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Thread: Heating control - physical wiring

  1. #1
    Automated Home Guru JonS's Avatar
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    Default Heating control - physical wiring

    I'm planning phase 2 of heating control to introduce per room zoning upstairs, currently its based on average temp of all upstairs rooms.
    I'd like the 24V suppliy to only be activated when there is demand, so connecting that to the switched boiler supply seems right.
    However I don't control my boiler directly with an Idratek relay - the Idratek zone valves call for heat, which triggers the physical motorized zone valves and the switched boiler supply is provided via switch on the zone valve output (orange wires IIRC). All 3 zone valve switch outputs are I think commoned.
    I currently do have a Idratek relay configured in the logic as the boiler, but it isn't actually connected to anything - I think I needed to do this to keep Cortex happy that there was a boiler for the HVAC object to control
    So should the boiler relay fit between the commoned outputs of the zone valve switches and the boiler, or be a switch of a fresh supply (on the same heating circuit of course)??
    Do I need a boiler relay at all and just use the existing set-up where the zone valves provide control of the boiler. Does that limit the control options for minimum loading of the boiler or more advanced hot water control (currently just a timer)??
    If I don't need a boiler relay, can I create an logical boiler rather than assigning a dummy relay?
    Thanks
    JonS

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    Automated Home Legend chris_j_hunter's Avatar
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    not sure I quite understand current set-up - but a separate HVAC object (and so individual profiles, etc) per Idratek zone-valve might be all you need to add ... ?

    Chris

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    Automated Home Guru JonS's Avatar
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    Hi Chris - I agree about the HVAC objects and their relation to the zone valve relays, but to power the zone valves I need 24V. Rather than have the PSU sit there keeping warm all the time I would like to have it switched but into which parts of the mains wiring? Also like to understand how to ensure the boiler relay allows the boiler object to benefit from the minimum loading feature to minimise cycling. With only a virtual boiler relay there is no supression of the boiler when a zone calls for heat. But maybe the HVAC and boiler minloading logic suppress the Zone valve from triggering so I don't need a physical boiler relay??? I guess I could experiment but don't like experimenting on the house as it leads to complaints!
    When Phase 3 comes with hot water control then I understand that the hot water can be used as a dump to allow small rooms to be heated without forcing the boiler to cycle. E.g. our smallest room has a sub KW radiator in it - the 24KW heater won't modulate efficiently down to that so switching in the hot water cylinder will heat the room, help the boiler run more efficiently and reduce the chance of an isolated boiler burn just for hot water. At least I think that's teh theory but the physical wiring to support it is a bit unclear.
    JonS

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    Automated Home Ninja marcuslee's Avatar
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    Quote Originally Posted by JonS View Post
    Hi Chris - I agree about the HVAC objects and their relation to the zone valve relays, but to power the zone valves I need 24V. Rather than have the PSU sit there keeping warm all the time I would like to have it switched but into which parts of the mains wiring? Also like to understand how to ensure the boiler relay allows the boiler object to benefit from the minimum loading feature to minimise cycling. With only a virtual boiler relay there is no supression of the boiler when a zone calls for heat. But maybe the HVAC and boiler minloading logic suppress the Zone valve from triggering so I don't need a physical boiler relay??? I guess I could experiment but don't like experimenting on the house as it leads to complaints!
    When Phase 3 comes with hot water control then I understand that the hot water can be used as a dump to allow small rooms to be heated without forcing the boiler to cycle. E.g. our smallest room has a sub KW radiator in it - the 24KW heater won't modulate efficiently down to that so switching in the hot water cylinder will heat the room, help the boiler run more efficiently and reduce the chance of an isolated boiler burn just for hot water. At least I think that's teh theory but the physical wiring to support it is a bit unclear.
    JonS
    Well just to chime in with my 2p. I think you're further ahead in understanding of all this, so my 2p is only to let you know how my system is currently setup which might aid in getting to where you want to go with yours. In answer to your question of:
    "Do I need a boiler relay at all and just use the existing set-up where the zone valves provide control of the boiler."
    The answer is yes obviously I guess, as that's how it's currently working?

    Specifically I suppose, FYI in the current setup I have, I have several zones, all with individual manifold valves linked to room stats. Also have a boiler which fires when any of the rooms request heat.

    Wiring side: room stats, manifold valves, boiler, and 2 port zone valve (with the orange and grey wiring I believe) all wiring into a wiring centre, a Heatmiser UH3.

    In my case, I suppose what my pertain to yours, is that the Heatmiser UH3, seems to just do some pretty basic logic which basically seems to do this:
    1. a room stat switches calling for heat
    2. UH3 supplies power to 2 port zone valve
    3. 2 port zone valve opens, meaning boiler supply is ok to go into manifold supply the manifold valves for the rooms
    4. orange and grey close, forming a circuit, which is used to inform the UH3 that the zone valve is open
    5. UH3 fires boiler

    Not very sophisticated, and amazing how much money they ask for for those UH3s IMO!

    So I suppose in your case, it's much the same except no need for the UH3 really as it's direct wired that when the 2 port zone valve is open, it sends signal to boiler that it's good to supply?

    Also I suppose what complicates things is you've 24v, whereas I've mains all the way through.


    What my system does lack however is the "minimum loading of the boiler or more advanced hot water control" you mention.


    Also I really want to get rid of the UH3 and switch it over to Idratek completely. Currently I just use Idratek to do the switching into the UH3 to let it know when a room needs heat. I'm not far off it, but there's a bunch of other things I want to do first. Also I'm not sure if we're staying on here, so there's a chance it might all go back to the traditional setup.



    [Also FYI for anyone reading the above, from what I've learnt, there's 2 trains of though with regards to even need a 2 port zone valve in front of the manifold valves. One that says it's needed (but for what real reason I haven't fathom'ed), and those that say it's complete waste of time in this setup, as the manifold valves will block the water supply where it's not required].

  5. #5
    Automated Home Guru JonS's Avatar
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    Thanks for the comments on this, I've had some discussions with Karam and Viv and conclude:
    - Each room with radiator actuator requires its own HVAC Object
    - Each HVAC object in the Upstairs plumbing zone connects to a Slave heating valve which physically is the Upstairs Zone Valve.
    - In my set-up the activation of the Upstairs Zone Valve will fire the boiler through the secondary contacts on the Zone Valve
    - So I do not need a physical boiler relay but can use a logical boiler object and still benefit from the minimum loading feature
    - The minimum loading feature operates by adding additional zones in order to achieve minimum loading when a lower than minimum zone calls for heat. I wrongly thought it suppressed the original zone until there was sufficient demand.
    - If I connect the 24V PSU to the Upstairs Zone Valve circuit it will only operate when an upstairs HVAC calls for heat, not when ever the boiler fires and will not require an additional relay, though I do need to check fuse ratings and demands.

    I chose 24V actuators to avoid the complication and safety requirements of 240V outlets at each radiator – so which ever type of actuator there are ramifications to consider!

    On the need for a plumbing Zone Valve in addition to radiator valves, I have a zone valve which I will keep as it means I can switch over to conventional controls by flicking a couple of change over switches and removing the actuator heads. In a larger set-up I think that the major zone valves (upstairs, downstairs, HW) prevent circulation in the pipes which may occur in practise on long runs, but I've no idea how big an effect it is.

    Thanks
    JonS

  6. #6
    Automated Home Legend Karam's Avatar
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    On the subject of the 24V supply, I'm not so sure about the gains from switching it. I presume you might have a Meanwell DR-60-24 (the one we tend to supply) and these have quite a low no load power consumption. I haven't got a figure for the DR-60 but the larger DR-100 is quoted as <1W. As against this the inrush current is 36A for the DR-60. Probably much better than an LED or CFL bulb but nonetheless regularly swiching SMPS's from cold probably doesn't do relay contacts much good. But I suppose no harm setting it up - at the end of the day if the relays spot weld then you're no worse off than being permanently on anyway and I guess its one less 'stand by'

  7. #7
    Automated Home Legend chris_j_hunter's Avatar
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    couple of thoughts ...

    >prevent circulation...

    unwanted thermo-circulation can happen not only in long-runs - we have a there-&-back loop between tank & heat exchanger that's just a metre or so long (mostly vertical), that connects by the heat-exchanger to another (longer more horizontal loop) and occasionally they give us significant heat losses ... mostly they're fine, but some nights in the small hours they get-going ... not sure why some nights & not others, and probably wouldn't know how the heat was being lost, but Cortex collects the data via QAIs & clip-on temperature sensors & it's clearly visible in the HVAC object plots ... we've a two-port motorised valve ready to be plumbed-in to hopefully stop this (hopefully, because hopefully stopping one loop will stop the other, too) ...

    >in-rush ...

    we've just added in-rush resistors to protect DRB relays during switch-on of two LED drivers - we bought good quality, but one of the relays has sometimes been sticking-on - bit of a mystery, why it's only sometimes & after maybe fifty occurrences the relay still works properly most of the time, many times a day, but we're trying 50ohm versions to see if they solve the problem ... we installed them yesterday, and initially put them behind the DRB - but they get a little warm, and we were worried about their long-term effect on wire insulation, heat shrink', and the PCB - so we reinstalled them alongside the drivers, in their own box (with added ventilation holes) instead ...

    Chris
    Last edited by chris_j_hunter; 8th October 2013 at 08:47 AM.

  8. #8
    Automated Home Guru JonS's Avatar
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    In-Rush:
    36A - that sounds high! I guess it is momentary, but enough to weld contacts. Engineering realities!
    Chris - please could you point to details of your in-rush resistors and how you've fitted (photo would be great!).
    Thanks
    JonS
    JonS

  9. #9
    Automated Home Legend chris_j_hunter's Avatar
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    details - see posts 12 & 13 here :

    http://www.automatedhome.co.uk/vbull...ght=1.5KE440CA

    photo's - too late, 'cos ours are now buried behind other things - but we put them between lamp & driver - cut the cable & soldered them between, covered with heat-shrink' and put them in a small square box, with glands for cable in & out, and four rows of 5mm holes drilled into the lid to allow some ventilation, box then wall mounted, in kitchen unit, behind microwave ovens - the LED lights being alongside, over the hob ...

    Chris

  10. #10
    Automated Home Legend Karam's Avatar
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    Quote Originally Posted by JonS View Post
    In-Rush:
    36A - that sounds high! I guess it is momentary, but enough to weld contacts. Engineering realities!
    JonS
    That's nothing compared to many Fluorescents and LEDs. It does initially appear a bit strange when you consider the steady state current is in 10's of mA, but its because there is a sizeable capacitor facing the incoming voltage. When this is 'cold' (discharged) and if you happen also to hit it at peak cycle then you will get very high current - we've been doing some measurements of our own recently and I can tell you it can be well over the 50A limit on our to be upgraded measuring kit... If you happen to have an audio device nearby when you plug in an innocent looking switch mode supply you will often hear a 'pop' - you can guess where that came from...

    Of course the spike only lasts over a very short period but over time this causes increasing wear on the contacts and the eventual propensity for underlying material to form spot welds. Certainly you can improve resilience with different contact materials but for the smaller relays the choice is more limited.

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