relay logic for 2-pump wet central heating system

John Stumbles · 2006-09-04T16:28:05+00:00

[I tried this query on the uk.d-i-y newsgroup without getting a solution.I'm x-posting it there for info to that group as I hope it may be usefulto others, with followups to s.e.d]I need to fix up proper controls on a wet (what I think leftpondians call'hydronic') Central Heating system that has separate pumps driving thespace heating (CH) and water heating (DHW) systems. Each part of thesystem has a time switch and thermostat determining when the pump for thatsystem's hydronic circuit needs to be driven. When the CH or (Boolean-OR)DHW systems are running the boiler must also run. The boiler has a'Switched Live' terminal which, when energised, causes it to run.I know I can do it with 2 relays with their contacts wire-ORed to drivethe boiler Switched-Live:L -----------+--------------------------+-------------+--------------+ | | | | o | o | o | o | | CH - programmer - HW | | A | B o | o | o | o | | | | | | | | | | | +-----------+--+ o | Room o | HW | | thermo | cylinder | o | -stat o | 'stat | | | ---------- | | | SL | +----+----+ +----+----+ | | | | | | | boiler | | ----- | ----- | | pump (>) | RLA | pump (>) | RLB | | N | | ----- ...

Sep 04, 2006 23 Replies

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Homer J Simpson 19 years ago

Yes. In Outlook Express you select View : Text Size : Fixed Font to view these.

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Christian McArdle 19 years ago

I just set my proportional font to be Courier New.

Christian.

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stevelup 19 years ago

You've been desigining digital logic circuits nine years more than I've been on this planet so how can I compete :)

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jasen 19 years ago

when you're reading on google groups and hit an ascii schematic select "show original" (under "show options") and you'll get a fixed pitch font rendering of the message (including the diagram).

Bye. Jasen

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