Table 7.1 Osg

[haptism]

Hi all hope all is well and nice layout for the forum, like it. Been flicking through the OSG and notice that in table 7.1 (max cable lengths for final circuits) that there are no cb's or rcbo's rated above 40A. Is this because they feel like no ones interested in anything above 40A, am i missing something, or have i gone mad. Thanks

 

[Dan]

Honestly it baffles me. All these acronyms and tables and graphs. Some bloody skilled sparks on here. Lol

 

[Richard Burns]

Those tables are only lists of standard circuits that can be installed by using the tables without calculation, therefor there is a limited choice of circuits all aimed at basic domestic installation.
(You should not be installing 10.5kW showers because they are stupidly overpowered!?!)

 

[haptism]

I know its a quick reference guide, which was why I had a look; it lists fuses et al above 40A but not cb's or rcbo's; just seems odd.

 

[haptism]

Those tables are only lists of standard circuits that can be installed by using the tables without calculation, therefor there is a limited choice of circuits all aimed at basic domestic installation.
(You should not be installing 10.5kW showers because they are stupidly overpowered!?!)

What about ovens, alot of domestic houses have them too !

 

[Andy78]

What about ovens, alot of domestic houses have them too !

An oven that requires more than a 40A supply belongs in a commercial kitchen and not a domestic property.

 

[Richard Burns]

Ovens up to 15kW can be installed on 6mm² T&E and 32A MCB.

 

[haptism]

Okay thanks, oversight on my memory.

 

[Wilko]

Hi - I haven't installed ovens that big, but isn't it going to click off the 32A mcb in a couple of minutes if all elements are turned on at initial start up? Just asking

 

[Richard Burns]

Hi - I haven't installed ovens that big, but isn't it going to click off the 32A mcb in a couple of minutes if all elements are turned on at initial start up? Just asking

I have done a calculation on a 14kW twin oven with five rings and made some assumptions about how long hob rings are on (1-2 min) and ovens (20-30 min) before they switch off and the results showed that after initial switch on of all rings and all ovens (a very unlikely scenario) the MCB would be 13 minutes away from tripping in the first minute before the thermostats start kicking in, on average about 1 hour from tripping when the rings start cycling and then once the ovens get up to temperature there is no risk of tripping for at least 20 minutes and on average about 3 hours from tripping.

I think if you turned everything on and kept putting pans of cold water on the rings and left the oven doors open then you could trip it.

However this is just my calculations and not a real world test.

 

[Wilko]

Thanks RB

 

[sam400]

I have done a calculation on a 14kW twin oven with five rings and made some assumptions about how long hob rings are on (1-2 min) and ovens (20-30 min) before they switch off and the results showed that after initial switch on of all rings and all ovens (a very unlikely scenario) the MCB would be 13 minutes away from tripping in the first minute before the thermostats start kicking in, on average about 1 hour from tripping when the rings start cycling and then once the ovens get up to temperature there is no risk of tripping for at least 20 minutes and on average about 3 hours from tripping.

I think if you turned everything on and kept putting pans of cold water on the rings and left the oven doors open then you could trip it.

However this is just my calculations and not a real world test.

What about when the boilers packed up and your heating the house using the open ovens and at the same time boiling water for your evening bath?
:mduck: