Electrical advice please.

[tosher]

Hi all. I want to leave 2 x 120 watt tubular heaters (green house type) on my boat over winter but to avoid any possibility of galvanic corrosion I don't want to connect the boat to the marina shore power in the normal way. So I am thinking of plugging a lead into the shore power bollard and taking it direct into the boat, fitting two 13amp sockets on the end of it and plugging the heaters into these sockets.  This will keep the boat electrics completely isolated from the marina system.  This sounds ok but are there any down sides to doing this??? The boat will not be occupied over winter.    Any advice much appreciated.     Many thanks.

[Tony Brooks]

1. Carefully check your insurance. One insurer was reported here to have said doing that would invalidate the insurance unless the heaters are rated for marine use.

 

2. Others will disagree but in my view the danger is if the mains lead can chaff through onto metal (like a windrow frame if you put it through a hopper). That would make the whole hull live and a great potential for corrosion and electrocution.  This may well invalidate your insurance if you needed to claim. However as long as can be as sure as possible this will not happen or that an unexpected flooding will not reach the plugs then it woudl be as safe as using an extension lead at home.

[pete.i]

It's what did I did for a couple of winters, including that really bad one we had a couple of years ago. I don't see any problems and I certainly didn't have any problems doing it that way but, no doubt, someone will come up with reasons as to why it is a bad idea.

[alan_fincher]

9 minutes ago, Tony Brooks said:

2. Others will disagree but in my view the danger is if the mains lead can chaff through onto metal (like a windrow frame if you put it through a hopper). That would make the whole hull live and a great potential for corrosion and electrocution.

 

Whilst I agree in principle, surely if there is a functioning earth leakage breaker on the shore power bollard, it would trip if the live wire chafed through and connected to the boat's shell?

I have always assumed as much, as I have a power lead passing in through a pigeon box, because my 230v inlet is inside the engine room, rather than on the outside of a cabin.  It it were possible for a cable to chafe and not trip te supply at the bollard, that would clearly be a "bad thing".

EDIT:

 

I agree that an insurer could wriggle out if the heaters in use were not marked as suitable for marine use.

Edited October 3, 2019 by alan_fincher

[Tony Brooks]

18 minutes ago, alan_fincher said:

 

Whilst I agree in principle, surely if there is a functioning earth leakage breaker on the shore power bollard, it would trip if the live wire chafed through and connected to the boat's shell?

I have always assumed as much, as I have a power lead passing in through a pigeon box, because my 230v inlet is inside the engine room, rather than on the outside of a cabin.  It it were possible for a cable to chafe and not trip te supply at the bollard, that would clearly be a "bad thing".

EDIT:

 

I agree that an insurer could wriggle out if the heaters in use were not marked as suitable for marine use.

 

That depends upon how restive the path through the water is. I know 60mA is not a lot but water may not be as conductive as many people think. I would hope the RCD would trip but I don't feel it is certain enough to rely upon - see some news todyt about a chap electrocuted by a meta;l flood light stand that presumably has a short to the metal - or the horses at Newbury a few years ago.

[jonathanA]

Obviously you need to make sure the metal of the heaters don’t come into contact with the hull or anything electrically connected to the hull. Those heaters usually come with plastic mounting brackets and I’d fix the heaters to a suitable piece of wood.

 

 

[alan_fincher]

10 hours ago, jonathanA said:

Obviously you need to make sure the metal of the heaters don’t come into contact with the hull or anything electrically connected to the hull. Those heaters usually come with plastic mounting brackets and I’d fix the heaters to a suitable piece of wood.

 

Why?

 

I would expect them to be double insulated, so no electrical connection of the outers to the supply.

 

I'd be more concerned about possible proximity to anything combustible than to the metal structure of the boat.  OK they are not supposed to get very hot, but I wouldn't want any possibility of them resting against anything flammable, or o anything fabric being able to fall on them.

 

That said the biggest problem with anything like this is that they are usually built to keep price as low as possible, rather than to a high standard that puts cost secondary.  I'm not sure you'll find anything certified as suitable for continuous use on a boat, but your insurer might have wriggle room if you buy cheap Chinese tat, and it subsequently overheats.

[Chewbacka]

14 minutes ago, alan_fincher said:

Why?

 

I would expect them to be double insulated, so no electrical connection of the outers to the supply.

 

 

The dimplex tubular heater instructions state that it must be earthed, so I would expect the metal tube to be connected to the supply earth.  This does not surprise me as they are often used in greenhouses etc where excess splashing will happen and if moisture were to get in, then water would provide a current path from the element to the case which if not earthed would result in a shock when touched.

[Alan de Enfield]

I have 2 similar to these (one running down each side of the engine room) and use them as 'freezing preventatives'.

They are 5 foot and 150 watts each.

 

They are on timers with one alternatively on, then a few hours (say) 09:00-15:00 hours both off, alternate heaters on / off for a few hours and then both on around 2:00am - 6am

 

It costs around £1.00 per day to run both of them on marina electric at 15p per unit.

 

https://www.tlc-direct.co.uk/Products/DXECOT6.html?source=adwords&ad_position=&ad_id=315107931576&placement=&kw=&network=u&matchtype=&ad_type=&product_id=DXECOT6&product_partition_id=350328635884&version=finalurl_v3&gclid=CjwKCAjw29vsBRAuEiwA9s-0B13GqJmV_P7HHDbbl64AvTelPujMvjzKQiubfbBa-JjHHUplG43YfxoCjMQQAvD_BwE

Edited October 4, 2019 by Alan de Enfield

[Chewbacka]

2 hours ago, Alan de Enfield said:

I have 2 similar to these (one running down each side of the engine room) and use them as 'freezing preventatives'.

They are 5 foot and 150 watts each.

 

They are on timers with one alternatively on, then a few hours (say) 09:00-15:00 hours both off, alternate heaters on / off for a few hours and then both on around 2:00am - 6am

 

It costs around £1.00 per day to run both of them on marina electric at 15p per unit.

 

https://www.tlc-direct.co.uk/Products/DXECOT6.html?source=adwords&ad_position=&ad_id=315107931576&placement=&kw=&network=u&matchtype=&ad_type=&product_id=DXECOT6&product_partition_id=350328635884&version=finalurl_v3&gclid=CjwKCAjw29vsBRAuEiwA9s-0B13GqJmV_P7HHDbbl64AvTelPujMvjzKQiubfbBa-JjHHUplG43YfxoCjMQQAvD_BwE

Cost a lot less with a thermostat.

As an aside I bought a little temperature data logger, set it to record every ten mins.  Left it on the floor next to my the toilet for Jan & Feb on the G&S canal.  Only went below freezing on just one day and then only by a degree or two.  I was surprised.

[Alan de Enfield]

5 minutes ago, Chewbacka said:

Cost a lot less with a thermostat.

Before the greenhouse heaters we tried with thermostats.

 

A dismal failure and they were on continuously.

It seemed as irrespective of what 'frost setting' you applied the operating temperature was 5*C.

We did have a prolonged 'cold spell' of several weeks and ran up a bill of £100's.

 

The current system works for us, keeps the damp down and keeps the engine room above freezing so no need to drain down all the plumbing,

[jonathanA]

3 hours ago, alan_fincher said:

Why?

 

I would expect them to be double insulated, so no electrical connection of the outers to the supply.

 

I'd be more concerned about possible proximity to anything combustible than to the metal structure of the boat.  OK they are not supposed to get very hot, but I wouldn't want any possibility of them resting against anything flammable, or o anything fabric being able to fall on them.

 

That said the biggest problem with anything like this is that they are usually built to keep price as low as possible, rather than to a high standard that puts cost secondary.  I'm not sure you'll find anything certified as suitable for continuous use on a boat, but your insurer might have wriggle room if you buy cheap Chinese tat, and it subsequently overheats.

All the ones I’ve seen from reputable sources required earthing. 

 

Fairly unlikely that the painted cases would make a path to the hull but it could happen as could the chafing of the supply cable....

 

obviously the op had his reasons but I would have thought the investment in a decent GI would have been worthwhile and save any problem

[alan_fincher]

56 minutes ago, jonathanA said:

All the ones I’ve seen from reputable sources required earthing. 

 

Fairly unlikely that the painted cases would make a path to the hull but it could happen as could the chafing of the supply cable....

 

obviously the op had his reasons but I would have thought the investment in a decent GI would have been worthwhile and save any problem

OK, I've seen ones with no earth connection at the plug.

Even with a GI, and going through the boats own 230V set up, I still think that Tony has a point about a potential insurance wriggle out if they can be demonstrated as not intended for continuous unattended use on a boat.

[jonathanA]

They’d be double insulated so no problem then ..

 

whilst  I know Tony makes this point every year about heaters what about all the people using domestic fridges washing machines and such like that are permanently installed on boats  ? 

Edited October 4, 2019 by jonathanA

[jradley]

4 hours ago, Alan de Enfield said:

I have 2 similar to these ....

.......150 watts each.

 

They are on timers with one alternatively on, then a few hours (say) 09:00-15:00 hours both off, alternate heaters on / off for a few hours and then both on around 2:00am - 6am

 

It costs around £1.00 per day to run both of them on marina electric at 15p per unit.

 

 

Somethings not right with the maths here.....

 

If you ran them both flat out all day,  300W = 0.3Kw * 24h = 7.2Kwh per day * 15p = £1.08 - you are being robbed somehow given you run them a lot less

[Tony Brooks]

54 minutes ago, jonathanA said:

They’d be double insulated so no problem then ..

 

whilst  I know Tony makes this point every year about heaters what about all the people using domestic fridges washing machines and such like that are permanently installed on boats  ? 

 

But apart heaters no other domestic appliance is normally running while you are away - possibly for some weeks. I only keep making the point to ensure the OP's check their insurer will not wriggle out of a claim.

[Alan de Enfield]

2 hours ago, jradley said:

Somethings not right with the maths here.....

 

If you ran them both flat out all day,  300W = 0.3Kw * 24h = 7.2Kwh per day * 15p = £1.08 - you are being robbed somehow given you run them a lot less

Thanks - now I'll have to go into the engine hole and check their ratings - I was guessing at 150w.

 

 

 

 

Edit to add :

 

Well they are both the same length but I can only see the rating on one of them.

 

360 watts

(assume both are the same )

 

 

Just to bring it back to the discussions - they have a label on.

In BIG RED LETTERS

 

"This Unit Must Be Earthed"

Edited October 4, 2019 by Alan de Enfield

[WotEver]

5 hours ago, jonathanA said:

They’d be double insulated so no problem then ..

I’d think that most unlikely. 

[jonathanA]

2 hours ago, WotEver said:

I’d think that most unlikely. 

Yep i agree - I’ve never seen a tubular heater that didn’t have an earth connection but that’s not to say there aren’t some (apparently)

[Momac]

On 03/10/2019 at 12:50, tosher said:

Hi all. I want to leave 2 x 120 watt tubular heaters (green house type) on my boat over winter but to avoid any possibility of galvanic corrosion I don't want to connect the boat to the marina shore power in the normal way. So I am thinking of plugging a lead into the shore power bollard and taking it direct into the boat, fitting two 13amp sockets on the end of it and plugging the heaters into these sockets.  This will keep the boat electrics completely isolated from the marina system.  This sounds ok but are there any down sides to doing this??? The boat will not be occupied over winter.    Any advice much appreciated.     Many thanks.

Does your boat not have a galvanic isolator fitted?

[tosher]

Thanks chaps for all your informative comments, much appreciated.        When my boat was lifted just over two years ago I was surprised and disappointed by the amount of galvanic activity on the hull, I replaced the anodes and re blacked it myself doing a thorough job with three coats of Rylards Rytex.  I mentioned this to the staff  when I returned to my marina and they carried out a check of the shore side wiring and said everything was ok.   When my boat was lifted again last month I found the hull was showing the same signs of galvanic activity as before.  I do have a galvanic isolator fitted as do the other boats on adjacent pontoons. I have previously left the boat plugged in to the marina supply over winter so this winter I want to try something different hence my OP.   The heaters I want to use are earthed and I sent details and a photo of them to my insurance company and they said it's fine to leave them switched on with the boat unattended over winter as long as they are firmly secured (as suggested in post 6).  Thanks again for your advice.

[mrsmelly]

16 minutes ago, tosher said:

Thanks chaps for all your informative comments, much appreciated.        When my boat was lifted just over two years ago I was surprised and disappointed by the amount of galvanic activity on the hull, I replaced the anodes and re blacked it myself doing a thorough job with three coats of Rylards Rytex.  I mentioned this to the staff  when I returned to my marina and they carried out a check of the shore side wiring and said everything was ok.   When my boat was lifted again last month I found the hull was showing the same signs of galvanic activity as before.  I do have a galvanic isolator fitted as do the other boats on adjacent pontoons. I have previously left the boat plugged in to the marina supply over winter so this winter I want to try something different hence my OP.   The heaters I want to use are earthed and I sent details and a photo of them to my insurance company and they said it's fine to leave them switched on with the boat unattended over winter as long as they are firmly secured (as suggested in post 6).  Thanks again for your advice.

Sounds to me like a change of mooring wouldnt go amiss?

[Chewbacka]

16 hours ago, mrsmelly said:

Sounds to me like a change of mooring wouldnt go amiss?

If your problem is caused by an adjacent boat moving to a different pontoon where no one has reported a problem maybe all it takes to fix it.  Of course if you do move and you continue having problems and your new neighbours start having problems as well, then it’s your boat that needs looking at.........