epsilonGreedy

13m distance from CU to cooker = poor design?

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Posted (edited)

As a development of my recent interior layout discussion thread here I have decided to move the kitchen to the front of the house. If the consumer unit remains in the utility room the result of the layout change will be a 13 meter horizontal run to the electric cooker. Is this a sign of a poor home circuit design?

 

At present heating will be via a combi boiler hence no HW tank or heating element. The only other high capacity circuits will be an infra red patio heater and a provision for a garage car charging port.

 

p.s. This is a 2-story newbuild 1500 sq ft in size, so all options can be considered at present.

Edited by epsilonGreedy

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Not a problem, really, at worst you might have to up the size of the cooker cable, but it's peanuts in terms of relative cost. 

 

At a guess I'd say that the total run from our CU to the hob in the island must be around 10 to 12m or so, although the ovens come off that run a few metres before that.  Electric showers are often a fair way from the CU, and they draw far more power than a cooker.  It's just a matter of sizing the cable in accordance with the regs, allowing for the volt drop and things like whether or not the cable run is partially, or wholly, within insulation and how it's fitted (there are different rating factors for clipped direct, run in conduit, through insulation etc).

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Our double electric ovens have a cable run of about 15m and it was not questioned by the electrician.

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My concern with moving the kitchen would be will that make a very long run for the hot water to reach the kitchen taps?  Where is the new kitchen location in relation to the combi boiler?

 

I am minded of my plumber friends house where he ended up with the hot water tank as far from the kitchen as it was possible, in a house twice the size of mine.

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24 minutes ago, ProDave said:

My concern with moving the kitchen would be will that make a very long run for the hot water to reach the kitchen taps?  Where is the new kitchen location in relation to the combi boiler?

 

I am minded of my plumber friends house where he ended up with the hot water tank as far from the kitchen as it was possible, in a house twice the size of mine.

 

On a similar vein, I have just got my hot water connected ( by immersion) and was pleased to find out that the 9m run from the DHW tank to the tap in 10mm plastic pipe only took 10 seconds to get hot water at the tap, it appears using 10mm pipe was a success (phew) and the flow at 2bar is very adequate .

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Shower circuits often take a tortuous route to the shower, often many times the shortest distance.

Just a matter of cable sizing really.

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Cable sizing PLUS correction factors.

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Important to use the right cable for long runs and high loads.

 

If my memory serves me correctly the max allowed voltage drop due to cable losses is around 5% (about 11.5V). So a 30A load on a minimum size cable could dissipate 345W.  Bigger cable might get the drop down to 2-3V which is still 60-90W.

 

 

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1 hour ago, Temp said:

Important to use the right cable for long runs and high loads.

 

If my memory serves me correctly the max allowed voltage drop due to cable losses is around 5% (about 11.5V). So a 30A load on a minimum size cable could dissipate 345W.

 

 

Crikey, I need to be careful.

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No, not you, the competent person engaged to design the scheme.

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7 hours ago, ProDave said:

My concern with moving the kitchen would be will that make a very long run for the hot water to reach the kitchen taps?  Where is the new kitchen location in relation to the combi boiler?

 

 

About the same distance as the electric supply.

 

Plan view distances to HW outlets are:

  • Downstairs toilet = 2m
  • Master bedroom ensuit shower & washhand basin = 6m
  • Kitchen Sink = 14m
  • Main bathroom (seldom used) = 13m

Best add 2m to all those numbers to account for vertical ups & downs plus radius of bends.

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Posted (edited)
5 minutes ago, dpmiller said:

No, not you, the competent person engaged to design the scheme.

 

 

He is cheap so I will need to keep an overwatch and double check the electrical science.

 

I have 4 months before the wiring starts but the regional power company has already created a plan for the assumed power meter location with associated trenches so I need to keep thinking 4 months ahead. Same goes for LPG gas tank hole, grey water drainage trenches and soil pipe drop locations. 

Edited by epsilonGreedy

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Posted (edited)

You can have a play with volt drop here:

 

https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

 

The calculation behind this is

 

volt drop = (mV/A/m) x lb x L

                                1000

 

Where:

 

mV/A/m is the mili volt drop per amp per metre. Get that from the regs or OSG. Cable spacing and the reference method means the volt drop for a particular cable can vary.

 

lb is the design current

 

L is the length in metres

 

and 1000...is erm 1000 :) to get it to volts.

 

Edited by Onoff
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Who’s your preferred LPG supplier ..?? 

 

And if you drop the pipework to the basins and kitchen to 10mm then you can reduce the time to get hot water to the taps. 

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1 hour ago, PeterW said:

Who’s your preferred LPG supplier ..??

 

Not sure as yet, someone here did mention a Humberside independent about 3 months ago. I followed up and he was keen to visit the plot and advise on where to sink the tank. The 2-year lock in price was good too.

 

1 hour ago, PeterW said:

And if you drop the pipework to the basins and kitchen to 10mm then you can reduce the time to get hot water to the taps. 

 

 

Noted though will the 10mm option be dependent on decent cold water pressure feeding into the combi or does it have its own pump? I have no experience of living with a combi boiler and had previously associated them with 1990's entry level rental properties.

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@epsilonGreedy

Start a new thread for the boiler / heating / DHW and that'll keep the this one focussed on the electricals ;) 

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LPG Direct is the one I probably mentioned.....

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