240v Electrical Problem

[WillCful]

Hi all, 

 

I have an lpg instant water heater supplied with power from the batteries via an inverter. The 3 core cable comes from the inverter to a 'domestic' fuse box and mcb then to a fused switch (13amp fuse I think) then to the appliance. 

 

When on the appliance works flawlessly but the challenge is getting it to come on! When switched off via the external switch it's reluctant to switch back on, I can usually get it to come on with some fiddling, throwing the switch a bunch of times, opening and shutting the water valves (!?) ... Sounds like a dodgy switch or electrical connection right?? Having traced the cabling looking for answers, I have found that the cable coming from the external switch is joined to the blue 3 core with spade connectors that all seem to be fine and (were, until I removed it to inspect) wrapped in heat shrink. There's then a short length of blue 3 core (maybe 30cm) that is connected to the long run of blue 3 core that goes back to the fuse box, again using crimped spade connectors wrapped in heat shrink, all seems good, no loose connections. Then at the back of the boat as the cable passes into the engine room where the fuse box is, the cable is spliced into another 3 core cable that disappears behind the rear bulkhead lining, I'm pretty sure it terminates back there somewhere and isn't connected to anything, maybe someone trying to future proof the addition of more 3 pin sockets? Again, the splices seem to be fine, no loose connections.

 

My next step is to try replacing the external switch to see if this is faulty (picking a new one up in the morning). Otherwise I can't really think what would cause this intermittent functioning? Like I say once it's on, it stays on. Is it just too much sketchy wiring that should be replaced with a new run of 'unbroken' 3 core, has anyone else experienced this kind of problem when running 240v appliances via an inverter? Finally, if there was a short somewhere I'd expect the mcb to trip? Which it doesn't.

 

Help much appreciated, thank you! 

[Slim]

24 minutes ago, WillCful said:

Hi all, 

 

I have an lpg instant water heater supplied with power from the batteries via an inverter. The 3 core cable comes from the inverter to a 'domestic' fuse box and mcb then to a fused switch (13amp fuse I think) then to the appliance. 

 

When on the appliance works flawlessly but the challenge is getting it to come on! When switched off via the external switch it's reluctant to switch back on, I can usually get it to come on with some fiddling, throwing the switch a bunch of times, opening and shutting the water valves (!?) ... Sounds like a dodgy switch or electrical connection right?? Having traced the cabling looking for answers, I have found that the cable coming from the external switch is joined to the blue 3 core with spade connectors that all seem to be fine and (were, until I removed it to inspect) wrapped in heat shrink. There's then a short length of blue 3 core (maybe 30cm) that is connected to the long run of blue 3 core that goes back to the fuse box, again using crimped spade connectors wrapped in heat shrink, all seems good, no loose connections. Then at the back of the boat as the cable passes into the engine room where the fuse box is, the cable is spliced into another 3 core cable that disappears behind the rear bulkhead lining, I'm pretty sure it terminates back there somewhere and isn't connected to anything, maybe someone trying to future proof the addition of more 3 pin sockets? Again, the splices seem to be fine, no loose connections.

 

My next step is to try replacing the external switch to see if this is faulty (picking a new one up in the morning). Otherwise I can't really think what would cause this intermittent functioning? Like I say once it's on, it stays on. Is it just too much sketchy wiring that should be replaced with a new run of 'unbroken' 3 core, has anyone else experienced this kind of problem when running 240v appliances via an inverter? Finally, if there was a short somewhere I'd expect the mcb to trip? Which it doesn't.

 

Help much appreciated, thank you! 

I suspect that the demand made by the water heater for power is insufficient  to  "wake up " the inverter  . Try putting an additional, constant, demand into the circuit ie incandescent bulb.

[BEngo]

How long has it been doing this, and have you changed anything electrical before it started playing up? 

 

Do you have a 240 v AC multimeter?

 

If so, start at the inverter and measure the voltage between blue and brown (or red and black if the wiring is ancient)  wires at each set of spade connectors with the heater set to ON, but not working. You should have about 200~ 250 volts at each.

What make and model of inverter is it? Some inverters go to sleep with no load and the water heater may not be big enough load  to wake it up.  Try plugging in a moderate 240v load, like a lamp.

 

N

[WillCful]

Thanks for the replies. Not sure of the inverter model, (I'll check tomorrow) by the look of it it's a fairly old and inefficient one... I'll try the trick of 'waking' it up, other items such as mobile phone etc. work just fine when plugged in to the 240v circuit. I'll try a phone and the water heater at the same time.

 

The water heater claims to pull 20w but I think this is just when it's igniting (it's a piezoelectric spark) and the rest of the time it's just whatever power is required to run the little digital display.

[WillCful]

1 hour ago, BEngo said:

How long has it been doing this, and have you changed anything electrical before it started playing up? 

 

Do you have a 240 v AC multimeter?

 

If so, start at the inverter and measure the voltage between blue and brown (or red and black if the wiring is ancient)  wires at each set of spade connectors with the heater set to ON, but not working. You should have about 200~ 250 volts at each.

What make and model of inverter is it? Some inverters go to sleep with no load and the water heater may not be big enough load  to wake it up.  Try plugging in a moderate 240v load, like a lamp.

 

N

Sorry, to answer your question I haven't changed anything electrical, except for some stuff on the 12v circuit. It's been working like this since I've had the boat. I've been trying to turn it off at night recently to save power from the inverter as our batteries are beginning to succumb to the ravages of time.

Edited January 26, 2022 by WillCful

[Tracy D'arth]

3 minutes ago, WillCful said:

Sorry, to answer your question I haven't changed anything electrical, except for some stuff on the 12v circuit. It's been working like this since I've had the boat. I've been trying to turn it off at night recently to save power from the inverter as our batteries are beginning to succumb to the ravages of time.

The failing battery voltage may well be the reason. Try it with a good battery.

[WillCful]

45 minutes ago, Tracy D'arth said:

The failing battery voltage may well be the reason. Try it with a good battery.

Ah, fair enough. The problem persists even when the engine is running though, and battery voltage is reading 13+ volts?