Saunier Duval boiler nearly killed my plumber

[flameport]

If the metal pump housing was live, so was any other metalwork connected to it. This would include the boiler casing, and therefore the cold water supply pipe and gas supply pipe.

As all of those items should be connected to the main earth terminal for the property, the fact that the pump casing could be live and yet still running indicates a serious and very dangerous problem with the electrical system in the property.

You need to get your electrical system checked NOW before it kills someone.

 

[mickyg]

not sure why you've had to wait so long for a part thats widely available, fitted to a number of group service appliances and stocked in most parts centres. No one gets electricuted by a boiler if they've carried out the necessary checks and the electrics are in order. Faulty engineer or badly faulty electrics.
If the pump body is live so will the whole appliance be, the entire heating system, gas and water pipework.

 

[Agile]

I generally avoid repairing S-D boilers where possible.

What I am surprised by is the OP assuming the part is faulty and the engineer assuming that he has done nothing wrong.

It needs a different engineer to examine the boiler to see what was wrong.

Now I dont know this boiler in detail but most similar models have a metal bodied pump screwed into a plastic veloute.

The pump is connected to the boiler wiring by a three pin connector which has L, N and E conductors.

The only way the body can be live is if the pin connections are wrong or if the connections between the cable and pump are wrong.

We need someone competent to check this AND advise us whats wrong.

99% of the time its likely to be an engineer mistake!

Tony

 

[bell824]

I generally avoid repairing S-D boilers where possible.

What I am surprised by is the OP assuming the part is faulty and the engineer assuming that he has done nothing wrong.

It needs a different engineer to examine the boiler to see what was wrong.

Now I dont know this boiler in detail but most similar models have a metal bodied pump screwed into a plastic veloute.

The pump is connected to the boiler wiring by a three pin connector which has L, N and E conductors.

The only way the body can be live is if the pin connections are wrong or if the connections between the cable and pump are wrong.

We need someone competent to check this AND advise us whats wrong.

99% of the time its likely to be an engineer mistake!

Tony

tony you are correct in what you say here with the body being plastic but lets not forget water is the perfect conductor for electricity,
as the system would have been filled at time of testing then this still should have earthed.

AS OTHER POSTS HAVE POINTED OUT FAULTY PART OR NOT GET HOUSE ELECTRICS CHECKED!!!!!!!

 

[Agile]

Oddly water is not a very perfect conductor for electricity.

I thought otherwise until I read a report on some tests which concluded that it was not necessary to earth rads in bathrooms.

Even if the pump body is live its unlikely that the 30 mA required to trip the RCD will flow.

Tony

 

[Onetap]

Oddly water is not a very perfect conductor for electricity.

I thought otherwise until I read a report on some tests which concluded that it was not necessary to earth rads in bathrooms.

Even if the pump body is live its unlikely that the 30 mA required to trip the RCD will flow.

Tony

Pure or de-ionized water won't conduct, it has a huge resistance. The conductivity depends on the amount of dissolved ions, the TDS. The water in a heating system would be full of of inhibitor, lime-scale and corrosion products and should be a fairly good conductor.

The possible cause is that the boiler's earth connection isn't connected, maybe why the repairs were required in the first place.

 

[Agile]

The conductance through a 15 mm tube of even dirty CH water is actually very low indeed.

Totally contrary to what I had expected.

Look up the report and your views will also be changed.

Tony

 

[ChrisOxford]

The conductance through a 15 mm tube of even dirty CH water is actually very low indeed.

Tap water (round these parts) IS certainly conductive enough to trip a 30mA RCD if it gets spilled on, say, an IEC connector on the back of a kettle, although I appreciate the terminals are only about an inch apart in that instance. This implies an impedance of under 8KΩ, I suppose.

A little rainwater in an external light fitting will do the same thing.

Similarly, if you're daft enough to operate a lightswitch with wet hands, you can certainly get much more than a mere tingle.

Will do some experiments myself, Tony

 

[ChrisOxford]

I thought otherwise until I read a report on some tests which concluded that it was not necessary to earth rads in bathrooms.

Maybe not, but equipotential bonding is still mandatory, of course

Would be very interested to read the report... could you post a link, please?

 

[Agile]

You can search for it on this forum.

As I understand it a rad in a bathroom fed by plastic pipe does not have to be bonded.

Yo9u are also missing the fact that a metre of tube is 1000 mm which has 1000 times higher resistance than a mm of water that you may touch.

Tony

 

[ChrisOxford]

You can search for it on this forum

How?

EDIT: Found it here: //www.diynot.com/forums/viewtopic.php?p=177038#177038

As I understand it a rad in a bathroom fed by plastic pipe does not have to be bonded.

Ah, that makes sense now, thanks. Opinions about bonding vary widely and the regs and recommendations seem to change all the time. I saw a Crittall window bonded once!

a metre of tube... has 1000 times higher resistance than a mm of water that you may touch.

That makes perfect sense too. So 1/1000th of the current.

P.S. Impressed you took your multimeter on your hols to the Seychelles

 

[Dvickersaff]

S-D engineer came and checked everything. Boiler had been turned off for 48 hours and not used. Boiler checked out ok and appeared to fire up. The pump housing was not live and no fault was showing on the PCB. All very strange and no real answers as to why the pump housing gave my engineer a shock or why it was showing the PCB to have stopped working as a result.

The assumption is that there my have been some moisture somewhere from when the old pump was removed that hadn't been dried off although my engineer swears he dried all the parts.

No real answers except that it is now working!

I've had so many issues with this boiler in the last 5 years and it is only 6years old so dont rate it at all.

 

[expertgasman]

A very intersting post. I don't do a lot of boiler work, and m not familiar with SD. If we assume the plumber DID get a belt, thenthee is clearly an issue, and rather than just slag off the OP and the plumber it is worth a bit more thinking. My initial thought was that it couldn't posibly happen, for the reasons john has covered. But something clearly did! Is the SD full of plastic hoses and connectors? If so, the pump may be isolated from the chassis earth, and would rely on the earth connection in the prewired lead/plug. If there was a fault on the pump, or the lead and plug AND the house had old style fuses in the consumer unit, then I could just about envisage an incident.

EDIT: Sorry, I posted this BEFORE I relaised there was a page 2 full of comments. I was reacting to page one.

 

[ChrisOxford]

The assumption is that there my have been some moisture somewhere from when the old pump was removed that hadn't been dried off...

Certainly when I've replaced water-carrying parts on my boiler, there's always been some water sloshed around during the process, some of which has sometimes ended up on the PCB in spite of taking precautions.

A very cautious approach with plenty of rags, a hairdryer and patience to allow things to dry off naturally has always worked for me.

Good luck with the boiler

 

[Rinso47]

We had a saunier duval boiler fitted in january 2008, we have had 6 years of hell, once the boiler is in the company do not give a damn, it has cost us thousands to try to keep it going, I am now giving up and after christmas will get a worcester, we have had new radiators, as instructed by the company, we have had more heat exchangers than you could shake a stick at, we have had a new appliance that blows through the system, winter is here and once again it is playing up, we were without heating and hot water for two of the coldest weeks last winter, if any one is thinking of having one of these, DON'T DO IT, pick an english make