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Thread: Boiler interlock - regulations question?

  1. #1
    Automated Home Guru jpdw's Avatar
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    Default Boiler interlock question

    Hi,

    Today is day#1 of our 4-day boiler replacement & CH overhaul. Plumber doing all the "wet" side, I'm supplying the HA control stuff.

    Our plumber leaves the electrics bit to his a colleague who will be here on day #4 to wire up. In the meantime, the plumber (who freely says he doesnt know the elec side of it - he leaves it to the spark) is questioning how our planned way of doing things will interlock with the boiler.

    I suspect this is because what we want is just a bit different (more sophisticated) than normal ....

    If this is really so, all is not lost because I have a couple of days to get the conventional bits to keep everyone happy, but meantime I'm hoping to get some comments from your knowledgable people...

    What is planned is based on the "old fashioned" zone valve & room stat approach, but with multiple zones and idratek relays replacing the "switching" part of a room stat. The live supply side of the idratek relay will be fed from a traditional timer (*), making the system even more analagous to a conventional one.

    I was planning to get it wired as follows:
    Time switched supply for each zone from the conventional timer/programmer;
    Fed into the live side of one idratek relay per zone;
    (Switched) Output from Idratek relays connected to motor drive on zone valve (one per zone);
    Microswitch contacts on each zone valve connected to boiler's call-for-heat (contacts fed from perm live)

    With all live/neutral connections coming from a single FCU (ie one point physical isolation and circuit protection).

    I realise the call-for-heat could be driven directly by another Idratek relay (agregating the multiple zone requests) but figured that I may as well use the zone valve microswitches because (1) they are there (2) greater similarity with conventional systems (3) physical interlock instead of logical interlock.


    Does anyone see a problem with this ?
    Or am I right in thinking the plumber is just being cautious?


    (*) as a first step.... as with many other HA HVAC, intention is to bypass this later on...
    Last edited by jpdw; 1st April 2008 at 03:04 PM.

  2. #2
    Automated Home Guru jpdw's Avatar
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    No replies... I guess I should post shorter questions :-)

    Anyway, in case anyone wonders, despite the sceptism of the plumber, the electrician seems reasonably happy with it, and the interlock is no issue at all.... just the plumber being a bit cautious.

    I created a neat schematic of the install to show how similar is to a conventional multi zone RF-stat install. I think that helped.

    Spark open to trying "non standard" (but still regulation compliant) HA stuff.... I must get his tel number for the future.....

  3. #3
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    The plumber is right.

  4. #4
    Automated Home Guru jpdw's Avatar
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    Quote Originally Posted by tabath View Post
    The plumber is right.
    I wasn't doubting that an interlock is a good idea - this was why I was using the microswitch on the zone valves to trigger the boiler (as opposed to a "logical interlock" where the ZV is controlled by 1 relay and the boiler by another -- relying on the control system to always open the ZV before the boiler etc).

    Anyway, the electrician took a quick look at my schematic and the Idratek QRI (4 relay unit) and was happy. He confirmed it was okay to the regs.

    So definately the plumber knowing the regs but not understanding the electric side of what I wanted so was being cautious before his spark mate got there.

    Job done... !

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