Circuit to indicate failure of a heating element

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I have a water tank with with 2 x 5kW heating elements (on separate
supplies).

Problem is: one is probably just about enough to supply all the hot
water I usually need, so how can I tell when one has failed?

I'd like to have an LED connected to each circuit, to warn me when the
element has failed.

Grateful if you would tell me how. I have a bit of electrical
experience, but next-to-no electronic.

(Power supply is UK mains - 230V, 50Hz AC)

 

[David L. Jones]

I have a water tank with with 2 x 5kW heating elements (on separate
supplies).

Problem is: one is probably just about enough to supply all the hot
water I usually need, so how can I tell when one has failed?

I'd like to have an LED connected to each circuit, to warn me when the
element has failed.

Grateful if you would tell me how. I have a bit of electrical
experience, but next-to-no electronic.

(Power supply is UK mains - 230V, 50Hz AC)

Perhaps overkill, but you could install two Cent-a-meter type power
consumption devices on just the line supplying the heaters:
http://www.centameter.com.au/products.htm
That way you can monitor your power consumption and easily check for a
failed element remotely.

Dave.

 

[ojc]

Perhaps overkill, but you could install two Cent-a-meter type power
consumption devices on just the line supplying the heaters:http://www.centameter.com.au/products.htm
That way you can monitor your power consumption and easily check for a
failed element remotely.

Dave.

Thanks Dave, I hadn't thought of this (though I was hoping to be able
to do it with a handful of components rather than 2 x expensive pieces
of kit.
Oliver.

 

[Baron]

I have a water tank with with 2 x 5kW heating elements (on separate
supplies).

Problem is: one is probably just about enough to supply all the hot
water I usually need, so how can I tell when one has failed?

I'd like to have an LED connected to each circuit, to warn me when the
element has failed.

Grateful if you would tell me how. I have a bit of electrical
experience, but next-to-no electronic.

(Power supply is UK mains - 230V, 50Hz AC)

You could probably do it with a ferrite toroid, some fine enamelled
wire, a diode and a LED. You would wind say 100 turns of wire on the
toroid connect the led and diode in parallel, connect the pair across
the toroid. Feed one leg of the heater through the core. You may need
one or two turns. The diode is only there to prevent reverse voltage
damaging the LED. You will need to play around a bit to get the turns
ratio right, but as long as current flows through the heater the LED
will glow.

 

[Jasen Betts]

Put them across each thermostat. Then they will light when the
switch is open.

and the light will be out when the thermostat is on, the element is broken,
or the ripple-control is off.

that's going to be confusing.

 

[Jasen Betts]

I have a water tank with with 2 x 5kW heating elements (on separate
supplies).

Problem is: one is probably just about enough to supply all the hot
water I usually need, so how can I tell when one has failed?

I'd like to have an LED connected to each circuit, to warn me when the
element has failed.

Grateful if you would tell me how. I have a bit of electrical
experience, but next-to-no electronic.

(Power supply is UK mains - 230V, 50Hz AC)

it's not a simple problem. water heating is often on a fairly complex
circuit
(ripple-control, meter, circuit breakers, switch, thermostat, heater)

also the heating element has two failure modes, one of which will blow
the breaker and the other won't.

also in normal use the boost element is only runs when the tank is
almost all cold.

 

[whit3rd]

I have a water tank with with 2 x 5kW heating elements (on separate
supplies).

Problem is:  one is probably just about enough to supply all the hot
water I usually need, so how can I tell when one has failed?

If you can reach the contacts, you can (1) measure voltage across the
heater, (2) connect (just for a second) a jumper across the
thermostat, (3) have an associate (or a remote TV camera)
monitor the power meter for the house.

If the heater has low voltage, that means its thermostat is OFF.
Connect the jumper then, and if the spark doesn't convince
you that it's heating, the confederate watching the meter can
tell you that it spun faster for those few seconds.
The same will work with clamp-type AC ammeters.

 

[amdx]

I have a water tank with with 2 x 5kW heating elements (on separate
supplies).
Problem is: one is probably just about enough to supply all the hot
water I usually need, so how can I tell when one has failed?
I'd like to have an LED connected to each circuit, to warn me when the
element has failed.
Grateful if you would tell me how. I have a bit of electrical
experience, but next-to-no electronic.
(Power supply is UK mains - 230V, 50Hz AC)

I think I have a circuit that will do what you ask, it still needs a few
tweaks, use it at your own risk.
If anyone on the group has any input on the circuit I'd like to hear it.
Also please go over the logic
and see if you think it will work.
http://i395.photobucket.com/albums/pp37/Qmavam/HeatingelementsensorLightJPG.jpg
Mike

 

[amdx]

I think I have a circuit that will do what you ask, it still needs a few
tweaks, use it at your own risk.
If anyone on the group has any input on the circuit I'd like to hear it.
Also please go over the logic
and see if you think it will work.
http://i395.photobucket.com/albums/pp37/Qmavam/HeatingelementsensorLightJPG.jpg
Mike

Here I've added a couple extra labels,
http://s395.photobucket.com/albums/pp37/Qmavam/?action=view&current=HeatingelementsensorLightJPG.jpg

 

[Jasen Betts]

I think I have a circuit that will do what you ask, it still needs a few
tweaks, use it at your own risk.
If anyone on the group has any input on the circuit I'd like to hear it.
Also please go over the logic
and see if you think it will work.
http://i395.photobucket.com/albums/pp37/Qmavam/HeatingelementsensorLightJPG.jpg

site seems to be down.

 

[amdx]

site seems to be down.

I just tried it, it worked, Please try again.
Mike

 

[Baron]

amdx Inscribed thus:

I just tried it, it worked, Please try again.
Mike

It seems very complicated just for a current indicator ! Yours seems
more like a complete system.

 

[amdx]

amdx Inscribed thus:


It seems very complicated just for a current indicator ! Yours seems
more like a complete system.

The OP ask for a circuit: "to warn me when the element has failed."
This circuit will do that ( I think).
He didn't ask for a current indicator, he ask for a circuit that will
indicate
that the thermostat is on but no current is flowing.
I'm open to a simpler design that meets his need.
Mike
Also this is pretty close to all electrical and very little electronic.

 

[Jasen Betts]

I just tried it, it worked, Please try again.
Mike

yeah, it's back.

it looks good. As it's safe to assume that the heating elements will
never fail while unpowered it will detect failure. even where elements
fail short-circuit and out the fuse on a load controlled circuit.

you can't power the bridge rectifier from the load controlled circuit

but if reset while the fuse on a load controlled circuit is blown it
will not re-detect that, but a relay could be added to handle that


but if the short takes out the master fuse (killing all the power to
the house) it it'll trigger it won't be obvious.

 

[Baron]

amdx Inscribed thus:

The OP ask for a circuit: "to warn me when the element has failed."
This circuit will do that ( I think).
He didn't ask for a current indicator, he ask for a circuit that will
indicate
that the thermostat is on but no current is flowing.
I'm open to a simpler design that meets his need.
Mike
Also this is pretty close to all electrical and very little
electronic.

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.

 

[amdx]

amdx Inscribed thus:


Yes it is. A simple current transformer and LED load in the live feed
will give an indication as long a current is flowing.

But I think he wants an indication when current doesn't flow.

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.

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.

A second fault condition is where the heating element sheath perforates
and allows current to bypass the thermostat.

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.

Mike

 

[amdx]

yeah, it's back.

it looks good. As it's safe to assume that the heating elements will
never fail while unpowered it will detect failure. even where elements
fail short-circuit and out the fuse on a load controlled circuit.

you can't power the bridge rectifier from the load controlled circuit

I'm not sure what that means? My circuit shows the bridge on the line side
of the thermostat.

but if reset while the fuse on a load controlled circuit is blown it
will not re-detect that, but a relay could be added to handle that

If needed you could put a normal indicating lamp across RY3s coil.
This would show that power is on.

 

[Baron]

But I think he wants an indication when current doesn't flow.

An un-lit LED will do that.

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 in 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.

Mike

I wish that were true. I've seen 30 amp fuses blow, switch and
thermostat contacts weld together when the heater sheath perforated.

 

[Jasen Betts]

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.

 

[amdx]

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