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Electricity and baths

Posted by Tim O\'Brien 
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Electricity and baths
21 May, 2014 14:19
Fellow enthusiasts,
Excuse the off-topic nature of this. I feel boaters may have some expert knowledge of these things.
I have a house where an extension was once done leaving a bathroom above part of the kitchen. Also placing the fuse box (trip switches) under the exact spot where an upstairs bath has been placed.
Now I know from my friend the sergeant that in the event of a spouse passing away in shocking circumstances it is not necessary to look very far for the culprit. I therefore banned the use of the bath. (Before you reach for the proverbial nose plugs, other baths are available). But in my house I am hardly the boss and the ban is being openly flouted by Higher Authorities (everybody).
So I got in an electrician who looked, seemed to pale, and never came back.
So I got in a plumber who opined that a potential leak would trip the trip switch and all would be well. Then he never came back.
The trouble is that I remember from school it was possible to stick some live 220V wires into a bucket without them blowing the fuse. (the addition of some salt was a neat way to release some chlorine gas and get a day off school, we felt, but the mix normally just boiled). Anyhow the point is that no fuse blew, no trip switch tripped.
On another occasion I remember when the Good Ship was driven off without disconnecting the shore power and live wires ended up in the river without anything blowing. I did not interview surrounding fish.
This all arose because I recently purchased a 1000v inverter and was advised by a better brain than mine that if the batteries on the boat did not drain immediately, the wiring would go on fire. So my questions are twofold:
(1) Have I wasted the price of an inverter?
(2) Is my family in danger of severe and immediate electrocution if they use the upstairs bathroom. (this is at home btw, not on my boat. My boat is not THAT big).
Any help gratefully appreciated...
Regards Tim
Re: Electricity and baths
21 May, 2014 18:59
Assuming its a 1000 "watt" not "volt" inverter my answers are

1 . its only a waste of money if you dont intend to use it ! A 1000 w inverter can use up to 85-100 amps , this requires cable to the batteries able to deliver this current, the longer the cable the thicker it needs to be , you should use at least 25 sq mm and this should be fitted with a fuse close to the battery to protect it. Batteries running inverters for any length of time should ideally be "deep cycle" , these deliver the power hour after hour provided they are adequately sized tor the demand. There have been some good articles in previous editions of IWN on this subject.

2 As to whether your bathroom poses a risk of electrocution to your family , provided they dont bring in electrical appliances in to it , and the bath doesnt leak or overflow , id say the risk is low to zero.

Re: Electricity and baths
21 May, 2014 19:53
If the bath is plumbed in copper the pipes should be bonded together,if its plastic no need ,as for the bath been over the consumer unit i wouldnt worry about it .
Re: Electricity and baths
21 May, 2014 21:11
[quote Tim O\'Brien]
(1) Have I wasted the price of an inverter?
Any help gratefully appreciated...
Regards Tim[/quote]

Hi Tim,
would a generator not be an easier solution if you really need all that 220V power on your boat?

(A few hours of drawing those currents would mean you would have to run the engine to recharge the batteries - more efficient to use a genny?)

Just looked at the microwave cooker in my house, 750W.. So I suppose if you want all the comforts of home on your boat then you "need" multiple kW of power..

Good luck,

Yacht 150 Ah
Re: Electricity and baths
25 May, 2014 11:41
If fibreglass bath and plastic pipes, I would still be inclined to ground the metal fittings, esp if you use an instant shower (which MUST be earthed anyway). It is highly unlikely that you would get a continuous connection from bath to fusebox via a water leak. Pure water is quite a poor conductor, though pure water is rare.

As far as using the inverter is concerned, mount it as close to the batteries as possible, but as has been said, drawing 1kW via inverter, or any other means, will drain your batteries pretty quickly. If you want the inverter just for very occasional and intermittent use, then ok, but whatever type of battery you use, you only get back about half the power you put into it.

Has anyone used a microwave with a quasi-sinewave inverter ? I had a uWave b low up and take the inverter with it, and haven't dared try again.
Re: Electricity and baths
26 May, 2014 13:52
on Mithril our previous boat we used a 1500w not true sinewave inverter to run a 750w microwave. The micro rattled a bit but was still going ok when we sold the boat 2 years later. It was a lot handier than starting a genny.
By the way, check the data plate on the back of the micro and you'll probably find that a 750w micro draws about 1200w.
We had two 160Ah batteries for domestic use and the leads were less than 1metre long. As the micro was only used for short bursts of less than 5 minutes, say three times a day, the solar panels were well able to keep pace.
I will pass no comment on position of bathroom, meter board etc. as one would need to see it !!
Re: Electricity and baths
26 May, 2014 20:14
Re; Bath over fuse board.

I have personal experience that would suggest that this arrangement might be unwise.

One evening, while having a bath, the late, great, and still sorely missed springer spaniel, Toby, decided to join me in what he considered "water sports" . With a single leap and belly flop, he managed to displace his 25 kilos of body weight in water onto the floor. I'm not sure if it was this tsunami, or the second one, caused by my dumping both of our carcasses onto the floor, that destroyed the kitchen below. In my case, I was only wet, but Toby had sponged more than his body weight in water in his copious coat, which he very efficiently off- loaded once removed from the bath.

As an aside, a rare find - a loss adjustor with a sense of humour, suggested that as the action had been "deliberate" on Toby's part, and not "accidental" , my policy would not cover this event. I laughed very nervously :-)


Re: Electricity and baths
27 May, 2014 08:34
I think the moral of this story is dont take a bath with your dog Peter,and i dont see the apparent danger with bath over mcb board. robbio
Re: Electricity and baths
27 May, 2014 11:25
[quote robbio c]I think the moral of this story is dont take a bath with your dog Peter,and i dont see the apparent danger with bath over mcb board. robbio[/quote]

Fire?? No? Maybe not.

BTW, it was Toby who decided to share the bath with me :-) I wouldn't like it to get out that We encourage bath sharing.


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