Heat Pump Running Costs

Cyrus

https://www.boards.ie/discussion/comment/121839906#Comment_121839906

Mine used 26 yesterday albeit near half at night rates which helps a bit

ColemanY2K

a glorious day, currently 8 degrees celsius outside according to the screen on the internal unit. the 8kW HP is on course to use circa 10kWh of energy today (4.8kWh used from midnight to noon so i pro rata to get ~10kWh).

on the face of it i'm pleased as that's just €3 per day (ignoring the solar contribution) however i'm unsure its running as it should. the data from shelly is showing the heat pump coming on for 20 minutes, run for 20 or so minutes and then turn off. rinse and repeat for the 24 hour period apart for a single one hour session in the early hours when it heats up the tank.

does this sort of schedule sound right or would it be considered short cycling? the stats are dumb and UFH is one single big loop. the call for heat is controlled by the indoor unit which has the 'ROOM' temperature set to 19 although the stats are saying anything from 21.5 to 22.5.

newhouse87

Heat demand won't be there to run all the timeat 8deg hence hp shuts off. Short cycling is much more frequent. 6 per hour is considered problematic cycling.

ColemanY2K

https://www.boards.ie/discussion/comment/121855222#Comment_121855222

It seems to keep the same routine no matter the temperature which I find odd but obviously works harder when it does come on as the temperature drops.

Something to keep an eye on, thanks for the feedback.

munsterfan2

Home assistant must have updated their energy dashboard recently, nice new visual of the data.

cromelex

https://www.boards.ie/discussion/comment/121865022#Comment_121865022

Latest release.

I need to fix something that will break when I update, but looking forward to having the ability to visualise the heat pump on that graph

ColemanY2K

https://www.boards.ie/discussion/comment/121865022#Comment_121865022

not great for the 1 in 12 men & 1 in 200 women who, like myself, are colourblind. i wish more companies could add lettering or symbols of some sort to help differentiate charts.

ColemanY2K

This is just a personal anecdote but thought it useful to share.

All week the heat pump was ticking along at 0.6kWh or lower with the dumb stats reading a steady 21 degrees. the mother in law arrives yesterday for a short break and says to the Mrs she's a bit chilly. So I cranked up 'ROOM' temperature setting on the indoor unit from 19 to 21 degrees (the house temperature is usually a couple of degrees above the 'ROOM' setting which would bring the house up to 23 degrees).

Last night I had a look at what shelly was recording in terms of consumption for the day. Lo and behold as soon as I made the change the HP went into overdrive. Consumption has doubled from 0.6 to 1.2kWh. It has been like that since 6pm yesterday and I presume will stay like that until the set temperature is reached.

Moral of the story, even modest adjustments can significantly affect the performance of a heat pump ...so if you're heat pump is running like crazy then by dialing down the settings a tad may have a significant impact on the HP's performance.

She's here till Tuesday 🥵

graememk

https://www.boards.ie/discussion/comment/121868871#Comment_121868871

Interesting on how long it will take to get the slab up to the higher temperature. And then how long it stays at that temperature after it gets turned down again.

johndoe11

https://www.boards.ie/discussion/comment/121868871#Comment_121868871

Yes, it makes a huge difference, if adjust the desired room as it offsets the heating curve.

If your desired room temp is not lower than your actual, you could probably lower your flow temp a bit and get them to match up. It made quite a big difference in efficiency for me. See below from my manual , line 1 is 21c desired room temp, 4 is 24 and 5 is 18. As you can see it makes an enormous difference to the curve if it is changed. It is best to have temp matched up to reduce compressor cycles and have the optimum heating curve slope. I'm using weather compensation.

Cyrus

massive difference now with heat pump usage,

mine was less than 8kh/w yesterday incl DHW, im expecting it to lower again as i have decreased the overnight temps down stairs (had increased it to 23 degrees over night on night rate to heat the house up a little and lower usage during the day)

ECO_Mental

Decided to switch off room stats over the weekend as they werent calling for heat anyway…having them off safeguards me for when someone opens a window as they want fresh air and it turns them on for no reason. Should see my daily usage trend done to the 4-6kWh day over the next week or two hopfully.

@Cyrus I dont know an I a believer in ramping up the heating at night before to predict the next day, what happens if the sun comes out the next day unexpectedly and heats the house up so you dont need heat and you have wasted all that energy for no reason. Better off just leaving it alone and if needs heat it will call for it.

ColemanY2K

i still have dumb stats and one single zone in my 2100 sq foot bungalow. i let mine just tick over to keep the house at a steady 21 / 22 degrees. very happy with its performance at the moment.

for dhw and heating the heat pump has used an average of 6.25 kWh per day this month (up to close of play yesterday) or based on my current tariff if i had to buy power then it would in theory cost €1.27 per day.

this doesn't take into account solar which has reduced the daily cost to zero for the month of April thus far. the way things are going it won't cost me anything to run between now and start of october.

Cyrus

https://www.boards.ie/discussion/comment/121992262#Comment_121992262

yeah normally id agree but our night rate is so cheap and when it was cold it was nice to wake up to a very warm house downstairs for not a large cost!

ECO_Mental

https://www.boards.ie/discussion/comment/121992452#Comment_121992452

Yeah I suppose if you are on one of those fancy smart boost rates that 7 or 8 cent there is no harm

andyd12

https://www.boards.ie/discussion/comment/121992397#Comment_121992397

I assume you have no actuators? Open loops everywhere?

ColemanY2K

https://www.boards.ie/discussion/comment/121992734#Comment_121992734

the actuators on both manifolds have been removed to turn all the zones into 1.

andyd12

https://www.boards.ie/discussion/comment/121992788#Comment_121992788

As I thought, thanks.

I am struggling with the dumb stats concept however… For example, one day its 0 degrees outside and no sunshine so no solar gain. The next day its 4 degrees outside and full sunshine so considerable solar gain. How is the system/HP sensing this kind of difference?

Cyrus

https://www.boards.ie/discussion/comment/121992892#Comment_121992892

through the internal thermostats? or maybe im wrong, he said dumb stats, are they not linked back?

andyd12

https://www.boards.ie/discussion/comment/121993230#Comment_121993230

Stats typically control actuators. I thought with the actuators removed the room stats are just a visual of the room temperature. But could be wrong. Interested to know how it's all controlled

Cyrus

https://www.boards.ie/discussion/comment/121995058#Comment_121995058

one stat will be controlling them (stat for zone 1) no?

ColemanY2K

The indoor unit has a built in stat. You set it to your preferred temperature and the HP does the rest.

I have 2.8m wide south facing window yet the temperature remains constant so all I can say is excessive solar gain isn't an issue.

newhouse87

https://www.boards.ie/discussion/comment/121992397#Comment_121992397

What tariff are you on with your electric provider?

ColemanY2K

https://www.boards.ie/discussion/comment/121995689#Comment_121995689

flogas bwg smart electricity

day 24 cents

night 18 cents

peak 28 cents

standing charge works out at 65 cents / day.

newhouse87

https://www.boards.ie/discussion/comment/121995730#Comment_121995730

V good, tried to get it but didn't have referral code. Think for non smart you didn't need code,just rang up and no questions asked.

ColemanY2K

https://www.boards.ie/discussion/comment/121995791#Comment_121995791

i'm probably one of the few boardsies who signed up to the bwg deal who actually works with a bwg affiliate 🤣

andyd12

https://www.boards.ie/discussion/comment/121995219#Comment_121995219

Is the preferred temperature a room temperature or HP flow temperature?

ColemanY2K

https://www.boards.ie/discussion/comment/121996149#Comment_121996149

It's the preferred room temperature.

I find whatever I set it to on the indoor unit the house stats report two degrees higher so in the photo below it's set to 19 degrees in order for the house to reach 21 degrees. I don't know why this is the case but it's something the plumber said would happen when he installed it and sure enough it has.

Other photos showing current temperatures of flow etc.

The house has been built to passive standards hence why I have a really low flow (supply line) temperature.

hold my beer

https://www.boards.ie/discussion/comment/121996207#Comment_121996207

My sitting room thermostat does somethimg similar but the opposite way. Constantly says the room is about 2 degrees warmer than it actually is. Bizarre, and very annoying.

Cyrus

https://www.boards.ie/discussion/comment/121996863#Comment_121996863

there is normally a calibration setting you can change (if its digital) my joule ones were 2 or 3 degrees out.