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Thread: Couple of questions on heating & bathroom lighting

  1. #1
    Automated Home Sr Member eddr's Avatar
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    Default Couple of questions on heating & bathroom lighting

    Hi all,

    Id Appreciate it if you can help me out with the following:

    1) What's the easiest way to control heating and water on a system that has a timer control for heating with a thermostat and water. Is it as simple as just putting the heating control on constant, then hooking into the thermostat somehow to control on/off ? And what about the hot water, how yould you do this? - Remember, easiest way!

    2) How does everyone do their bathroom lighting - Do you have a button in the bathroom or outside it, or no button atall (Just a PIR and door sensor for presence)

  2. #2
    Automated Home Legend Karam's Avatar
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    1) It should be possible to wire an IDRATEK relay in parallel with the existing thermostat connection (call for heat). Then, as you suggest, you turn the existing thermostat to a low temperature (now can just act as a backup) and keep the heating set to ON at all times. The IDRATEK driven relay now acts as your thermostat albeit a more sophisticated one.

    As you might already have gathered, the Cortex HVAC object does not have the traditional concept of timers. Instead it uses 24/7 set point profiles. That is, the heating (or cooling) is always under control. For the heating side you will probably have the profile set to a relatively low temperature overnight so that it is likely that the heating will in effect be off at night - but really this is now a matter of controlled choice. During the daytime you can do something similar, but people who install a properly sensorised system can then make use of the 'unoccupied' back off profiles.

    If you want to go beyond the simple answer the next step is to consider controlled actuators for your radiators (if you have a radiator based system). This would then allow you to have independent control of rooms or zones.

    For Hot water it depends a bit on how your existing system is plumbed and wired (various priority schemes), but you may be able to just have another relay across the timer output relating to the HW. You can then just have the HW timer permanently off and have the relay acting in its place.

    In choosing the relay module for the heating demand I'd recommend that you either use an independent module such as the SRH, or if using a multichnannel module that none of the other channels are likely to be used for timed relay operations (at Reflex level not Cortex timed). This is because it is always best to operate this relay in a 'keep alive' mode. Meaning that if Cortex fails to update, the heating fails into the off state.

    2) You can have IDRATEK button modules in the bathroom so long as the mains switching itself (and anything that might be construed as connected to mains) is done outside of the danger zones or well inaccessible to anyone in those areas (including indirect conduction around a physical obstacle via water). So a DRB or SRH is not a good idea but a QBI, DBI or DFP is ok. Or you can have a third party device connected to a digital input. But its not uncommon to have buttons outside and motion/light level sensing inside. In a well sensorised installation it shouldn't be necessary to touch the button regularly.

  3. #3
    Automated Home Ninja Viv's Avatar
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    1/ Assuming you are not zoning your heating then, as you say, you can just put an Idratek relay across the Thermostat contacts. Set you heating to constant and turn your thermostat down to lowest temp. You can use an Idratek Zone valve or Boiler object to energise the relay. The demand coming from a HVAC object. If your zoning its a bit more complicated.

    Cortex provides a Hot Water object. Think you need to look at the help to decide how to wire that up.

    2/ Regarding Bathrooms, recently we have been fitting a BRS module in the Bathrooms and the seperate relay unit is housed in a pattress on the outside of the bathroom to switch the mains. So this is like some Bathrooms where the light switch is on the outside of the room.
    We still fitted dual pattress in the bathroom with a blank panel next to the BRS to allow a possible upgrade to a DFP module when the customer realises they want to intercom whilst in the bath!

    Viv.

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    Automated Home Sr Member eddr's Avatar
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    Thanks to the both of you for that information - At the moment the plan is just to go with the 'simple' option which you suggest, relays for the outputs from the timer.

    And as for the bathroom - Looks like there will be no switch unless we run into problems with lights turning off when people in there etc, but I don't see how this could happen as Cortex will know someone is in there with door closed and PIR being set off etc.

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    Moderator Gumby's Avatar
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    Quote Originally Posted by eddr View Post
    but I don't see how this could happen as Cortex will know someone is in there with door closed and PIR being set off etc.
    You are in the shower and hence invisible to the PIR, since IR doesn't get through glass very well. Someone comes in and then leaves. Cortex logic treats the occupancy as pulled out and since there are no PIR re-triggers after various timeouts the lights may go off.

    I have a temperature sensor on the hot feed pipe to the shower, which both helps determine to run the bathroom extractor fan and also overrides the lighting logic temporarily.

    You may be able to position your PIR more favourably, but you have to consider splash zones as per regs.
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    Default Pipe sensor

    I seem to remember reading about pipe sensors on the forum before; can you expand a little on your setup? I had been wondering if this would be more accurate than humidity sensing because I wasn't sure how you would compensate for outside humidity. How long does it take the pipe to cool down after the shower stops? - if its too well insulated then might this be a problem? An alternative might be some sort of flow rate sensor but I haven't seen any that don't need to be plumbed in.

  7. #7
    Automated Home Ninja Viv's Avatar
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    For Fan control by humidity (and other activities) see

    Help | Cortex Logic Objects | For Network Nodes | Fan Control

    You could combine Humidity and pipe sensors using this Fan Control object.

    Viv.

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    Automated Home Legend chris_j_hunter's Avatar
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    the only non-invasive sensors we've seen are ultrasonic, and rather expensive ...

    but a clip-on temperature sensor placed close to the water outlet might work, even with insulated pipe runs (that's our hope, anyway) ....

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    Moderator Gumby's Avatar
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    Quote Originally Posted by simbarr1 View Post
    I seem to remember reading about pipe sensors on the forum before; can you expand a little on your setup? I had been wondering if this would be more accurate than humidity sensing because I wasn't sure how you would compensate for outside humidity. How long does it take the pipe to cool down after the shower stops? - if its too well insulated then might this be a problem? An alternative might be some sort of flow rate sensor but I haven't seen any that don't need to be plumbed in.
    I've got a clip-on thermistor sensor (Rapid Electronics) that monitors the temp of the hot feed to the mixer. Actually got others just logging CH pipes too. These feed into QAI.

    Using the shower gives very quick rise in temp, and since the pipe is uninsulated it also cools down quite quickly. So a reasonably proxy for shower occupancy/usage. See attachment for this morning's usage (two showers in quick succession). Note that you can set different thresholds and the "shower finished" threshold can actually be quite a lot higher than ambient to get a quick decisions - the boiler delivers water at about 55 whatever the flow rate, so if the pipe temp is 45 it means flow has stopped and it's cooling.

    Humidity can give a quick peak depending on location of the sensor, but the absolute value is a bit subject to what else is going on weatherwise, especially for turning off a humidity fan. Viv's new fan control object improves this significantly since it allows you to have a reference humidity level in a "dry" room that helps factor out the weather.

    Since you can now affect the lighting automation mode from other objects, you can trigger a macro to temporarily change the automation mode whilst shower is occupied and then return to normal afterwards.
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    Moderator Gumby's Avatar
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    PS: I'm not worried about the pipe being uninsulated - the run is about 2m total from boiler to mixer. Since showers occur once a day I don't think the heat loss is significant given the low volume of water compared to the volume heated for a shower, and even insulated the water would cool down before the next day's shower.
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