Heat Pumps - post here.

There is the possibility that a floor could take a few hours to really start releasing it's heat and therefore, while heated from maybe 2 to 6, could really be nearer waking hours before heat is released

on the monitoring side of things loads of options.. i have purchased over time a bunch of aqara temp sensors and collect temp/humidity data in home assistant..

If you have a Daikin it most likely has weather compensation settings.

Weather compensation is independent from tariffs/batteries etc. It is from a physics perspective the most efficient and stable method of putting heat energy into a house.

To add: if you are getting different temps between rooms then that is a hydraulic flow balancing issue. The valves on the radiators/UFH are where that is solved. Think of it like this: the weather compensation settings are used to get the overall average temp of the house, and the individual rooms are then balanced at radiator/UFH valves to distribute that average heat evenly.

your flow temp obviously isnt high enough but that said what are you trying to do, UFH takes time to heat up, are you trying to go from 20 - 22.5 in 2 hours? Really with UFH you shouldnt have zones either.

As mentioned you shouldn’t have zoning.

You will never have “warm” floors - your body heat is 37C. Anything cooler than that will not feel warm and cosy underfoot! The purpose of UFH is not to have warm floors.

You should have a mindset that it will take 24 hours for the rooms to reach set temperature. Timers are the wrong idea. Leave every zone on and adjust your flow temp curve to reach the desired temp in 24 hours. Adjust the curve it by 1 deg at a time.

The first goal should be to achieve a stable room temp over days. Only then can you start to think about tuning for lifestyle / out of home etc.

It must be warmer than 21 when the sun is shining then (although can't recall much of that lately 😆) heatpump are good for stable comfortable temps but you don't get the blast of heat , is it really getting cold or what do the stats say ?

Just wondering what people's real world electric bills are relative to their house size.

I've heard some absolute horror stories in relation to heat pumps and electric bills. A bill of 1500 odd euro for December and January for example. It's a big (3000 square ft at a guess) A Rated house.

I appreciate some of that bill could be attributed to additional winder use (cookers, washing machines, dryers etc) but the vast bulk of it appears HP related.

I've heard a few such horror stories of 4 figure bimonthly bills in the winter and 400-500 odd rest of year or more.

Is some of the cause of these bills the simple fact that these pumps aren't in any way adjustable on a room by room basis and that they are on at all times, even with no one in the house coupled with the fact that these houses are generally, what I would call huge, with unrealistic expectations from home owners in relation to wrapping themselves up a bit while inside?

Linked to this I have seen rsome pieces on air to air system, which for smaller houses do look like and option for retrofit .....what are people's thoughts?

Firstly unless they are monitoring the heatpump separately then it's a bit difficult to comment on that , secondly what would you expect gas or oil to cost for a similar house over the same period ?

For what it's worth my heatpump (so house heating and hot water ) cost me 160 from 1 dec to 31 Jan, that's for a 2100 sq foot A3 rated house.

@hold my beer You are coming at this from the wrong angle. You cannot try and get the heatpump to adjust for different rooms - you hav to adjust the different rooms for the heatpump.

If a room is cool, then you need to increase the temperature going into that room, by increasing the FLOW in that zone (via the adjusters on the UFH manifold). Take a photo of your starting point before making changes.

If a room gets too warm, then you need to reduce the FLOW in that zone.

You also have to be aware as to whether any zones control the turning on and off of the heatpump.

The target scenario is all zones constantly calling for heat. But start by getting each zone downstairs hitting the same temperature

For me I use under 2500kWh per year for the the heatpump and associated pumps and controls. That covers all heating, cooling and DHW.

I don't see and point in stating cost as everyone will have different electricity prices. House is about 200sqm with an 8kW air to water.

It's always under 20 degrees but comfortable.

I don’t think it is right to compare usage as there are many variables but my heat pump costs €250 a YEAR to maintain 20-21 room temps all year and the house is 115 sqm.

Yes I fully agree, I think it’s what you are happy with yourself from a house comfort and usage perspective. I suppose the better way to put it is for me I feel this is the best way of doing it rather than disagree with how others do it if you get me.

The night loading does make perfect sense and while I do have the temp increase for the offices kick in around 7am to get the first hour on night rate (as I’m charging the battery at this time so it used from the grid) I don’t really need to load at night as it is very rarely that I can’t get from 8am to 11pm on the battery even just letting the heating work away as needed so I am using night rate all day. A lot of the time only the coldest 2 or 3 rooms call for heat on and off during the day anyway and very cold weather tends to be accompanied by clear sunny days (this lots of self generation) and solar gain so counter intuitively very cold weather isn’t the worst from an usage perspective.

Out of interest I had a look at the heat pumps data on the indoor unit there as the app only gives energy usage but not heat generated. The average COP since install is 2.8. I reckon looking at the plot for Jan it is closer to 2.5 but it only gives a bar chart and not the actual number so have to estimate a bit as the axis has very few data points and of course my usage falls between two.

@SodiumCooled you are correct that one size doesn't fit all, but you should somewhat consider the potential longevity of the unit.

Stop start ing is not good for the compressor, and I think your COP is somewhat reflecting this.

As you say, you are happy with 9kWh usage on average per day, but maybe it could go lower with better optimization ???

I would suggest to anyone to focus on what zone or zones can trigger the call for heat and at least ensure that the call for heat is constantly there.

Then adjust the flow rates on the UFH manifold for any zones getting too warm

When I say max the thermostats yes that is turn them up as high as they can go.
This is so the room thermostats are not controlling the demand for heat.
Instead the weather compensation curve is controlling the temperature in your house.
This keeps the heat pump running constantly at the lowest temperature to replace the heat which leaving through the outer envelope of your house whilst maintaining a content temperature within that envelope.
If you use room thermostats the heat pump is using more power/energy to heat the rads to get the room to temperature and then turning off, the room slowly loses heat to the outside. The rads cool down. When the room temp eventually drops the room thermostat calls for heat. The heat pump starts up again and heats the water in the rads to get the room back to 20c. The heat pump uses more power at the start of this cycle and uses more power to heat to a higher flow temperature.

Regarding your attic, that should be kept the same temp as your upstairs bedrooms, even if its not used much.
Think of your whole house as an envelope for heat to be kept within, if you use thermostats to control the temperature in each zone and you set downstairs as 20c and upstairs as 17c, heat will move from the hotter zone to the cooler zone and the heating system will use more energy to maintain the 20c in the downstairs.

8 Kw seems oversized. Here is a heat pump calculator

Heat Pump Size Calculator Ireland - Ireland's Heat Pump Comparison Experts

My home has a HLI Heat Loss Indicator Value of 1.02 (You can find this value on your BER cert)
If my home was 150m2 I would need a 4kw or 5kw Heat pump.
The higher the power rating of the heat pump the more electricity it is going to use.
Does your 150m2 include the attic?
Anyway if it is oversized it will have some impact on efficiency but not enough to worry about.

The thermostatic valves are the ones on the rads, I start them on the middle setting in my case 3 and turn them up or down to change the temp in each room.
I have the bathrooms on 5 and the bedrooms on 2, the living room on 3 and the kitchen on 4 (mine go from 1 to 5)
I don't think it makes that much difference in the bedrooms, but it does in the bathrooms.

13c outdoor temp is when I have set the heat pump to come on. It was set to 15c when it was installed but the house is well insulated and between solar gain, human and dog bodies, and all the electrical devices in the house giving off heat the house doesn't need any heating until the outside temp is 13c to maintain 18 to 20c inside. Your house may vary.

-7c outdoor is just a point I picked as most cold outdoor temp, you could pick any temp that is lower than the coldest night where you live. This just sets the max flow temperature your heat pump goes to.

So if you look at the sloped line. That indicates that when the outside temperature is between 13c and -7c (horizontal line on the bottom) the heat pump will heat the flow temperature to a corresponding temp from 20c to 33c (vertical line on the left)
You need to set a temperature at -7 that will maintain the room temperature you want in your house as the outside temperature changes from 13c to -7c.

Even if you want to use the thermostats to control the room temps, lowering the weather compensation curve temps will help efficiency, you will just have some stop starting of the heat pump as the room thermostats control demand.

My daily usage for the heat pump (heating only) changes with the outdoor temp. I used 254kwh in January.
So an average of around 8kwh per day. My heat pump is very basic so I don't get much info from it.
My COP was 4.3 for the month, I would guess it goes down to 3.5? when the outside temps are below 0c
If my house was 150m2 and had a 5kw Heat pump I would expect to use up to 400kwh?

However the biggest money saver I would recommend to you would be to get enough battery capacity to cover your electricity usage for the coldest days and get a cheap night time tariff.
I am on Pinergy EV tariff, 6c from 2am to 5am. I can charge my battery around 15kwh in that time.
This covers almost all of the coldest days if I restrict use of my washing machine/dryer/dishwasher to also using cheap night time rate from the grid. My daily power usage in winter costs about 1 euro.
In summer I can charge the battery for 6c and sell whatever I dont use at the end of the day back to them for 25c.

If I needed more than 15kwh I would possibly go for a different tariff with a longer cheap time, although Pinergy pay 25c per kwh export, so maybe not.

Thanks for the detailed response. I needed to get to my laptop to respond. I had another look and my house is A3 actually, I can't find the BER cert but I understand it is invalid due to an extension being put on before I bought but I think I have one included as part of my solar installation.

You have given me a much better understanding of how it should work and it certainly makes sense for the weather compensation curve to do the work.

My January results don't seem to be showing but I used about 300kWh in December, the same last February, I can just see 12 months and they are my highest too, but I would say we haven't been keeping the house as warm as we would like all the time, although it might just be the case of wearing a jumper when wfh.

Oh the battery, I have just gone for a 9kwh battery which I knew wouldn't be enough over the coldest 3 months. I wasn't convinced regarding the pay back on the second battery but I didn't really think about changing how I use my HP. Having live energy use dats is very powerful, even with smart meter data on esb website you are a couple of days behind and broken down by the hour only. There was somewhere I saw my data that had the weather temp graph next to it and it was very interesting, strong alignment. I can't recall where. Either ESB or Electric Ireland.

Below is my curve, I take it the horizontal is outside temp. and the vertical is LWT? Too high?

Does the 15 mean off?