Un-usual 3 phase problem

[ipf]

That was the only option Darkwood i thought would be open to me, other than using 3 separate meters. There is always the option of multiple coin timers on contactors but then you run the risk of overpaying. However the heaters can be split into 4 areas so limits turning off locally. Time could then be calculated by the KW per coin.

IPF, it has only ever been measuring 6kw (2 x heaters) so cant over charge. only ever under charged when any are turned off.

Biggest job i have is trying to explain the options available to the client, if we are struggling to get our heads round it this then they need to sit down for a while.

Sorry if I misunderstood NEEDA, I thought you meant the tarrif had been adjusted. Not my area really. Too much thought maybe.

 

[needasparks]

I guess your correct, 30 years ago no one dreamed any of the heaters would be turned off and assumed full load but people now want it in all the colours and all the sizes with a cherry on top.

Its rum o'clock so as said gonna sleep on it.

 

[needasparks]

I like your thinking! Something like this maybe?
View attachment 8185

I wish it was that easy, Thats the part that wont work as neutral is at unity on three phase resistive load.
Think about it, if each phase runs 100amps would you have 300 amps on the neutral. 120 deg blah, blah blah.

 

[Kamikaze]

Interesting problem!

After banging my head against the wall for a while, how about this, put the meter on the neutral associated with these 3 phases only??? Probably needs more thought.

edit

probably a very dangerous way of doing it!
The heaters would still be live when the meter disconnects the neutral.

I like your thinking! Something like this maybe?

 

[ufkir]

why not work out what you get for a £1 lets say its an hour then wire from the load side of the meter to a timer thats set to give you an hour when energised and make the timer control your contactor so that it dosnt matter which heaters they turn off they only get one hour. one prob is that if they put in £3 at once they wont get 3hours unless you can adjust the meter.

 

[Knobhead]

I like your thinking! Something like this maybe?

View attachment 8189

Sorry kid that was the idea I dumped. Look in to how vector currents in the neutral work.

In = √((L1²+ L2²+ L3²)-((L1*L2)+(L1*L3)+(L2*L3)))

 

[Kamikaze]

It’s that Kirchhoff putting a spanner in the works again….lol. More thought required on this one, but I’m determined a creative solution is better than an expensive one. Back to the drawing board!

 

[malcolmsanford]

The obvious way for me is not to try and change a system that's worked for 30 yrs but to try and stop the people switching the heaters off, how are they doing this?

If there is a simple switch FCU they are activating remove the FCU and replace with a double pole keyswitch and if needed series a fuse holder into it on a grid arrangement. Or just enclose the FCU in a lockable enclosure.

If they are switching off from the equipment then bypass the switch on the equipment and utilize as above. If certain units are not needed then again on request the owner/caretaker can isolate them.

Would this work

 

[Kamikaze]

Just a timer coin meter which switches the coil on a 3 phase contactor would be the most sensible idea.

 

[Knobhead]

Just a timer coin meter which switches the coil on a 3 phase contactor would be the most sensible idea.

But not legal see #26

 

[alli]

I'd be sneaky and put the meter on a different phase and tell everybody who'll listen that you have changed the system to stop people having free electric, even though it is a load of crock! Then when they turn off the radiators they think use the money. They still be charged. HeHe

 

[ipf]

Rotate the control phase on a regular basis? If legal (#26). Wont solve it completely but will certainly put a spanner in the mix. I think ?

 

[Knobhead]

If any alterations are made they have to comply with http://www.ofgem.gov.uk/Consumers/Pages/Resaleofgasandelectricity.aspx
I’m surprised the landlord hasn’t ended up in court all ready.

The maximum amount landlords or “resellers” are permitted to charge for gas or electricity is the amount they have paid for it, plus VAT at the appropriate rate; this is termed the Maximum Resale Price or MRP. Any standing charges can be recovered by the Landlord by dividing it on a pro-rata basis according to usage between all the tenants.

 

[ipf]

Tony, I,ve a client who is splitting an old works into a couple of ind. units with individual office units upstairs. Your info leads me to believe that each office would have to be metered individually to comply. Correct? He intends to include costs in rent which would be approx not exact.

 

[HandySparks]

The OP says that this is a hall used by the public for hire. According to the "Guidance for Resellers" document, the rules only apply when the electricity is for domestic use.

I would just fit a coin operated timer and contactor. Maybe add a notice that heat is charged on a timed basis only, irrespective of the number of heaters actually switched on.