Circuit to indicate failure of a heating element

[Baron]

amdx Inscribed thus:

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:gugv38$s1e$1@news.motzarella.org...
amdx Inscribed thus:


"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:gugm3o$9e2$1@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

ojcouzens@gmail.com> wrote in message


news:c0bd19c8-c289-4d83-a972-ec71a29d7409@r3g2000vbp.googlegroups.com...
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

--
Best Regards:
Baron.

 

[amdx]

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:guh78f$vir$1@news.motzarella.org...

amdx Inscribed thus:


"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:gugv38$s1e$1@news.motzarella.org...
amdx Inscribed thus:


"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:gugm3o$9e2$1@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

ojcouzens@gmail.com> wrote in message


news:c0bd19c8-c289-4d83-a972-ec71a29d7409@r3g2000vbp.googlegroups.com...
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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

--
Best Regards:
Baron.

 

[amdx]

"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:guh46j$e3j$1@reversiblemaps.ath.cx...

On 2009-05-14, amdx <amdx@knology.net> wrote:

"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:gugm3o$9e2$1@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

ojcouzens@gmail.com> wrote in message
news:c0bd19c8-c289-4d83-a972-ec71a29d7409@r3g2000vbp.googlegroups.com...
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

site seems to be down.
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

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.

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 wrote:

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:guh78f$vir$1@news.motzarella.org...
amdx Inscribed thus:


"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:gugv38$s1e$1@news.motzarella.org...
amdx Inscribed thus:


"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:gugm3o$9e2$1@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

ojcouzens@gmail.com> wrote in message



news:c0bd19c8-c289-4d83-a972-ec71a29d7409@r3g2000vbp.googlegroups.com...
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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

An un-lit LED will do that.

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 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.



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

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

--
Best Regards:
Baron.

 

[Jasen Betts]

On 2009-05-14, amdx <amdx@knology.net> wrote:

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Jasen Betts" <jasen@xnet.co.nz> wrote
On 2009-05-14, amdx <amdx@knology.net> wrote:
ojcouzens@gmail.com> wrote in message
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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.

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]

"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:guj4l3$4d5$2@reversiblemaps.ath.cx...

On 2009-05-14, amdx <amdx@knology.net> wrote:

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Jasen Betts" <jasen@xnet.co.nz> wrote
On 2009-05-14, amdx <amdx@knology.net> wrote:
ojcouzens@gmail.com> wrote in message
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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.

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

 

[Baron]

amdx Inscribed thus:

"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:guj4l3$4d5$2@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Jasen Betts" <jasen@xnet.co.nz> wrote
On 2009-05-14, amdx <amdx@knology.net> wrote:
ojcouzens@gmail.com> wrote in message
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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.

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

--
Best Regards:
Baron.

 

[amdx]

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:guhpjd$2pp$1@news.motzarella.org...

amdx wrote:


"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:guh78f$vir$1@news.motzarella.org...
amdx Inscribed thus:


"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote in message
news:gugv38$s1e$1@news.motzarella.org...
amdx Inscribed thus:


"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:gugm3o$9e2$1@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

ojcouzens@gmail.com> wrote in message



news:c0bd19c8-c289-4d83-a972-ec71a29d7409@r3g2000vbp.googlegroups.com...
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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

An un-lit LED will do that.

But how do you know if it is un-lit because the thermostat has not
triggered current flow
or because the element is open.
Mike

 

[Jasen Betts]

On 2009-05-15, amdx <amdx@knology.net> wrote:

"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:guj4l3$4d5$2@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Jasen Betts" <jasen@xnet.co.nz> wrote
On 2009-05-14, amdx <amdx@knology.net> wrote:
ojcouzens@gmail.com> wrote in message
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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.

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

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.

to other equipment
|
|
+-------[p]-+-[f]----[t]-------.
| |
(phase) -------[E]-+-[L]---[P]---[F]----[T]---. |
230VAC | |
[R] [r]
| |
(neutral)----------+-----------------------------+---+--...
|
+-------------------------------- earth
_|_
///
ground peg


[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)

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.

Two element water heater example:
http://tinyurl.com/pucsqn
(http://waterheating.rheem.com/content/resources/documents/Reference%20Material/Parts%20Breakdown/3000.pdf)

 

[Baron]

Jasen Betts wrote:

On 2009-05-15, amdx <amdx@knology.net> wrote:

"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:guj4l3$4d5$2@reversiblemaps.ath.cx...
On 2009-05-14, amdx <amdx@knology.net> wrote:

"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Baron" <baron.nospam@linuxmaniac.nospam.net> wrote
amdx Inscribed thus:
"Jasen Betts" <jasen@xnet.co.nz> wrote
On 2009-05-14, amdx <amdx@knology.net> wrote:
ojcouzens@gmail.com> wrote in message
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

site seems to be down.
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.

--
Best Regards:
Baron.

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.

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.

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


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.

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.

to other equipment
|
|
+-------[p]-+-[f]----[t]-------.
| |
(phase) -------[E]-+-[L]---[P]---[F]----[T]---. |
230VAC | |
[R] [r]
| |
(neutral)----------+-----------------------------+---+--...
|
+-------------------------------- earth
_|_
///
ground peg


[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)

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.

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.

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.

Ours is like that a single unit that provides metering and control.

Two element water heater example:
http://tinyurl.com/pucsqn

(http://waterheating.rheem.com/content/resources/documents/Reference%20Material/Parts%20Breakdown/3000.pdf)

--
Best Regards:
Baron.

 

[ojc]

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.