Economy 7 supply cable advice required

[Bob Harris]

I'd like to first state that i don't intend to carry out the works myself, i just want to understand what would be required so i can make sure i wont be getting ripped off again.

I have a building at the end of my garden that i use as my home office.
At the moment the only heat source is a portable Dimplex oil free electric heater. What i want to do is have an economy 7 storage heater fitted.

I have several economy 7 storage heaters in my house on their own wiring circuit.
How do i get the power supply out to my garden building without digging up the patio and lawn?

The current armored cable supplying the garden building is burried deep underground but reenters the house in my hallway where the consumer units are located.

 

[endecotp]

Obviously you want to avoid digging up the garden again if you can...

If it were me, I'd try to find a low-wattage storage heater that can be connected to the existing wiring without overloading it. Then I'd connect a timeswitch locally in the shed to turn the heater on at night. The difficulty is that you will need to guess when the E7 cheap periods are. I don't know how consistent they are from night to night. Or maybe it's possible to buy an E7 radio switch?

Is your shed sufficiently well insulated for a storage heater to work well?

 

[EFLImpudence]

That depends on whether the whole supply is switched to cheap rate at night or

the cheap rate is only supplied to the heaters at night.

 

[JohnW2]

That depends on whether the whole supply is switched to cheap rate at night or the cheap rate is only supplied to the heaters at night.

Indeed so. I believe that the original E7 installations were of the latter type but that, now, most of them (like mine) are of the former type. If that (the former) is what the OP has, then he can (without any modification or addition to the cabling) obviously just install any storage heater in the outbuilding for which the capacity of the current supply cable is adequate. This is where one probably has to hope that the person who initially installed the cable to the outhouse was "thinking future-proofing"!

Kind Regards, John

 

[AndyPRK]

If your swa cable is 3? or 4 core you could use the spare core for the heater.

Worth a peek at one end.

 

[Bob Harris]

That depends on whether the whole supply is switched to cheap rate at night or

the cheap rate is only supplied to the heaters at night.

I have no idea and my electricity supplier is closed until monday. Is there anyway i can find out this infor mation myself?

 

[JohnW2]

I have no idea and my electricity supplier is closed until monday. Is there anyway i can find out this information myself?

Your supplier might well not even know - it depends upon how your installation is wired.

Are your storage heaters currently witched off ('Summer'!) and do you have a meter which shows both 'normal' and 'off-peak' readings?

Kind Regards, John

 

[Bob Harris]

I have no idea and my electricity supplier is closed until monday. Is there anyway i can find out this information myself?

Your supplier might well not even know - it depends upon how your installation is wired.

Are your storage heaters currently witched off ('Summer'!) and do you have a meter which shows both 'normal' and 'off-peak' readings?

Kind Regards, John

Yes, heaters are all currently switched off. My meter does indeed show low and normal readings.

 

[JohnW2]

Yes, heaters are all currently switched off. My meter does indeed show low and normal readings.

OK - so if you wait until late (or early!) enough for the E7 to be on it's 'low/night' rate, you could then switch on a largish load (fan heater, tumble dryer etc.) plugged into one of your normal sockets and watch and see which of the low rate and normal rate readings responded by increasing.

Kind Regards, John

 

[Bob Harris]

Yes, heaters are all currently switched off. My meter does indeed show low and normal readings.

OK - so if you wait until late (or early!) enough for the E7 to be on it's 'low/night' rate, you could then switch on a largish load (fan heater, tumble dryer etc.) plugged into one of your normal sockets and watch and see which of the low rate and normal rate readings responded by increasing.

Kind Regards, John

Great, thanks!

 

[endecotp]

That depends on whether the whole supply is switched to cheap rate at night or

the cheap rate is only supplied to the heaters at night.

I have no idea and my electricity supplier is closed until monday. Is there anyway i can find out this infor mation myself?

Post a photo of your meter, consumer unit and associated things.

 

[Lectrician]

True economy 7 will give low rate units to the whole installation, providing a switched output too for storage rads/immersion.

Older installs where just heating is cheap rate were known as simply off peak, or white meter. There are some modern tariffs that provide differing rates though, some have three rates, and differing grouping.

A three core cable would be unsuitable to directly feed peak/off peak due to the shared neutral, but you could take an off peak feed from the off peak CU to feed a contactor (L and N). The contactor could switch the third core. You would need to feed both the switched and unswitched core from the same MCB though, due to shared neutral.

 

[Bob Harris]

That depends on whether the whole supply is switched to cheap rate at night or

the cheap rate is only supplied to the heaters at night.

I have no idea and my electricity supplier is closed until monday. Is there anyway i can find out this infor mation myself?

Post a photo of your meter, consumer unit and associated things.

Image

• Bob Harris
• 21 Aug 2016

Electric meter economy 7

Meter

Image

• Bob Harris
• 21 Aug 2016

Consumer unit

Consumer unit

Image

• Bob Harris
• 21 Aug 2016

Economy 7 consumer unit

Economy 7 Consumer Unit for heaters

Image

• Bob Harris
• 21 Aug 2016

Outbuilding consumer unit

Outbuilding Consumer Unit

 

[endecotp]

Based on that first photo, I reckon you get all your electricity at the cheap rate when it is active.
(I don't think I've ever seen an installation where this wasn't the case.)

 

[JohnW2]

Based on that first photo, I reckon you get all your electricity at the cheap rate when it is active. (I don't think I've ever seen an installation where this wasn't the case.)

It wasn't the case when I moved into my present house, nearly 30 years ago. It was on an E7 tariff. There were separate 'normal' and 'low rate' meters, the latter (just feeding storage heaters) supplied via a contactor (controlled by a timeswitch). Hence only the storage heaters benefited from the cheap rate.

Kind Regards, John