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thoughts on this,on drawings, water heaters are on a ring main circuit,dedicated to the heaters,there are 4 of these.
Listening to spark ninja this could prove a problem with the overloading & balancing of this ring.
Why would consultants decide on a ring ,instead,like the good old days,all heaters are cabled back.
 
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Wilko

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Hi - tell us a bit more about the loads and the RFC design and I'm sure you'll get plenty of commentary :) .
 
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They are 4 x 3kw heaters on ring circuit,approximately 60 meters of cabling,rcbo 32 amp c type.
 

Wilko

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They are 4 x 3kw heaters on ring circuit,approximately 60 meters of cabling,rcbo 32 amp c type.
Last I checked 3kW is 12.5A at 240V and so 4 heaters means 50A. I would assume all heaters will be on together first thing in the morning, so no diversity. Maybe I've missed something ...
 
If the water heaters don't store any water, they are of the instantaneous type and the On-site Guide suggests an allowance for diversity for such heater that results in the maximum demand being 32.6A. Given the UK power supply is often above 230V, I would say that this load is acceptable on a 32A RFC.

The designer could have made a mistake though and specified heaters that do store some water. In this case, the OSG's guidance is that diversity cannot not be applied. 2 x 32A RFCs would be required.
 
T

Toneyz

For all the schools we have done the consultants have always designed on radials.
 
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For all the schools we have done the consultants have always designed on radials.
Agree,really can’t see the point of this circuit.
It’s ridiculous,the tpn DB installed is a 6 way ie:18 circuits,the number of circuits on the drawing relates to 14 circuits,there are already a couple of extra circuits to be added,this all specified by consultants,kinda mad mad mad
 

TJ Anderson

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Are they instantaneous or stored water type?

Depending where they are positioned in that ring could mean that one leg is being overloaded.
3kW fixed loads is not a good idea on a ring. They would have to be fused spurs with fuses running at limit, although you could probably argue load is determined and fit DP switches.
 
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Cheers to all,will look @heaters Monday to find what they are,& will question the design.
 

davesparks

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Just because they can do it, and probably justify it by calculation, doesn't mean that it is the best way to do it.
 
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Always radials back to DB for me,other sparkies on site,attitude just do what’s on drawing.
That applies to everything including guessing positions on rooms,without asking for a detailed drawing,then when 2nd fix comes a knocking,it’s all wrong,& blamed on me.
 
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