Discuss Underfloor heating with economy 7 ? in the Electric Underfloor Heating Wiring area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

I came across something like this in a 1960s flat. Surprised to find that it was on night tariff, it heated up the whole floor slab and slowly released throughout the day. Original installation, still working 50 years on
Gran had that setup in her sheltered flat. It was terrible, really really terrible.
Floors were hard because she could only have thin carpets, and temperature regulation was really really rubbish. Part of the problem was the south facing window - so on sunny afternoons the place would be roasting but still getting heat from the uncontrolled storage heater (aka floor slab). But that was only part of the problem - as mentioned, heat output is highest in the early hours when fully heated, and lowest in the evening (when you most want it) as the slab cools.
 
Gran had that setup in her sheltered flat. It was terrible, really really terrible.
Floors were hard because she could only have thin carpets, and temperature regulation was really really rubbish. Part of the problem was the south facing window - so on sunny afternoons the place would be roasting but still getting heat from the uncontrolled storage heater (aka floor slab). But that was only part of the problem - as mentioned, heat output is highest in the early hours when fully heated, and lowest in the evening (when you most want it) as the slab cools.
I have experienced a similar thing in an old flat. It was always too hot in the daytime.
 
I assume it is electric underfloor heating? ?

If so, there's little point having it on E7. The floor will heat up when you are asleep and then switch off just about when you wake up.
 
Yes we have e7 underfloor
stone oversite/100mm celotex / 100mm concrete/cable elements /50mm concrete /carpets
works very well room stat and contactor to control takes 2 days to heat up then stays constat all winter
cheaper running than our other house
 
If so, there's little point having it on E7. The floor will heat up when you are asleep and then switch off just about when you wake up.
Indeed, many years ago one of my grand mothers moved into a flat with electric off-peak underfloor heating. It was truly terrible.
The theory was that using off-peak it would heat up the big concrete slab, which would keep the flat warm all day.
In practice, it meant that the floor was hot first thing in the morning and the flat a bit over heated. After a while it would all start cooling down. If it was a sunny day, then the sun would stream in through the large front window and the place would overheat for the afternoon. If there was no sun then things would just keep cooling down. And then in the evening, it would be getting cool or cold.
And of course, this was back in the 70s (IIRC) so not insulated to modern standards, hence needing considerable heat input - and meaning that only thin carpets & no underlay could be used. Not very comfortable underfoot.
 
Yes we have e7 underfloor
stone oversite/100mm celotex / 100mm concrete/cable elements /50mm concrete /carpets
works very well room stat and contactor to control takes 2 days to heat up then stays constat all winter
cheaper running than our other house
Thanks for your reply @gaz101 are you saying you keep the UFH on day and night on a room thermostat to keep the temp constant all winter rather than switch on and off daily? Thanks
 
It is wired from the e7 timer only heats at night
Sorry not sure I understand that question. I can set the time the water is heated on the economy 7 panel and the UFH has zones to which we can set the times and temps.we pay a cheaper rate for electric at night on economy 7 compared to daytime hours.
 
OK but have you tried it? No
I think I will just get it wired in and test it with a simple on off switch and see
How long it stays warm.. Also have a high wattage matting... If its stays warm until late afternoon I will be happy and it will cost next to nothing as economy seven is so cheap?
If it doesn't work then I can get it wired with normal supply and metre etc?
 
OK but have you tried it? No
I think I will just get it wired in and test it with a simple on off switch and see
How long it stays warm.. Also have a high wattage matting... If its stays warm until late afternoon I will be happy and it will cost next to nothing as economy seven is so cheap?
If it doesn't work then I can get it wired with normal supply and metre etc?
Did you test this out? I'm still unsure of the most economical way to operate my UFH with the economy 7 meter the builder installed. Be interested in your test results. Does the floor retain enough heat during the day from it being switched on at night when electric is at it's most cheapest? Thanks
 
Alot depends on how it's installed... i.e. do you have enough thermal mass to play with. Normal electric UFH is not designed to work this way.
 
A builder built my house, so I have no idea what thermal mass even is ?but you probably suspected that!) I have heard talk that UFH retains the heat well esp if you have good insulatio in the building. I'm hoping I can switch it on for a few hours at the cheap rate (as it takes a long time to warm) and it will retain a temperature comfortable enough to not need the an extra heater during the day/eve? ?‍♀️?‍♂️?‍♀️
 
Retaining heat and the type of heating source are different things. A well insulated building will retain heat regardless of where that heat came from.
Also, a big slab of concrete will indeed contain quite a bit of heat - but then the heat input to the room from that slab is uncontrolled. In some respects, the worst thing is a big heavy slab because it stores a lot of heat so it can't be turned down quickly. That's a problem with night storage heaters, because even though they have a damper to control air flow based on room temperature, to give the best results they need adjusting every day to suit expected heat demand for the following day - otherwise you either under-heat on cold days or over-heat on hot days.
Similarly, with a big heavy slab, yes you can store heat from off-peak lecky. But unless the room heat loss doesn't drop below the heat input rate from the slab to the room, then you'll end up with the room too hot. In practical terms you'll get more heat in the room in the morning (slab is hot), and less in the evening when it's typically most needed in a domestic environment because the slab will already have lost some of it's heat. Of course, a really massive slab will lose less temperature during the day for a given heat loss - but the flipside is that control operates over an even longer timescale.

As others have said, you may be better storing (at least some of your heat) in a wet system that can be easily controlled to output the heat where you want it when you want it. But that does need quite a large tank of water.

If you have rooms with a significant solar input (big windows, especially south facing) then you'll have serious over-heating problems (on sunny days) with a big slab of heated concrete.
 
Retaining heat and the type of heating source are different things. A well insulated building will retain heat regardless of where that heat came from.
Also, a big slab of concrete will indeed contain quite a bit of heat - but then the heat input to the room from that slab is uncontrolled. In some respects, the worst thing is a big heavy slab because it stores a lot of heat so it can't be turned down quickly. That's a problem with night storage heaters, because even though they have a damper to control air flow based on room temperature, to give the best results they need adjusting every day to suit expected heat demand for the following day - otherwise you either under-heat on cold days or over-heat on hot days.
Similarly, with a big heavy slab, yes you can store heat from off-peak lecky. But unless the room heat loss doesn't drop below the heat input rate from the slab to the room, then you'll end up with the room too hot. In practical terms you'll get more heat in the room in the morning (slab is hot), and less in the evening when it's typically most needed in a domestic environment because the slab will already have lost some of it's heat. Of course, a really massive slab will lose less temperature during the day for a given heat loss - but the flipside is that control operates over an even longer timescale.

As others have said, you may be better storing (at least some of your heat) in a wet system that can be easily controlled to output the heat where you want it when you want it. But that does need quite a large tank of water.

If you have rooms with a significant solar input (big windows, especially south facing) then you'll have serious over-heating problems (on sunny days) with a big slab of heated concrete.

Retaining heat and the type of heating source are different things. A well insulated building will retain heat regardless of where that heat came from.
Also, a big slab of concrete will indeed contain quite a bit of heat - but then the heat input to the room from that slab is uncontrolled. In some respects, the worst thing is a big heavy slab because it stores a lot of heat so it can't be turned down quickly. That's a problem with night storage heaters, because even though they have a damper to control air flow based on room temperature, to give the best results they need adjusting every day to suit expected heat demand for the following day - otherwise you either under-heat on cold days or over-heat on hot days.
Similarly, with a big heavy slab, yes you can store heat from off-peak lecky. But unless the room heat loss doesn't drop below the heat input rate from the slab to the room, then you'll end up with the room too hot. In practical terms you'll get more heat in the room in the morning (slab is hot), and less in the evening when it's typically most needed in a domestic environment because the slab will already have lost some of it's heat. Of course, a really massive slab will lose less temperature during the day for a given heat loss - but the flipside is that control operates over an even longer timescale.

As others have said, you may be better storing (at least some of your heat) in a wet system that can be easily controlled to output the heat where you want it when you want it. But that does need quite a large tank of water.

If you have rooms with a significant solar input (big windows, especially south facing) then you'll have serious over-heating problems (on sunny days) with a big slab of thanks.
 
Yes, solar input is (often) welcome.
But not when you know you've spent a fortune on heating up that big slab of concrete and now have the windows open to get rid of the heat. And that's where any sort of uncontrolled (or poorly controlled) heat input fails - you end up with too much heat and end up throwing some of it away.

With controllable heating - e.g. traditional radiators or UFH without a huge thermal mass - you turn off the heat sources (or the controls do it automatically) when there's other heat coming in. But you can't do that when the controlled heat input was done yesterday - hence my comment that storage heaters really need adjusting every day for tomorrow's demands.
 

Reply to Underfloor heating with economy 7 ? in the Electric Underfloor Heating Wiring area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock