Most efficient way to run underfloor heating

Talldave

matelodave said:

Look at the balancing as well, if upstairs is toasty warm and down stsirs isn't, then it might be worthwhile turning the upstairs TRVs down a bit just in case they are diissipating more heat than the heat pump is delivering and starving the underfloor system downstairs. Does the floor seem warm to the touch. If you've got carpets, have you got low tog carpet and underlay.

Surely you need to balance by closing the lockshield valve? The TRV just determines what temperature the rad is shut off at.

matelodave

Yes you are correct if you are trying to do a rebalance of the system - but instead of mucking up all the settings it's easier to wind the trv's down and see if the u/f heating gets warmer, especially if you aren't sure if you've got a problem.

Balancing takes a bit more effort and possibly involves tweaking the flow rates in the u/f system loops as well which is a bit more complicated - ideally you need a couple of thermometers or a differential one to do it properly.

I'm a firm believer in doing minor tweaks that are easily reversible, only one at a time and giving the system enough time to settle and evaluating the result before faffing around with something else.

You should also be aware that the flow and return temperatures across a heatpump system are a lot lower than across a normal high temperature boiler and the heatpump will shut down if you reduce the flow too much.

Mouldymeat3

Is there an open flue in the room? If so, throttling that draught back to a trickle will make a significant difference.

There is no mention of a separate zone valve and switching arrangement for the radiators.

My earlier disjointed rambling was to illustrate how I came to leave ours on 24/7 during the heating season. The Beast from the East showed up the deficiencies. We went away for that week and left it on frost-protect until the day before our return. It took 3 days to recover. An easterly gale strips the heat from the building even with 4 inches of insulation.

matelodave

The other thing that people don't understand is "thermal blocking" 

It's pretty obvious if you put a towel or blanket over a radiator then you'll reduce the amount of heat that gets dissipated. The same is true of underfloor heating, especially in a living room or bedroom.

Putting a large settee, two big chairs, a sideboard and various other large items of furniture, not forgetting a nice fluffy rug will reduce the amount of heat that the floor can dissipate.
The same in a bedroom if its got u/f heating, a big double bed, wardrobe, chest of drawers etc has the same effect.

Ideally you need furniture that has legs, so the heat can escape rather than being blocked.

You could do the sums, eg our lounge is 28 sq.m and the heating gives out around 50w/m2 = 1400kw however two large armchairs, a settee, tv/music centre and a floor standing display unit take up about 8 sq.m which reduces it by 400w, add to that any reduction from the carpet and underlay so we are well down on the design parameters.

Interestingly we had a new low tog carpet & underlay fitted earlier this year and the room gets warmer quicker - the original underlay was not suited to underfloor heating although low-tog stuff had been specified when it was ordered ten years ago but that's not what got fitted at the time.

dllive

Ive just taken a few photo of what Ive got. I will list my questions/comments underneath each.

Each zone downstairs has one of these on the wall. I think these are the sensors/thermostats? Am I right in saying that this is showing me the current temp is 16.5; its getting the current temp from the air rather than the floor; and the heating is actively 'on'?
Perhaps, rather than fiddle with the schedule, I should leave these all on at 17 and then increase when Im using that room?


This is on the wall upstairs. I have a little handheld device too which Ive schedule when the radiators come on upstairs, although I use the TRVs on the radiators to increase/decrease heat. Is the above wall unit the sensor/thermostat?


I couldnt work out how to use the scheduler. Perhaps I dont need to if Im using schedulers on the upstairs handheld device and the downstairs sensors? Is there a benefit to using the scheduler on the Ecodan rather than the sensors I have inside?


The compensation curve. Is this an optimum setting?


Ive looked at a few videos on Ecodans, and it seems mine doesnt have the additional functionality. For example, I can only toggle the Legionella setting off/on. But some videos Ive seen, they can adjust the temp, how long it come son for etc...
The DHW I can either toggle Eco or Normal. Is it best to have it on Eco?


Is this good? I consider myself and partner 'low consumption users'. By that I mean we have 1 shower each day; a bath every few days; tend to put jumpers on rather than crank the heating.


Big jump from Sep to Oct. Is this a good thing? (This is the energy that the heat pump is producing?)


Is this the energy that the house is consuming, or that the heat pump is consuming? (I assume the latter).
Im concerned that 2020 is consuming 3x what was consumed in 2019!!
Should I think of it as Delivered energy minus Consumed energy equals the actual energy its taking to heat the house and DHW?


I think this is showing the heating as being controlled by the compensation curve. (I forget what the options it was giving me were.)


Is this quite good for a household of 2 'low consumption users'?


I know what the middle 2 panels mean, but what does the left and right panels show?
Sorry about all the questions, I know theres some very basic things that I should probably know. TBH, I miss the days when I just had to flick a switch on an old boiler and know that Id have to wait 30 minutes for some hot water!! Nice and simples!
Thanks

matelodave

This is my interpretation of what you've got - bear in mind I'm not an expert just a long time user of a heatpump and I dont have an Ecodan either. I did have a lot of input into the design of my system and I do know how it works but I havent a clue on how yours ins plumbed or wired or how the controls interact with the system

However here goes - going through your piccies from the top down -
1 - these look like programmable thermostats and are probably operating the u/f loop actuators and possibly enabling a pump and the heating unit - I dont know coz I dont know what you've got. I'd suggest that you find the instruction manual and set them for 17 during the times that you dont want the place heated and 20 for when you do, however bear in mind the time delay so if you want the temp at 20 you may have to tell the system to turn on 3 or 4 hours before hand and off again a couple of hours before you want it to shut off. You need to try and work out how long it takes to raise the temp from 17-20 and back down again. Just turn them up when you want heat wont help as they'll take several hours to take effect.

2 - this is a receiver for a wireless thermostat and might be operating a zone valve to turn the upstairs zone on and off, again It's hard to know without config information of bothe plumbing and the wiring

3 - not having an Ecodan I'm not sure what this shows but I'm guessing that it means the h/p might be on all the time

4 - this is the weather compensation which looks about right  -  you can shift it down a bit on another screen if you want to experiment a bit. Dont fiddle with this until you know what you are doing

5 - This is obvious the hot water and I'd guess that leaving it on Eco is probably the best although I dont know what timings you've got - is it continuous or timed and what temperature is it set to ( we have just an hour or so a day at 45 degrees) Likewise the legionella setting - you only need 60 degrees for about half an hour a fortnight because anytime the heatpump tries to haet above around 55 degrees it will use an immersion heater, which is something you need to avoid.

6 - delivered energy actually doesn't look everso bad based on a 30 day November its around 7.4kwh a day for hot water (I can only guess ours from the consumption and the estimate a COP of 2.5 (although its a lot better in the summer) - you might be able to reduce it a bit if you reduce the tank temp, use less hot water and reduce the legionnaire cycles.

7 & 8 these are self explanatory but if you divide consumed energy by delivered energy is will give you a rough idea of your COP which isn't everso good at less than 2. Ideally you want it nearer 3-3.5. This might be a consequence of keep turning it on and off and not letting it idle away at a lower temperature - we use less energy and keep more comfortable  by letting it chunter away with minimal interference. Something you can only test out but you do have the advantage of being able to see what effect adjusting it has on the COP

10 - indicates that you are using the weather compensation
11 - allows you to shift the compensation curve up & down with out altering the slope. Personally I'd try shifting it down by say -5 degrees which will reduce your flow temperatures by five dgrees  - try it a for a week to see how it affects your heating warm up times running the pump longer but at lower temperatures improves its efficiency

12 - if you compare this with the November delivered screen you'll see that your hot water COP was about 2.8 but your heating was only 1.7 so I guess you need to do a bit of work on the heating controls to try and optimise them

13 - I'm guessing that the left panel allow you to boost your hot water temperature by overriding the schedule time.temp (you'd nee to check the handbook. Likewise I recon the r.h panel shows consumed power (496kwh) against delivered energy (885kwh) for the current month divide 885 by 496 equals a COP of 1.78 which isn't ever so good - you should be aiming for at least 2.5 if not 3. getting the flow temperature as low as you can commensurate with satisfactory temperatures should be your aim bearing mind that on/off operation is not ideal, low and slow is the mooto. Think of driving a car, you get much better MPG if you cruise along a 50 rather than thrashing up and down the gears and travelling at 70 or 80. You'll still get there even though it will take a bit longer but you can save a lot of money.

That's my take on it all as an enthusiastic amateur 

BTW your screens are quite intuitive, mine is all text and with nested codes so a lot harder to interpret. Having info on generated energy v consumed energy gives you a much better feel of what is going on and what effect any changes might be having

dllive

Thanks so much @matelodave ! I appreciate all the time youve spent on this!
Ive read your answers and Ive made some notes. I will go and fiddle with the console and come back with any further questions if thats ok. Ill also google things like COP etc...
The learning curve is a lot steeper than the compensation curve! 

matelodave

COP is the ratio of the energy input to the energy output ie how much leccy goes in (in kwh) and how much heat you get out in (kwh) so a COP of three means you get 3kwh our for one in. 
Most heatpumps have their COP specified at 7degrees outside with a flow temperature of 35 degrees and they usually come up with a figure of around 3.8-4. However if you increase the flow temp then the COP will drop, likewise if you reduce the outside temperature the COP will drop so if you have high flow temps  and low outside temps then the COP will drop.

Also be aware that if the immersion/back-up heater kicks in (which it will if your hot water temp  is set above about 55 degrees) it has a COP of 1, so you need to avoid using it. I've disabled mine.

If you look at the specifications for your heatpump it will tell you what the COP is is (sometimes at several flow or outside temperatures) However these are nigh on impossible to achieve in real life and will obviously vary as the outside temperature varies.

A bit like my MPG analogy above, with a bit of careful tweaking (like gentle driving) you can improve your system COP but you cant actually replicate the manufactures specs unless you operate it under identical conditions.

My heatpump is now over ten years old but I reckon at a guess (because I cant easily measure it) we get COP of around 3. I can measure it's consumption using an Efergy energy monitor but I cant measure the amount of delivered energy.

That's based on my calculated energy requirement of about 10,000kwh for heating (my EPC say's 12600) and we use about 3500kwh for heating and around 3500-3700kwh for hot water and all our other electrical needs,( based on what we use during the spring and summer when the heating isn't really being used) MY RHI is calculated on a deemed COP of 2.5

dllive

Ive just taken a photo of the badge on the side of the unit:

So looks like the COP is between 3.34 to 4.54. (in ideal conditions)

matelodave

have a shufti here instructions for the controller - info on what all the stuff means and what they do -  starts at about page 33  https://library.mitsubishielectric.co.uk/pdf/download_full/2362

looking your COP label it's got a COP of 3.34 at an air temp of 2 degrees and a flow of 35 and a COP of 4.54 at an air temp of 7 degrees with a flow temp of 35 degrees, so you can see how the efficiency drops by a factor of 1 with just a temperature difference of 5 degrees.

I'm not sure if it's a linear extrapolation in the upwards direct but its a fair assumption that running with a flow temp of 40 degrees could also decrease the COP by a factor of 1 but a rule of thumb is that 1 degree increase above 35 degrees increases the consumption by about 2.5%, so running it at 45 degrees could easily increase your energy consumption by some 25%