Hi

Few years ago I bought a 2kW petrol generator to keep the home running
when the mains power failed. Used several times, no probs except that
the CH boiler locked out when the generator was switched in. A reset and
all worked fine.

Last week had another power cut but this time the CH boiler locked out
after about 30 secs even after re-setting (several times). Everything
else in the house works OK, including gas fired Rayburn cooker, which is
just the same sort of technology as the boiler.

Any thoughts on what is upsetting the boiler? -it's a normal wall
mounted balanced flue unit from Vaillant.

Thanks
--
Richard

Richard Walker writes:

Any thoughts on what is upsetting the boiler? -it's a normal wall
mounted balanced flue unit from Vaillant.

I guess the generated mains has something wrong enough about it that
the boiler doesn't like it.

Or some part of the system is on a circuit which is dead in a powercut
so the boiler gives up.

Jon

On Mon, 08 Jan 2007 16:50:02 +0000, Richard Walker wrote:

Hi

Few years ago I bought a 2kW petrol generator to keep the home running
when the mains power failed. Used several times, no probs except that
the CH boiler locked out when the generator was switched in. A reset and
all worked fine.

Last week had another power cut but this time the CH boiler locked out
after about 30 secs even after re-setting (several times). Everything
else in the house works OK, including gas fired Rayburn cooker, which is
just the same sort of technology as the boiler.

Any thoughts on what is upsetting the boiler? -it's a normal wall
mounted balanced flue unit from Vaillant.

Thanks

What arrangements are used to switch over the suppies.
What arrangements are used to earth the installation?
A polarity problem is centre stage here, especially if the gas lights but
then goes out after a few seconds.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

In message ,
Richard Walker writes
Hi

Few years ago I bought a 2kW petrol generator to keep the home running
when the mains power failed. Used several times, no probs except that
the CH boiler locked out when the generator was switched in. A reset
and all worked fine.

Last week had another power cut but this time the CH boiler locked out
after about 30 secs even after re-setting (several times). Everything
else in the house works OK, including gas fired Rayburn cooker, which
is just the same sort of technology as the boiler.

Any thoughts on what is upsetting the boiler? -it's a normal wall
mounted balanced flue unit from Vaillant.

Heap of **** on the mains?

Incorrect earthing resulting in the boiler not flame sensing properly ?

--
geoff

Ed Sirett wrote:
On Mon, 08 Jan 2007 16:50:02 +0000, Richard Walker wrote:

Hi

Few years ago I bought a 2kW petrol generator to keep the home running
when the mains power failed. Used several times, no probs except that
the CH boiler locked out when the generator was switched in. A reset and
all worked fine.

Last week had another power cut but this time the CH boiler locked out
after about 30 secs even after re-setting (several times). Everything
else in the house works OK, including gas fired Rayburn cooker, which is
just the same sort of technology as the boiler.

Any thoughts on what is upsetting the boiler? -it's a normal wall
mounted balanced flue unit from Vaillant.

Thanks

What arrangements are used to switch over the suppies.
What arrangements are used to earth the installation?
A polarity problem is centre stage here, especially if the gas lights but
then goes out after a few seconds.

Thanks, Ed

The gennie is switched in with a dp change over switch which isolates
house from grid supply then switches gennie power into house. Normally
switch boiler off at its isolating switch before switching in gennie,
then switch boiler on when gennie has settled down. House is earthed as
normal, gennie chassis is connected to house earth but not separately
earthed.

Supply from generator is clearly lumpier than mains - a discernible
flicker to lights. Might this be the problem? And if so, I wonder why it
used to work but doesn't now?

Cheers
--
Richard

Richard Walker wrote:
Ed Sirett wrote:
On Mon, 08 Jan 2007 16:50:02 +0000, Richard Walker wrote:

Hi

Few years ago I bought a 2kW petrol generator to keep the home
running when the mains power failed. Used several times, no probs
except that the CH boiler locked out when the generator was switched
in. A reset and all worked fine.

Last week had another power cut but this time the CH boiler locked
out after about 30 secs even after re-setting (several times).
Everything else in the house works OK, including gas fired Rayburn
cooker, which is just the same sort of technology as the boiler.

Any thoughts on what is upsetting the boiler? -it's a normal wall
mounted balanced flue unit from Vaillant.

Thanks

What arrangements are used to switch over the suppies. What
arrangements are used to earth the installation?
A polarity problem is centre stage here, especially if the gas lights but
then goes out after a few seconds.
Thanks, Ed

The gennie is switched in with a dp change over switch which isolates
house from grid supply then switches gennie power into house. Normally
switch boiler off at its isolating switch before switching in gennie,
then switch boiler on when gennie has settled down. House is earthed as
normal, gennie chassis is connected to house earth but not separately
earthed.

Supply from generator is clearly lumpier than mains - a discernible
flicker to lights. Might this be the problem? And if so, I wonder why it
used to work but doesn't now?

Cheers
--
Richard

Generators are generally center tapped, so you end up with +115v on one
phase and -115 on the other.
This may cause a problem with your boiler.
With the generator running and the grid supply off, what are the voltage
measurements between...

L&N -
L&E -
N&E -


Sparks...

Sparks wrote:
Richard Walker wrote:
Ed Sirett wrote:
On Mon, 08 Jan 2007 16:50:02 +0000, Richard Walker wrote:

Hi

Few years ago I bought a 2kW petrol generator to keep the home
running when the mains power failed. Used several times, no probs
except that the CH boiler locked out when the generator was switched
in. A reset and all worked fine.

Last week had another power cut but this time the CH boiler locked
out after about 30 secs even after re-setting (several times).
Everything else in the house works OK, including gas fired Rayburn
cooker, which is just the same sort of technology as the boiler.

snip
Generators are generally center tapped, so you end up with +115v on one
phase and -115 on the other.
This may cause a problem with your boiler.
With the generator running and the grid supply off, what are the voltage
measurements between...

L&N -
L&E -
N&E -


Sparks...
Hmmm... Voltage between L&E and N&E is just 85v when no load,
disconnected from the house wiring. Voltage between L&N is 240v. Thought
I had a reasonable understanding of electricity, but this has me
puzzled. Should I not connect the generator earth to the house earth?
--
Richard

"Richard Walker" wrote in message
...
Sparks wrote:
Richard Walker wrote:
Ed Sirett wrote:
On Mon, 08 Jan 2007 16:50:02 +0000, Richard Walker wrote:

Hi

Few years ago I bought a 2kW petrol generator to keep the home
running when the mains power failed. Used several times, no
probs
except that the CH boiler locked out when the generator was
switched
in. A reset and all worked fine.

Last week had another power cut but this time the CH boiler
locked
out after about 30 secs even after re-setting (several times).
Everything else in the house works OK, including gas fired
Rayburn
cooker, which is just the same sort of technology as the
boiler.

snip
Generators are generally center tapped, so you end up with +115v
on one
phase and -115 on the other.
This may cause a problem with your boiler.
With the generator running and the grid supply off, what are the
voltage
measurements between...

L&N -
L&E -
N&E -


Sparks...
Hmmm... Voltage between L&E and N&E is just 85v when no load,
disconnected from the house wiring. Voltage between L&N is 240v.
Thought
I had a reasonable understanding of electricity, but this has me
puzzled. Should I not connect the generator earth to the house
earth?
--
Richard

Is this one of the 'inverter' generators where they don't control the
engine speed, but put the output though an inverter to produce correct
frequency and voltage ?

If so, and if meant for the american market, it couuld be centre
earthed 115(L) - 0(E) - 115(N) possibly.

AWEM

On Thu, 18 Jan 2007 10:45:26 +0000, Richard Walker wrote:

Hmmm... Voltage between L&E and N&E is just 85v when no load,
disconnected from the house wiring. Voltage between L&N is 240v.

Off load the rather primative AVR in the alternator will be confused. I
would be at all surprised at odd readings, load it up with a couple of
hundred watts or so and see what happens.

Thought I had a reasonable understanding of electricity, but this has
me puzzled. Should I not connect the generator earth to the house
earth?

No, when the power fails you cannot rely on any of the supply wires to be
what it should be, live, neutral or earth. What you should do is bond the
generator chassis to a local (good) earth spike, bond one of the
generator phases to the chassis and thus the local earth creating a
"neutral" and have an RCD at the generator and run extension cables to
the kit you want to power and plug them in.

It gets very messy and has lots of implications if you want to use the
house wiring direct. Back feeding the main supply *HAS* to be avoided at
all costs, not even the remotest chance of it happening by forgetting to
open a switch somewhere. I do have vauge memories that you do have a
proper break before make change over switch though. If that is the case
the the bonding described above should sort things out but the supply
earth should not really be connected. Hence the RCD as the earth loop
impedance via the local spike will probably be rather high.

--
Cheers
Dave. pam is missing e-mail

In message ,
Richard Walker writes
Sparks wrote:
Richard Walker wrote:
Ed Sirett wrote:
On Mon, 08 Jan 2007 16:50:02 +0000, Richard Walker wrote:

Hi

Few years ago I bought a 2kW petrol generator to keep the home
running when the mains power failed. Used several times, no probs
except that the CH boiler locked out when the generator was
switched in. A reset and all worked fine.

Last week had another power cut but this time the CH boiler locked
out after about 30 secs even after re-setting (several times).
Everything else in the house works OK, including gas fired Rayburn
cooker, which is just the same sort of technology as the boiler.

snip
Generators are generally center tapped, so you end up with +115v on
one phase and -115 on the other.
This may cause a problem with your boiler.
With the generator running and the grid supply off, what are the
voltage measurements between...
L&N -
L&E -
N&E -
Sparks...
Hmmm... Voltage between L&E and N&E is just 85v when no load,
disconnected from the house wiring. Voltage between L&N is 240v.
Thought I had a reasonable understanding of electricity, but this has
me puzzled. Should I not connect the generator earth to the house earth?

The earth needs to be fairly close to neutral for flame sensing to work

sounds like the flame sense signal is getting lost

--
geoff

raden wrote:

The earth needs to be fairly close to neutral for flame sensing to work

sounds like the flame sense signal is getting lost

Yep, it sounds to me as if the generator output is completely floating
(IT system). The OP needs to earth one side of its output to define a
neutral point and create a TN-S system. As someone else said you
mustn't rely solely on an earth provided by the public mains, but
there's no reason not to connect your means of earthing in parallel with
a supplier's earth (unless you intentionally have the house as a TT
installation).

Section 551 of BS 7671 refers.

http://groups.google.com/group/uk.d-...e=source&hl=en
has further information.

--
Andy

On Fri, 19 Jan 2007 01:37:17 +0000, Andy Wade wrote:

As someone else said you mustn't rely solely on an earth provided by
the public mains, but there's no reason not to connect your means of
earthing in parallel with a supplier's earth

Except you can't trust the suppliers earth to remain earth under fault
conditions. It could become live with the mains supply behind it.
Remember there are no overload cut outs in the earth (or neutral) wiring
and that wiring is of a hefty size so lots of current, lots of heat, melt
down or *BIG* bang...

Having pondered about use of a generator under mains failure situations
I've decided the a local earth spike to generator chassis, one phase of
the alternator to chassis, RCD on generator output and extension leads to
the appliances is by far the easiest and safest method. One day the CH/HW
system will be fed via a plug top (still on it's own switched fused spur
though) to enable easy transfer to a generator.

(unless you intentionally have the house as a TT installation).

I can never remember the letters to supply type. Is that no supply earth,
local earth only?

--
Cheers
Dave. pam is missing e-mail

In an earlier contribution to this discussion,
Dave Liquorice wrote:


Having pondered about use of a generator under mains failure
situations I've decided the a local earth spike to generator chassis,
one phase of the alternator to chassis, RCD on generator output and
extension leads to the appliances is by far the easiest and safest
method. One day the CH/HW system will be fed via a plug top (still on
it's own switched fused spur though) to enable easy transfer to a
generator.

Prompted by this thread, I decided to check out my own emergency
arrangements today.

A couple of years ago I bought a Honda EU20i generator with the idea that
this would run the electrical side of my CH plus a few other bits and pieces
in the event of a prolonged power outage. At the same time, I installed an
earth spike for the generator and re-wired the CH to run off a 13A plug. I
fitted an RCD plug on a 4-way extension lead. The plan was that I would plug
the RCD plug into the generator and plug the CH plus other things (freezer,
emergency light, TV?) into the 4 13A outlets.

So far, I have not had occasion to use it in anger. I've been meaning to
test it in *summer* just in case it were to do anything nasty to the boiler
PCB - when it would be less devastating - but haven't got around to it.

Anyway, in the light of Geoff's comments about neutral needing to be close
to earth for flame detection to work, I looked at the generator output
today - and sure enough L & N are each 120v away from E, and 240v from each
other.

After all that, I have a couple of questions.

1. The boiler is a Mk I Baxi Solo 70PF. Can Geoff or anyone else please
advise:
a) Do N & E need to be close for this boiler to work?
b) How sensitive is the PCB to quality of mains in general?

2. The generator uses an inverter to produce its 'mains' output
a) Is it likely to mind if I strap N to E?
b) If I connect them, how should I do it - bit of wire or via a resistor (if
latter, what spec?)?
[It would be easy to do physically. The genny has 2 13A outlets - so I could
plug a cobbled 13A plug (with N&E internally connected) into one of the
outlets, and my RCD extension lead into the other one]
c) If the genny *does* mind, could I achieve the same thing with an
isolating transformer with one side of its output strapped to earth?

TIA!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Fri, 19 Jan 2007 09:40:21 +0000, Dave Liquorice wrote:

On Fri, 19 Jan 2007 01:37:17 +0000, Andy Wade wrote:

As someone else said you mustn't rely solely on an earth provided by
the public mains, but there's no reason not to connect your means of
earthing in parallel with a supplier's earth

Except you can't trust the suppliers earth to remain earth under fault
conditions. It could become live with the mains supply behind it.
Remember there are no overload cut outs in the earth (or neutral) wiring
and that wiring is of a hefty size so lots of current, lots of heat, melt
down or *BIG* bang...

Having pondered about use of a generator under mains failure situations
I've decided the a local earth spike to generator chassis, one phase of
the alternator to chassis, RCD on generator output and extension leads to
the appliances is by far the easiest and safest method. One day the CH/HW
system will be fed via a plug top (still on it's own switched fused spur
though) to enable easy transfer to a generator.

When you do that make the socket an unswitched one, then the boiler has an
isolator (as you have to remove the plug to turn it off), and so complies
with the electrical rules.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

On Fri, 19 Jan 2007 22:05:45 +0000 (UTC), Ed Sirett wrote:

One day the CH/HW system will be fed via a plug top (still on it's own
switched fused spur though) to enable easy transfer to a generator.

When you do that make the socket an unswitched one, then the boiler has
an isolator (as you have to remove the plug to turn it off), and so
complies with the electrical rules.

It would be unswitched to stop "little fingers" "accidentally" switching
it off. A plug would satisfy the requirements provided it was fitted with
a 3A fuse not at 13A one.

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:

Except you can't trust the suppliers earth to remain earth under fault
conditions. It could become live with the mains supply behind it.
Remember there are no overload cut outs in the earth (or neutral) wiring
and that wiring is of a hefty size so lots of current, lots of heat, melt
down or *BIG* bang...

That's why you have main equipotential bonding and an equipotential
zone. If it's a situation where it's impractical to create an
equipotential zone (e.g. an outbuilding with a damp floor) you should be
using TT in any case.

(unless you intentionally have the house as a TT installation).

I can never remember the letters to supply type. Is that no supply earth,
local earth only?

Yes, essentially no metallic path between your main earth terminal and
the earthed point of the source of supply.

--
Andy

In message , Roger Mills
writes

Anyway, in the light of Geoff's comments about neutral needing to be close
to earth for flame detection to work, I looked at the generator output
today - and sure enough L & N are each 120v away from E, and 240v from each
other.

After all that, I have a couple of questions.

1. The boiler is a Mk I Baxi Solo 70PF. Can Geoff or anyone else please
advise:
a) Do N & E need to be close for this boiler to work?

Neutral and earth are connected at the local sub station

I can't put a quantitative figure on it, but I would have thought not
more than a few (tens of?) volts

b) How sensitive is the PCB to quality of mains in general?

Not something I really need to concern myself with, so I don't really
know, but

In your case, there are two different pcbs, one made by pactrol (blue)
and one made by Honeywell (white)

The pactrol one is more primitive (three transistors) than the honeywell
one (which has an actual IC on it). I think that the pactrol pcb would
be more robust to mains fluctuations, but this is only a gut feeling



2. The generator uses an inverter to produce its 'mains' output
a) Is it likely to mind if I strap N to E?
b) If I connect them, how should I do it - bit of wire or via a resistor (if
latter, what spec?)?
[It would be easy to do physically. The genny has 2 13A outlets - so I could
plug a cobbled 13A plug (with N&E internally connected) into one of the
outlets, and my RCD extension lead into the other one]
c) If the genny *does* mind, could I achieve the same thing with an
isolating transformer with one side of its output strapped to earth?

Someone will be along with the relevant regs in a while, IIRC, it's been
discussed several times before

--
geoff

In an earlier contribution to this discussion,
raden wrote:


1. The boiler is a Mk I Baxi Solo 70PF. Can Geoff or anyone else
please advise:
a) Do N & E need to be close for this boiler to work?

Neutral and earth are connected at the local sub station

I can't put a quantitative figure on it, but I would have thought not
more than a few (tens of?) volts

Hi Geoff - many thanks for your response.

Just to be sure what you mean, are you simply saying that, because N & E are
joined at the substation, they will necessarily be within a few volts (or
10's) of each other by the time they reach domestic premises. Or are you
saying that the boiler's flame detection won't work if they are more than a
certain distance apart?


b) How sensitive is the PCB to quality of mains in general?

Not something I really need to concern myself with, so I don't really
know, but

In your case, there are two different pcbs, one made by pactrol (blue)
and one made by Honeywell (white)

The pactrol one is more primitive (three transistors) than the
honeywell one (which has an actual IC on it). I think that the
pactrol pcb would be more robust to mains fluctuations, but this is
only a gut feeling
That's interesting. I don't know which one I've got - I'll have a look. From
memory, I think it's blue rather than white and I don't remember seeing any
ICs on it - so it's probably the Pactrol one. My genny is actually reputed
to produce very clean mains. I haven't yet looked at it on a scope, but had
perhaps better do so, to see whether any spikes are produced when loads are
applied or removed.

I think the main issue is this business of the output being 50/50 eaither
side of earth - and whether I can tie N&E together without wrecking
anything.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

In message , Roger Mills
writes
In an earlier contribution to this discussion,
raden wrote:


1. The boiler is a Mk I Baxi Solo 70PF. Can Geoff or anyone else
please advise:
a) Do N & E need to be close for this boiler to work?

Neutral and earth are connected at the local sub station

I can't put a quantitative figure on it, but I would have thought not
more than a few (tens of?) volts

Hi Geoff - many thanks for your response.

Just to be sure what you mean, are you simply saying that, because N & E are
joined at the substation, they will necessarily be within a few volts (or
10's) of each other by the time they reach domestic premises. Or are you
saying that the boiler's flame detection won't work if they are more than a
certain distance apart?

I'm saying that it won't work



b) How sensitive is the PCB to quality of mains in general?

Not something I really need to concern myself with, so I don't really
know, but

In your case, there are two different pcbs, one made by pactrol (blue)
and one made by Honeywell (white)

The pactrol one is more primitive (three transistors) than the
honeywell one (which has an actual IC on it). I think that the
pactrol pcb would be more robust to mains fluctuations, but this is
only a gut feeling
That's interesting. I don't know which one I've got - I'll have a look. From
memory, I think it's blue rather than white and I don't remember seeing any
ICs on it - so it's probably the Pactrol one. My genny is actually reputed
to produce very clean mains. I haven't yet looked at it on a scope, but had
perhaps better do so, to see whether any spikes are produced when loads are
applied or removed.

I think the main issue is this business of the output being 50/50 eaither
side of earth - and whether I can tie N&E together without wrecking
anything.

--
geoff