Welding with Surge Protector?

Submitted: Saturday, Sep 28, 2019 at 14:05
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I have an AOR Quantum that needs a chassis strengthening gusset welding in place. I have been informed that the PCB in the Truma HWS needs to be removed prior to any welding or it could be damaged. Why should I would like to know is would it be ok to leave it in situ if a Surge Protector/Anti-Zap device is used, also would the batteries need to be disconnected?
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Reply By: Allan B (Sunshine Coast) - Saturday, Sep 28, 2019 at 14:48

Saturday, Sep 28, 2019 at 14:48
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Shaker,

When welding on a vehicle (or anywhere else for that matter) if the welder's earth clamp is correctly connected to the job site on the same piece of metal that is being welded, then the welding current is confined to the zone between the welding site and the earth clamp. No other part of the vehicle would be aware of the process occurring. No harm should occur to anything.
Imagine if you will, the frequent welding on vehicles in a body shop without incident.

A "Surge Protector/Anti-Zap device" is neither needed nor any guarantee of protection anyway. In general, such devices are of no value to anyone but the salesman. Having such on battery jumper leads for example always brings a smile to an electrical engineer.
Disconnect the battery if it makes you feel better but the truth is that it actually acts as a shunt against stray voltage spikes if the welder was clumsy.

Tell you what, if you blow up the Truma's circuit board, I'll pay for a new one.



Cheers
Allan

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Follow Up By: Member - nickb "boab" - Saturday, Sep 28, 2019 at 15:12

Saturday, Sep 28, 2019 at 15:12
Agree , although as a welder for many years / years ago we were always told to disconnect the battery ?
but some time ago I was convinced by someone that it wasn't necessary , so no longer disconnect the battery .
Cheers Nick b
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Sep 28, 2019 at 16:08

Saturday, Sep 28, 2019 at 16:08
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Yes Nick, I have seen all sorts of problems caused by welders waving the electrode around everywhere, but confined to the weld site should create no problems.

About the battery..... there are a whole heap of circuits distributed in a vehicle, but they all connect to the battery eventually. Now that battery has a very low electrical impedance, less than one ohm. So if a rogue source of electrical energy greater than 12v somehow gets on to that wiring network it is going to be very smartly shunted to 'earth' (-ve) before it can do harm elsewhere. Disconnect the battery, at either positive or negative, and you have lost the benefit of that shunt. It is that simple.
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Follow Up By: Member - nickb "boab" - Saturday, Sep 28, 2019 at 18:13

Saturday, Sep 28, 2019 at 18:13
Thanks Allan : not understanding electronics of the new motor cars I do get a little nervous when welding on my PX Ranger and for only peace of mind I do disconnect the battery , but for nothing else & and we were always told to put the earth right next to where we will welding which makes sense .
cheers
Cheers Nick b
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Reply By: RMD - Saturday, Sep 28, 2019 at 15:14

Saturday, Sep 28, 2019 at 15:14
Shaker,
What are the qualifications of the person stating the board has to be removed, or, what is their understanding of electrical processes? I agree with Allan as to the welding and localized use of handpiece and earth clamp. Most likely that process will not even be connected to the Truma unit in any way. Simply unplugging it's 12v feed will cause a relaxation in your worry level.
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Reply By: Member - Rowdy6032 (WA) - Saturday, Sep 28, 2019 at 16:25

Saturday, Sep 28, 2019 at 16:25
I know zilch about welding but the AOR owners manual 2009 states "if any welding is required to be carried out on your Quantum, the batteries MUST be disconnected prior to this task."

Ignore it at your peril.

Regards
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Sep 28, 2019 at 16:29

Saturday, Sep 28, 2019 at 16:29
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AOR build campers and vans. What do they know about electrical engineering?
It is a common myth.
Ask them "why". It would be an interesting response.
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Allan

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Follow Up By: Member - Rowdy6032 (WA) - Saturday, Sep 28, 2019 at 16:35

Saturday, Sep 28, 2019 at 16:35
They advise this as the circuit board in the gas heater is about $800 to replace and this can also affect other electrical components, eg, batteries, inverter, charger.

I would sooner be safe than sorry for the time it takes to disconnect the battery. Know idea if they are right or wrong.

I would suggest Shaker follow it up with AOR if he has concerns. It is also discussed on the Members Forum.
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Sep 28, 2019 at 16:40

Saturday, Sep 28, 2019 at 16:40
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So if you disconnect the battery, begin welding and the heater circuit board karks it, will AOR replace it free-of-charge? Suggest you get that in writing.
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Allan

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Follow Up By: Shaker - Saturday, Sep 28, 2019 at 16:55

Saturday, Sep 28, 2019 at 16:55
AOR tell you to remove the Truma PCB!
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Follow Up By: GerryG - Saturday, Sep 28, 2019 at 19:43

Saturday, Sep 28, 2019 at 19:43
I too have given up disconnecting the vehicle battery and for that matter, the alternator as well when I have welding to do.
As suggested, I also place the earth clamp on the actual metal I'm about to weld, but I wonder sometimes what would happen if I arc off on this piece of metal and the other piece isn't touching the clamped piece? Would the circuit travel back to a suitable place where it will complete the circuit? (eg, the alternator?)
So, I have added a 12" lead with its own clamp, to my welder lead, so now I have two clamps which I place on each side of the weld. Paranoid? Maybe. But, touch wood, I've never had problems.
I must admit, I've never considered the battery acting as a shunt.
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Sep 28, 2019 at 22:42

Saturday, Sep 28, 2019 at 22:42
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Yes Gerry, there is always a possibility of the weld rod contacting a body part which is not in solid contact with the welder earth clamp. Weld current could then seek to return to the clamp via whatever path is available which can include negative wiring connections of a rating unable to carry the possible current with the result of fusing the wiring component. A long shot indeed, but possible.
Disconnection, or otherwise, of the battery would play no part in this scenario.

Your double-clamp scheme is a good idea.

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Allan

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Reply By: Member - Ross N (NSW) - Saturday, Sep 28, 2019 at 16:26

Saturday, Sep 28, 2019 at 16:26
Hi Shaker
As an owner of a similar camper may I ask why the chassis needs a gusset?
Is it precautionary or as a result of damage?
Ross Nielsen
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Follow Up By: Shaker - Saturday, Sep 28, 2019 at 16:57

Saturday, Sep 28, 2019 at 16:57
I would prefer to discuss it privately, you can call me.
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Reply By: Member - shane r1 - Saturday, Sep 28, 2019 at 20:18

Saturday, Sep 28, 2019 at 20:18
I totally agree with Allan. We did exhaust work for years. Don’t actually recall why I made the decision to not disconnect or attach a device of any sort, but attached the earth clamp to the exhaust and welded on hundreds of vehicles over the years, with no problems.
The battery acting as a shunt, absorbing any voltage spike makes sense too. My guess is all the other electrical devices on a vehicle are potentially still able to receive a voltage spike even when the battery is disconnected, so leaving the battery connected is the safest way. The battery will handle quite a large short voltage kick! And buffer the rest of the system.
There’s a lot of myths out there! And paranoia is rife.

Safe welding.
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Follow Up By: Member - Neil T6 - Monday, Sep 30, 2019 at 18:00

Monday, Sep 30, 2019 at 18:00
I'll go along with that. Using a Mig to weld exhausts in place we never disconnected any thing. Ground properly connected to the exhaust system and weld away.
From memory there was some theories around the time of changing from generators to alternators that diodes could be blown.
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Reply By: RMD - Saturday, Sep 28, 2019 at 22:48

Saturday, Sep 28, 2019 at 22:48
I wonder if AOR has ACTUALLY gone and welded on their vehicles while a Truma unit is installed to see if the Truma suffers any trauma. ie, a test to destruction, or a Shane has mentioned, paranoia and myths are being perpetuated.
I recently asked a caravan mob about their claims for battery charging and storage. It mentioned not storing batteries on concrete. Absolute rubbish but in their manual. Another one is when charging wet cells with screw tops, the tops have to be unscrewed while charging is being done. Does that mean the same battery has it's tops out while under the bonnet and the alternator is delivering 5 times more charge rate to that battery than the piddley charger was able to do? furphy?
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Sep 29, 2019 at 08:22

Sunday, Sep 29, 2019 at 08:22
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RMD, maybe AOR had a Truma failure in a general period that welding had also been done and promptly blamed the welding. Pretty common behaviour when seeking a scapegoat. If a Truma can fail due to welding on the vehicle then the Truma has pretty poor electronics.

"Not storing batteries on concrete"? Is that rubbish still being perpetrated?

The 'cap removal whilst charging' thing has its roots way back when it was common practice to bench-charge batteries with a pretty constant current until the electrolyte boiled and then continue "giving it a good boil" for some further time. The battery tops were awash from acid spray. But it gave them a "good healthy charge". Really did happen.

Working in the electrical industry for 60 years you get to see it all. And to those who doubt my acumen........ you do learn a thing or two.
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Allan

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Follow Up By: Jarse - Sunday, Sep 29, 2019 at 08:31

Sunday, Sep 29, 2019 at 08:31
If it *is* an issue, wouldn't just pulling the 12v fuse and pulling the 240v plug (if fitted) be sufficient to isolate the heater?
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Follow Up By: Member - shane r1 - Sunday, Sep 29, 2019 at 08:57

Sunday, Sep 29, 2019 at 08:57
Hey, Allan and RMD,
The battery thing is one of the other myths I was thinking of.
Cold , decreases a batteries performance, but doesn’t damage it. Same battery that wouldn’t start the car on a frosty morning probably would when the day warms up.
Heat is part of what kills batteries. Over the years , have seen batteries moved from hot locations (under bonnet) to under tray in a Ute case , and then the battery was performing for years as it should. We had a ford tractor, the battery was on top of the engine under the bonnet, one year per battery, then we moved it out and got years out of them.
Even had one Harley owner claim , a piece of rubber under the side stand on his bike keep his battery from going flat.
But I guess this myth will be with us forever!
Cheers
Shane
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Sep 29, 2019 at 09:42

Sunday, Sep 29, 2019 at 09:42
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Hi Jarse,

Now, before someone asks, I have not sat down with a Truma heater and a welder and performed experiments!!! And I don't need to.

Pulling the Truma 12v fuse does not achieve "isolation". There is still wiring attached to the Truma input. Just don't stick your welding rod on it. In point of fact, this wiring is waving around in the breeze like an antenna and could conceivably pick up an electrical charge if sufficient of such was present, but rather unlikely.
If that wiring was still connected to the battery then the battery acts as a pretty good shunt against voltages over 12v. Typical power supply inputs to electronic devices include capacitors that also provide shunt paths for unwanted induced voltages to protect the electronic components further within the circuit.

Isolation alone does not always provide maximum protection against unwanted electrical intrusion. It is common to isolate then "earth" the circuit.

Cheers
Allan

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Follow Up By: Ron N - Sunday, Sep 29, 2019 at 16:09

Sunday, Sep 29, 2019 at 16:09
Re the "not storing batteries on concrete" - a very sensible move in the day when batteries had wooden separators and battery cases were made from hard rubber that was slightly porous.

Storing these batteries on concrete was a no-no, as the porosity of the hard rubber case led to slow discharge.

Fast forward to the late 1960's and early 1970's, and battery cases are now being made from polypropylene - as they still are today.
As a result, the belief that batteries self-discharge on concrete, is no longer a valid issue, as it was, when battery cases were made from hard rubber.

In fact, there is at least one good reason to store your batteries on concrete, particularly if you reside in a high temperature region.
Because heat is the killer of batteries, storing batteries on cool concrete will more than likely improve their lifespan - provided you keep them charged, of course.

If you live and work in a hot climate, your battery has only 2/3rds the lifespan of a battery being used in a cold climate - so anything you can do to reduce your battery temperature will have a life-lengthening effect on it.

Cheers, Ron.
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Sep 29, 2019 at 17:05

Sunday, Sep 29, 2019 at 17:05
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Ron,
The batteries of the 1950's indeed had cases composed of a rubber compound. it was somewhat fragile to impact but served well to contain the acid without reaction or degradation. They certainly were not "slightly porous" as you suggest. If so then the supporting steel trays in vehicles would soon corrode. Corrosion around a battery in a vehicle was more likely due to overcharging with accompanying acid boil-out.
If acid were to leak onto a concrete floor it would be obvious due to the chemical reaction and would etch the concrete.. It would not lead to cell discharge unless there were corresponding leakage in more than one cell to complete a current path.

How do I know all this? Well, in the 1950's I was the Range Electrician of Range 'E' at Woomera. I had two electrical assistants caring for about 350 lead acid batteries which were used in firing circuits, camera drive supplies etc. It was quite a business charging these batteries and carting them around to places of use and I got to learn quite a bit about those batteries. In the charging shed they were stored on the concrete floor then arrayed on timber tiers for convenience but in the places of use they invariably sat on the concrete floor. At no time did I experience discharge of unconnected batteries whilst sitting on concrete or any sign of case porosity. One or two cracks, yes.

However the origins of the myth may lie in even earlier lead-acid battery construction in which rather fragile rubber 'cell-jars' were contained within wooden crates. If these crates were subjected to moisture on their bottoms then unequal expansion would occur to distort and weaken the wooden crate. The concrete floors of the time were not particularly waterproof and easily contributed the offending moisture. Thus may lie the dictum of not placing these batteries on a concrete floor or even an earthen one.
Cheers
Allan

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Reply By: Allan B (Sunshine Coast) - Sunday, Sep 29, 2019 at 10:32

Sunday, Sep 29, 2019 at 10:32
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Not to negate anything I have said above, there is a circumstance with arc welders and sensitive electronic products.

As well as an arc welder producing intense heat it is normal for the arc to generate high frequency electromagnetic radiation. This is well considered in the health issues of professional welders. This radiation can also present as interference to sensitive electronic devices in the near-field. A well known example is heart pacemaker products. It is conceivable that electronic products installed near to the weld site could be influenced by this electromagnetic field.

The power supply circuit to the electronic product is normally well protected from such assault. Of more sensitivity would be any input signal circuits such as Hall-effect ammeters where it is more difficult to protect.

Of recent interest is the multitude of vehicle management systems and their associated input transducer circuits. Welding on a vehicle would present these devices with electromagnetic interference. The fact that we are not hearing accounts of incidents relating to such failure perhaps indicates that the likelihood of damage is low to zero.

Accordingly, the probability of products like the Truma being sensitive to damage due to welding is even lower than the vehicle management modules and their input transducers. So disconnect it during welding if it makes you feel better..... but I am damned if I can understand how it would help.

Cheers
Allan

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Follow Up By: RMD - Sunday, Sep 29, 2019 at 15:12

Sunday, Sep 29, 2019 at 15:12
Allan,
The way I see it is, if the battery is disconnected, the battery is then removed from being able to quench anything and any induced voltages high enough to affect CMOS/MOSFET devices is more likely to and able to easily present itself to the sensitive device without being nullified in any way.
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Follow Up By: Allan B (Sunshine Coast) - Sunday, Sep 29, 2019 at 15:28

Sunday, Sep 29, 2019 at 15:28
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RMD,
Yes, I agree absolutely. It is obvious to anyone with electrical training and experience.
How these myths get started is beyond me but they do and are readily accepted.
Cheers
Allan

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