Jump to content

Immersion heater switch tripping shore RCD


Featured Posts

I have a new boat (built 2014) and am in the early stages of learning. The top-right white switch in the below image is labled in the owner's manual as "Switched-spur unit for immersion heater". When I switch it on, it trips the RCD on the shore hook-up. The immersion heater is a Surejust calorifier. Can anyone advise what I should check in order to try to find the problem? Many thanks for any help.

post-25277-0-92515200-1472399233_thumb.jpg

Link to comment
Share on other sites

Very likely a defective immersion heater element. Although disappointing that it's only lasted a couple of years. Perhaps worth looking the the connections to the actual heater element, sometimes you can get damp/corrosion that causes a leakage to earth in that area. Otherwise, it probably needs a new element.

Link to comment
Share on other sites

Also check that it is really an RCD that's tripping. IT might be a MCB or RCBO and if so it could be that the immersion heater is drawing more current than the MCB/RCBO is set to.

 

RCBs trip on earth leakage from wither conductor.

 

MCBs trip on excess current

 

RCBOs trip on both.

Link to comment
Share on other sites

Was the immersion working ok till recently??

Assuming not, it is possible if it has not been used for a long time that some damp has got into the 'sand' that surrounds the heating wire in the metal sheath. I had this on a new cooker and the element needed drying out, after which it was fine.

The easiest way to dry it out is to connect it to a non RCD protected supply and get it hot for a an hour or so. However there is no RCD protection whilst doinh this, and if the element has a more serious fault them this should not be done.

If you are not sure, get an electrician to check it for leakage and breakdown voltage.

Link to comment
Share on other sites

What size (wattage) is it ?

 

If it is a 'small' marine one they are fairly expensive - I have just replaced our 1200w one at a price of £60 and it had to be imported from Italy.

 

If it is a 'domestic' one then they are only £13.98 from Tool station.

It may also be related to a faulty thermostat, they are only £8.22 from tool station.

 

It is a simple job to replace so don't be afraid to try it yourself (for the sake of £20 or so) if nothing else appears to be the problem, replacement may be the answer.

Link to comment
Share on other sites

Many thanks for the very useful replies. The below image shows the RCD, the left-most with the yellow button, which is tripping. The boat has recently been lorried from Wigrams Turn to Saul Junction. At Wigrams the immersion and hot water was working fine. At Saul Junction it has not worked and the tripping RCD began. Any further thoughts?

post-25277-0-68107700-1472403722_thumb.jpg

Link to comment
Share on other sites

Try it on another RCD supply, it may be that the bollard you are using is over sensitive.

If not then check for any damp under the immersion cap and cable joints. If that all looks ok then you will need to get a sparky to measure the element leakage using a 'megga', or substitute a new element to confirm if the element has excessive leakage.

As always, as you are working withe mains voltages, if not sure get help.

Link to comment
Share on other sites

Looking at the pic I noticed a lot of green in it, I would associate this with damp, could this have any bearing on the OP's problem?

Phil

That's the bollard I believe. So no, not associated I wouldn't think.

Link to comment
Share on other sites

I used to be a Tattenhall marina same group as Saul and my Bollard kept tripping every time I plugged in many tests later I plugged in to the next door bollard all worked fine. Another guy tried the 1st bollard same result it tripped again no trouble on another bollard. So Tattenhall has a duff bollard they agreed but did not fix it in the year before I left. So it could be the bollard at Saul definitely try another preferably one that someone else has used so you know it works. Another other possibility is your batteries are low and the charger is pulling a lot of amps so switching the immersion on overloads the supply.

Link to comment
Share on other sites

The small (1Kw) immersion heaters can be unreliable and the law of 'clumps of damp earth' applies in you case, is that the immersion heater is at the bottom end of your calorifier. Tis for mine... But then I don't have shore power (yet)

Link to comment
Share on other sites

Immersion heaters in general have a habit of weeping around the tube where the thermostat fits. I have replaced many that displayed this problem. Only needs a bit of moisture to knock an RCD out.

Link to comment
Share on other sites

The new Surejust (well all the ones I've fitted this year) elements are Titanium so let's hope they are less susceptible to corrosion and micro leakage that causes this kind of issue. The Surecal is a standard size but do not be tempted to buy a domestic one, they are all too high wattage unless you have a really good shore supply and the overheat trip is set low enough to be activated by the heating coil from the engine.

Link to comment
Share on other sites

I see the shore supply has 4MCBs connected to the RCD. If each of these 4 have a small amount of leakage,perhaps supplies to other boats, the sum total, when the immersion is switched on can take it past the 30mA trip current. Try disconnecting all the other connected loads at the shore supply and see if it still trips. You may not be popular with other users though! Loads need to be unplugged, simply switching off the mcb may not change anything.

Bill

Link to comment
Share on other sites

Well, he's plugged into the bollard but it doesn't trip until he switches on the immersion - which is on the boat.

But the RCD maybe over sensitive and trip too easily. So it could be a bollard problem, or as in the post above a combination of boats, or a problem on the boat.

Until the op has done some of the checks/investigations suggested above it will not be clear if the problem is on or off the boat.

Link to comment
Share on other sites

Thanks for the further replies. I have tried:

1. Unplugging all other boats on the say bollard - still trips

2. Plugging into the next bollard along - still trips

 

I guess this means the problem is on the boat. I shall begin to investigate further.

Link to comment
Share on other sites

Some progress in pictures. The immersion is a Surecal titanium immersion heater (model: TI2-11/RTS Plus A). I removed the black plastic cover of the thermostat and found that it sits within a pool of rusty water. I'm sure this water has arisen from leakage from the calorifier/thermostat, rather than elsewhere. Any advice on how to proceed?

post-25277-0-23452100-1472492263_thumb.jpg

post-25277-0-72135900-1472492633_thumb.jpg

Link to comment
Share on other sites

There are a lot of water droplets on the white/blue plastic bitty. Looks like condensation to me. Perhaps the problem is cold water in the tank vs warm muggy weather providing plenty of water vapour to condense?

 

As a starting point maybe try drying the area off with kitchen roll etc, and then blowing warm air over it for a while eg from a hair dryer.

Edited by nicknorman
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.