IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Change over relay for mains supply
Topic Summary:
Created On: 08 August 2014 06:41 PM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 08 August 2014 06:41 PM
User is offline View Users Profile Print this message



mattrowland

Posts: 33
Joined: 05 January 2006

I want to put together a 2 pole change over relay unit that will switch between a standard mains grid supply and an economy 7 supply. The control voltage is 24-29Vdc. Contact rating 240Vac at 20A. Does this have to be an approved relay/contactor (like with G59- NB. I know this is a different beast). Are there solid state relays that will do this? Advice appreciated.

Matt
 08 August 2014 09:14 PM
User is offline View Users Profile Print this message


Avatar for slittle.
slittle

Posts: 3559
Joined: 22 November 2007

I would use a pair of mechanically interlocked contactors with a 24v coil.

Over rating the contacts is always a good move too in my opinion



Stu
 08 August 2014 09:32 PM
User is offline View Users Profile Print this message



broadgage

Posts: 1311
Joined: 07 August 2007

Generally, if an economy 7 tariff is in use, then all electricity from any subcircuit in the installation will charged for at the reduced rate during the relevant hours. Outside of these hours all energy used will be charged for at the higher rate.

Therefore nothing is to be gained by use of any changeover arrangement.
 08 August 2014 09:34 PM
User is offline View Users Profile Print this message


Avatar for slittle.
slittle

Posts: 3559
Joined: 22 November 2007

That's a good point as I've got E7 but no contactors or indeed off peak heating load....

Stu
 09 August 2014 12:14 AM
User is offline View Users Profile Print this message



allaway

Posts: 86
Joined: 08 July 2007

Originally posted by: broadgage

Generally, if an economy 7 tariff is in use, then all electricity from any subcircuit in the installation will charged for at the reduced rate during the relevant hours. Outside of these hours all energy used will be charged for at the higher rate.



Therefore nothing is to be gained by use of any changeover arrangement.


Actually there is.

There are three tariffs in this situation:

Standard Tariff; applicable to all power on one supply

E7 - off-peak; a low rate tariff available for the 7 hour period

E7 - peak; charged at a premium over standard tariff.


The OP wants to supply everything he can during the off-peak period and obtain the low rate tariff but during the peak period would prefer to use a standard tariff supply for the remaining circuits and avoid the premium E7 - peak tariff.
 09 August 2014 09:08 AM
User is offline View Users Profile Print this message


Avatar for AncientMariner.
AncientMariner

Posts: 527
Joined: 14 December 2004

Seems strange that the OP has both a Standard Tariff Meter and an E7 Meter at the same location?

Also, if such a changeover contactor was fitted, would the short break in supply be acceptable at changeover times?

A small UPS for a pc is one thing, having one for each TV etc, is something else.

Cheers!

-------------------------
Clive S Carver GCGI IEng MIET
 09 August 2014 01:22 PM
User is offline View Users Profile Print this message



alancapon

Posts: 5790
Joined: 27 December 2005

Originally posted by: allaway
. . . The OP wants to supply everything he can during the off-peak period and obtain the low rate tariff but during the peak period would prefer to use a standard tariff supply for the remaining circuits and avoid the premium E7 - peak tariff.

Interesting. It always used to be a condition of E7 that no other tariffs could be installed in the property.

I would be wary of the changeover arrangement. If the changeover operates too quickly, you may start destroying things due to over-voltage effects. Ideally, you either want a break for several seconds to allow any appliance motors to stop, or you need a UPS to "ride through" the changeover.

Regards,

Alan.
 09 August 2014 06:34 PM
User is offline View Users Profile Print this message


Avatar for potential.
potential

Posts: 1278
Joined: 01 February 2007

In the old days of Economy 10 (and other tariffs) an additional meter was fitted that didn't supply anything other than storage heaters.
Perhaps this the OP's situation?
 10 August 2014 11:34 AM
User is offline View Users Profile Print this message



allaway

Posts: 86
Joined: 08 July 2007

Originally posted by: potential

In the old days of Economy 10 (and other tariffs) an additional meter was fitted that didn't supply anything other than storage heaters.

Perhaps this the OP's situation?



My E10 has only ever had one meter (prior to that E7 too) and they have always been dual reading with an internal set of contacts for the off-peak load.



Reminds me of a problem a few years back when I was asked for advice on a problem as I knew the house layout. The house owner had contacted his supplier because the storage heaters were permanently ON and charging. Twice it was "checked" and "no fault found".

When I looked into it, all consumption was being charged at off-peak 24 hours per day. We traced the fault and where some floor boards had been nailed down, with 4" nails, one had gone through a cable. This caused the meter changeover contacts to weld together. The fault was not outwardly apparent as it was on a 4mm ring and the nail was no longer in contact with the cable - close but vaporisation of the copper left a small gap. As such the meter indicated it was on Peak, but consumption was on the Off-Peak dials.
 11 August 2014 11:09 AM
User is offline View Users Profile Print this message



mattrowland

Posts: 33
Joined: 05 January 2006

Thanks for the replies. In this instance there are two meters. One for E7, supplying storage heaters and one for the standard consumer unit. The relay change over would be to supply a bespoke power supply unit containing battery storage. Matt
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.