Diversity Calc Commercial Dishwasher 6.5kW single element

[Ray Pooley]

It is a 6.5kW thermostatically controlled water heater if you ignore the rest of the gubbins.

So that would be a Purpose #6 for diversity ie: None allowed. = 28A.

But you could treat if like a cooker too. Purpose #3 ie: 10A + 30% FL current over the 10A. = 15.4A

What do you think?

Thanks

 

[telectrix]

not like a cooker, as the D/W only has 1 element. you could allow some diversity due to cycling on/off though.

 

[Ray Pooley]

not like a cooker, as the D/W only has 1 element. you could allow some diversity due to cycling on/off though.

You would think so as it is only on for about 3 minutes per wash cycle. The question is : How much? There is no specific purpose in the OSG for dishwashers.

But if you think about a 6.5 kW cooker with all hotplates on and the oven on
full blast Christmas morning when you first switch it on.

What's the difference?

That's why I am thinking cooker equivalent.

 

[telectrix]

no, a cooker has several elements. all will not be drawing current at the same time, and all may not even be switched on. there is no guidance for your D/W situation. but you can make some allowance using experience and common sense. if you think of a shower. that is thermostatically controlled, but no diversity is allowed.

 

[Ray Pooley]

no, a cooker has several elements. all will not be drawing current at the same time, and all may not even be switched on. there is no guidance for your D/W situation. but you can make some allowance using experience and common sense. if you think of a shower. that is thermostatically controlled, but no diversity is allowed.

Which would be Purpose #6. 28A. Can you suggest a diversity caculation for this dishwasher based on your experience and common sense?

 

[DefyG]

An electrical shower might have 2 elements for low and high settings but diversity is not normally applied to that so cant see how you can to a single element dishwasher can either!

 

[Ray Pooley]

An electrical shower might have 2 elements for low and high settings but diversity is not normally applied to that so cant see how you can to a single element dishwasher can either!

That's reasonable. it's just a big kettle really. But when you're only heating up 20L of water to 95C over a three minute period? Like I said, if it was all the hotplates on a hob and the oven of a 6.5kW oven at first you can be drawing 28A until the tstats start kicking in.
Right? And there's a diversity for that. Purpose #3.

 

[telectrix]

a 6.5kW load should be on it's own circuit, so no problems with overloading a ring/radial socket circuit. it then comes down to whatever other loads are on the installation.
if generally a reasonable level, say 30A, no worries. but say you have a quiescent draw of 80A on a 100A incoming main fuse, that's when you need to do some calculations and consider ways of inhibiting 1 or more loads when D/W is used. ( changeover switching).

 

[Ray Pooley]

a 6.5kW load should be on it's own circuit, so no problems with overloading a ring/radial socket circuit. it then comes down to whatever other loads are on the installation.
if generally a reasonable level, say 30A, no worries. but say you have a quiescent draw of 80A on a 100A incoming main fuse, that's when you need to do some calculations and consider ways of inhibiting 1 or more loads when D/W is used. ( changeover switching).

You would think so. The DW I am writing about is actually plugged into a 13A socket on a radial with a B32 MCB and various other devices attached. Nobody micromanaged these devices with regards to when they are used. I was checking the pump on the DW and noticed the 6.5kW on the data plate. My thoughts immediately went to the 13A plug and socket that the machine is attached to. This is why I am harvesting opinions. There really is no sign of damage and there is no history of overload or other related issues on that radial or anywhere else. So you have to wonder don't you? The machine was installed by the shop who supplied it. It looks like he just came along with the machine, shoehorned a 13A plug onto the end of the cable and plugged it in. Whether he knew what diversity was when he did so is another matter. Maybe that's just luck rather than by design. But I am wondering whether to mention it or not to the owner or let sleeping dogs lie. It's not what I am there to do and it would require a considerable effort to give it its own circuit as the full load would require with no diversity. I am leaning towards mentioning it. But if you were to consider it along the same lines as a cooker then to draw attention to it might be a little alarmist and unneccessay. In theory a B32 should take at least 96A to trip. Right? Can't really see that happening.

 

[JBW175]

What does it say in the Manufacturers Instructions? Should be able to find a copy online.

 

[Ray Pooley]

What does it say in the Manufacturers Instructions? Should be able to find a copy online.

It recommends its own circuit just as you would for a cooker. "Do not use adaptors, multiple socket-outlets or cables of inadequate type and section or with extension connections not compliant with plant engineering standards in force". So it shouldn't be the way it is.

 

[DefyG]

None of that makes it 'right' or 'correct' as far as the regs goes.
If you are looking for confirmation that applying diversity will allow you a smaller circuit cable/OCD (15.4A) then I'm sorry it doesn't get my vote.
The analogy of a cooker doesn't carry any weight either, as a cooker is several elements as previously mentioned so diversity can be applied per OSG.
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So it shouldn't be the way it is.

Correct! ...... think you are finally getting the message!

 

[JBW175]

It recommends its own circuit just as you would for a cooker. "Do not use adaptors, multiple socket-outlets or cables of inadequate type and section or with extension connections not compliant with plant engineering standards in force". So it shouldn't be the way it is.

In that that case I’d mention it to the owner and advise accordingly just to put my conscience at ease.

Is there any chance you can clamp it and see what it’s drawing at full load?

 

[DefyG]

just as you would for a cooker

Really? I find it hard to believe the instructions would say that!

 

[Ray Pooley]

Really? I find it hard to believe the instructions would say that!

Not verbatum. So. C1, C2 or C3 then. If you had to.