Yes, I think JohnW2's idea of a 20amp might be more appropriate
Commercial dishwasher on a 32amp ring main
- Thread starter bwallum
- Start date
Yes, I think JohnW2's idea of a 20amp might be more appropriate
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My view as well, usually running the cable is the biggest part of a radial job in a decorative environment so might as well leave a bit of spare capacity for the future.
Re the 40 minutes to heat up versus two kettles. The heater element in the boiler of the DW is 2.8kW and there is a lot of water to heat to fill up the bottom sump. The water is heated in the boiler at start up then dumped to the sump. It does this half a dozen times to fill the tray. The fuse blows when the water pump kicks in (0.735 kW rated) to mix the water after every boiler dump. As noted above by JohnW2 there is probably a higher spike on start up. Once up to temperature a 2.2kW heater in the sump keeps the water hot. Heat up is just once a day, thereafter the load is 2.2kW plus 0.735kW (plus spikes as the water pump kicks in for every wash cycle).
I haven't worked with commercial dishwashers but have had the odd peek at glass washers. One of the things I did notice is when a glass washer isn't used for a while the pump for the wash cycle can seize up. A stalled motor may cause overcurrent. Just wondering if something similar is occurring, or the pump is jammed with something? Or a blocked filter?
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Big brakes on.....I followed up the suggestion that 15 amps or so would not necessarily blow a 13amp fuse for a short time (thanks JohnW2). I'm pleased that I did. I have a single phase version. The 3 phase version has a much larger 6kW boiler heater. The literature is quite clear. I questioned the manufacturer again about the fuse blowing and they said (news) that some earlier models were fitted with a 6kW single phase element and that was not in the current range and not in the documentation they sent to me. Definitely not final ring circuit 2.5mmT&E stuff. If it is a 6kw heater then that would blow a 13amp fuse quickly and yet not trip the 32amp ring protection. The dishwasher works fine but now disabled until a new radial service is in place with a 32amp rcbo protected 4mm T&E dedicated supply, might even go to 6mm.
You're welcome. I'm actually far from convinced that 15A would blow a 13A fuse ever (i.e. no matter how long the 15A flowed). If it were a 13A Type B MCB, rather than a fuse, it would carry about 14.7A (+13%) indefinitely and about 18.9A (+45%) for about an hour. I think BS1362 fuses (as in plugs and FCUs) are 'worse' ('more tolerant') than that, so a 13A one may well carry 15A 'indefinitely' and 20A+ for an hour or so (and perhaps even higher currents for shorter periods) - I need to look up the operating characteristics of those fuses!
As you say, if that's a possibility you need a 32A dedicated circuit in 4mm² (or maybe even 6mm²) cable. If you haven't got one, is there any possibility that you could beg, borrow or steal a clamp meter to determine how much current this DW is actually drawing?
Kind Regards, John
Just wondering, do you have the circuit diagram for the unit? In my experience, it would be slightly strange to have a single 6kw heater in a unit that is designed for 3 phase. It is much more likely that it has 3 separate heaters that can be configured for single phase, high load or 3 phase, lower load. One unit I worked on came configured for 32a single phase, which is what we had when we got it, but a refurb later, it was reconfigure for a 3phase supply at about 12a per phase.
Unfortunately, it seems that the OP probably does not have documentation relevant to that question ...
Kind Regards, John
How come you're not aware of fuse characteristics, time-current curves etc?
Whatever his answer to that, I can also join the club (I don't necessarily keep such information in my head!) ...How come you're not aware of fuse characteristics, time-current curves etc?
Kind Regards, John
What I meant was that the whole idea that a 13A fuse might not blow as soon as you put more than 13A through it seemed a novel one to him.
... just as it 'seems to be a novel idea' to very many people. I'm not really sure why you were asking the OP why he was not one one them (particularly given that there is no real answer to a question like that!)!
Kind Regards, John
is it because the OP was writing as if he was intending to install a new circuit in a public building?
Very probably, but a statement about that might have been more appropriate than 'beating about the bush' with a question to which there couldn't really be a useful answer ("How come you don't know X?")!
Kind Regards, John
I was just gobsmacked that an electrician had no idea about fusing and non-fusing currents, even if he couldn't remember what the factors are for BS 1362 fuses.
So is the suggestion that someone who is not an electrician, and doesn't know what he's doing, is installing circuits in a public building? Which might also be a place of work?
So is the suggestion that someone who is not an electrician, and doesn't know what he's doing, is installing circuits in a public building? Which might also be a place of work?
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