Gas fridge

[ditchcrawler]

 

 

And so we are led deep into the realms of the vanishingly unlikely. It's this ridiculous protecting against minuscule risks that brings the BSS into disrepute.

 

How many deaths or serious injuries, (or even just substantial explosions) have been caused in the last ten years by chain being stored in gas lockers? None is the answer, I suspect.

 

 

 

 

(Speeling ejit.)

More than winch motors causing an internal spark at the same time that they were full of a gas air mixture of between 2.1 and 10.2 % I would bet. But depending on construction, something we DON'T KNOW it may be possible to damage the pipe work, or regulator with a chain flapping abaout

[gazza]

A bit more meat on the bone.

 

The locker is huge in area but not in depth. The bottle and reg are on the bulkhead, the winch at the pointy end (surprisingly ) a good 4' apart.

 

The motor while not labled intrinsically safe looked at least ip66 - there is virtually no risk of it being a source of ignition. I had it to bits to free off the winch gypsy and to enable a BSS pass without having to reposition the bottle on the bathing platform.

The boat is built to lloyds register standards by a well respected builder. It's survived 27 years without going bang!

All electrical connection are correctly sleeved and covered meaning no risk of a short. The direction relay is solid state so again, no risk of ignition

If it were on a coastal marina none of the silly interpretation of the BSS would apply. She's less at home halfway up the Nene.

 

This year's bss passed no problems with the winch re-installed because the guy who tested it was familiar with the design and construction of vessels of this type. The last tester was not.

Edited April 14, 2016 by gazza

[MtB]

Duplicate edit.

Edited April 14, 2016 by Mike the Boilerman

[MtB]

Duplicate edit

Edited April 14, 2016 by Mike the Boilerman

[MtB]

Duplicate edit.

Edited April 14, 2016 by Mike the Boilerman

[MtB]

The locker is huge in area but not in depth. The bottle and reg are on the bulkhead, the winch at the pointy end (surprisingly ) a good 4' apart.

 

The motor while not labled intrinsically safe looked at least ip66 - there is virtually no risk of it being a source of ignition.

 

 

And the most stupid thing is, should the winch motor happen to ignite a lockerful of gas at a concentration in air between the lower and upper limits of concentration for explosion, all that would happen is the gas locker lid would get blown open with a hefty thump.

 

And probably no-one would notice until later as they were busy raising the anchor and getting under way!

[gazza]

 

 

And the most stupid thing is, should the winch motor happen to ignite a lockerful of gas at a concentration in air between the lower and upper limits of concentration for explosion, all that would happen is the gas locker lid would get blown open with a hefty thump.

 

And probably no-one would notice until later as they were busy raising the anchor and getting under way!

Indeed!

 

My friend was mortified at the thought of having to reposition the bottle on the bathing platform - something the bss frowns on (but doesn't prohibit) due to the risk of impact damage.....

She couldn't understand how it was OK on previous BSS inspections - prior to their ownership she was on the Whittam under BW reign.

[colinwilks]

I may be missing something but the message I'm receiving from this thread (eg MtB and Alan Fincher) is that it is quite safe to run a gas fridge in a potentially unventilated area without risking exposure to carbon monoxide. Is this what you're saying?

[gazza]

I may be missing something but the message I'm receiving from this thread (eg MtB and Alan Fincher) is that it is quite safe to run a gas fridge in a potentially unventilated area without risking exposure to carbon monoxide. Is this what you're saying?

Yes. it has been likened to having a candle burning.

 

Our's is in a ply enclosure in the cockpit, it feels right to me to have it connected to a flue. i'd rather get most of the heat out of the are via the flue. Even on electric it helps to train the hot air out.

[MtB]

I may be missing something but the message I'm receiving from this thread (eg MtB and Alan Fincher) is that it is quite safe to run a gas fridge in a potentially unventilated area without risking exposure to carbon monoxide. Is this what you're saying?

 

 

Broadly speaking, yes.

 

BUT.... this isn't definitive, there may be exceptions. A gas fridge MUST be installed with the written manufacturer's instructions, not in accordance with what some blokes on the internet wrote. So if the manufacturer says it must have a flue, then it must.

(And if the manufacturer says it doesn't need a flue, then it doesn't.)

[colinwilks]

Thanks Gazza and Mike,

The heat is not an issue but the potential for CO is.

"RTFM", as we used to say in the computer industry!

[MtB]

Thanks Gazza and Mike,

The heat is not an issue but the potential for CO is.

"RTFM", as we used to say in the computer industry!

 

 

The potential for CO is mitigated by servicing the thing annually, in accordance with the manufacturers instructions.

 

The reason they produce CO is that servicing them is an utter PITA, so it never gets done. Very few people empty out the whole of the contents of their fridge to remove it from its hole and service it, preferring to 'do it another day'. And that day never arrives.

 

My view is that a gas fridge should be fitted at eye level facing along the length of the boat, so a hatch can be constructed to access the back of the fridge from the other side. This way servicing it becomes easy, and the requirement to fit gas pipe in a boat 'as high as reasonably practicable' is more easily met.

[cereal tiller]

 

 

The potential for CO is mitigated by servicing the thing annually, in accordance with the manufacturers instructions.

 

The reason they produce CO is that servicing them is an utter PITA, so it never gets done. Very few people empty out the whole of the contents of their fridge to remove it from its hole and service it, preferring to 'do it another day'. And that day never arrives.

 

My view is that a gas fridge should be fitted at eye level facing along the length of the boat, so a hatch can be constructed to access the back of the fridge from the other side. This way servicing it becomes easy, and the requirement to fit gas pipe in a boat 'as high as reasonably practicable' is more easily met.

The installation method you describe is exactly how my Gas fridge has been fitted,the Burner is 1 Meter from floor level and the top of the flue is 240 mm below the ceiling.

 

Easy to see the flame colour and very easy to clean ,and,has not gathered any fluff around the burner assembly

 

The cabin lining above the Fridge barely gets warm even though the Flue is open

 

Have placed a C.O. Meter in various positions around the Flue and have been unable to detect a significant amount of unburnt gas.

 

 

 

CT

[MtB]

The cabin lining above the Fridge barely gets warm even though the Flue is open

 

 

Point of order M'lud....

 

CT';s flue is not 'open', that means something else. His fridge is correctly described technically as 'flueless'.

 

The flue on a Morco is 'open'. The Morco is an open-flued appliance. CT's frdge is a flueless appliance.

Edited April 19, 2016 by Mike the Boilerman

[MtB]

Have placed a C.O. Meter in various positions around the Flue and have been unable to detect a significant amount of unburnt gas.

 

 

 

Another point of order M'lud!

 

A CO detector detects CO, not unburned propane.

 

(Although strictly speaking, CO is unburned gas. Just not the gas one would expect to find when looking for say, a gas leak. CO burns just fine, just like butane and propane. In fact it was a major constituent of 'Town gas' before we found the north sea stuff.)

 

Had CT used a gas analyser to look for CO2, a primary constituent of flue gas (i.e. burned gas) he would have found plenty. But CO2 is harmless in low concentrations.

Edited April 19, 2016 by Mike the Boilerman

[nicknorman]

Thread hijack: my fancy electronic 3 way caravan fridge intermittently locks out on gas, it has auto-ignition and "flame-rectification" flame supervision which seems flaky. The electrode is bathed in flame, it all looks quite clean, but every couple of days it locks out and even when it doesn't, there is a lot of clickery from the igniter for a good while after its lit (it lights instantly). Any ideas? I'll maybe try cleaning the ground connection path between the burner and the control box but other than that, is it a matter of a new control box? Anything else to try first?

[MtB]

Thread hijack: my fancy electronic 3 way caravan fridge intermittently locks out on gas, it has auto-ignition and "flame-rectification" flame supervision which seems flaky. The electrode is bathed in flame, it all looks quite clean, but every couple of days it locks out and even when it doesn't, there is a lot of clickery from the igniter for a good while after its lit (it lights instantly). Any ideas? I'll maybe try cleaning the ground connection path between the burner and the control box but other than that, is it a matter of a new control box? Anything else to try first?

 

 

Yes, the continuing clickage is because it's failing to detect the flame and thinks it's still not lit.

 

An AC microammeter is series with the ignition lead should typically show two or three uAmps IIRC if it can withstand the sparks! If you have the correct rectification current (check with the manufacturer) then it must be a busted PCB. Mending them can present an interesting challenge if you can get it to bits.

[Tony Brooks]

Thread hijack: my fancy electronic 3 way caravan fridge intermittently locks out on gas, it has auto-ignition and "flame-rectification" flame supervision which seems flaky. The electrode is bathed in flame, it all looks quite clean, but every couple of days it locks out and even when it doesn't, there is a lot of clickery from the igniter for a good while after its lit (it lights instantly). Any ideas? I'll maybe try cleaning the ground connection path between the burner and the control box but other than that, is it a matter of a new control box? Anything else to try first?

 

Not sure if this helps but The Alde 23xx igniters do that when they fail. That is they keep clicking even though the flame has lit. I understand they "measure" the resistance of the spark gap that decreases when the flame ionises the spark path or something like that. Certainly check the spark wiring and "earth" connections then it may be a new igniter.

[nicknorman]

Yes, the continuing clickage is because it's failing to detect the flame and thinks it's still not lit.

 

An AC microammeter is series with the ignition lead should typically show two or three uAmps IIRC if it can withstand the sparks! If you have the correct rectification current (check with the manufacturer) then it must be a busted PCB. Mending them can present an interesting challenge if you can get it to bits.

Thanks. I'll see if I can find my old analogue meter. Fortunately the van is still under guarantee but you know what I'm like, I'd prefer to fix it myself if I can, but that probably doesn't extend to board-level repairs! I bought the caravan (2nd hand) in Aberdeen and it's now ensconced at the gliding club in the middle of the highlands 90 miles away, but apparently there are roaming caravan gas fridge technicians and they will send one out if I give up.

I understand they "measure" the resistance of the spark gap that decreases when the flame ionises the spark path or something like that.

Yes but it's cleverer than that, it doesn't just check for the low resistance of the flame (ionised plasma) since that might just be a bug or bit of wet grass. Instead they use "flame rectification" which, as a result of the dissimilar area of the electrode end vs the burner, causes an aysmmetrical ac current to flow when a symmetric AC voltage is put across the gap. A bit like a thermionic diode. It is the asymmetry of the current that is the confirmation of the flame. Edited April 19, 2016 by nicknorman

[MtB]

Yes and

 

Thread hijack: my fancy electronic 3 way caravan fridge intermittently locks out on gas, it has auto-ignition and "flame-rectification" flame supervision which seems flaky. The electrode is bathed in flame, it all looks quite clean, but every couple of days it locks out and even when it doesn't, there is a lot of clickery from the igniter for a good while after its lit (it lights instantly). Any ideas? I'll maybe try cleaning the ground connection path between the burner and the control box but other than that, is it a matter of a new control box? Anything else to try first?

 

 

Mike Blackrose had this problem too. Might be worth PMing him to see if he got anywhere with it (although he flounced over the CA board being deleted IIRC so may not respond).

 

On reflection I'm not sure exactly what's happening. What exactly do you mean by 'locking out'? Most fridges have just a pilot-sized flame and that's it. Does the PCB shut the gas off after a set period of sparking? Or do you mean the fame just goes out and a thermocouple device shuts off the gas? If the latter, then this is a separate fault from the PCB continuing to throw sparks after the flame has established.

 

Another thing, you say the electrode is bathed in flame. Strictly, the gap between the two electrodes needs to be filled with flame or rectification doesn't happen.

[nicknorman]

Yes and

 

 

 

 

Mike Blackrose had this problem too. Might be worth PMing him to see if he got anywhere with it (although he flounced over the CA board being deleted IIRC so may not respond).

 

On reflection I'm not sure exactly what's happening. What exactly do you mean by 'locking out'? Most fridges have just a pilot-sized flame and that's it. Does the PCB shut the gas off after a set period of sparking? Or do you mean the fame just goes out and a thermocouple device shuts off the gas? If the latter, then this is a separate fault from the PCB continuing to throw sparks after the flame has established.

 

Another thing, you say the electrode is bathed in flame. Strictly, the gap between the two electrodes needs to be filled with flame or rectification doesn't happen.

This fridge has a thermostat that shuts the gas on and off as required to maintain the temperature unlike the older ones where the flame was on constantly. So it is after it has shut off, and then needs to come on again, that the problem occurs. The burner has lit but it carries on sparking. It then gives up and flashes the on light until such time as I switch it off and on again, which is what I mean by "locked out". It is just a button press to switch it off and on again but that is no good if I'm not there and awake!

 

However you other point is EXCELLENT as I didn't check that the base of the flame was touching the burner so that is definitely something to do, thanks. Pretty sure there is only one electrode, I think it arcs onto the burner but I'll check.

 

Edit: if you listen carefully you can hear both the sound of the lit flame roaring a bit, and the clicking of the igniter, so I definitely know the flame is lit but it's not being detected properly.

Edited April 19, 2016 by nicknorman

[ditchcrawler]

 

 

The potential for CO is mitigated by servicing the thing annually, in accordance with the manufacturers instructions.

 

The reason they produce CO is that servicing them is an utter PITA, so it never gets done. Very few people empty out the whole of the contents of their fridge to remove it from its hole and service it, preferring to 'do it another day'. And that day never arrives.

 

My view is that a gas fridge should be fitted at eye level facing along the length of the boat, so a hatch can be constructed to access the back of the fridge from the other side. This way servicing it becomes easy, and the requirement to fit gas pipe in a boat 'as high as reasonably practicable' is more easily met.

I have seen one similar to that but with an external door behind it opening outside.

[Theo]

Snip

 

(Although strictly speaking, CO is unburned gas. Just not the gas one would expect to find when looking for say, a gas leak. CO burns just fine, just like butane and propane. In fact it was a major constituent of 'Town gas' before we found the north sea stuff.)

That's the problem. I no longer have the option of putting my head in the gas oven as a suicide method.

 

Curses

 

N

[nicknorman]

This fridge has a thermostat that shuts the gas on and off as required to maintain the temperature unlike the older ones where the flame was on constantly. So it is after it has shut off, and then needs to come on again, that the problem occurs. The burner has lit but it carries on sparking. It then gives up and flashes the on light until such time as I switch it off and on again, which is what I mean by "locked out". It is just a button press to switch it off and on again but that is no good if I'm not there and awake!

 

However you other point is EXCELLENT as I didn't check that the base of the flame was touching the burner so that is definitely something to do, thanks. Pretty sure there is only one electrode, I think it arcs onto the burner but I'll check.

 

Edit: if you listen carefully you can hear both the sound of the lit flame roaring a bit, and the clicking of the igniter, so I definitely know the flame is lit but it's not being detected properly.

 

Lots of gliding at the weekend with an inter-club league competition. I took a visitor up in my ASH25 2-seater glider for some rock polishing in the mountains (always gets the flatland visitors going!) but anyway it transpired in conversation that he was a travelling caravan service engineer, gas safe bod (including boats) and knew my fridge model intimately. Design problem with the electrode - calcification tend to build up. Design problem with the burner - chrome plated which tends to flake off, there is a replacement stainless steel burner, issues with the ground return path to the pcb.

 

He also knew a lot about gas regulators and the problems with gas condensate which apparently is worse these days because Calor clean out their cylinders less regularly.

 

My regulator is also playing up a bit and the dealer where I bought the caravan added an extension hose so that I could have a large external cylinder, trouble is the hose has a low point where it trails on the ground and that will trap condensate. My bod said this was not really allowed as there is a max length of hose you are allowed and cylinders should not be in service just standing on the ground. But fortunately it is in the Highlands of Scotland where regulations don't apply!

 

Anyway, what a joy to have a conversation with a "professional" who really knew his stuff, no bullshit. A rarity though IMO! Only trouble was I was also having to concentrate on avoiding large lump of granite and eagles trying to have a go at us so I probably missed half of what he was saying!

[MtB]

Veryyyyy interesting. I've never heard of 'gas condensate'. Did he say if this is a same 'honey-like' gloop that accumulates in gas service pipes over long periods? Or something else?

 

I'm a bit puzzled about calcification building up on the electrode. Where does the calcium come from?