Electric toilet - cable size

[Bat & Frog]

Hi, I'm looking at running cables for a sanimarine or similiar toilet, which the spec says draws 20A. Given that this will be 11m (22m for calc) from the dc supply I'm coming up with a cable size of 10mm(squared) . While the toilet draws this current, its only for 6 seconds so little chance of the cable heating. Is 10mm really necessary ?

Thanks

[ChrisPy]

Hi, I'm looking at running cables for a sanimarine or similiar toilet, which the spec says draws 20A. Given that this will be 11m (22m for calc) from the dc supply I'm coming up with a cable size of 10mm(squared) . While the toilet draws this current, its only for 6 seconds so little chance of the cable heating. Is 10mm really necessary ?

Thanks

probably yes, if you are concerned about volts drop along the cable, which at 22m return path may be significant.

in narrowboats where the cable runs tend to be long, the critical factor when determining cable sizes is often volts drop, not the ultimate current capacity.

have you calculated the volts drop?

Edited August 15, 2009 by ChrisPy

[dor]

I would say the 10mm is necessary if that is what the volt drop calculation comes up with. The cable heating up is not the issue, it is the volt drop which will affect the performance of the pump/macerator.

[nb Innisfree]

Hi, I'm looking at running cables for a sanimarine or similiar toilet, which the spec says draws 20A. Given that this will be 11m (22m for calc) from the dc supply I'm coming up with a cable size of 10mm(squared) . While the toilet draws this current, its only for 6 seconds so little chance of the cable heating. Is 10mm really necessary ?

Thanks

 

I installed 40 mm cable to our macerator which is 4m away and then carried on further in 6mm for fridge and pumps, bit OTT but thats what I had at the time, start up surge of macerator is much higher than 20 A. If you are installing cables why not go OTT? nothing to lose except a few more squids

Edited August 15, 2009 by nb Innisfree

[Phil Ambrose]

I installed 40 mm cable to our macerator which is 4m away and then carried on further in 6mm for fridge and pumps, bit OTT but thats what I had at the time, start up surge of macerator is much higher than 20 A. If you are installing cables why not go OTT? nothing to lose except a few more squids

 

Agreed, bigger the better to combat voltage drop, my leccy toilet improved dramaticaly when I upped the cable size.

 

Phil

[Yoda]

Hi, I'm looking at running cables for a sanimarine or similiar toilet, which the spec says draws 20A. Given that this will be 11m (22m for calc) from the dc supply I'm coming up with a cable size of 10mm(squared) . While the toilet draws this current, its only for 6 seconds so little chance of the cable heating. Is 10mm really necessary ?

Thanks

 

In reality you need to have a 24 volt supply for any high powered device, as it is more efficient. I suggest that you run a bus bar along the boat and then take power off using cable.

[nb Innisfree]

I installed 40 mm cable to our macerator which is 4m away and then carried on further in 6mm for fridge and pumps, bit OTT but thats what I had at the time, start up surge of macerator is much higher than 20 A. If you are installing cables why not go OTT? nothing to lose except a few more squids

 

Just to add I agree with Yoda and in fact that is what we have + Leesan macerators are more powerful in 24v than 12v and even more in 230v

[Arnot]

Hi, I'm looking at running cables for a sanimarine or similiar toilet, which the spec says draws 20A. Given that this will be 11m (22m for calc) from the dc supply I'm coming up with a cable size of 10mm(squared) . While the toilet draws this current, its only for 6 seconds so little chance of the cable heating. Is 10mm really necessary ?

Thanks

There are two possible answers to this one...

 

The first is that the size of cable depends on the size of the t**ds!

 

The second and more sensible answer is that the cable is rated to allow the inrush current surge that motors demand to start cleanly. The 20A rating is a guide to the fuse size to prevent motor burnout if it stalls far any reason, the cable size rating is for the surge current. To be honest, if the stall current is above 20A, and the length of the runs is 22m overall, I would suggest larger than 10mm on a 12v system.

 

Regards

 

Arnot

[Justme]

Fit a bat local to the toilet & keep it charged using a thinner cable as it will only need a trickle?

 

Oh & I made the cable size 18mm2 using the amps x distance in M one way div 12 method from another thread in this forum.

[Arnot]

Fit a bat local to the toilet & keep it charged using a thinner cable as it will only need a trickle?

This is a very good way of doing it, it gets round the need for massive cables and the voltage drop issues very neatly.

 

It is a technique used to supply higher motor and other intermittent high loads at the front of longer boats, bow thrusters spring to mind here.

 

But- you will need to install some way of isolating the battery when it isn't in charge, otherwise the local battery could keep circuits live when the master switches were off. The way I do it is to use a volatge sensetive relay located near the local battery end, then if it boat is not "on charge" and the master switches are off, only the local battery and pump wiring are live.

 

Regards

 

Arnot

[Canal Shop Man]

Fit a bat local to the toilet & keep it charged using a thinner cable as it will only need a trickle?

 

Oh & I made the cable size 18mm2 using the amps x distance in M one way div 12 method from another thread in this forum.

Surely this is way over the top for what you need! This would add the cost of the battery, the cost of an isolator, the problems of venting if the battery is in the cabin, the cost of a battery box, etc, etc.

Why make life difficult? Using 10mm cable will be fine, thicker won't do any harm. Unless the boat has 24 volt system already, just use a 12 volt toilet

[Justme]

The 20mm2 cable it needs is going to cost about £100 for the 22m length.

 

Thats would cover a small bat & all bits needed to do the job.

[Bat & Frog]

Thanks all, maybe i'll have the toilet 240v ! Interestingly a friend wired his 12v sanimarin with 2.5mm artic (using 2 of 3 wires) and works fine, even after 2 1/2 years.

 

If I do have to put in such a big cable as suggested, I think there may have to be a few spurs, especially as it gets used so little.

 

Anyway, cheers

[smileypete]

Thanks all, maybe i'll have the toilet 240v ! Interestingly a friend wired his 12v sanimarin with 2.5mm artic (using 2 of 3 wires) and works fine, even after 2 1/2 years.

 

If I do have to put in such a big cable as suggested, I think there may have to be a few spurs, especially as it gets used so little.

 

If the wiring duct is fairly accessible then it's possible to double up later on.

 

Some motors are fussy about voltage, some not so much.

 

cheers,

Pete.