Have a gas wall oven with two supply gas valves/solenoids in series -
safeguard against one sticking open, one presumes. Coils are
connected in parallel. These are situated on TOP of (doh!) the oven
shell - not the brightest move but placed there no doubt for service
access - tick.

Original coils were by Goyen Controls, and lasted 20 years before one
failed. By then Tyco had moved in (TYCO=TakeYourCompanyOver). Tyco
replacement lasted about 18 months,during which time the other Goyen
coil died. Ever since, the Tyco replacements (at ~$A70 each) have
lasted about 18 months.

It transpires that about the time I got the first Tyco coils, they had
transitioned the Oz factory to ROHS. Now these coils are 240VAC so
the winding wire is as fine as all getout. How is it terminated? Ah,
it is SOLDERED to 1/4" QC/Faston terminals which protrude out through
the epoxy/"thermoplastic" former. Evidently thermal cycling is
causing solder joint failures, but the necessary surgery with a Dremel
to reach the joint would - apart from compromising the overall
integrity and insulation characteristics - probably take out untold
turns of the coil itself, rendering the operation pointless.

On Wed, 07 Sep 2016 19:48:21 +0800, pedro wrote:

I should add that coil failure mode is open cct when hot - as in,
half-way through cooking a meal - and continuity returns when cooled
to near room temperature. Also that replacing the wall oven comes
with a penalty of having to carry out significant kitchen mods.
Grrrr!

On Wednesday, September 7, 2016 at 7:53:21 AM UTC-4, pedro wrote:
On Wed, 07 Sep 2016 19:48:21 +0800, pedro wrote:

I should add that coil failure mode is open cct when hot - as in,
half-way through cooking a meal - and continuity returns when cooled
to near room temperature. Also that replacing the wall oven comes
with a penalty of having to carry out significant kitchen mods.
Grrrr!

And why it is that when we built our summer house, we went to Propane for heat, hot water & cooking. More costly than electric appliances, for sure. But we have NEVER had an issue with appliance failure - apart from two floods that finally took out the refrigerator. The house is now elevated, so that will no longer be an issue.

Peter Wieck
Melrose Park, PA

On Wed, 7 Sep 2016 06:12:08 -0700 (PDT), "
wrote:

And why it is that when we built our summer house, we went to Propane for heat, hot water & cooking.

Grid independence, I'm sure.

We went with gas because the power system here was flakey and could go
out for hours at a time. Our gas hotplates have one 'D' cell
providing ignition, while the wall oven does require AC for the
igniter/flame-monitor/gas-control (BUT that's all able to be jury
rigged off a PC UPS in about a minute flat) so cooking during a
blackout is a non-event.

On Wed, 07 Sep 2016 19:48:21 +0800, pedro wrote:

Original coils were by Goyen Controls, and lasted 20 years before one
failed.

I think you can still buy Goyen valves, solenoids, and rebuild kits:
https://www.baghouseamerica.com/dust...genuine-parts/
http://cleanairsystems.com/products/solenoid-valves-for-air-gas-and-water.html
http://www.uniairproducts.com/uap/goyen/goyen.shtml
etc...


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 07/09/2016 21:48, pedro wrote:
Have a gas wall oven with two supply gas valves/solenoids in series -
safeguard against one sticking open, one presumes. Coils are
connected in parallel. These are situated on TOP of (doh!) the oven
shell - not the brightest move but placed there no doubt for service
access - tick.

Original coils were by Goyen Controls, and lasted 20 years before one
failed. By then Tyco had moved in (TYCO=TakeYourCompanyOver). Tyco
replacement lasted about 18 months,during which time the other Goyen
coil died. Ever since, the Tyco replacements (at ~$A70 each) have
lasted about 18 months.

It transpires that about the time I got the first Tyco coils, they had
transitioned the Oz factory to ROHS. Now these coils are 240VAC so
the winding wire is as fine as all getout. How is it terminated? Ah,
it is SOLDERED to 1/4" QC/Faston terminals which protrude out through
the epoxy/"thermoplastic" former. Evidently thermal cycling is
causing solder joint failures, but the necessary surgery with a Dremel
to reach the joint would - apart from compromising the overall
integrity and insulation characteristics - probably take out untold
turns of the coil itself, rendering the operation pointless.


Can you buy the same coil type but in a 24 Volts AC version? If so, that
plus a transformer may be more reliable than the 240VAC version.

On Wed, 07 Sep 2016 19:01:28 -0700, Jeff Liebermann
wrote:

On Wed, 07 Sep 2016 19:48:21 +0800, pedro wrote:

Original coils were by Goyen Controls, and lasted 20 years before one
failed.

I think you can still buy Goyen valves, solenoids, and rebuild kits:
https://www.baghouseamerica.com/dust...genuine-parts/
http://cleanairsystems.com/products/solenoid-valves-for-air-gas-and-water.html
http://www.uniairproducts.com/uap/goyen/goyen.shtml

BHA didn't seem to have the coils. The other two are Pentair outlets
(Pentair is slightly majority Tyco owned) and will be selling the same
parts I currently repeat purchase (*) from Pentair/Tyco here in Oz.
These are surprisingly made locally (Sydney) as they were in the "old"
Goyen days. It's fair bet that any I source nowadays will have the
ROHS curse on them.

I did some Dremel surgery today on one of the dead coils. Despite
having differing copper resistivity figures at hand (no consequence)
and the wire diameter testing my micrometer, from known ohms of a good
coil and some spreadsheeted maths I guesstimate it is 33 or 34AWG.

Maybe Chris' suggestion is worth investigating. The surgery wasn't
enough to find the dodgy termination, but thicker winding wire *may*
get a better joint.

(*) I date-mark the parts as they go in. The one that just failed was
one day short of 18 months, on an oven that gets used about once a
week on average.

On Thu, 8 Sep 2016 18:01:33 +1000, Chris Jones
wrote:

On 07/09/2016 21:48, pedro wrote:
Have a gas wall oven with two supply gas valves/solenoids in series -
safeguard against one sticking open, one presumes. Coils are
connected in parallel. These are situated on TOP of (doh!) the oven
shell - not the brightest move but placed there no doubt for service
access - tick.

Original coils were by Goyen Controls, and lasted 20 years before one
failed. By then Tyco had moved in (TYCO=TakeYourCompanyOver). Tyco
replacement lasted about 18 months,during which time the other Goyen
coil died. Ever since, the Tyco replacements (at ~$A70 each) have
lasted about 18 months.

It transpires that about the time I got the first Tyco coils, they had
transitioned the Oz factory to ROHS. Now these coils are 240VAC so
the winding wire is as fine as all getout. How is it terminated? Ah,
it is SOLDERED to 1/4" QC/Faston terminals which protrude out through
the epoxy/"thermoplastic" former. Evidently thermal cycling is
causing solder joint failures, but the necessary surgery with a Dremel
to reach the joint would - apart from compromising the overall
integrity and insulation characteristics - probably take out untold
turns of the coil itself, rendering the operation pointless.


Can you buy the same coil type but in a 24 Volts AC version? If so, that
plus a transformer may be more reliable than the 240VAC version.

Well the winding wire will be heavier gauge at 24VAC. Whether that
will achieve a more reliable ROHS solder bond is unsure, but it
probably couldn't be any worse.

In article ,
says...



(*) I date-mark the parts as they go in. The one that just failed was
one day short of 18 months, on an oven that gets used about once a
week on average.

Have you checked the voltage at the coils ? No more than you are using
that oven it seems there may be something more than just the coils going
on.

I have had very little experiance with the lead free solder, but as it
melts at a higher temperature it would seem to me that it should be
beter for the simple joints as far as the thermal cycling.

On 08/09/2016 19:17, pedro wrote:
On Thu, 8 Sep 2016 18:01:33 +1000, Chris Jones
wrote:

On 07/09/2016 21:48, pedro wrote:
Have a gas wall oven with two supply gas valves/solenoids in series -
safeguard against one sticking open, one presumes. Coils are
connected in parallel. These are situated on TOP of (doh!) the oven
shell - not the brightest move but placed there no doubt for service
access - tick.

Original coils were by Goyen Controls, and lasted 20 years before one
failed. By then Tyco had moved in (TYCO=TakeYourCompanyOver). Tyco
replacement lasted about 18 months,during which time the other Goyen
coil died. Ever since, the Tyco replacements (at ~$A70 each) have
lasted about 18 months.

It transpires that about the time I got the first Tyco coils, they had
transitioned the Oz factory to ROHS. Now these coils are 240VAC so
the winding wire is as fine as all getout. How is it terminated? Ah,
it is SOLDERED to 1/4" QC/Faston terminals which protrude out through
the epoxy/"thermoplastic" former. Evidently thermal cycling is
causing solder joint failures, but the necessary surgery with a Dremel
to reach the joint would - apart from compromising the overall
integrity and insulation characteristics - probably take out untold
turns of the coil itself, rendering the operation pointless.


Can you buy the same coil type but in a 24 Volts AC version? If so, that
plus a transformer may be more reliable than the 240VAC version.

Well the winding wire will be heavier gauge at 24VAC. Whether that
will achieve a more reliable ROHS solder bond is unsure, but it
probably couldn't be any worse.


It is possible that the solder has dissolved too much of the fine wire,
making it too thin. I have had a lot of trouble soldering very fine
wire, especially with lead-free solder - the wire will get thinner as it
dissolves in the molten solder, leaving it even less robust than its
original fragile state. Leaded solder that was deliberately
pre-saturated with copper ("Savbit") was supposed to be good for
preventing that, but I found it generally unpleasant to use.

As your coils develop their faults over time, I also wonder if the
manufaturer left some fairly active flux inside the encapsulation that
might be slowly eating the wire near the solder joint when it is warm.

Perhaps you can tell whether the break is at the solder joint, by
measuring the low-frequency capacitance of each terminal of the damaged
coil with respect to everything else. I doubt that knowing where the
break happens would be much use to you, but it is something the
manufacturer should be looking into.

On Thu, 08 Sep 2016 17:17:11 +0800, pedro wrote:

On Thu, 8 Sep 2016 18:01:33 +1000, Chris Jones
wrote:

On 07/09/2016 21:48, pedro wrote:
Have a gas wall oven with two supply gas valves/solenoids in series -
safeguard against one sticking open, one presumes. Coils are
connected in parallel. These are situated on TOP of (doh!) the oven
shell - not the brightest move but placed there no doubt for service
access - tick.

Original coils were by Goyen Controls, and lasted 20 years before one
failed. By then Tyco had moved in (TYCO=TakeYourCompanyOver). Tyco
replacement lasted about 18 months,during which time the other Goyen
coil died. Ever since, the Tyco replacements (at ~$A70 each) have
lasted about 18 months.

It transpires that about the time I got the first Tyco coils, they had
transitioned the Oz factory to ROHS. Now these coils are 240VAC so
the winding wire is as fine as all getout. How is it terminated? Ah,
it is SOLDERED to 1/4" QC/Faston terminals which protrude out through
the epoxy/"thermoplastic" former. Evidently thermal cycling is
causing solder joint failures, but the necessary surgery with a Dremel
to reach the joint would - apart from compromising the overall
integrity and insulation characteristics - probably take out untold
turns of the coil itself, rendering the operation pointless.


Can you buy the same coil type but in a 24 Volts AC version? If so, that
plus a transformer may be more reliable than the 240VAC version.

Well the winding wire will be heavier gauge at 24VAC. Whether that
will achieve a more reliable ROHS solder bond is unsure, but it
probably couldn't be any worse.
Can the valves be relocated to a cooler location? Or can you
substitute more robust valves made for hot location use?
Eric

On Thu, 08 Sep 2016 17:15:16 +0800, pedro wrote:

It's fair bet that any I source nowadays will have the
ROHS curse on them.

Ok, I see you've done your homework. Yes, ROHS is epidemic
everywhere.

I did some Dremel surgery today on one of the dead coils. Despite
having differing copper resistivity figures at hand (no consequence)
and the wire diameter testing my micrometer, from known ohms of a good
coil and some spreadsheeted maths I guesstimate it is 33 or 34AWG.

That's rather thin and could easily fuse. According to the wire
table:
https://en.wikipedia.org/wiki/American_wire_gauge
#34 will fuse at 5A. What do you measure for coil DC resistance?

Maybe Chris' suggestion is worth investigating. The surgery wasn't
enough to find the dodgy termination, but thicker winding wire *may*
get a better joint.

I agree. Heavier wire may solve or delay the problem. Methinks it
would be interesting to know what temperature the solder joint is
experiencing. A thermistor or thermocouple glued to as close to the
solder connection as possible might provide some interesting numbers.
If the position of the solenoid above the oven is the problem, that
will show it. Perhaps adding a metal heat shield between the coil and
oven?

For fusing, perhaps a small value resistor or "surgistor" in series
with the coil might reduce the peak current enough to let the thin
wire survive. With an inductor, there should NOT be an inrush peak,
but I'm thinking some kind of glitch, spike, or peak might be arriving
via the 240VAC line.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

En el artículo , pedro
escribió:

(*) I date-mark the parts as they go in. The one that just failed was
one day short of 18 months, on an oven that gets used about once a
week on average.

You seem to have the fault identified, but just to add another
perspective - since you're getting multiple failures of the solenoid
coils, and you're /assuming/ RoHS lead-free soldering is to blame
without having (yet) found evidence, perhaps you could look at other
common factors. Is the supply voltage to the coils stable, for
instance? Loose connection causing unstable voltage/surges/sags at the
coil? Voltage too high? etc. etc.

--
(\_/)
(='.'=) systemd: the Linux version of Windows 10
(")_(")

It's fair bet that any I source nowadays will have the
ROHS curse on them.

Ok, I see you've done your homework. Yes, ROHS is epidemic
everywhere.



I would like to see the bureaucrats that mandated ROHS to now do a cost/benefit analysis to compare the cost in money ___and lives___ due to ROHS failures vs due to leaded solder.

m

tiny wire is inherently unreliable

adding a transformer and using 24V valves is a good idea.

or use 120V valves and wire the 2 in series instead of parallel?

m

Totally agree with Chris. The possibility of residual flux. Add heat and it corrodes quickly.

I had issues with a manufacturer of wafer probes which I unfortunately was unable to solve. Took some SEM photos of the probes which turned black after heating at 200 C.

Solution was to boil the probes as received in baking soda and water, clean and then electroless gold plate them.

Later, the manufacturer went to 60/40 solder of the mechanical portion rather than spot welding. they used SN96 for the needles. They were unable to go back to the old process, but would solder ours with Sn96.

I also agree with the ZNR or some type of transient supression.

If you have too, I would investigate adding some sort of forced cooling.

I had buzzing issues with new 24 VAC valves (non gas) from a reputable company which was traced to dust during manufacturer. All of the valves received had to be cleaned prior to use. they were used with an Inert gas as the air medium which had no lubercation.

Poor manufacturing such as dust could be causeing a higher temperature than usual.

Corona dope might be able to be used to re-insulate a repair. Be sure to clean the flux off.

Under another note, a gas dryer at home has been operating for nearly 48 years with the same electric gas valves. As you said use is 3-4 times per week.
Preventative maintenance generally was cleaning of the ducts internal and external. Painting was done rarely.

The last failure was a cascade of events where the grease in the blower bearing transmission froze up. This cause the bearing to fail, which caused the fan blower belt to fail and the dryer drum belt to fail.

The fixes employed at this point was:
1. The set screw for the fan pulley was changed to brass tipped.
2.PM's will include looking at the transmission.
3.Special thrust washers were added to the drum tensioning pulley shaft and the fan shaft.
4. A special grease was selected for the transmission.
5. The drum light was changed to LED based.
6. A gasket was made for the outlet stream.
7. Nylon hinges (lint filter door) were replaced and painted with epoxy paint
8. Material of the lint filter door bumpers changed.
9. Always on the lookout for ignitors - I have two spares.
10. Replace a lid clip.
11. Replace the drum belt. 1st time in 50 years.

The to do list includes
1. Characterizing the ignitors. Possibly building a capacitance welder.
2. Rebuilding the lint filter.
3. Possibly adding an hour meter.
4. Add a dust ring to the timer shaft.
5. Make the sheet metal screws - machine screws

FWIW: A company does rebuild 50's style oven thermostats with ROHS compatable capillary tubes.

One issue I had was threading the capillary through the outer cavity and the oven cavity double wall. I placed the sensor in a straw which was easy to thread through the double wall and then cut the straw off.

Sorry about the "noise". Hopefully it's useful to somebody.

On Thu, 8 Sep 2016 10:08:04 -0400, Ralph Mowery
wrote:

Have you checked the voltage at the coils ? No more than you are using
that oven it seems there may be something more than just the coils going
on.

The line voltage is in the range 240-242, the coils are embossed 240V.

I have had very little experiance with the lead free solder, but as it
melts at a higher temperature it would seem to me that it should be
beter for the simple joints as far as the thermal cycling.

In my relatively limited lead-free solder experience (just the service
bench - where I always use leaded solder for rework) the joints seem
to develop a dry crystalline characteristic over time when in
situations subjected to thermal cycling. IMHO it isn't a melting
point issue but an alloy characteristic.

On Thu, 08 Sep 2016 08:17:12 -0700, Jeff Liebermann
wrote:

On Thu, 08 Sep 2016 17:15:16 +0800, pedro wrote:

It's fair bet that any I source nowadays will have the
ROHS curse on them.

Ok, I see you've done your homework. Yes, ROHS is epidemic
everywhere.

I did some Dremel surgery today on one of the dead coils. Despite
having differing copper resistivity figures at hand (no consequence)
and the wire diameter testing my micrometer, from known ohms of a good
coil and some spreadsheeted maths I guesstimate it is 33 or 34AWG.

That's rather thin and could easily fuse. According to the wire
table:
https://en.wikipedia.org/wiki/American_wire_gauge
#34 will fuse at 5A. What do you measure for coil DC resistance?

Maybe Chris' suggestion is worth investigating. The surgery wasn't
enough to find the dodgy termination, but thicker winding wire *may*
get a better joint.

I agree. Heavier wire may solve or delay the problem. Methinks it
would be interesting to know what temperature the solder joint is
experiencing. A thermistor or thermocouple glued to as close to the
solder connection as possible might provide some interesting numbers.

Indeed. It would be handy to have a thermoprobe with logging on it.
Note to self: see where I can borrow one.

If the position of the solenoid above the oven is the problem, that
will show it. Perhaps adding a metal heat shield between the coil and
oven?

The dual valve mechanism is bolted to the oven. The coils (see ebay
item# 322017672259 for the ones we "consume" - but at a much better
price than he's asking ...) sit over the metal housing which encloses
the valve plunger (armature) and has a metal spacer each end for
location and ?thermal separation?. So it would be necessary to
elevate the entire incoming gas pipe/valve syhstem to relieve
conducted heat to any significant degree. And if it IS the cycling -
rather than the actual temperature reached - which causes the failures
then reducing the latter may achieve nothing.

For fusing, perhaps a small value resistor or "surgistor" in series
with the coil might reduce the peak current enough to let the thin
wire survive. With an inductor, there should NOT be an inrush peak,
but I'm thinking some kind of glitch, spike, or peak might be arriving
via the 240VAC line.

Dunno. Could do (but it'd be 18 months before I'd know if it made a
difference).

On Thu, 8 Sep 2016 18:36:23 +0100, Mike Tomlinson
wrote:

You seem to have the fault identified, but just to add another
perspective - since you're getting multiple failures of the solenoid
coils, and you're /assuming/ RoHS lead-free soldering is to blame
without having (yet) found evidence, perhaps you could look at other
common factors.

Fair comment.

Is the supply voltage to the coils stable, for instance? Voltage too high?

Without logging it (and I don't have access to a Dranetz any more) I
would venture that it is. Reading taken at random times show good
regulation, and nothing else in the place which is surge-prone
(electronics and incandescents) is dying at all.

Loose connection causing unstable voltage/surges/sags at the
coil?

Nope, snug as.

On Fri, 9 Sep 2016 00:48:54 +1000, Chris Jones
wrote:

It is possible that the solder has dissolved too much of the fine wire,
making it too thin. I have had a lot of trouble soldering very fine
wire, especially with lead-free solder - the wire will get thinner as it
dissolves in the molten solder, leaving it even less robust than its
original fragile state. Leaded solder that was deliberately
pre-saturated with copper ("Savbit") was supposed to be good for
preventing that, but I found it generally unpleasant to use.

As your coils develop their faults over time, I also wonder if the
manufaturer left some fairly active flux inside the encapsulation that
might be slowly eating the wire near the solder joint when it is warm.

Really don't know. The Pentair/Tyco/Goyen engineer that I discussed
this with asked for a failed one to be returned for evaluation - so I
sent two (as I have a pile of them otherwise just gathering dust).
When I followed up a few weeks later, he had departed and his
replacement was unaware of the whole matter, and could find no record
of their return despite supplying him the RMA number.

He also declined my offer to send more, really being disinterested in
finding out the reason for the failure.

Perhaps you can tell whether the break is at the solder joint, by
measuring the low-frequency capacitance of each terminal of the damaged
coil with respect to everything else. I doubt that knowing where the
break happens would be much use to you, but it is something the
manufacturer should be looking into.

The failure mode is going open cct when hot. As they cool continuity
returns.

I have made up a test lead with pea lamps that I connect up so there
is a (6V) lamp in series with each coil. When there is a failure I
connect this into circuit and re-energise the oven. (Doesn't take
long, I'm getting pretty polished at that now!) It typically takes
about ten minutes to get back up to failure temp. Then I can see
which coil is going O/C and replace it from my stock of new spares.

To be able to test it would require a fair bit of setting up.

See above re manufacturer "interest". They sell quite a number of
these during our winters as they are used in gas wall furnaces. I
guess they are figuring that as long as they keep selling them as
replacements, why investigate.

On Thu, 08 Sep 2016 08:12:34 -0700, wrote:

Can the valves be relocated to a cooler location?

See reply to JL for what would be involved.

Or can you substitute more robust valves made for hot location use?

The Pentair people (valve manufacturer) said they have no such
solution.

On Thu, 08 Sep 2016 08:17:12 -0700, Jeff Liebermann
wrote:

What do you measure for coil DC resistance?

Missed that bit. Around 1600 ohms.

In article ,
says...

On Thu, 08 Sep 2016 08:12:34 -0700, wrote:

Can the valves be relocated to a cooler location?

See reply to JL for what would be involved.

Or can you substitute more robust valves made for hot location use?

The Pentair people (valve manufacturer) said they have no such
solution.

Have you looked into another valve company ?

I retired a few years ago from a large company and we had hundreds of
valves similar to that and very few of them failed, especially the
coils. Most did operate on 120 volts.

Not sure how the valves are in your oven, but maybe you could try 2 of
the 120 volt coils in series.

On Fri, 09 Sep 2016 16:09:10 +0800, pedro wrote:

On Thu, 08 Sep 2016 08:17:12 -0700, Jeff Liebermann
wrote:

What do you measure for coil DC resistance?

Missed that bit. Around 1600 ohms.

Assuming 240VAC, that's:
P = E^2 / R = 240Vrms^2 / 1600 = 36 watts
That's way too high dissipation for a solenoid valve.
Are you sure those are 240VAC solenoids and some other AC voltage? Are
the solenoids run by 240VAC or some other voltage?

Also, could you check the eBay listing number? I want to see the coil
specs. Nothing found:
http://www.ebay.com/sch/i.html?_nkw=322017672259




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article ,
says...

On Fri, 09 Sep 2016 16:09:10 +0800, pedro wrote:

On Thu, 08 Sep 2016 08:17:12 -0700, Jeff Liebermann
wrote:

What do you measure for coil DC resistance?

Missed that bit. Around 1600 ohms.

Assuming 240VAC, that's:
P = E^2 / R = 240Vrms^2 / 1600 = 36 watts
That's way too high dissipation for a solenoid valve.
Are you sure those are 240VAC solenoids and some other AC voltage? Are
the solenoids run by 240VAC or some other voltage?

Also, could you check the eBay listing number? I want to see the coil
specs. Nothing found:
http://www.ebay.com/sch/i.html?_nkw=322017672259





Jeff I think you are mixing up the AC and DC power formulas.

I am sure the impedance of the coil at 60 Hz is more than the DC
resistance.

That would make the wattage less than what you have calculated using a
DC equation.

A quick check of the Goyen catalog shows they draw about .05 to .07 Amps
depending on the coil at 240 volts.
That is around 10 to 16 watts. The DC resistance of the coils was not
given. The coils on many of the valves can be changed to several
voltages.

On Fri, 9 Sep 2016 15:37:02 -0400, Ralph Mowery
wrote:

Jeff I think you are mixing up the AC and DC power formulas.

I am sure the impedance of the coil at 60 Hz is more than the DC
resistance.

The DC resistance averages around 1600 ohms. According to my calcs
there are around 4700 turns in the coil, so at 50Hz the impedance
incorporates a significant reactance. The coil (obviously) has a
ferrous valve plunger in its core.

They are marked 240VAC 50Hz (= our supply here in Oz) and the one I
attacked with the Dremel is marked 5W.

On Fri, 9 Sep 2016 10:03:15 -0400, Ralph Mowery
wrote:

Have you looked into another valve company ?

No

I retired a few years ago from a large company and we had hundreds of
valves similar to that and very few of them failed, especially the
coils. Most did operate on 120 volts.

Of course at 120V the wire would be twice the diameter. If it is
corrosive flux at work, it would take longer to eat it away. If it is
failing Pbfree solder bonds, who knows.

Not sure how the valves are in your oven, but maybe you could try 2 of
the 120 volt coils in series.

I am considering that. Meanwhile SWMBO is considering a replacement
oven (which as you'd all know, means a complete new kitchen)

On Fri, 9 Sep 2016 15:37:02 -0400, Ralph Mowery
wrote:

Jeff I think you are mixing up the AC and DC power formulas.

Oops. Y'er right.
Big rush - No time - No brain - No excuse.

A quick check of the Goyen catalog shows they draw about .05 to .07 Amps
depending on the coil at 240 volts.

Ok, that's better and less than the 5A fusing current for #34 awg.

That is around 10 to 16 watts. The DC resistance of the coils was not
given. The coils on many of the valves can be changed to several
voltages.

10 - 16 watts might get the coil quite warm if energized continuously.
Probably not enough to melt solder, but certainly will add a few
degrees to the heat from the furnace.

I don't think it's overheating from the furnace or the warm coil. It
will get hot, but not enough to melt solder. Since various other
solenoids have failed in the same manner, I don't think the failures
are caused by some kind of soldering defect. The long time that it
takes to fail might be the copper wire slowly dissolving in the
solder. However, my limited experience indicates that most of the
damage occurs immediately during soldering, not many months later.
With a 5A fusing current and the rather large inductance of the
solenoid, I don't see a high current "surge" fusing the #34 wire.

Offhand, I was thinking something else might be happening here.
Something like a sharp edge on the solenoid terminal slowly cutting
its way through the copper wire every time the solenoid is energized.
It might be 50 Hz vibration work hardening of the wire causing
embrittlement. However, these are unlikely to have also occurred in
the other replacement solenoids, that also failed. It might be the
difference in coefficient of thermal expansion between the epoxy and
the copper wire. Usually, some paper or tape wrapping will provide
room to expand, but again it would be an amazing coincidence if the
same problem appeared in a competetors solenoid.

That leaves external influences, such as line voltage glitches and
surges. Get your Dranetz power quality monitor/logger back, borrow
something, or just setup a data logger on the AC line.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 09 Sep 2016 23:22:39 -0700, Jeff Liebermann
wrote:

I don't think it's overheating from the furnace or the warm coil.

Sorry, that should be oven, not furnace (in multiple places).

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"Assuming 240VAC, that's:
P = E^2 / R = 240Vrms^2 / 1600 = 36 watts
That's way too high dissipation for a solenoid valve.
Are you sure those are 240VAC solenoids and some other AC voltage? Are the solenoids run by 240VAC or some other voltage? "

Ummm, where is the "L" in your equation. If it is 1600 ohms DC resistance it is likely to have considerable inductance. There is also usually some type of metal core which takes it even higher.

That reminds me of a time I threw together a thermostatic control for a window unit air conditioner in a hydroponic grow room. I put the box together with a little transformer and a relay, a DC operated relay. Come to find out once it started it would not stop. I used an electronic thermostat so there was no worries about leveling it or anything, plus he liked the ability to set the timer. Turns out the SOB used a small triac and with DC it would never shut off so I had to start over. Wasn't so bad, just get a different relay and eliminate the rectifiers and filter.

But, the DC relay would not run on AC, and that had to be because of the inductance. I wound up using one for an air conditioning condensing unit, you know, like in back of the house. Typical 24 VAC job, which is what the thermostat was designed for. Put a long ass wire on it too because he wated to be able to place it wherever. he had something like 4,000 watts worth of lights and the thermostat has to be a bit away from them, and also away from the window unit.

In the end it worked but I had learned the hard way you just can't interchange relay with DC and AC coils. And damn, 1600 ohms is alot for just about any wire. Much more than that and it almost ain't wire !

"Jeff I think you are mixing up the AC and DC power formulas. "

I just posted something to that effect not having seen your post. I know the guy is smart and I guess he just had a blonde moment.

In article ,
says...



A quick check of the Goyen catalog shows they draw about .05 to .07 Amps
depending on the coil at 240 volts.

Ok, that's better and less than the 5A fusing current for #34 awg.

That is around 10 to 16 watts. The DC resistance of the coils was not
given. The coils on many of the valves can be changed to several
voltages.

10 - 16 watts might get the coil quite warm if energized continuously.
Probably not enough to melt solder, but certainly will add a few
degrees to the heat from the furnace.



WE had hundreds of that brand where I worked and some were pulsed every
30 seconds or so and some were almost always on. Hardly any problems
with the coils. The ones that were on most of the time ran hot enough
that you would almost burn your hand. Some of them were where the room
temperature was over 100 deg F. The plant made polyester and the
process required about 300 deg C of heat. I said room, but those areas
were not occupied except to check on the equipment from time to time.

Most problems were either the rubber disk wearing out or the plunger
enlarging due to all the beating they take or the spring wearing out.
The plunger is enclosed so no way for it to touch the coil form. While
it could be something in the coil, I would think that as many that he
changed out it must be something external.

One other thing, is the coil all the way seated on where the plunger is
? If not it could be drawing enough current to burn out the wire. We
often left the coil hooked up to the conduit and just changed out the
mechanical part. Mainly did that to keep from having to go to another
floor and find the power source for the coil. Found that we needed to
stick a large screwdriver or other item in the core of the coil or a
fuse would blow or the coil would burn out.

On Sat, 10 Sep 2016 05:07:13 -0700 (PDT), wrote:

"Jeff I think you are mixing up the AC and DC power formulas. "

I just posted something to that effect not having seen
your post. I know the guy is smart and I guess he just had a
blonde moment.

Not that smart yesterday. I was on hold with a customer trying to
walk them through a messy problem. I'm easily distracted by paying
work. I also have a problem with some meds. In the morning, I take a
sustained release vasodilator, which initially causes a rather radical
drop in blood pressure. When that happens, the brain goes offline or
is reduced to operating at the speed of a snail for a while. I just
took a pill for breakfast and am posting drivel while waiting for my
ISP's support people to call me back, something that has been rumored
to happen at geological intervals.

In addition, the OP reverse engineered the oven wiring and produced a
schematic of sorts. Generally quite good but a few mistakes. One was
showing an SCR keying the solenoids instead of a Triac. If it were an
SCR, it would rectify the AC going to the solenoids. That would
produce some DC on the solenoids which would raise the dissipation.
However, I didn't catch that at the time and was still concentrating
on the DC part of the puzzle. Somewhere along the line, I simply
forgot about the inductance.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 09 Sep 2016 16:08:29 +0800, pedro wrote:

On Thu, 08 Sep 2016 08:12:34 -0700, wrote:

Can the valves be relocated to a cooler location?

See reply to JL for what would be involved.

Or can you substitute more robust valves made for hot location use?

The Pentair people (valve manufacturer) said they have no such
solution.
I meant outside of the oven enclosure. Bypass the valves with plumbing
in the enclosure and then put the valves somwhere else in the gas
supply line.
Eric

On Saturday, September 10, 2016 at 9:26:40 AM UTC-7, Jeff Liebermann wrote:

...the OP reverse engineered the oven wiring and produced a
schematic of sorts. Generally quite good but a few mistakes. One was
showing an SCR keying the solenoids instead of a Triac. If it were an
SCR, it would rectify the AC going to the solenoids.

A triac can also rectify, if the gate has become insensitive (or
too responsive to noise). If you use the triac to run
an AC relay, and the relay to activate the valve, the valve is immune
to rectification (and if the relay burns up, it's cheap to replace).

Or, just replace the triac on suspicion

Even a small amount of rectification in the triac circuit will walk the
magnetic core toward saturation and remove inductive back-EMF. Next
event: the coil burns up.

"I'm easily distracted by paying
work. I also have a problem with some meds. "

Yeah those pesky paying customers. Why can't they just pay and leave us alone ? LOL

Those vasodilators can have side effects. But if you take one a day you could take it after supper, or even cut the pills in half. If you have a BP meter you might want to consider lowering the dosage is you are having side effects.

You know I am not an MD and I know you are not stupid enough to blindly take by advice, but I believe they pay too much attention to BP these days, at least some doctors. Think about out ancestors on the battlefield with swords and shields fighting for hours ad hours, what was their blood pressure 300/200 ? According to some doctors they should have just dropped dead. A late friend of mine who got me into doing the research on nutrition a long time ago postulated it might be a copper deficiency. And believe it or not, hypertension can also be caused by a sodium deficiency. The sodium in normal table salt is not absorbed and metabolised by the body because of the anti-clumping agent, which might also inhibit other minerals' proper usage in the body. If you use salt, get unrefied sea salt if possible. I got two kinds, one is from the dead sea and one is from up north, I usually mix them.

At least get the kind that clumps up. Evidence - back when salt would clump up in the summer and you had to put rice in it, doctors were not telling people to limit their salt intake. If you already use Kosher salt you might not have that problem but the unrefined stuff is still better because of the mineral content. Most chronic conditions are caused by mineral deficiencies. Not all, but enough to make it a concern.

I think last time I went in my BP was like 140/70. The big spread indicates the heart is working well. When the spread goes down that is a bad sign. When it goes under 40 there might be a problem. I have talked to an MD about this. Also, some would think 140/70 is high but they did not say a word about it, or even suggest any medication.

i use very little salt these days. For one this unrefined stuff tastes different. It is like it is not as strong, but it is easier to oversalt things. Take and put too much regular table salt on something and it's like oh well, but this stuff it is like UGH.

"Somewhere along the line, I simply
forgot about the inductance. "

Take a spark plug wire off your car and...

Nevermind.

On Sat, 10 Sep 2016 11:46:46 -0700 (PDT), whit3rd
wrote:

On Saturday, September 10, 2016 at 9:26:40 AM UTC-7, Jeff Liebermann wrote:

...the OP reverse engineered the oven wiring and produced a
schematic of sorts. Generally quite good but a few mistakes. One was
showing an SCR keying the solenoids instead of a Triac. If it were an
SCR, it would rectify the AC going to the solenoids.

A triac can also rectify, if the gate has become insensitive (or
too responsive to noise). If you use the triac to run
an AC relay, and the relay to activate the valve, the valve is immune
to rectification (and if the relay burns up, it's cheap to replace).

Or, just replace the triac on suspicion

Even a small amount of rectification in the triac circuit will walk the
magnetic core toward saturation and remove inductive back-EMF. Next
event: the coil burns up.

Good idea. However, I just took a 4th look at the schematic. There's
a diode and 10K resistor from the gate to ground. Those are fed from
a CMOS gate going through a capacitor (value unknown). I may have
been wrong, but this thing now looks like an SCR instead of a Triac.
If it is an SCR, the current through the parallel solenoids would have
a rather high DC component. (Yeah, I know... indecision is the key to
flexibility).

Pedro... could you post your schematic somewhere or could you give me
permission to do so?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 10 Sep 2016 10:05:58 -0700, wrote:

Can the valves be relocated to a cooler location?

See reply to JL for what would be involved.

Or can you substitute more robust valves made for hot location use?

The Pentair people (valve manufacturer) said they have no such
solution.
I meant outside of the oven enclosure. Bypass the valves with plumbing
in the enclosure and then put the valves somwhere else in the gas
supply line.
Eric

Yes that is a possibilty, but in our over-regulated environment it'd
require all sorts of recertification, almost like the
aviation/aerospace industries. Having been exposed to THAT industry
it's a path I don't want to tread out of MY wallet.

On Sat, 10 Sep 2016 10:25:09 -0400, Ralph Mowery
wrote:

WE had hundreds of that brand where I worked and some were pulsed every
30 seconds or so and some were almost always on. Hardly any problems
with the coils.

Ralph, should I presume that was with pre-ROHS vintage coils? As I
mentioned in my O/P, the original pair (which were pre-ROHS) both
lasted two decades. Subsequent ones were 15-18 months AND the oven
gets less use nowadays as the kids migrate outwards. Not a
statistically significant sampling for some, but sufficiently damning
from where I stand/sit.

Most problems were either the rubber disk wearing out or the plunger
enlarging due to all the beating they take or the spring wearing out.
The plunger is enclosed so no way for it to touch the coil form.

We haven't had the moving parts show any issues, just coils.

While it could be something in the coil, I would think that as many that he
changed out it must be something external.

Nothing external has changed, except our supply voltage has been
"harmonised" with rest-of-Oz i.e. reduced from the original 254V rms
down to 240V rms.

One other thing, is the coil all the way seated on where the plunger is
? If not it could be drawing enough current to burn out the wire. We
often left the coil hooked up to the conduit and just changed out the
mechanical part. Mainly did that to keep from having to go to another
floor and find the power source for the coil. Found that we needed to
stick a large screwdriver or other item in the core of the coil or a
fuse would blow or the coil would burn out.

Appreciate the question. It is seated down properly. The frame which
sits over the coil/valve assembly as part of it is actually a snug fit
(you need to slide the coil into it and align the holes, it's a press
fit) and then the frame is held down over the valve plunger "cylinder"
and screwed down. No unintended magnetic/air gaps.

There is also a "spacer" pressed into each end of the coil bobbin the
ensure it is located correctly (radially).

Pics of the valve assemblies in situ:

http://imgur.com/xGlio51
http://imgur.com/3NB4ALX

and of the coil post-Dremel (*):

http://imgur.com/An9XCk8
http://imgur.com/wH0l3eP

(*) I needed effective bobbin length/diameters to calculate turns and
hence deduce a credible wire gauge to match the known DC resistance.

On Sat, 10 Sep 2016 19:32:11 -0700, Jeff Liebermann
wrote:

Pedro... could you post your schematic somewhere or could you give me
permission to do so?

It's now at http://imgur.com/yOpwRzV alongside the pics.