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Thread: Controlling a thermal-store / hot-water tank

  1. #1
    Automated Home Legend chris_j_hunter's Avatar
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    Default Controlling a thermal-store / hot-water tank

    Looks like thermostats to monitor thermal-stores & hot-water tanks over-temperature hazards are fairly crude devices ... the water shouldn't boil & lead to over-pressure due to the steam ... but the usual overheat 'stats are normally set to cut-in at about 85degC, to be on the safe side, whereas for max' heat capacity / economical 'store size, it would be good to run with teh water close to boiling - say 95degC (which washing machines seem to manage) - plus they require a button-press to reset ...

    so, 'wonder it Idratek could help ... the logic could be smarter (!), and maybe Reflex could be used to provide safety in-case of of PC failure or Windows going off on a jaunt & getting stuck ... what sort of temperature sensor would one use, and how would it be connected - presumably to an analogue input channel / module, though maybe there are digital options, too ... ???

    Anyone tried or had a look at this, by any chance ??

    Chris
    Last edited by chris_j_hunter; 6th February 2008 at 11:23 AM. Reason: serious typo !

  2. #2
    Automated Home Legend Karam's Avatar
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    Just out of interest Cortex does have a facility for controlling hot water tank temperature such that you can have different set points at different times of the day. This presumes that you have some form of temperature sensor feedback of course.

    I guess in terms of safety cut outs you could use the safety in numbers approach. Multiple thermistors connected to one or more analogue input modules and to one or more cutout mechanisms (relays?). It is probably not so likely that you'd already have multiple analogue input modules in an installation but quite often you will find you have more than one modules with an unused relay channel so typically this part would involve no extra expense. The cut out response can be programmed at the Reflex level notwithstanding Cortex ie. Cortex can just monitor but not be involved in the cut out response itself. It is entirely possible to run independent Reflexes alongside Cortex - just, unless managed properly, not often a good idea due to potential conflicts of interest.

    Karam

  3. #3
    Automated Home Sr Member ludditeal's Avatar
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    Sort of following on from this thread..

    As the weather is improving and will be our first full year running the store I have plumbed in a first stage heat dump which is run from a pump connected to one of the relays in a Quad relay unit and will circulate the store water to some outside piping. I already have the store wired up with sensors connected via analogue sensors (QAI) which then feed into a "virtual" DTS which gives me temperature displays on the panels.

    What I want to do now is for the heat dump relay to be triggered when the top sensor of the thermal store goes above a certain value and then either run for a certain period or ideally until the temp goes below another value.

    I am struggling to see how to implement this so looking for some help guidance as I couldn't see how to do it with Macros/Fuzzy/Logic functions.

    Suggestions?

    Cheers
    Allan

    (The second stage heat dump I plan and/or fallback if Cortex is down is to connect the Solar control station over-heat relay to a water valve and literally flush hot water down the drain. Any suggestions for a valve would also be appreciated otherewise I will be on the lookout for a washing machine to take to bits!).

  4. #4
    Automated Home Legend Karam's Avatar
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    Can you not simply do this using some user defined temperature threshold actions (click on graph icon in temperature object behaviour menu to access these). Or am I missing a wider point?

    If I'm not missing a point then the above could be used to trigger a timed pump relay pulse or you can use (going above) one threshold to switch on the pump and (going below) another threshold to switch off.

  5. #5
    Automated Home Sr Member ludditeal's Avatar
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    Thanks Karam, that is exactly what I needed and hadn't spotted. I was obvioulsy expecting it to be more difficult!

    Need to test it now and watch some of my "free" hot water dissapear

    Cheers
    Allan

  6. #6
    Automated Home Legend Paul_B's Avatar
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    Sorry to dig up quite an old thread but the information is pertinenet to my question.

    I am just about to replace by old gas non-condensing boiler with a thermal store and Viessmann gas condensing boiler. Over the next few years I'm going to add a log stove with back boiler and solar thermal, hence the thermal store to act as a buffer for different heat sources. I am slightly concerned the normal heating controls will not be able to efficiently cope with this setup. So as a safeguard / better solution I want to add temperature sensors on all pipes so I can feed into Cortex and let it control the boiler, valves and thermal store. What is the recommended sensors for this?

    Paul

  7. #7
    Automated Home Legend chris_j_hunter's Avatar
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    we use these, clipped onto pipes :

    http://www.rapidonline.com/Electroni...-sensors-76422

    these, inserted into pockets & tile-adhesive, or taped to ducts :

    http://www.rapidonline.com/Electroni...th-Lead-122892

    and these, for room comfort sensing :

    http://www.titanproducts.com/categor...lack_Bulb.html

    all wired into QAIs ...

    several, working for a while, without problem ...
    Last edited by chris_j_hunter; 15th December 2012 at 12:06 AM.

  8. #8
    Automated Home Jr Member jcmiguel's Avatar
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    I have a 1500 L thermal store that has pockets specifically for temp monitoring. I just hooked thermistors into an analogue module and all has been well for the last 4 years. I only had an incident last year where a pipe burst during Christmas eve and we were away. House was frozen in our return and boiler went to error mode but elsewhere every thing was fine

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