One for the sparkies - Kitchens, cookers and house renovation
One for the sparkies - Kitchens, cookers and house renovation
(OP)
Folks
We are in the middle of renovating our kitchen and are looking at what to do with our cooker. At the moment we have a 'normal' electric cooker wired into a 45A isolator switch.
We are looking to change it for a electric range cooker and have had our electrician out to look at the house wiring. The incoming supply is 100A.
One of the cookers we are looking at states the suggested supply is 32.2A at 230V. However I see in the installation instructions that the maximum electrical load is 18.4kW. Based on my high school physics equates to 80A at 230V.
Another cooker we looked at had a electrical load of 11.1kW at 230V, and a total hob load of 13.25kW at 230V. Based on this cooker our electrician has advised we need to upgrade the wiring and the isolator to the cooker to 63A and install a new 63A RCD.
This is where I am confused. The first cooker states what supply it needs (32.2A) but if all the hobs and ovens were on at full power it would be running at 18.4kW. Is that possible or would it blow the fuse?
If it needs upgrading, then so be it, but I would like to understand why.
The suppliers websites seem unhelpful to me, and none have responded to my queries.
http://falconappliances.com/products/range-cooking...
http://www.rangemaster.co.uk/range-cooking/classic...
Cheers
Phil
We are in the middle of renovating our kitchen and are looking at what to do with our cooker. At the moment we have a 'normal' electric cooker wired into a 45A isolator switch.
We are looking to change it for a electric range cooker and have had our electrician out to look at the house wiring. The incoming supply is 100A.
One of the cookers we are looking at states the suggested supply is 32.2A at 230V. However I see in the installation instructions that the maximum electrical load is 18.4kW. Based on my high school physics equates to 80A at 230V.
Another cooker we looked at had a electrical load of 11.1kW at 230V, and a total hob load of 13.25kW at 230V. Based on this cooker our electrician has advised we need to upgrade the wiring and the isolator to the cooker to 63A and install a new 63A RCD.
This is where I am confused. The first cooker states what supply it needs (32.2A) but if all the hobs and ovens were on at full power it would be running at 18.4kW. Is that possible or would it blow the fuse?
If it needs upgrading, then so be it, but I would like to understand why.
The suppliers websites seem unhelpful to me, and none have responded to my queries.
http://falconappliances.com/products/range-cooking...
http://www.rangemaster.co.uk/range-cooking/classic...
Cheers
Phil





RE: One for the sparkies - Kitchens, cookers and house renovation
David Simpson, PE
MuleShoe Engineering
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RE: One for the sparkies - Kitchens, cookers and house renovation
You need to apply a degree of realism: how likely are you to run every cooking ring at full power simultaneously with the grill on high and the oven warming up from cold? The average load will be far below the theoretical maximum because no real-world cooking will ever use everything simultaneously: this is what we refer to as 'diversity'. Diversity can be applied among loads within an installation, or in this case to individual loads within an appliance. I suspect this is what the manufacturer has done when suggesting a breaker size.
RE: One for the sparkies - Kitchens, cookers and house renovation
So if the manufacturer is taking diversity into account does that then mean, using their recommendation then we would not be able to use our expensive cooker at full power?
I'm thinking Christmas day when we have my family and her family round and are cooking the turkey, ham, nut roast and accompaniments I can see us using all the ovens and hobs simultaneously, albeit possible not all at full power. Granted this is not a daily occurrence, but is still feasible once or twice a year.
Or would the manufacturer be assuming that you are using all the hob/ovens concurrently but have some method which takes into account the fact you may not be using them all at maximum power, so states something like, 2 hobs a 100%, 2 hobs at 80% and 2 at 60% plus 2 ovens at 100% and 2 ovens at 75%?
These cookers are very expensive so I am loath to spend money on them if there will be restrictions on how they can be used.
The electrician has said that you don't really get 63A isolators for the home so he would be installing an industrial one, a yellow box with a red rotary switch. Now, I am sure that people have wired these things in before and I have never see a big yellow box in a kitchen. He is maybe just being conservative.
RE: One for the sparkies - Kitchens, cookers and house renovation
RE: One for the sparkies - Kitchens, cookers and house renovation
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: One for the sparkies - Kitchens, cookers and house renovation
Even with your scenario, you would not have everything turned on high at one time, several of those burners would be just simmering sauces and the like. Even the ovens would probably be started at different times so they would not be full on coming up to heat simultaneously. They will not draw anything like full power while you are roasting the turkey and baking the ham.
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RE: One for the sparkies - Kitchens, cookers and house renovation
Still the recommend connecting with 6mm² cross section cables though! I found on the web that consumption is 0.92Kwh.
If you reckon you are going to be drawing a true 80A then according electrical safety standard even 16mm² cable would be insufficient!
Seems like you've got a specialist installation there!
RE: One for the sparkies - Kitchens, cookers and house renovation
We have double checked with the manufacturers and they have said 10mm² cable and 45A switch.
I have also had a read through the IET Wiring Regs regarding diversity and it seems pretty clear that it can be allowed for.
So I am happy, as is the manufacturer. It just seems it's our electrician that is not although he hasn't explained why.
RE: One for the sparkies - Kitchens, cookers and house renovation
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: One for the sparkies - Kitchens, cookers and house renovation
BS7671 gives various ampacities base on type cable used and the method of its installations.
Waross said: "In Canada, for years, the standard range breaker was 40 Amps. Everything turned on high would trip this breaker in a few minutes. But the diversity is such that it never happens. Assuming that the new cooker is approved locally and not imported from another jurisdiction, You should be safe using the manufacturer's the suggested supply of 32 Amps."
I may misunderstand because of the difference between US and UK terminology, but a switch is not a breaker.
You want a breaker, and yes, RCBO is preferred as Artisi said. And you need the electrician to verify the wire you have currently installed is indeed 10mm2.
So:
1. change the switch for a breaker, RCBO preferred, 45A per manufacturers spec.
it is wrong to install less because in the US, our code specifies "all equipment shall be installed as the manufacturer intended."
2. verify you have the correct wire size already installed
3. after step 1 and 2, bob's your uncle.
RE: One for the sparkies - Kitchens, cookers and house renovation
RE: One for the sparkies - Kitchens, cookers and house renovation
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RE: One for the sparkies - Kitchens, cookers and house renovation
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RE: One for the sparkies - Kitchens, cookers and house renovation
In some jurisdictions (Australia is one), an isolator (switch...?) is required next to the appliance, and is often a good idea anyway. This allows someone to isolate the appliance without having to go back to the switchboard (though that too is often sensible). None of this negates the requirement for proper circuit protection back at the source (panelboard, main switchboard, distribution board and so on, not all these terms are correct but are often interchanged with each other). I'm not surprised that domestic isolators top out at 63A.
An RCD can actually mean a few things, though strictly speaking they're not all correct. An RCD can be a pluggable module that attaches to the side of a circuit breaker, it can be a separate module with its own operating contacts, or it can be built into a circuit breaker (in this case its referred to as an RCBO, but is often called an RCD).
A standalone RCD can cover off earth fault protection on a number of downstream breakers, cheaper to install but often annoying as any fault on any downstream circuit will open the lot. RCBOs get around this as every circuit has its own overcurrent and earth fault protection, much nicer as only the affected circuit trips.
None of this is likely to be relevant for NEC or equivalent codes though.
RE: One for the sparkies - Kitchens, cookers and house renovation
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: One for the sparkies - Kitchens, cookers and house renovation
It used to be that RCBOs were generally two poles wide, and wouldn't directly fit as a breaker upgrade, but this is no longer the case.
Also, as I mentioned, having one RCD covering 3 GPO circuits, or 2-3 lighting circuits (which didn't always require an RCD, now they do) is a royal pain if one device trips the RCD as the whole lot goes down.
There is also the RCD extension to a CB that takes up one pole and actuates the breaker next to it, I don't see any reason (though I've not checked standards recently) why they would not be accepted, but given they're the same price as a new RCBO theres no point.
RE: One for the sparkies - Kitchens, cookers and house renovation
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RE: One for the sparkies - Kitchens, cookers and house renovation
An RCBO combines the functions of a miniature circuit breaker and an RCD in one case, so it provides overload, short-circuit and sensitive earth fault protection. Changes implemented in the 17th Edition of the UK wiring regulations now require sensitive earth fault protection - i.e. a 30mA RCD or 30mA RCBO - in situations where there was previously no requirement. This has resulted RCBOs becoming more popular as a simple and convenient means to comply with the regs, and the cost has reduced as volumes have increased.
RE: One for the sparkies - Kitchens, cookers and house renovation
Assumed load diversity for cooking appliances in domestic premises -
"10A plus 30% of full load of connected cooking appliances in excess of 10A, plus a further 5A if a socket outlet is incorporated in the control unit."
So your 80A theoretical load would require a minimum protective device and wiring rated at [10A + (0.3*80)]= 34A. If you have a socket outlet on the cooker control then the minimum rating would be 39A. In both cases the next largest standard size MCB or RCBO is either 40A or 45A depending on brand. This matches what the manufacturer suggested as the minimum cable and switch size.
RE: One for the sparkies - Kitchens, cookers and house renovation
The approach has been load tested. It cooked the Turkey, Glazed Gammon, Pigs in Blankets, Sausage Stuffing, Roast Potatoes, Roast Winter Vegetables, Brussel Sprouts with chestnuts and red cabbage with honey with absolutely no dramas on Christmas day. The lights stayed on and the beer, wine and whisky flowed merrily.
RE: One for the sparkies - Kitchens, cookers and house renovation
Actual Pigs in Blankets not Sausage Rolls, how colonial of you Ussuri?
(Sorry, way off topic.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: One for the sparkies - Kitchens, cookers and house renovation
what wire gage is the Canadian/Australia/UK ? equal to those "area" values? I've always seen wire gages in house installations and powerplant controls as nbr 10, 12, 14, 16, 22, etc. only in the original and ancient "gages" of the 1890's.
A US-designated GFI (ground fault interrupter) is required now for all 120 VAC plugs near water (bathroom and kitchen and clothes/wash room obviously), but they would not be allowed for the 220 VAC of our stoves and ovens. Overseas (non-Canadian) household plugs are already 220 VAC, so maybe GFI equivalents are already at the stove? Rather than hard-wired stove connections from the breaker box?
RE: One for the sparkies - Kitchens, cookers and house renovation
Bill
--------------------
"Why not the best?"
Jimmy Carter