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.

 

[Wilko]

Hi - if I understand correctly an intermittent load of 28A has been connected to a 13A plug. What happens to the 13A fuse? It sounds potentially dangerous to me.

 

[Ray Pooley]

Hi - if I understand correctly an intermittent load of 28A has been connected to a 13A plug. What happens to the 13A fuse? It sounds potentially dangerous to me.

This is in fact the actual gist. It should blow at 1.66 times the rate which is about 21 amps. But it doesn't. Why doesn't it if it gets to 28A? I wouldn't mind sticking a clamp meter on it to see what the actual draw is just out of curiosity but I can't really. If you look at te theory it shouldn't work. But it does and without any noticable issues. For the last three years.

 

[DefyG]

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

I wouldn't on someone else's word.
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If you look at te theory it shouldn't work. But it does and without any noticable issues. For the last three years.

And we've all come across similar instances where showers have been connected to a 2.5 t&e straight off a 32A RFC.

It works but it doesn't make right or correct!

Not sure what the real issue is here, why were you looking at the DW in the first place, if 'Its been working ok for the last 3 years', why or just curious?

 

[westward10]

I find it highly unlikely this appliance for the last three years has been connected for 6.5kw through a 13A plug and never had an issue. From this link it indicates it can be connected for different power ratings however for 13A the flex will require changing.

Maidaid Amika 50XL-D Undercounter dishwasher - 18 plate -

Maidaid Amika 50XL-D Undercounter dishwasher - 18 plate . 20+ years experience. Free delivery, expert advice & service

www.chefsrange.co.uk

 

[snowhead]

As above, there's no way it's survived with 6.5kw on a 13amp plug.
It's most likely been converted from 6.5kw heater to 2.1kw heater by the supplier, either from new or as used.

 

[DefyG]

It's most likely been converted from 6.5kw heater to 2.1kw heater by the supplier, either from new or as used.

So not a fixed 6.5kW load as per original OP, but one that can be terminated probably for 1ph 2.1kW element, which would account for it being ok (Not tripping or any thermal damage) on a 13A plug/socket.
And at 6.5kW could be 3ph??

 

[Ray Pooley]

Built and delivered from warehouse as stock 25/09/2017. 4.0mm² 3 core black flex.
Three years old. New to the customer. That's the way it is. I don't have a picture of the plug ans socket. I'll take one tomorrow. The problem it has is a faulty main boiler thermostat. This is the first issue it has had since new.
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An interesting experiment by John Ward. The destruction of a power cable. The point to note in this video is that the plug is a 13A plug and fuse. These continue to serve current up to 23.4 VAC.
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And here's teh video.

View: https://www.youtube.com/watch?v=rfU5lzXAHAQ&t=61s&ab_channel=JohnWard

 

[DefyG]

Why would anyone put it on a 13A plug when the nameplate clearly states 30A?
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Not sure what your point is with the video ............ Its still doesn't qualify for diversity and is currently incorrectly terminated .... 'in my book'!

 

[snowhead]

I'm not sure why this thread has run to 23 posts.
As above a 13amp plug and socket is not suitable for a 6.5kw load, if that's what it really is.
Diversity doesn't come in to it.
It needs a suitable plug / socket or connection and a suitable supply to it, if the existing one is not.

 

[davesparks]

The data plate clearly states that it has a power consumption of 6.5kW and requires a 30A supply so that is what it should be connected to. If they want it on a plug then a 32A plug would be appropriate.

Diversity cannot be applied to the supply to the appliance if it is a single heating element as that element will only be either on or off, appliances with multiple heating elements controlled by different thermostats can have diversity applied as they will all be cycling on and off at different times.

Diversity can be applied when considering the supply to the DB that then feeds this machine (assuming it is fed from a DB which feeds multiple circuits) but this does not have any bearing on the supply to the machine itself.

As to how the plug has not burned out yet, it is probably probably luck or an incorrect fuse or a modified appliance......

 

[pc1966]

At 30A a genuine 13A fuse would below somewhere between 1s and 40s, so it seems very unlikely it really is that sort of a load.

 

[DPG]

You say it has 4mm flex fitted. Can you show a picture of the 13A plug to show how it has been fitted.

 

[Jim_e_Jib]

In the link that Westward provided in #19, it says:

Machine will be set for 30amp supply with relevent cable, if they are ordered for 2.6kw 13 amp supply, the cable will need to be changed by the installation engineer as a UK 3 pin plug will not fit onto the cable

Has it been supplied as the 2.6KW unit and the installation engineer just butchered a 13amp plug on the supplied cable rather than replacing it?

 

[Vortigern]

Hope it's got a PAT test cert.

 

[DPG]

In the link that Westward provided in #19, it says:

Machine will be set for 30amp supply with relevent cable, if they are ordered for 2.6kw 13 amp supply, the cable will need to be changed by the installation engineer as a UK 3 pin plug will not fit onto the cable

Has it been supplied as the 2.6KW unit and the installation engineer just butchered a 13amp plug on the supplied cable rather than replacing it?

Yes, It sounds like they're put a 13A plug on 4mm flex to me!

 

[Ray Pooley]

For the record. Plug and socket undamaged. No signs of overheating on plug or socket. Been lke this for 3 years. Machine was brought in to replace a 3.1kW machine. Installed by the vendor.

 

[DPG]

So, can you post a photo of how the plug is wired. And how the cord grip is fitted. Have you looked yet? I think we all know how it's going to look.

 

[telectrix]

It's easy to fit a plug on a 4mm flex. first curt back the sheath so the cord grip can clamp om the pretty coloured conductor basic insulation. then cut half the strands off the stripped ends. Don't forget to fit 1.5mm ferrules before inserting into the pins. Tighten with a calibrated torque screwdriver. And remember to fit the "plug top" before inserting into the socket outlet, wich, of course will be the 3rd double along a 4 socket unfused spur.

 

[Ray Pooley]

It's easy to fit a plug on a 4mm flex. first curt back the sheath so the cord grip can clamp om the pretty coloured conductor basic insulation. then cut half the strands off the stripped ends. Don't forget to fit 1.5mm ferrules before inserting into the pins. Tighten with a calibrated torque screwdriver. And remember to fit the "plug top" before inserting into the socket outlet, wich, of course will be the 3rd double along a 4 socket unfused spur.

Exactly right except the strands don't appear to have been trimmed. No ferrules in this case.

 

[DPG]

Exactly right except the strands don't appear to have been trimmed. No ferrules in this case.

So it's connected up in a non suitable way which should be sorted ideally.

 

[snowhead]

Did you check the current to see if it really is 6.5kw?

 

[Ray Pooley]

So it's connected up in a non suitable way which should be sorted ideally.

Not recommened that's true. But here's what I know. There are no signs of damage to either plug or socket after 3 years of service 7 days a week. About 3,300 wash cycles. The plug has a 13A fuse in it that is in tact and has never needed to replaced. That's not to say that the current doesn't rise above 13A. I posted a John ward video earlier that show John destroying a power cable. The socket, plug and fuse that John uses in his experiment are all 13A and don't appear to suffer even though the current gets as high as 23A over a period of about 30 minutes. Theoretically the fuse should have blown at 21A.

Did you check the current to see if it really is 6.5kw?

No. It's not what I am there to do. I don't think I need to tbh. It's going to me more than 13A. This is purely an observation. I will make a recommendation but I doubt it will be followed up. There are no signs of damage to either plug or socket after 3 years of service 7 days a week. About 3,300 wash cycles. The plug has a 13A fuse in it that is in tact and has never needed to replaced. That's not to say that the current doesn't rise above 13A. I posted a John ward video earlier that show John destroying a power cable. The socket, plug and fuse that John uses in his experiment are all 13A and don't appear to suffer even though the current gets as high as 23A over a period of about 30 minutes. Theoretically the fuse should have blown at 21A. Finally, the circuit is supported by a B32 so the only weak link, so to speak, is the actual plug and socket. From the owner's perpective there doesn't appear to be any real incentive to go to the expense of installing a dedicated circuit.

 

[DPG]

Not recommened that's true. But here's what I know. There are no signs of damage to either plug or socket after 3 years of service 7 days a week. About 3,300 wash cycles. The plug has a 13A fuse in it that is in tact and has never needed to replaced. That's not to say that the current doesn't rise above 13A. I posted a John ward video earlier that show John destroying a power cable. The socket, plug and fuse that John uses in his experiment are all 13A and don't appear to suffer even though the current gets as high as 23A over a period of about 30 minutes. Theoretically the fuse should have blown at 21A.

No. It's not what I am there to do. I don't think I need to tbh. It's going to me more than 13A. This is purely an observation. I will make a recommendation but I doubt it will be followed up. There are no signs of damage to either plug or socket after 3 years of service 7 days a week. About 3,300 wash cycles. The plug has a 13A fuse in it that is in tact and has never needed to replaced. That's not to say that the current doesn't rise above 13A. I posted a John ward video earlier that show John destroying a power cable. The socket, plug and fuse that John uses in his experiment are all 13A and don't appear to suffer even though the current gets as high as 23A over a period of about 30 minutes. Theoretically the fuse should have blown at 21A. Finally, the circuit is supported by a B32 so the only weak link, so to speak, is the actual plug and socket. From the owner's perpective there doesn't appear to be any real incentive to go to the expense of installing a dedicated circuit.

I would strongly recommend that they look at it. Will only get worse over time not better.

And get a suitable method of connection that is compatible with 4mm cable.

 

[westward10]

Not recommened that's true. But here's what I know. There are no signs of damage to either plug or socket after 3 years of service 7 days a week. About 3,300 wash cycles. The plug has a 13A fuse in it that is in tact and has never needed to replaced. That's not to say that the current doesn't rise above 13A. I posted a John ward video earlier that show John destroying a power cable. The socket, plug and fuse that John uses in his experiment are all 13A and don't appear to suffer even though the current gets as high as 23A over a period of about 30 minutes. Theoretically the fuse should have blown at 21A.

No. It's not what I am there to do. I don't think I need to tbh. It's going to me more than 13A. This is purely an observation. I will make a recommendation but I doubt it will be followed up. There are no signs of damage to either plug or socket after 3 years of service 7 days a week. About 3,300 wash cycles. The plug has a 13A fuse in it that is in tact and has never needed to replaced. That's not to say that the current doesn't rise above 13A. I posted a John ward video earlier that show John destroying a power cable. The socket, plug and fuse that John uses in his experiment are all 13A and don't appear to suffer even though the current gets as high as 23A over a period of about 30 minutes. Theoretically the fuse should have blown at 21A. Finally, the circuit is supported by a B32 so the only weak link, so to speak, is the actual plug and socket. From the owner's perpective there doesn't appear to be any real incentive to go to the expense of installing a dedicated circuit.

It's no good speculating and watching YouTube videos. In my guessed opinion from the link I posted in #19 is that the load is nowhere near what you are predicting and that it has been altered to enable 13A operation but the flex has not been reduced in csa. Or it is exceeding the13A rating but nowhere near what you think. If you are going to suggest someone takes action with this be precise with your information and measure the current draw.

 

[Ray Pooley]

It's no good speculating and watching YouTube videos. In my guessed opinion from the link I posted in #19 is that the load is nowhere near what you are predicting and that it has been altered to enable 13A operation but the flex has not been reduced in csa. Or it is exceeding the13A rating but nowhere near what you think. If you are going to suggest someone takes action with this be precise with your information and measure the current draw.

It hasn't been altered.

 

[Jim_e_Jib]

Are you not even the tiniest bit curious to see what current it is drawing though?

If it is drawing 28 or so amps, you have the nirvana of 13A plugtop and socket combinations and should be recommending the combination to everyone!

 

[Ray Pooley]

Are you not even the tiniest bit curious to see what current it is drawing though?

If it is drawing 28 or so amps, you have the nirvana of 13A plugtop and socket combinations and should be recommending the combination to everyone!

Yes I am. If she acts on the recommendation I will check it before I change it.