp of PV
5kWh DC coupled battery
Blog: https://thegreeningofrosecottage.weebly.com/
Heatpump Stats: http://heatpumpmonitor.org/system/view?id=60
Posted by: @bontwoodyA better way to think about it is that if you turned off the weather dependency then you would have to have a set water temperature of 43 degrees C all the time to account for those days which are cold, then you really would be wasting the energy in the extra 3 degrees on the warmer days.
I dont think 3 degrees sounds like a large differential, some HPs allow the weather dependency curve (line really) to be adjusted in its gradient giving more or less of a differential. If yours does you could try a bit or trial and error to find the right setting for you. For instance if your current setting is 43 degrees at -2 outside and 40 degrees at 15 outside, you might be able to adjust that to 43/-2 and 35/15 and see if that is warm enough on the warmer days.
Hi Simon, If you want it automated then use WC, but one can just use the control panel to adjust target water temperature up or down. If the buffer is quite large it could be more complicated. The problem with WC is that outside temperature is the only variable. Solar gain and the thermal capacity of the house tend to make a significant difference, the former quite quickly and the latter relatively slowly. Emitters also, but all the rads need to be matched across the house so that all rooms warm up at the same rate.
Phil
With a flow temp of 43C, properly adjusted weather compensation should save you about 15% in running costs. If this doesn't matter to you then leave it as it is, otherwise it should be adjusted correctly as suggested by bontwoody.
Filipe is of course right that ambient temp is not the only variable, but that's not really the point. Weather compensation (with balanced radiators) will get you 'most of the way there' with the lowest flow temperature for any given ambient. That makes for max efficiency.
The general recommendation for operating heat pumps efficiently is:
balance the radiators
get weather compensation adjusted so the rooms are at the right temp with the TRVs fully open
use TRVs and thermostats as temperature limiters (to shut down rooms where solar gain takes over) not temperature controllers
leave the HP on most if not all of the time , perhaps with a 3C nighttime set back if the HP controller can do that ('slow and low')
The closer you can get to this the more efficient your running will be.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
- 22 Forums
- 2,070 Topics
- 45.3 K Posts
- 42 Online
- 3,343 Members
Join Us!
Trusted Installers
Struggling to find a reliable heat pump installer? A poor installation can lead to inefficiencies and high running costs. We now connect homeowners with top-rated installers who deliver quality work and excellent service.
✅ Verified, trusted & experienced installers
✅ Nationwide coverage expanding
✅ Special offers available
Latest Posts
-
RE: Heat pump installation and BUS Grant timings
@johnmo Hi, looks like i might be getting the schemes...
By StuChi , 39 minutes ago
-
RE: Home energy storage & battery register
I totally agree that self install is certainly going to...
By Abernyte , 2 hours ago
-
Check the detailed specs. 7kW Vaillant is actually 8kW...
By JamesPa , 3 hours ago
-
RE: Jokes and fun posts about heat pumps and renewables
@transparent ‘Protein’s extra Luv’.
By Toodles , 4 hours ago
-
RE: Getting the best out of a heat pump - is Homely a possible answer?
@johnnyb I was on Smart, mostly because I was on Agile ...
By Arundalep , 17 hours ago
-
RE: Forum updates, announcements & issues
@editor Fairy Nuff Mars, I doubt that my ramblings woul...
By Toodles , 23 hours ago
-
RE: Antifreeze top up for my heat pump - is this a rip off?
@johnmo You are correct, standard Ethylene glycol used ...
By Brendon Uys , 23 hours ago
-
RE: Confusion about heat pump sizing
We’ve published a deep dive into heat pump sizing, and ...
By Mars , 1 day ago
-
We’ve published a deep dive into heat pump sizing, and ...
By Mars , 1 day ago
-
RE: Kensa GSHP finally installed - now to start the optimisation process
Just had a quick scan of the manual and should be weath...
By Johnmo , 2 days ago
-
RE: Potentially more choice including air to air heat pump grants
Hi all, I agree, the consultation documents are alway...
By madbilly , 2 days ago
-
RE: Commencing on an ASHP Installation Process
I think those are pretty much the standard figures that...
By JamesPa , 2 days ago
-
RE: Load Compensation and Weather Compensation
I think that maybe what the adia thermal system does, b...
By JamesPa , 2 days ago
-
RE: Enabling WiFi: Samsung ASHP on Smart Things App
@old_scientist @profzarkov thanks to you both for the v...
By Grahamh-uk , 2 days ago
-
RE: Nibe F2040 periodic warm water increase fails
@tribol here's an official reply from NIBE on your case...
By Mars , 2 days ago
-
RE: Vaillant & OVO partner up to offer Heat Pump Plus
@ecodan-efficiency On the other hand, the fact that the...
By Richard24738 , 3 days ago
-
RE: How accurate was your heat loss survey?
@scalextrix for our house 1950s detached the air leakag...
By Judith , 3 days ago
-
-
RE: Air Changes per Hour - ACH and the MCS requirement
@matwin If you plan to commission one it might b...
By JamesPa , 4 days ago