My first electricity bill...

[Ultima357]

13 hours ago, joe90 said:

My floors don’t feel warm either but the house is a steady 21’ give or take 1’. My buffer is 80 litres, my ASHP is on 24/7 controlled by a stat on the buffer tank and has never run out (that I have noticed). My total electricity usage in mid winter is £130 ish.

Do you think its better to run it 24hrs rather than as I do, which is to leave on but set it back a degree or two at night? With our passive construction, it doesn't come on at night. In the morning I bring in the zones as needed over a couple of hours or so, so that it doesn't suddenly get a huge heat demand. 

[joe90]

48 minutes ago, Ultima357 said:

Do you think its better to run it 24hrs rather than as I do, which is to leave on but set it back a degree or two at night? With our passive construction, it doesn't come on at night. In the morning I bring in the zones as needed over a couple of hours or so, so that it doesn't suddenly get a huge heat demand. 

Well mine takes many hours to change temp (probably because of the low flow temp) but yes mine runs 24/7 and only comes on when the hallway stat gets below 21’ so may be worth trying

[SteamyTea]

This running 24/7, setting back temperatures, or using at fixed times is all a bit confusing.

My take on it is that even a system that is set for fixed temperature and run 24/7 does not actually do that.

All it is doing is taking a que from the room thermostats and switching on if needed.

Using a set back temperature basically just delays the switching on until the conditions are met i.e. between 8AM and 12 Noon, temperature less than 18°C.  This is no different than using a thermostat with a large hysteresis.  It is also what a buffer tank can do, but between the heat source and the room.  There is possibly a reason to have the temperature variation within the buffer tank larger than the room thermostat hysteresis i.e. buffer temp range ± 5°C, room stat hysteresis ± 1°C.

 

Run a lower temperature system at fixed times is alright, as long as it is powerful enough to reach the target temperature within a reasonable time i.e. 1 hour.

[AliG]

A houses' heating energy usage is driven by its heat losses. Whether you replace these losses over 24 hours or 10 hours you will use the same amount of energy. So theoretically whether the heating is on (regulated by thermostat) all the time or some of the time it should not make any difference. It won't be exactly the same but near enough.

 

However, if the house has high heat losses as they traditionally had, then turning the heating off during the night or when you are out allows the temperature to temporarily be below a comfortable temperature which will save some energy. You will still need most of the energy to get back up to the target level but there will have been a period when you were saving some energy as it was colder. The smaller temperature differential will modestly reduce energy losses. The worse insulated a house is, the more it will benefit from this. Most of the houses on here will see such small changes in temperature over a few hours as to eliminate any benefits from this factor.

 

With an ASHP the COP is better the lower the temperature the water is heated to. Thus you want to run the UFH flow at the minimum temperature required to offset the house's heat loss over 24 hours. To run it less than 24 hours would require a higher flow temperature and lower COP. Running it more or less than 24 hours a day will probably not make much  difference unless you adjust the flow temperature at the same time.

 

 

Edited January 28, 2021 by AliG

[ProDave]

13 hours ago, bigreadie said:

Just started the readings...as the immersion and heat pump have their own meters so will be able to see what the consumption is.  I don't have regular readings but i know that the meters were all at zero when installed so can work out a daily average from that.  I'm also planning changing to an always on programme to see how that compares...surely it won't cost any more!!

I would be interested to see the daily readings for heat pump an immersion once you have a few days readings.

[Ultima357]

7 hours ago, joe90 said:

Well mine takes many hours to change temp (probably because of the low flow temp) but yes mine runs 24/7 and only comes on when the hallway stat gets below 21’ so may be worth trying

I have 14 individual zones, so very controllable. We run at 22 to 23 degrees during the day and set back to 21 overnight. Like you, I find UFH not very responsive but then again mine is cast into the fully insulated floor slab, so 155 tons of concrete heat store and generally the pipes are in the middle of 150mm thick slab. So I guess it can't be that responsive. We rarely lose more than 1 degree overnight (22:00 to 07:00),so guess its not going to make a huge difference. 

[Redoctober]

13 hours ago, PeterStarck said:

What's the immersion for. It could well be using a lot of electricity, have you tried turning it off.

 

Just bumping this question as I too would like to know - we have an immersion and it is never switched off! Is this something I could change by switching it on and off when necessary? But I suppose in order to do that I would need to know its purpose.

[joe90]

5 minutes ago, Redoctober said:

 

Just bumping this question as I too would like to know - we have an immersion and it is never switched off! Is this something I could change by switching it on and off when necessary? But I suppose in order to do that I would need to know its purpose.

Immersions are usually back ups, legionella dosing (on a timer) or built into the ASHP to raise DHW to higher temps. What’s your set up?.

[Redoctober]

14 hours ago, joe90 said:

Immersions are usually back ups, legionella dosing (on a timer) or built into the ASHP to raise DHW to higher temps. What’s your set up?.

 

Hi @joe90  Not sure what the set up is other than the "system" is controlled by a central control panel and then there are seperate units for each room. I have attached some images which may help fill in the gaps of my limited knowledge. I do know though that the main control panel has been set up to allow a regular "legionella"  flush so to speak, which brings into question my immersion heater switch. Both these wall units are on 24 / 7 and one is labeled "water heater".

 

 

 

 

 

Edited January 29, 2021 by Redoctober
tidy up

[joe90]

@Redoctober, personal choice but quite a few of us don’t believe in/operate a legionella cycle. Why not try turning off the immersion and see what happens, mine are only used fir backup.

[ProDave]

Yes definitely turn off the immersion heater switch.

 

If the immersion is controlled by the HP controller for anti legionaires it should not be in 24/7

[Redoctober]

Thanks @ProDave and @joe90 i  will give that a go - sadly though you are dealing with a right numpty and knowing my luck I will switch the wrong one off - Is the one marked "water heater" that I should turn off and see how things change? ?

[ProDave]

Yes turn off the "water heater" switch and report back the changes.

[joe90]

I do think the other switch should have a label (if done by a professional ?‍♂️).

[Trw144]

On the subject of legionella, our biomass boilers are programmed to raise the temperature once a week to kill it (70 degrees from memory), the rest of the time we tend to keep lower temps.

Edited January 29, 2021 by Trw144

[TonyT]

I wouldn’t be overly concerned about legionella in a domestic situation 

 

heating a tank is helpful, but if there isn’t a destratification pump it may not heat the whole body of the tank....

Edited January 29, 2021 by TonyT

[john0wingnut]

On 27/01/2021 at 19:47, bigreadie said:

..is £820 for the quarter.  I appreciate it is winter and the pump works harder but I wasn't expecting that.

 

Lighting wise I have the open fitted with spots (only since Dec) and appliance wise (again since Dec) couple of ovens, hob, 2x F/F and a dishwasher which leads me to think the UFH is the culprit.

 

I have looked at the UFH pump (a wilo 25/6) and found that the setting on this was not correct for the UFH so have change the profile as per the manual but couldn't work out what speed to set so went for the medium. I only have 5 zones from the 10 zone manifold active ( four controlled by a neostat) and one zone (bedroom)that is on but with the little TRV so comes on and off with the open plan.

 area.  Flow rates are set to 1.5ish l/m.  I have a 40l buffer but have found that when the heating comes on this drains and before the required room temp is reached it empties and I am pumping cold water around the system.  None of the floors are warm (which the wife is most annoyed by) although the house does not feel cold.

 

The UFH pipes etc was installed by the screed company and the water works and pump by a reputable plumbers.  I connected the flow and return to the cylinder and when the commissioned that they said there was no issues with the plumbing between the two.  I would have called someone out to have a look but I am skint now...any ideas please?

 

thanks in advance  

 

 

Hi

 

I have a NIBE 2040 12kw unit with 100l buffer, and our bills are nowhere near that. 
 

We have a bungalow about 180sqm, all UFH.

 

It has taken me a while to fine tune the system - we have an SMO20 controller - is this what you have?

 

You should also have multiple temp probes:

flow and return from ASHP, one in the buffer, and one on a pipe labelled “heat medium return” 

 

I now have max flow line temp set to 40 degrees  and the temperature curve is 8 with an offset of +1.

 

There are multiple settings around when the immersions kick in, and these need setting correctly, as when setup incorrectly, they are overused and will hike the bills up.

 

Take a look at your degree minutes setting. Should be 100. Lower = short cycling.

 

As previous posts mention, your buffer temp prob should tell the SMO20 to call for more heat when it goes below a set temp, so the floors should never run a lower temp than the flow line being required by the set heat curve.

 

Where have you placed your outdoor air sensor?