Electric wet central heating confusion

Jimmymcmahon

Good evening all,
We moved into our current property back in December last year.
We did a uswitch as soon as we moved into the property in order to transfer to the energy supplier that we had in our previous property. This took 51 days to complete and as such we received a bill from the supplier for the 51 days use. As you can imagine, we were very alarmed when we saw that the bill came to £631.71 for little over 1 and a half months electric. According to the bill, during the 51 day period we had apparently used 4318 kWh of energy. That averages at about 80 units of electric per day.

To put it into context :-
There are two of us living in a 4 bedroom townhouse.
We both work full time and are out of the house most of the day.
Night time use is nothing untoward (we watch TV, we make a few brews, wash some clothes, dishwasher use etc). The reps we have spoke to at both energy suppliers were equally as shocked at the apparent usage. So much so, there is an engineer due to attend the property at the end of the month to install a check meter as it is suspected the meter is faulty.

In the interim, we are trying to rule out potential causes of the high electricity use in the unlikely event that the usage is indeed genuine.

The one thing that we cannot seem to get our heads around is the heating / hot water system and how this combines with the Economy 10 plan we receive from our energy provider.

This is a purely electric property with no gas supply.
There are wet radiators in each room and we understand that these are fed via an "Electromax combined electric flow boiler and direct unvented water heater".

There is a timing unit next to the boiler / heater which has been configured by the previous tenant to force the boiler "on" to "charge / heat up" overnight.

There is also a Danfoss control unit / thermostat in the hallway which allows us to turn the heating up or down or on / off completely.

We are on an Economy 10 electricity tariff with the new supplier who's off peak / lower rate times are as follows :-
13:00hrs - 16:00hrs
20:00hrs - 22:00hrs
00:00hrs - 05:00hrs

Are my following assumptions about how this type of heating is supposed to work correct :-
The boiler will "charge up" overnight using the lower rate electricity i.e (in the 00:00hrs - 05:00hrs window or whatever window we set it to on the timing unit next to it.
If we wake up in the morning and then turn the heating on (via the Danfoss unit), will we be using kWh / electricity the moment we turn the heating on or will the radiators be filled with already heated water from the overnight "charge" that we have already done? I assume it is the latter otherwise it makes the overnight "charge" pointless in my eyes.

If we left the heating on, and the overnight "charge" ran out a few hours later for example, I assume we would then be using on demand electricity again to keep the heating on? Is there a way to tell when this occurs? i.e can you tell when the overnight "charge" runs out and the kWh's meter starts ticking again?

The reason I ask this, is that the previous tenants had the Danfoss unit set to run on a programme. I.e the unit was programmed to maintain certain temperatures throughout different periods of the day. We assumed that this had been fine tuned by the previous tenants, so we just left it on since moving in, however the extortionate bill would suggest otherwise (if it does not turn out to be a faulty electricity meter and the heating is indeed the cause). Some of the radiators have TRV's on them and I assume that the concept of the Danfoss unit on the wall is that if we set it to 17 degrees for example, the heating would come on and once 17 degrees or higher is reached, the TRV's would detect this and the heating would switch itself off? Once the temparature dropped below 17 degrees, then the heating would automatically come on again until it reached / exceeded 17 degrees? Is that correct?

Each time the heating comes on to reach the 17 degrees set, I would see a flame icon appear on the Danfoss unit, which would indicate the heating is being forced on. Are these forced on heating periods coming from the overnight "charge" or am I using more on demand electricity again at these points ?

Apologies for the lengthy post and quite possible complete misunderstanding around this topic but I am essentially looking for some advice around the most cost efficient way to use the heating system we have, without churning through lots of kWh / ending up with extortionate bills. We would just like to be able to use the heating "normally" without having to get to the point where we are sat in 4 layers of clothes / gathered around a candle for fear or funning up huge bills

Any advice would be greatly appreciated

Many thanks in advance

Jimmymcmahon

As a new user I am unable to add direct links to the post above.
To see the pictures I tried to add, please put https:// infront of each of the links below

ibb.co/n8UPt5
ibb.co/bAczRQ
ibb.co/bEs50k

Cheers

molerat

Firstly you probably have the most expensive form of central heating known to man in a large house- you ARE going to get big bills.


Did you provide the move in readings to the supplier or did you rely on the agents to do it ? Having a check meter fitted before you have done thorough checks yourself could be costly - if the meter is accurate you will be billed around £80 for the service.


Depending on which model you have this eats 6-9 kWh when heating, the flame does mean it is using electric but not necessarily at full power. You need to try and get the unit only working during the off peak periods. You also need to ensure the boiler (flow) temperature has not been turned up to maximum and adjust the TRVs to a reasonable temperature.

EachPenny

jimmymcmahon wrote: »

There is also a Danfoss control unit / thermostat in the hallway which allows us to turn the heating up or down or on / off completely.
...
Some of the radiators have TRV's on them and I assume that the concept of the Danfoss unit on the wall is that if we set it to 17 degrees for example, the heating would come on and once 17 degrees or higher is reached, the TRV's would detect this and the heating would switch itself off? Once the temparature dropped below 17 degrees, then the heating would automatically come on again until it reached / exceeded 17 degrees? Is that correct?

Unless your TRV's are some kind of smart device linked to the wall mounted controller/thermostat then the answer is no, this isn't how the system works.

The TRV's each control the flow of water into the radiator they are fitted to. As the room air temperature nears the desired level the TRV will reduce the flow of water into the radiator, thereby reducing the amount of heat produced in that room. As the room air cools, the TRV will increase the flow to the radiator. Be aware that TRV's are not precise - the actual air temperature in the room may be quite different to the setting of the TRV.

The unit on the wall would normally control the system on a 'whole-house' basis. The radiator(s) in the room where the control/thermostat is located wouldn't normally have a TRV. The control knows that you want a certain temperature at a certain time of the day so will start the heating system and run it until that temperature is reached, then cycle it on and off to maintain the required temperature. But the temperature it is monitoring is only that of the room it is in, the temperatures in all the other rooms will vary according to how the TRV's are set and a whole load of other factors the details of which aren't relevant to this question.

There is usually another thermostat internally in the boiler which monitors the circulating water temperature (the water going from the boiler around the radiators). Each radiator is only capable of transmitting a certain amount of heat for a given set of temperatures. Taking the system as a whole, if most of the TRV radiator valves have closed, only the radiators with open TRV's (or no TRV) will transmit heat, which means the temperature of the circulating water increases. The boiler thermostat will be set to a certain circulating water temperature and when this is reached the boiler will shut down. It will stay shut down until the radiators have dispersed some heat and the circulating water temperature drops. This is what molerat is saying about the flow temperature - if it is set too high the boiler is not taking a rest and will go on supplying unnecessary heat which the radiators don't need to maintain the room temps.

Hope that helps

rtho782

Rip that system out and install an air to water ASHP. Your bills will immediately drop to about 1/3 of what they are now, due to increased efficiency, and then you will get large RHI payments that cover the rest.

Direct electric heating of water is awful for efficiency.

J_B

jimmymcmahon wrote: »

As a new user I am unable to add direct links to the post above.
To see the pictures I tried to add, please put https:// infront of each of the links below

ibb.co/n8UPt5
ibb.co/bAczRQ
ibb.co/bEs50k

Cheers

https://ibb.co/n8UPt5
https://ibb.co/bAczRQ
https://ibb.co/bEs50k

Does that work?

Cardew

rtho782 wrote: »

Rip that system out and install an air to water ASHP. Your bills will immediately drop to about 1/3 of what they are now, due to increased efficiency, and then you will get large RHI payments that cover the rest.

Direct electric heating of water is awful for efficiency.

Who pays?;) The OP is a tenant.

There is a timing unit next to the boiler / heater which has been configured by the previous tenant to force the boiler "on" to "charge / heat up" overnight.

collectors

Hi, there are pros & cons on a lot of systems. I was a little short on money when i moved into my bungalow & weighed up the outlay on LPG/OIL/ELECTRIC as i don't have natural gas. Forget electric as this should be outlawed as it will mostly take oil, gas,wood chip & so on to produce it. I am an electrician & would of said to any of my customers, do not go electric heating if its at all possible. I skiped the existing NS heaters within 2 days of moving in .
At the time of my installation "2012" it was down to oil or LPG. To fit just the tanks & boiler with oil would have been around £3000.00. For the LPG was £1400.00, that's quite a bit of LPG to put in my tank. I must point out that i had a jcb here at the time & it only took 40mins to dig a hole for the new underground gas tank.
My place is equal to a 4 bed 3 bath detached & i am a bit tight with the heating, "2 hours in the morning & 4-5 in the evening & 2 hours each day with hot water. In the winter it's around a £100.00 per month, & that's 14 rads & a big HW tank.
The only adaptation i had on the boiler was to change the supplied gas jets "10 minutes work"
In the long run LPG will cost me slightly more than oil, but no way as expensive as electric & it sound like you have a system that could be adapted very easily. .
Just a note: I put my boiler in the cold loft to save some room. DONT. My boiler has an inbuilt program that brings on the pump at 6deg & fires the boiler up at 3deg as a frost protection. If i had the boiler in the house i bet i could of saved £10.00 a month in the winter as everything is very well lagged in the loft. .
Just a quick edit. There might be a faulty frost stat kicking in if fitted.

Good luck

Chris

molerat

Not a lot of use to the OP as they live in rented so cannot change and need to make the most economical use of the system they have.

EachPenny

rtho782 wrote: »

Direct electric heating of water is awful for efficiency.

Really? Any figures to support that? Bear in mind you need to consider the efficiency of the system as a whole, and the way it is used, not just the efficiency of the machine that produces usable heat from an energy input. The science of efficiency is complex and rarely black-and-white.

I have just noticed that the OP doesn't mention anything about the method of heating their hot water. Hopefully they have immersion heater(s) operating in the cheap period, but I'd want to check to make sure the electric boiler is not being used to heat hot water - that wouldn't be cheap, or efficient.

collectors

molerat wrote: »

Not a lot of use to the OP as they live in rented so cannot change and need to make the most economical use of the system they have.

OK, I'm a Muppet for not fully reading it properly.
If the person writing this thread could say if they are the tenants or owners. Thanks
Must admit at those prices i would change the system myself if there is a landlord involved that would contribute..