Pressure relief valve are usually 3-3.5 bar. I would charge them up to over
this pressure. If they are only good for 3 bar then you may end up with
gooky water all over your carpets if the pressure vessel fails and pressure
rises right up.
Checked by AVG anti-virus system (http://www.grisoft.com ).
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While on the subject of heating, do you know what the u-value is of
a cavity wall with standard brick outer skin (LBC Tudor), 75mm cavity
filled with rockwool and block inner. The reason I ask is that the
blocks are not 'breeze' blocks (about half the weight of concrete
blocks) nor are they 'thermal' (1976 built). Each block has oblong holes
going right through them vertically. I am using a U value of 0.5 on the
Myson calculator, but else where I have seen 0.83.
Another problem is that the 'builders' who assembled this house dropped
so much mortar down the cavity (and the gas flue blocks) that it is
actually a solid wall up to about 6-8 inches ABOVE the dpc. Strangely
enough there is no obvious sign of water penetration, The bridging of
the cavity means I have a nasty cold radiator around the entire
perimeter of the ground floor - what sort of correction should I allow
for the actual boiler output needed. (Its actually less than 20Kw
so the Keston won't have any problems).
A non-thermal concrete block isn't likely to have much insulative capacity
when compared with the 75mm of rockwool in the cavity, so it won't make much
practical difference exactly what type of uninsulated block it is.
Using 75mm rockwool, unplastered, I get:
(100mm Topcrete): 0.40 (concrete blocks)
(100mm TopLite7): 0.35 (insulated blocks)
To calculate around the bridged zone, just treat the bridged area as a solid
brick wall for heat loss calculations. The U-value will be around 2.1 for
this area. No wonder it feels cold!
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