Remote shore power monitoring - circuit breaker issue

[Bugsworth Tippler]

On 22/10/2018 at 17:39, Loddon said:

That looks like a 32amp RCBO fed with what looks like 2.5sqmm cable  so should be changed anyway for a 16amp version.

 

I don't understand why this should be so. If the RCCB can handle 32amp surely there wouldn't be a problem with a lower current? It seems to be difficult to get a 16A version with the correct dimensions. My understanding of how these devices work is very limited so I would be happy to have the above statement explained.

[GUMPY]

Its an rcbo which protects against over current as well as earth leakage. 2.5mm cable is rated at 27amps so in the event of an over current fault the cable could overheat/catch fire and the breaker wouldn't trip.

There are plenty of DP RCBO available

here one for starters

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F153172277385

I have assumed there are no other breakers on that cable

Edited October 27, 2018 by Loddon

[Bugsworth Tippler]

Thanks for the explanation Loddon. Item now ordered and the old one will be replaced asap. Maybe I was searching for the wrong thing but all I seemed to come up with were slim-line units or second-hand offerings.

In answer to your question, there are no other breakers on the circuit. There is an in-line galvanic isolator between the land column supply (which doesn't trip) and an earthed 20amp battery charger plugged into the circuit covered by the breaker (which does trip) - nothing else.

[blackrose]

I have an oil filled electric radiator that's fitted with a thermostat. If I leave the boat in winter I leave it set to 5C so I don't need to remotely monitor the temperature inside the boat. Of course that's not going to work if your shore power keeps tripping. I think that's what you need to sort out first, not the techy remote monitoring gizmo.

Edited October 28, 2018 by blackrose

[Chewbacka]

6 minutes ago, blackrose said:

I have an oil filled electric radiator that's fitted with a thermostat. If I leave the boat in winter I leave it set to 5C so I don't need to remotely monitor the temperature inside the boat. Of course that's not going to work if your shore power keeps tripping. I think that's what you need to sort out first, not the techy remote monitoring gizmo.

But the techy gizmo could tell him when the power has fail?ed 

[Bugsworth Tippler]

Techy gizmo is on the back-burner with my first priority to stop the RCBO tripping. I also usually have an electric heater attached to a thermostat over winter and the Webasto comes on automatically at 4 deg C. This, being 12v powered, will deplete my batteries which is why I need to ensure that the battery charger is functioning properly at all times. Belt and braces but both rely on a continuous 240v power supply. Techy gizmo would keep me informed of problems.

[rusty69]

I never really understand why a boat is heated in the winter when vacant. I assume if the central heating systems and engine is appropriately protected with antifreeze type stuff that the only potential problem area is the fresh water system.

 

Is it because it is hassle to drain down the calorfier that people heat their boats? Tis a genuine question.

 

 

[GUMPY]

Just a thought.

A diesel heater of the eber/mikuni/webasto type run using a frost stat is a surefire way of breaking the heater!

Reason is it switches on when temp drops temp rises and it goes off shortly after this causes it to coke up rapidly.

If you are running it on a frost stat you need to somehow set a minimum run time of a couple of hours so it gets decently hot and burns off all the carbon.

 

[Bugsworth Tippler]

27 minutes ago, rusty69 said:

I never really understand why a boat is heated in the winter when vacant. I assume if the central heating systems and engine is appropriately protected with antifreeze type stuff that the only potential problem area is the fresh water system.

 

Is it because it is hassle to drain down the calorfier that people heat their boats? Tis a genuine question.

 

 

Though I drained the calorifier on my previous boat during winter I don't on the current one; mainly because I spend a few nights on it during the winter period as it has central heating the previous one lacked. Draining the calorifier would not be that easy either. So I keep the temperature from dropping to zero and use chemical dehumidifiers as well, to absorb moisture and prevent condensation from damaging wood surrounding the windows.

[GUMPY]

32 minutes ago, rusty69 said:

 

Is it because it is hassle to drain down the calorfier that people heat their boats? Tis a genuine question

in some ways yes as we are on the boat 3days a week so we CBA to drain it down every week. 

[rusty69]

2 minutes ago, Bugsworth Tippler said:

Though I drained the calorifier on my previous boat during winter I don't on the current one; mainly because I spend a few nights on it during the winter period as it has central heating the previous one lacked. Draining the calorifier would not be that easy either. So I keep the temperature from dropping to zero and use chemical dehumidifiers as well, to absorb moisture and prevent condensation from damaging wood surrounding the windows.

Thanks. Yes, i suppose if you continue to use your boat occasionally throughout the winter it would make sense. 

2 minutes ago, Loddon said:

in some ways yes as we are on the boat 3days a week so we CBA to drain it down every week. 

If ever i get to that stage, i reckon I'll put an electric blanket round it

[Bugsworth Tippler]

17 minutes ago, Loddon said:

Just a thought.

A diesel heater of the eber/mikuni/webasto type run using a frost stat is a surefire way of breaking the heater!

Reason is it switches on when temp drops temp rises and it goes off shortly after this causes it to coke up rapidly.

If you are running it on a frost stat you need to somehow set a minimum run time of a couple of hours so it gets decently hot and burns off all the carbon.

 

The frost stat is a dangly thing in the cupboard where the central heating top-up tank lives. I believe it was fitted at the same time as the Webasto heater by Kings Lock Chandlery. I take your point about burning off carbon but am not aware that a minimum run time can be user determined - I'll have to look into that. Also, I've no idea how long the Webasto fires up for as I'm never on the boat when it does so in these circumstances. The idea of the electrical heater (set at 5 deg C) was to reduce the use of the Webasto and the depletion of the batteries whose battery charger keeps getting switched off by the tripping RCD/RCBO or whatever (the one that will be replaced in a couple of days).

 

Edited to identify dangly thing :

http://www.webastomarine.co.uk/shop/vclose1.asp?prd=123548&cat=4737002020

Edited October 28, 2018 by Bugsworth Tippler

[cuthound]

3 hours ago, rusty69 said:

I never really understand why a boat is heated in the winter when vacant. I assume if the central heating systems and engine is appropriately protected with antifreeze type stuff that the only potential problem area is the fresh water system.

 

Is it because it is hassle to drain down the calorfier that people heat their boats? Tis a genuine question.

 

 

 

I have electric heaters set to come on at 5°C and a dehumidifier on my boat over winter.

 

It saves draining the calorifier down and enables me to de-winterise the boat and take it for a winter cruise in about 5 minutes.

[Col_T]

7 minutes ago, cuthound said:

 

I have electric heaters set to come on at 5°C and a dehumidifier on my boat over winter.

 

It saves draining the calorifier down and enables me to de-winterise the boat and take it for a winter cruise in about 5 minutes.

Which leads me to a question about the best way to leave a boat over winter. With electric heaters and a de-humidifier, presumably you leave windows closed - but what about the rest of the ventilation. Is that all blocked up, to prevent the warmth from the heaters escaping - would that increase condensation? If the normal ventilation is not blocked up, then surely the warmth from the heaters will get ventilated out of the boat?

 

All education gratefully received.

[Bugsworth Tippler]

1 hour ago, Col_T said:

Which leads me to a question about the best way to leave a boat over winter. With electric heaters and a de-humidifier, presumably you leave windows closed - but what about the rest of the ventilation. Is that all blocked up, to prevent the warmth from the heaters escaping - would that increase condensation? If the normal ventilation is not blocked up, then surely the warmth from the heaters will get ventilated out of the boat?

 

All education gratefully received.

I have no answer to the best way to leave a boat over winter as that would depend on the boat, the availability of an electrical supply and the owner's proximity and boat usage in the winter and me knowing what I was talking about. I had a boat with no 240v system and no power supply and with only a solid fuel stove for heating. Over the years I replaced all of the copper piping with plastic (the first time because ice had punctured a lengthy run of pipe in several places) and drained the calorifier (sometimes in the dark when the forecast threatened an early onslaught of winter and I daren't leave it to freeze overnight). Having drained off the water system this boat was left unheated (abandoned) for the winter. It did not have a Paloma-type gas water heater which I believe are very prone to fracture due to freezing. The current boat has an electrical heater to ward off sub-zero temperature and dehumidifying 'things'. I keep the windows closed but don't block up ventilators. Heat may well escape in that way but some movement of air through the boat can only be good IMO.

 

Having returned from a short break I was able today to return to the boat to investigate in the light of the useful advice given previously. Needless to say the RCBO had tripped. But what else did I find?

 

UNNNBELEEEVABBBBLE! The RCBO which has been tripping is supplied through a 13amp plug which can plug into a 13amp socket (inside the boat) linked the socket (on the outside of the boat) which is fed from shore power. The 13amp plug can be plugged into the inverter when the boat is away from its mooring  so the boat's 240v system is wired to the shore OR the inverter but can't be connected to both at the same time. I don't know why, but I thought I'd look at this plug and discovered that the positive wire was not firmly into the brass hole on the end of the 'prong', held tightly in place with the brass screw; NO, it was jammed underneath the brass bit with the hole and screw, held in place presumably by the plug casing itself. I've no idea who did this (previous owner or contractor) and it may have been a genuine error (if done by a long-sighted individual who has lost his glasses and torch on a moonless night) but I strongly suspect (or hope) that, having fixed it, my RCBO may stop tripping. This remains to be seen, but I will be changing the RCBO for the one with correct power when it arrives.

[Chewbacka]

It’s not an uncommon method to use a plug on a flying lead to connect the boat system to either shore power or inverter.  Cheaper and easier if you are not sure of what you are doing than a selector switch.

The disadvantage is that the power is limited to 13A as that is the fuse in the plug rather than the full 16A that is available at many shore supply points.

 

The rcbo is being used only as an rcd as it will never trip due to excessive current as the 13A fuse will blow first.

 

So all in all a bit of a bodge, but doesn’t sound unsafe APART from the unacceptable method of connecting the ‘live’ wire which could either come free or if it stays in place could also dangerously overheat underheavy load.

 

 

 

[Bugsworth Tippler]

"The rcbo is being used only as an rcd as it will never trip due to excessive current as the 13A fuse will blow first."  That's what I was thinking. As it happens the shore power supply trips when you draw more than 6 amps so even that fuse is over the top.

 

And I don't need to change the RCBO to the 16amp one I just bought?

Edited October 28, 2018 by Bugsworth Tippler

[cuthound]

3 hours ago, Col_T said:

Which leads me to a question about the best way to leave a boat over winter. With electric heaters and a de-humidifier, presumably you leave windows closed - but what about the rest of the ventilation. Is that all blocked up, to prevent the warmth from the heaters escaping - would that increase condensation? If the normal ventilation is not blocked up, then surely the warmth from the heaters will get ventilated out of the boat?

 

All education gratefully received.

 

Yes, I block the mushroom vents with bath sponges folded in half, cover the low level louvre vents with cardboard held Inn place with blutac and close all windows.

 

 Since doing this I have had zero issues with sticking doors, damp or condensation.

[Chewbacka]

2 hours ago, Bugsworth Tippler said:

"The rcbo is being used only as an rcd as it will never trip due to excessive current as the 13A fuse will blow first."  That's what I was thinking. As it happens the shore power supply trips when you draw more than 6 amps so even that fuse is over the top.

 

And I don't need to change the RCBO to the 16amp one I just bought?

I would change the rcbo as the 16A is more suitable, but it’s not a priority, but is a quick job assuming it’s easily swapped - din rail fitting is standard assuming that’s what it’s mounted on.

[MtB]

6 hours ago, Bugsworth Tippler said:

"The rcbo is being used only as an rcd as it will never trip due to excessive current as the 13A fuse will blow first."

 

Will it? Really?

 

A 13a fuse may well take a second or ten to blow depending on the actual current flowing. Fuse speed ratings can get as complicated as you want them to get. Have a goggle!

[Chewbacka]

A 16amp supply passing through a 13A fuse followed be a 32A rcbo will Under most conditions cause the fuse to fail before the 32A breaker or possibly the 16A shore supply will trip.  But I can’t think of an overload situation where the 32A rcbo will fail first.

[cuthound]

MCBs typically trip instananeously on 3 to 5 times rated current, depending on type. BS1362 fuses instantaneously blow on 2 times rated current.

[MtB]

3 minutes ago, cuthound said:

MCBs typically trip instananeously on 3 to 5 times rated current, depending on type. BS1362 fuses instantaneously blow on 2 times rated current.

 

I haven't read the BSs but is that really true?

 

I have the impression in my mind that fuses take a finite amount of time to blow, which is dependent on the degree of overload. The smaller the overload, the longer a fuse will carry on conducting. A 13a fuse for example, is most unlikely to fail instantaneously, if ever, when passing 16a. This was my point really. Is this wrong? 

 

It is a common misconception that a 13a fuse limits the current to 13a, IIRC. 

[cuthound]

Yes. I used to design or approve others designs for power installations for critical power applications.

 

Both fuses and breakers take a variable time to blow dependent upon the level of overload. The manufacturers provide charts detailing this. The curves for breakers are less linear and indeed large breakers for commercial applications have user adjustable settings to allow the designer to influence the shape of the curve to get better discrimination with other breakers upstream.

 

Fuses to the various BS Standards give much closer and reliable protection than equivalent breakers, but need periodic replacement to prevent nuicance blowing due to ageing and (obviously) once blown take longer to restore power compared to just resetting a breaker.

[Bugsworth Tippler]

Hello again. Thanks to everyone who contributed to this thread which has helped me improve my boat a little and hopefully given me a little more piece of mind when the really bad weather comes.

 

Here's the latest update. Today I visited the boat again and found that the old RCBO had not tripped which suggested that the plug rewire may have solved the problem. Anyway I replaced the old 30 amp RCBO with a new 16 amp RCBO.

 

I also plugged in an Envirotxt gizmo fitted with a 1pmobile sim card. After a few texts to it from my mobile phone to set it up it seemed to work perfectly. I returned home and was amusing myself finding out the temperature on the boat when I got a text message to say the Envirotxt gizmo was no longer powered. Feeling a little deflated that I still seemed to have a problem, but happy to know about it, I resolved to go and investigate if the weather forecast was for low temperatures. 15 minutes later I got a text from the gizmo to say that power was restored. So my RCBO can't have tripped and the RCBO on the shore pillar can't have tripped (unless someone switched it back on - unlikely) and it must have been some extremely unfortunate coincidence of the power supply being cut off somewhere else. Hurrah! I think the gizmo is going to be very helpful and, though expensive, I will save a lot of petrol money on unnecessary trips to the boat to check that my thermostatically controlled electric frost prevention heater is still operable.

 

Wireless texting alarms and remote Webasto switching on can wait for now.