In article ,=20
says...
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"Paul Roman" wrote in message
...
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snipped
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So with Part L of the building regs excluding the use of an uncontrolled
rad as the by-pass and the boiler manufacturer (Keston) requiring a 10
to 15 degree C drop across the by-pass it seems to leave 2 options:-
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1. Bridge flow and return between boiler and zone valves with an
automatic by-pass valve on a sufficiently long loop of 22mm pipe to lose
the required 10-15 degrees. This seems to be what all the system layouts
I've seen seems to show.
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________ __|Zone valve|___-HW
| | |
| Boiler |Flow_________________________________|
| | | |
| | | |
| | | |
| | =AF=AFAuto bypass=AF=AF=AF| =AF=AF|Zone val=
ve|=AF=AF=AF-Rads
| | |
| |Return=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF= AF=AF=AF=AF=
=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF""""" ""
=AF=AF=AF=AF=AF=AF=AF=AF
In my situation this would entail a couple of holes through the side of
the chimney breast into the adjacent airing cupboard. What length of
22mm pipe would be needed to lose 10-15 degrees? It also seems to be a
pointless waste of heat as the cupboard will already be warmed by the HW
cylinder.
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2.Bridge the auto by-pass valve across one of the zone valves.
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________ __|Zone valve|__________-HW
| | |
| Boiler |Flow____________________|
| | | |
| | | =AF=AF|Zone valve|=AF=AF=AF=AF=AF=AF|=
=AF=AF=AF-Rads
| | | |
| | =AF=AFAuto bypass=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=
=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF
| |
| |Return=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF= AF=AF=AF=AF=
=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF=AF""""" ""
=AF=AF=AF=AF=AF=AF=AF=AF
This, to me, seems the more elegant solution. When both zone valves are
shut the burner shuts off. The pump automatically over-runs for a
further 2 minutes which causes the by-pass valve to open. As only 2 of
the 7 rads have TRV's (the rest will have lockshields once the system is
balanced) the pump will have its required un-impeded flow and there is
sufficient pipework to achieve the required 10-15 degree drop.
Alternatively I could use the hot water circuit instead but as a lot of
the time the tank would be full of hot water I wouldn't get the required
temperature drop.
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I've now mailed and spoken to Keston and its obvious from their replies
they don't understand my questions.
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Also while all your replies have been useful and informative they seem
to relate to systems installed before the new regs came in since last
April. I'd be very interested to hear from Ed or John or any one else
who've installed a system since then. What is normal practice since Part
L came in? Are installers simply ignoring the boilers requirement for a
temperature drop across the by-pass circuit? Or are they creating an
(artificially) larger loop for the by-pass circuit? Or are they still
using a rad as a by-pass?
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Thanks for your responses.
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Paul
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Is your system vented or unvented ?
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Its going to be sealed.

BTW did my diagrams come out OK or do I need to repost with a=20
narrower page setting?