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I was going by Figure 2.3 in OSG. Table 4.2 shows that earthing conductors as small as 2.5mm² can be used for local earth not less than 1Ω for a TT supply. With such a local earth, surely the maximum fault current is less than 230A.

My understanding is that mains isolators incorporating 100 mA RCD are used with TT supplies and a local earth as the local earth cannot take the full fault current. They are only needed if there are some circuits not protected by 30 mA RCD/RCBO.

Their installation manual suggests that the hot flow is pre-set - so you only need a timed valve. The control mechanism looks simple - a bimetallic on-off thermostat to prevent over heating. You could modulate cold flow but probably not with a thermostatic mixer. With such a simple control, you...

I think you'll need about 150mm of PIR insulation board to satisfy the minimum requirement equivalent to 250mm mineral wool.

Should we put the collar below the plasterboard with noggins above to support the plasterboard and collar while the collar expands? I'm tempted to put a ring of 18mm WBP ply between the noggins and the plasterboard both to take the fixing screws and for full support of the plasterboard...

Be aware that if you go for a single-panel radiator, you'll maximise the heat loss through the external wall. If the radiator is over-sized, use reflective foil behind the radiator to reduce radiator output and heat lost through the wall.

My BI told says I have to fix the intumescent collar to something structural. I guess that would be easier with noggins between joists above plasterboard.

I've nothing against heat pumps, I think they are a sensible way of heating. Heat pumps use energy to to raise temperature so they are most efficient for small temperature differences. My point was that air-sourced heat pumps produce less extra heat in cold weather. If you live on granite...

I agree, simply replacing a cooker on the old flex shouldn't be a cause for worry. As a completely separate issue, if the OP has doubts about the house electrics then it may be time to get in an electrician for a Periodic Inspection Report (PIR).

I have had similar issues with Windows driver updates for XP Pro. On this old Compaq Evo I HAVE to use the video driver that came with the system. Neither of the available drivers from Windows update will allow the system to recover properly from standby. On an old Acer XP1301 laptop, I have...

I am not an electrician. 45A is quite big for a cooker circuit and more common for electric showers. A 32A circuit is usually appropriate for household cookers up to 15kW plus a 13A socket. With a 32A circuit a 6mm² flex would be appropriate. Household cooker circuits use a 'diversity'...

I got the impression that the office of the Deputy Prime Minister published a lot of documents. So that might have been John Prescott???

The BCO can only tell you to do what is possible. If there is not enough space for sufficient insulation to meet current Part L Building Regs, then the BCO can only tell you to fit as much as you can. You might get better insulation with exotic materials but they must pay for themselves in...

How about a remote water heater then a pressure balancing thermostatic shower? Googled http://www.fastlec.co.uk/redring-powerstream-instantaneous-c-1743_8_11.html

Within the permitted zone (25% to 40% of span) for holes, they must be drilled through the middle of the joist (the neutral axis) as the top and bottom are considerably stressed. The permitted 12.5mm notch in the first 33% of the span is in the region of shear rather than bending. I don't see...

As far as I can make out, rings circuits have many practical advantages over radial/tree circuitslonger cables possible narrower cables needed shallow back boxes two CPCs simple geometry (no more than one outlet on an unfused spur) a degree a fault tolerance (poor connection less likely to...

With Part L I think you're supposed to get the U-value of external walls down to 0.28 W/m²/°C, which might require something like 70mm of PIR insulation (Kingspan or Celotex) on solid masonry walls.

Have you had quotes for ground source heat pumps? My sister lives in Sweden on granite and have replaced their oil heating with a ground source heat pump. The trouble with air source heat pumps is that they get inefficient at cold temperatures. Rather than insulate the cellar walls and floor...

:oops: one problem with looking at 'similar topics'

Forget underfloor heating. Your house was built for fitted carpets. :( Heat is lost at the edges. A large warehouse needs no insulation under the floor as the ground just warms up. If you must have underfloor heating, keep it away from external walls. Even with an insulated floor you should...