Most efficient way to run underfloor heating

matelodave

The Salus thing is a programmable thermostat in the same way as the other units down stairs are. You set the programme times and temperatures on it, so it should be somewhere that's representative of the temperature that you want (not in a spare room or in a cupboard or windowsill). A lot of people will have them on the wall on the upstairs landing. Hopefully both it and the others enable the heating unit and pump ( you need to check that they do) in which case you don't need to faff around with the heating unit timers, just the flow temperature otherwise they'll all be fighting each other.

In the end it's a case of "suck it and see" to work out what suits you best.

I'm experimenting with mine at the moment, so give it a couple of days and I'll show you how some of the adjustments affect mine (it will take a whole day for each tweak to take effect and produce a result).

We have our hot water set for just two hours a day but I'm having a fiddle with that as well

The following graph shows my power consumption since midnight, I've turned off the compensation so its running at a constant 35 degrees. the peak at 12:00 to just after 13:30 was the 200 litre water tank being heated from 30 to 45 degrees.
I'll have a try at 40 degrees tomorrow and then with compensation on Friday to see how it affects the consumption - the heating is under control of the room stats and it's been about 5 degrees outside.(I might have some temp graphs as well)

dllive

Thanks for all your posts @matelodave , very helpful! 

matelodave

Here's my power consumption for today (3 Dec)- the the heatpump was set for a constant 40 degrees but no other tweaks or adjustments to any other controls.. Hotwater was on from 12:15 to 13:30 and heated from 35degrres to 40 degrees. I suspect that it was colder last night as the pump came on a couple of times and its been cold and wet all day today. Outside temp 4 degrees. You can see that it used more energy than yesterday (2 Dec). I'll turn weather compensation on tonight to see what it looks like tomorrow (BTW it took from 08:00 to 18:00 for the lounge temp to increase from 17 to 19 degrees)

dllive

matelodave said:

Here's my power consumption for today (3 Dec)- the the heatpump was set for a constant 40 degrees but no other tweaks or adjustments to any other controls.. Hotwater was on from 12:15 to 13:30 and heated from 35degrres to 40 degrees. I suspect that it was colder last night as the pump came on a couple of times and its been cold and wet all day today. Outside temp 4 degrees. You can see that it used more energy than yesterday (2 Dec). I'll turn weather compensation on tonight to see what it looks like tomorrow (BTW it took from 08:00 to 18:00 for the lounge temp to increase from 17 to 19 degrees)

Thats a nice little chart that yours generates.
After a couple of days since I set it, I find 17 degrees for the UFH is fine. Its just enough to take the chill off. I dont spend enough time downstairs to justify increasing it. Although that may change as winter bites.

Having the DHW heat to 45 deg. for 1 hour per day has been fine.

I think changing that 'big zero' on the Ecodans interface hasnt done anything. I think that number is only if you have the target flow temp mode on. Whereas I have it running in compensation mode. When I reduced it to -5, I was expecting to go into the compensation chart and see it reduced accordingly to 41 degrees, but it hadnt.

I will continue to watch videos and perhaps Ill find the answer. Ill be curious of your findings if and when you post them.

matelodave

Changing that big zero would have shifted the whole compensation curve down by 5 degrees - it doesn't alter the shape of the curve or the compensation setting screen but just moves it up and down. so the h/p wont actually try to get to 46 it will just stop at 41 (check the actual flow temp, not the setting)
It's useful to allow a a bit of a boost without having to keep adjusting the compensation slope. In fact I can also set timers on mine so which allows a bit of a boost in the mornings and evenings but normal operation during the day. I'll try drawing a piccy to show you how it works

dllive

I forgot to say, when I changed 'the big zero' (perhaps my new nickname!) I took photos:

This is just after I changed it (obviously). The icon just to the left of the -5 figure shows the system is in compensation mode.

What I was expecting to see on the above screen is the flow temp reduced by 5 degrees. But its still showing as 47. Perhaps thats expected. (from what youre saying, it is)

I also found this helpful screen which I presume is the current state of the DMH/heating. (I havnt seen it until now because I had to hold a button down for 3 seconds).

matelodave

It's not ever so good a drawing but it demonstrates what happens when you shift the compensation adjustments.
My unit's default (thick black line) was a flow temp of 39 degrees at -10 outside and then decreasing to 24 degrees at +15 outside. Shift it by +5 degrees move the whole slope upwards (the maroon line) or downwards by -5 degrees (green line) - the slope does not change. 
However if you alter the compensation slope( light blue line) you can alter the transition points and make it steeper so now the max flow temp is 36 degrees but it now occurs at 0 outside (35 degrees happened at -5 before) and we get a bit more heat up to 10 degrees but a bit less after than default. I found that default was a bit low at 0 degrees so tweaked mine to the dark blue line but as you can see you can still easily shift the whole lot up by + or -5 without altering the slope if you want to. Our unit is running at around 35 degrees when its +7 outside and 40 when its freezing which just about suits our heating profile. (the sweet spot is the yellow blob in the middle)
It did take me a long time to get my head around it and I spent the first couple of months tweaking and adjusting my controls (I did have the use of a multichannel temperature data logger which helped me measure and record what was going on and how it affected the temperatures in various places - I'll put up one of the graphs)

matelodave

The graph below shows the heatpump temps, room temps and outside temp. I've got a least dozen pages of plots to help evaluate and tweak the settings - this isn't the final tweak but is pretty representative of what is going on). Unfortunately I didn't have the capabilty to plot the power consumption when I was doing all this.

Top trace (mauve) is the flow, dark blue is the return - the big peak between 0500 and 0600 is the hot water heating. You'll also note that the heating system was shut down from about 2300 to about 0300 that's due to the room stats not calling for heat (they were all set a bit too low at 16 degrees so the place cooled down too far and then takes a long time to recover) The settings are just about OK down to 0 degrees.

Yellow is the lounge and blue is the study/.The two peaks on the lounge plot caused by unauthorised use of a fan heater which turns off the u/f in there and it doesn't then recover. The yellow trace shows how long it takes to heat the lounge so we dont let it get as low overnight anymore.

Green is the outside temp and it's noticeable how the flow/temp reduces slightly when the outside temp rises due to the compensation.

dllive

Just thought Id give you a quick update.

As far as I understand it, my settings are set to continuous; DMH 45 deg; Flow temp 40 deg (the default comp curve which Ive reduced by -5). This is what this screen is telling me. 

On my consumer unit Ive got the following:

Immersion is showing 220.64

Heat pump is showing 8105.48

So I presume the immersion has only ever come on when its done the legionella purge. (I changed this setting last week to be 60 degrees for 30 minutes, once every 14 days. It was running at 65 degrees every 7 days. So from now on this immersion figure shouldnt go up much).

As of today Im going to be taking daily readings twice per day. Ill be reading the consumed/delivery figures and the immersion/heat pump figures on the consumer unit.

Other than fiddling with that 'big zero' number (which Ive currently got as -5), Im not sure what else I can do to get a better COP. Ecodan videos say its best to leave it on continuously, becuase the Ecodan will then only deliver whats actually needed. Or perhaps I should try putting the DHW on a timer for 1 hour per day. But then doesnt that defeat the whole point? (ie the system is being let to cool down)

You say "...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" what can I do/try? Set the timers?

You say "Hopefully both it and the others enable the heating unit and pump (you need to check that they do) in which case you don't need to faff around with the heating unit timers, just the flow temperature otherwise they'll all be fighting each other.". Ive checked this, and yes they do. On my handheld thermo stat, if I see the heating isnt on, I increase the temp (or do manual override) and I see the flame icon appear and can hear the receiver click on. Same with the downstairs stats.

I have 2 methods of changing times and temperature: On the Ecodan, and on the handheld/wall stats. Im confused which ones I should be using. From what Ive read, its best to leave the Ecodan on continuously, and control the timing and temperature with the handheld/wall stats.

matelodave

Leave the Ecodan on continuously and it will maintain the flow temperature at whatever it's set to, either fixed or in line with the heat curve. The pump will then be controlled by the room thermostats.

You can time the hotwater if you wish. My hotwater is only activated for two hours a day before we get up and gives us all the hot water that we need. It takes around 1.5 hours to heat the tank to 45 degree and then stops - we don't need to keep the hot water tank topped up all day.

Regarding the room stats, we have eight programmable stats (which is probably overkill) one for each room. These are timed to raise and lower the room temperature according to it's use but non of them are set to go lower than 17 degrees during the "off" periods. We also have two eight port manifolds, one in the hall which feeds the hall, bedrooms and bathroom) and the other in the utility room which feeds the kitchen, lounge and dining room. The thermostats work like yours, opening the manifold flow actuators and controlling the heat pump and circulating pump

To give you an idea this is how mine are set.
Bedroom 1 & bathroom, 19C at 06:00, 18C at 09:00, 19C at 20:00, 17C at 22:00 (when we get up and retire)
Study - 19C at 08:00, 17C at 17:00 (as that's when its being used)
Spare bedroom - 17C continuous, unless its in use
Hall - 18C at 07:00, 17C at 22:00 (it's a big hall and the main thoroughfare through the bungalow)
Lounge & Dining room 19C at 07:00, 17C at 22:00 (its in use all day and the dining room is linked by an archway)*
Kitchen 18C at 0700, 17 at 09:00, 18C at 12:00, 17C at 14:00, 18C at 17:00, 17C at 19:00 just for the times its in use but it doesn't seem to get everso cold in there anyway.

*The lounge temperature drops to around 17 overnight and then takes most of the day to get back to 19 degrees - we do sometime up the temp to 20 in the lounge in the evening especially if its wet and windy outside - our bungalow is very exposed out in the Cambridgeshire fens and wind and rain seem to suck the heat away a lot faster than a cold crisp or even foggy day

The heatpump is set to run on compensated with an upper temp of 42 at -10 and lower temp of 25 at 15 degrees and I have a timed uplift of the heat curve at 07:00 to 09:00 of +5 (to give it a bit of a boost in the mornings) and then +2 from 17:00 to 22:00. Most of the time it runs between about 32-37 degrees but when it gets very cold it can get up to 45C but its quite rare. (it did it this week) It does crank up to 55 when its's heating the hotwater tank and the immersion kicks in when the sterilisation function is activated, but only to get it from 55 to 60 so it's only on for 30 minutes a week. I can decide when I want it to sterilise and the temperature but it does it every week, I cant extend.

This keeps the place comfortably warm, even this week when the temps were down to - 3 all day on both Sunday Monday with freezing fog and ice on the outside unit heat exchanger.

We then just let it get on with it and it still runs overnight if necessary to to prevent the house temp from dropping below 17C