Heat Pump/Heat Curve question

[ArthurMcB]

Hi,

I have a danfoss geothermal heatpump.

Our house is pretty warm and our bills are pretty high!

I have tried adjusting the control on wall inside but it doesnt have much of an affect and bills remain very high.

Am I right in saying, if i adjust the heat curve within the heat pump settings itself that might be a more effective way to get my desired temperature? I was thinking of using trial and error and adjust it by 1 degree to see if it makes a difference.

Does anyone have any advice re this?

Thanks.

 

[AJAM]

This video might help

How To OPTIMISE Heat Pump Settings!

Adam shows Rachael (@techpoodle on twitter) what all the settings do on her heat pump controls and how to optimise them!Join 'Heat Geeks Heating Help for Hom...

www.youtube.com

But as a general rule with heat pumps, you want to run them low and slow. So you mostly leave it on all/most of the time, but with low flow temperatures (35-40C).

 

[ArthurMcB]

Thanks for that AJAM. I watched that video.

He seems to be using a remote controller whereas my settings are on the pump itself but id say same concept applies.

Is it correct to say that the lower the heat curve the lower your bills and so goal is to find optimum curve that is comfortable temp? I reduced temp today from 28 to 26 as house was quite warm. Is this same as flow temperature you mentioned?

Thanks again.

 

[nephster]

What temperature is it set to for the rooms? Surely not 28!!
A normal temperature would be 21 or so.
The flow temperature is a different thing, this will be something north of 35 degrees.
The heat curve is to do with getting the flow temp optimised with reference to the outside temperature, so that's it's working at its most efficient to keep your rooms at the desired temperatures.

 

[ArthurMcB]

What temperature is it set to for the rooms? Surely not 28!!

Set to 20 on the thermostat on wall inside.

Below is my current heat curve settings (cant share an image of it). Any questions/comments on it, does it look ok?

Heat curve = 26°
Min = 14°
Max = 44°
Curve +5 = 1°
Curve 0 =0°
Curve +5 = 0°
Heat Stop = 16°

 

[Zenith63]

I have tried adjusting the control on wall inside but it doesnt have much of an affect and bills remain very high.

Might be a silly question, but are you sure that internal thermostat is connected to the heatpump and not part of the legacy heating system? I just recently put in a Viessmann heatpump and as the weather has now cooled down I'm playing around with the temperature and heat curves to get the house temperature right. With the Viessmann though it only uses the temperatures/curves you set in the app or on the heatpump itself and an external weather sensor, there are no room sensors. But I do have a bunch of old thermostats on the walls to catch out unsuspecting future owners

 

[Nenagh52]

Hi,

I have a danfoss geothermal heatpump.

Our house is pretty warm and our bills are pretty high!

I have tried adjusting the control on wall inside but it doesnt have much of an affect and bills remain very high.

Am I right in saying, if i adjust the heat curve within the heat pump settings itself that might be a more effective way to get my desired temperature? I was thinking of using trial and error and adjust it by 1 degree to see if it makes a difference.

Does anyone have any advice re this?

Thanks.

What do you mean by high?
Do you know how much juice your heat pump alone is using every day?

 

[AJAM]

Set to 20 on the thermostat on wall inside.

Below is my current heat curve settings (cant share an image of it). Any questions/comments on it, does it look ok?

Heat curve = 26°
Min = 14°
Max = 44°
Curve +5 = 1°
Curve 0 =0°
Curve +5 = 0°
Heat Stop = 16°

Arthur, do you have rads or underfloor heating? Rads would need flow temps of 35-45oC, but underfloor might only need flow temps of 23-28oC.

Also there are 3 different ways to setup a heatpump.
1. Room Temperature Target - The heatpump is connected to a room thermostat and supplies heat to try to match the target temperature
2. Weather compensation - The heatpump monitors outside temperature and adjusts heat based on that (This is where the heat curve is used. It's also considered to be the most efficient)
3. Set flow temperature - Heatpump supplies at a set flow temp - This should only really be used during commissioning and testing as it would lead to the house being too hot

I don't know enough about Danfoss to have any judgement on your settings. But I have heard a few heat engineers recommend that you keep turning down the heat curve until you feel cold. Then move it up 1 from there.

 

[ArthurMcB]

What do you mean by high?
Do you know how much juice your heat pump alone is using every day?

Our electricity bill is high by all accounts its 13000kwh per annum (if that makes sense?) Roughly is 3 times national avg.

are you sure that internal thermostat is connected to the heatpump and not part of the legacy heating system?

There are legacy thermostats throughout house but theres 1 central one we have been told to use by past owner and plumber that did original install in 2009.

@AJAM thanks again. Yes have undefloor heating and as i understand it our pump is set up per your 2nd option.

 

[Zenith63]

What size is the house and heatpump Arthur? Anything else using electricity like an EV, or is that 13,000kWh mostly heating and lighting?

 

[ArthurMcB]

What size is the house Arthur? Anything else using electricity like an EV, or is that 13,000kWh mostly heating and lighting?

House is 3,300 sq feet. No EV but a lot of washing machine use. Other than that nothing out of the ordinary. Electriciry company have even said to me that we re very high domestic users

 

[_OkGo_]

House is 3,300 sq feet.

Our electricity bill is high by all accounts its 13000kwh per annum (if that makes sense?) Roughly is 3 times national avg

A little perspective is needed here...

Firstly, your property is over 300sqm! That is comfortably more than twice the national average for property size in Ireland.

Secondly, the national average electricity usage used by the CRU of 4200kWh's is old, before many homes had HP's so it was mainly domestic use, i.e. lights, cooking, appliances etc. But it also included 11,000kWh's of space heating.

Applying that to a reasonably efficient HP with a COP of 3.5, that equates to an additional electricity usage of 3,100kWh. So in reality the average usage, in an average sized house, with a HP is more likely to be 7,300kWh.

At 13,000kWh for 306sqm, your property is using 42.5kWh per SQM comfortably putting it in A2 category for BER. I would say your HP is already running very efficiently but you just have a massive house...cue the tiny violin

I have tried adjusting the control on wall inside but it doesnt have much of an affect and bills remain very high.

Am I right in saying, if i adjust the heat curve within the heat pump settings itself that might be a more effective way to get my desired temperature?

But going back to your original issue, we had a similar problem last with the thermostats in that the builder installed fairly basic and useless stats that had too much hysteresis so the house was always fluctuating in temperature. When set too low, the heating just didn't come on.

After a bit of research, I found Heat Geek who has a lot of good videos and info around setting up your heating using weather compensation only. After a little trial and error, we are now at a fairly consistent 21°C all through winter. The thermostats are no longer part of the heating regulation, they are just set to max so that they are always on.

It has definitely improved our efficiency and reduced usage but realistically, you will still be a heavy user purely because of the size of your home

 

[ArthurMcB]

Heat Geek

Thanks, ill check the videos out.

At 13,000kWh for 306sqm, your property is using 42.5kWh per SQM comfortably putting it in A2 category for BER

Can I ask - how did you calcuate this. The BER is B3.

I would say your HP is already running very efficiently

Im not so sure. Our bills are very high even allowing for having a large house. From speaking to others with similar house, our bills are off the charts. Through process of elimination its obvious to me that the heat pump is the culprit so if theres any way I can make it more efficient i will. Adjusting the heat curve might be the answer so ill trial reducing it and hopefully that will do the job.

the national average electricity usage used by the CRU of 4200kWh's is old

Is it? I didnt know that. Its still the only measure im aware of re national average.

 

[ClubMan]

Secondly, the national average electricity usage used by the CRU of 4200kWh's is old, before many homes had HP's so it was mainly domestic use, i.e. lights, cooking, appliances etc. But it also included 11,000kWh's of space heating.

Something doesn't add up here?

 

[_OkGo_]

Is it? I didnt know that. Its still the only measure im aware of re national average.

Just to be clear, I don't think the figure is wrong but it was last revised in 2017 so is based on data when very few HP's were installed so the 4200kWh is domestic use only. But the CRU also includes 11,000kWh of gas in their national average figures.

So for you to compare apples with apples, you need to divide the gas usage by your HP COP and add it to the average domestic usage. For a fully electric household, the average would be ~7000kWh.

Can I ask - how did you calcuate this. The BER is B3.

This is why so many people don't like the BER system. For you to buy the house, the seller had to get one done but it is finger in the air stuff for a lot of the inspectors. And they don't actually check the real electricity usage over the previous years.

The occupier has as much an influence on the BER as the construction of the property. Have a look at the sample BER cert here.

Your usage (13,000kWh) divided by your property size (306sqm) gives 42.5kWh/sqm/yr which falls into A2 category of 25-50kWh/sqm/yr

house. From speaking to others with similar house, our bills are off the charts

Do these other properties have gas heating by any chance??

 

[Zenith63]

Through process of elimination its obvious to me that the heat pump is the culprit

Your electricity bills in summer vs winter should give you a good sense of whether it’s the heatpump or not. In August our 16kW ASHP used a total of 65kWh heating hot water for showers, no heating of the house. For October it looks like we’ll use 300kWh to cover water for showers and heating the house to a fairly warm temperature during the day.

To me your usage sounds a bit high, but as you’re saying the house feels too warm that probably explains it. I’d do as suggested above and decrease the heat curve until the house feels a little cold, then go back up a degree or two. You have nothing to lose, the settings can just be put back to defaults if you’re not happy with the outcome. I’m in the process of working mine down at the moment as this is the first winter with it.

 

[ArthurMcB]

Do these other properties have gas heating by any chance??

At least 1 similar house with just geothermal pump and bills are a lot lower.

@Zenith63 thanks, this is what ill do. A bit of trial and error

 

[Zenith63]

At least 1 similar house with just geothermal pump and bills are a lot lower.

@Zenith63 thanks, this is what ill do. A bit of trial and error

Have you had a look in the menus of the heatpump to see if it tells you how much power it's consuming, or perhaps there's an app you can connect? At the very least I think the Danfoss will tell you how many hours the 'internal immersions' have been running for, ideally you'd want that to be as low as possible. I know our system is newer, but in the app I can see live how much power it is using and has done over the last few months.

 

[Blackrock1]

OP i think you need to compare your bills to houses of a similar size and make sure that their oil or gas is also included in the comparison, i doubt you are going to be expensive when you compare.

My dad told me my electricity bills were high until we totalled his total heating and electricity costs which came in more than double ours.

 

[dem_syhp]

Do you know what was your energy use, in KwHr a year in your previous home (assuming you lived somewhere else)? If you'd gas/oil for heating/water, it will give you a good idea of what proportion of your energy use is not heating home/water.

I've been surprised at how much energy others use - even same sized families / same size houses can use very different amounts. Similarly, don't compare costs - people can pay different rates for the same thing.