Yes it is. A simple current transformer and LED load in the live feed will give an indication as long a current is flowing. The problem that I see is that the current will cease, when switched off, or the thermostat has opened. The first should be obvious and the second is not a fault condition, but the indicator LED will go out.
A second fault condition is where the heating element sheath perforates and allows current to bypass the thermostat. That would cause the LED to light, suggesting everything is working properly. Placing the indicator circuit in the neutral or low side could overcome that issue. It also assumes that the boiler and heating element case is properly earthed. Which in the UK is a requirement.
But I think he wants an indication when current doesn't flow.
RY3 is self latched after reset is pushed and is held latched by current through the NC contacts of RY1 (when the thermostst is open). When the themostat closes (and breaks the NC contacts of RY1), current should flow the heating element and current transformer this will energize RY2, which keeps the coil of RY3 energized. So no indication happens but if no current flows RY2 is not energized, this stops the current through RY3 causing the indicator lamp to light.
I'm not sure on this one, but I don't think you would get enough current flow through the water to energize RY2 with the current transformer.
you will get enough through the live half to blow the fuse. (and until then it's still heating the water) the CT is on what would be the neutral leg of the 240V element, so yeah there won't be much through that, especially after the fuse blows.
Hmm! Here in the states with 240V, both sides are live. When wiring a standard water heater you connect 240V to the element and ground the case. No neutral involved. If you know how the UK system is wired could post a schematic on ABSE, photobucket or whatever site pleases you? Sure would be nice for the original poster to chime in. Mike
In the States a domestic supply is 110.0.110 where the 0 is the neutral and I belive is also earthed or at earth potential. In the UK there is only 230.0 where 0 is the neutral and at earth potential
components involved in the domestic power circuit of a typical 2 element electric storage water heater on a 230V system. I've drawn this according to what's done in NZ and AU. UK uses a ring-main so the ordering of the switch and fuse might be reversed.
[E] entry fuse (where the electricity enters the dwelling) [p] [P] power meters (connection to neutral not shown) [L] load control (connection to neutral not shown) you can think of it like a switch that's not under the consumer's control.
[F] [f] fuses (or circuit breakers)
[S] [s] switch [T] [t] thermostat [R] [r] resistive heating element
The element on the load controlled circuit [R] will be mounted near the base of the water cylinder and is only available while the load controller is closed, electricity on this circuit is charged at a cheaper rate. the other element and its thermostat will be near the top (maybe 2/3 the way up) the thermostat may be set to a sligtly lower temperature, to only operate when most of the hot water has been used up. (hot water is less dense and floats on top of cold water) in this way most (or all) of the hot water needed can be made using cheap off-peak electricity (could be 1/3 the price) but the upper element is available to provide hot water when all the cheap hot water is used up.
Sometimes the load control and/or meters are combined into a single unit.
Yes the fuse comes after the switch ! The logic being that there should be no voltage on the fuse while being replaced. It protects from flash burns if the circuit is live when the fuse is replaced.
Correct ! Often called "Economy 7" because for a 7 hour period overnight the charge rate is reduced. Water heating and storage heating is commonly run on a separate circuit that is timer controlled.
Ours is like that a single unit that provides metering and control.
Thanks everyone for your help. I've been away hence haven't replied until now. Will now go through the various suggestions in detail & put something in place.
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