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UK Caravanning (uk.rec.caravanning) A forum for the discussion of caravanning undertaken by residents of the United Kingdom, whether in the UK or abroad. It encourages the interchange of views on the merits of models of caravan, makes of tow car, accessories, caravan sites, caravan clubs, and other related topics. The term caravan is to include trailer vans, motor caravans and trailer tents.

Propex heater fault



 
 
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  #1 (permalink)  
Old October 24th 03, 11:24 PM posted to uk.rec.caravanning
HN
external usenet poster
 
Posts: 43
Default Propex heater fault

Hi Guys

Is there anyone here who's familiar with the electrical side of the
older Propex 1.6kW heater?

Reason I ask, is 'cos an old one of these has come my way, and which I
would like to get working properly and use.

Symptoms at the moment:-

With gas connected, 12v connected direct to a well charged
battery(12.8v), and a switch put in circuit with the control
wire(orange), the "Stand By" light is illuminated.

Upon switch on, the "Burner On" light illuminates, the fan starts up
and the gas lights immediately. After 16 seconds however, there is a
click, and the "Lock Out" light illuminates, the "Burner On" light
goes out, the fan stops, and the gas solenoid valve closes.

I have already found one bad connection on one of the push connectors
on the solenoid valve, and re-soldered it. Experimentation has shown
that this 16 second(always 16 seconds) run time seems to be regardless
of whether the system is hot or cold, or whether the gas supply is on
or off. Monitoring the voltage at the heater connector reveals that
before switch on, the voltage reads about 12.7v. While the heater is
running, it reads 12.48v, and when it "Locks Out" the voltage returns
to 12.7v.

The through flow of air is very good, and after several 16 second
runs, it blows pleasantly warm air just like I would expect from a
1.6kW fan heater. The combustion air flowing through the burner tube
seems adequate as the flue spiggot gets hot but not dangerously so,
whereas the casing does not get hot enough to be uncomfortable to
touch.

Am I correct in my belief that this is an electrical fault?

Does anyone have a circuit diagram for this heater? Unfortunately I
have no documentation at all.

TIA

Neil
(Please reply via NG)

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  #2 (permalink)  
Old October 24th 03, 11:54 PM posted to uk.rec.caravanning
Peter Milnes
external usenet poster
 
Posts: 191
Default Propex heater fault

There should be a thermostatic flame failure device which is always in the pilot
flame. This will keep the gas supply flowing after the delay at start up (which
is to allow the device to warm up). The device should be on a bracket which
enables it to be placed into the flame from the pilot jet or the main flame. The
control circuit is detecting no heat from the device and will "lock-out" the gas
ensuring that no fires can occur.

Cheers, Peter.

"HN" wrote in message
...
: Hi Guys
:
: Is there anyone here who's familiar with the electrical side of the
: older Propex 1.6kW heater?
:
: Reason I ask, is 'cos an old one of these has come my way, and which I
: would like to get working properly and use.
:
: Symptoms at the moment:-
:
: With gas connected, 12v connected direct to a well charged
: battery(12.8v), and a switch put in circuit with the control
: wire(orange), the "Stand By" light is illuminated.
:
: Upon switch on, the "Burner On" light illuminates, the fan starts up
: and the gas lights immediately. After 16 seconds however, there is a
: click, and the "Lock Out" light illuminates, the "Burner On" light
: goes out, the fan stops, and the gas solenoid valve closes.
:
: I have already found one bad connection on one of the push connectors
: on the solenoid valve, and re-soldered it. Experimentation has shown
: that this 16 second(always 16 seconds) run time seems to be regardless
: of whether the system is hot or cold, or whether the gas supply is on
: or off. Monitoring the voltage at the heater connector reveals that
: before switch on, the voltage reads about 12.7v. While the heater is
: running, it reads 12.48v, and when it "Locks Out" the voltage returns
: to 12.7v.
:
: The through flow of air is very good, and after several 16 second
: runs, it blows pleasantly warm air just like I would expect from a
: 1.6kW fan heater. The combustion air flowing through the burner tube
: seems adequate as the flue spiggot gets hot but not dangerously so,
: whereas the casing does not get hot enough to be uncomfortable to
: touch.
:
: Am I correct in my belief that this is an electrical fault?
:
: Does anyone have a circuit diagram for this heater? Unfortunately I
: have no documentation at all.
:
: TIA
:
: Neil
: (Please reply via NG)
:

  #3 (permalink)  
Old October 26th 03, 02:17 AM posted to uk.rec.caravanning
HN
external usenet poster
 
Posts: 43
Default Propex heater fault

On Fri, 24 Oct 2003 23:54:04 +0000 (UTC), "Peter Milnes"
wrote:

There should be a thermostatic flame failure device which is always in the pilot
flame. This will keep the gas supply flowing after the delay at start up (which
is to allow the device to warm up). The device should be on a bracket which
enables it to be placed into the flame from the pilot jet or the main flame. The
control circuit is detecting no heat from the device and will "lock-out" the gas
ensuring that no fires can occur.

Cheers, Peter.

Thanks Peter

Since my original post, I figured there had to be a thermocouple in
there somewhere, so I opened the thing up today to have a look. I
also figured that the fault had to be thermocouple related as the
running time interval of 16 seconds is the same with or without the
gas turned on.

The Propex heater is a hot air blower with a tubular heat exchanger.
It has no pilot flame, as it only ignites when called for by the
control circuitry/thermostat.

I found 2 devices fixed to the combustion chamber in such a way that
their "business ends" were inside the tube and close to the jet end of
the chamber. One of these had a thick wire(not unlike car HT lead)
connected to it, which I concluded must be the igniter, and the other
had a thin blue wire connected, which I assumed must be the
thermocouple by default.

I removed both to inspect them and clean if necessary.

However, the 2 devices look absolutely identical! They are both a
pink ceramic sleeved electrode(stiff wire, not normal thermocouple
bulb) resembling the igniter one would find in a domestic central
heating boiler, with a spade lug on the outside for the wire
connection.

So unless this heater relies on the conductivity of the flame between
the 2 electrodes(about an inch apart along the combustion chamber
tube) to determine whether or not there is flame, I can only think
that I have a heater with 2 igniters and no thermocouple!!! Which
would of course explain why it doesn't stay alight! But that's silly
isn't it.

What I need is someone who has one of these things to tell me what the
thermocouple looks(or should look) like.

While I'd got it apart, I checked the gas jet, air holes, and burner
tube. All of which were perfectly clear of obstruction.

Sadly I haven't found anything useful via a web search.

Perhaps I shall have to phone Propex on Monday. )

It can't be much of a problem, these things are really quite simple
inside.

Neil

  #4 (permalink)  
Old October 26th 03, 06:10 PM posted to uk.rec.caravanning
Daz
external usenet poster
 
Posts: 1
Default Propex heater fault

"HN" wrote in message
[snip]
However, the 2 devices look absolutely identical! They are both a
pink ceramic sleeved electrode(stiff wire, not normal thermocouple
bulb) resembling the igniter one would find in a domestic central
heating boiler, with a spade lug on the outside for the wire
connection.

So unless this heater relies on the conductivity of the flame between
the 2 electrodes(about an inch apart along the combustion chamber
tube) to determine whether or not there is flame, I can only think
that I have a heater with 2 igniters and no thermocouple!!! Which
would of course explain why it doesn't stay alight! But that's silly
isn't it.


not silly at all - flame conductivity is the method used by carver cascade
water heaters to lock out the gas if the flame is extinguished...
iirc the cascades use the conductivity between earth and the electrode to
detect flame.

it might be worth checking the flame detect electrode is a low resistance -
i had a cascade showing the same symtoms and it was the joint between the
wire and the metal electrode within the ceramic housing that had failed.

hth

darren


  #5 (permalink)  
Old October 27th 03, 12:59 AM posted to uk.rec.caravanning
HN
external usenet poster
 
Posts: 43
Default Propex heater fault

On Sun, 26 Oct 2003 19:10:30 -0000, "Daz"
wrote:

"HN" wrote in message
[snip]
However, the 2 devices look absolutely identical! They are both a
pink ceramic sleeved electrode(stiff wire, not normal thermocouple
bulb) resembling the igniter one would find in a domestic central
heating boiler, with a spade lug on the outside for the wire
connection.

So unless this heater relies on the conductivity of the flame between
the 2 electrodes(about an inch apart along the combustion chamber
tube) to determine whether or not there is flame, I can only think
that I have a heater with 2 igniters and no thermocouple!!! Which
would of course explain why it doesn't stay alight! But that's silly
isn't it.


not silly at all - flame conductivity is the method used by carver cascade
water heaters to lock out the gas if the flame is extinguished...
iirc the cascades use the conductivity between earth and the electrode to
detect flame.

it might be worth checking the flame detect electrode is a low resistance -
i had a cascade showing the same symtoms and it was the joint between the
wire and the metal electrode within the ceramic housing that had failed.

hth

darren

Thanks Darren, I will check that out tomorrow.

Neil

  #6 (permalink)  
Old October 27th 03, 11:55 PM posted to uk.rec.caravanning
george.connelly
external usenet poster
 
Posts: 5
Default Propex heater fault

I have no specific knowledge of the Propex heater but I have found they all
use the same devices. First the fan should come on to purge the system
before attempting to light the burner. If the flame lights then it should
stay lit and the spark stop, if it doesn't then there are one or two
possibilities.
The flame failure device is simple enough in principle. For the gas valve to
work it needs a circuit for the voltage to flow though it to earth, if the
earth side is held positive by just a small amount then voltage cannot flow.
The flame failure device is know as an 'ion sensor' this allows a small
positive voltage (about 0.5v) to go to earth via the 'ions' in the flame,
(and is the earth side of the valve), once this has happened then you have
0v or negative or earth if you like. To the control circuit this is just
like you throwing a switch to allow a complete circuit to earth. So now the
start cycle can stop but the gas valve remains open and so the flame stays
lit and all is well. However if either their is no gas (not your problem)or
the flame is not correct, then no way to earth, and so it shuts down.
If the flame is not correct, i.e. not pure blue in colour at it's base, then
no ions, no route to earth. This would suggest an obstruction stopping the
correct gas/air mix, as I said I don't know the propex, but is often caused
by a spider leaving a nest in the burner inlet tube or possibly another form
of blockage in the inlet or outlet ducts.
Beyond this a fault on the circuit board or connection between, will be the
cause.
One more thing, I consider 16 seconds to be far to long a start cycle, 10
being the maximum while the gas valve is open. This often happens if the
'trimmer' resistor goes a little high, and would suggest your control board
has at least one fault.




"HN" wrote in message
...
On Sun, 26 Oct 2003 19:10:30 -0000, "Daz"
wrote:

"HN" wrote in message
[snip]
However, the 2 devices look absolutely identical! They are both a
pink ceramic sleeved electrode(stiff wire, not normal thermocouple
bulb) resembling the igniter one would find in a domestic central
heating boiler, with a spade lug on the outside for the wire
connection.

So unless this heater relies on the conductivity of the flame between
the 2 electrodes(about an inch apart along the combustion chamber
tube) to determine whether or not there is flame, I can only think
that I have a heater with 2 igniters and no thermocouple!!! Which
would of course explain why it doesn't stay alight! But that's silly
isn't it.


not silly at all - flame conductivity is the method used by carver

cascade
water heaters to lock out the gas if the flame is extinguished...
iirc the cascades use the conductivity between earth and the electrode to
detect flame.

it might be worth checking the flame detect electrode is a low

resistance -
i had a cascade showing the same symtoms and it was the joint between the
wire and the metal electrode within the ceramic housing that had failed.

hth

darren

Thanks Darren, I will check that out tomorrow.

Neil



  #7 (permalink)  
Old November 3rd 03, 02:30 AM posted to uk.rec.caravanning
HN
external usenet poster
 
Posts: 43
Default Propex heater fault

On Tue, 28 Oct 2003 00:55:50 -0000, "george.connelly"
wrote:

I have no specific knowledge of the Propex heater but I have found they all
use the same devices. First the fan should come on to purge the system
before attempting to light the burner. If the flame lights then it should
stay lit and the spark stop, if it doesn't then there are one or two
possibilities.


snip

Thanks for that George, that is very useful information.

When I get the time, I shall check out the electronic circuitry. I
have a few ideas of my own to check first, then I can trace the
circuit board and draw up a circuit diagram. It's fairly basic - 1 x
741 op amp, 1 x 555 timer, and 1 x medium power transistor, the rest
being passive bits and a couple of relays.

Other things are taking priority at the moment though (

Neil

 



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