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Adding geyser control to smart home - wiring question


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Hey Guys

Overview

I've wanted to add geyser control to my smart home (Home Assistant) for some time, my DB is full so no space there. My original idea was to run a 12V DC Sonoff which would then control a solid state relay to switch the geysers on and off (I don't want to run this type of current through a Sonoff), I received the SSR's and they were faulty on arrival so I shelved the idea, this was several months ago. I then came across a post on the forum where someone used a 40A 220V relay also controlled by a Sonoff so I thought this was probably a better way of doing it as I wouldn't then need a 12V transformer to power the Sonoff I could just run everything off AC which is easier.

Question

Running it this way the relay which is rated at 40A will comfortably handle the load, my question is this, do I need to run a separate AC plug point for the Sonoff (which will be a pain because its outside) or can I tap off from the AC after the isolator for the Sonoff without the current going through the Sonoff as well? I suspect this is OK and that the high current will only pass through the external relay. I've attached a rough sketch as reference.

My aim is to shift my geyser from coming on in the morning at like 6am when everyone gets up and then because my batteries are low and there is no solar power it draws this off mains so I want to rather switch the geysers on at 10am and 11:30am so that it pulls this from the inverter and not Eskom.

 

Thanks. 

Geyser Control sketch.jpg

Geyser Control.png

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2 hours ago, Jatho said:

Running it this way the relay which is rated at 40A will comfortably handle the load, my question is this, do I need to run a separate AC plug point for the Sonoff

90574F38-DAC5-4C20-B00D-60AEE5851B19.thumb.jpeg.ca01bb9bf959a92c77019de289d177a1.jpegYou can use the supply for geyser to also control the sonoff, but I would recommend installing a small 4A fuse or 4A circuit breaker in the event of a sonoff failure. I fitted a 10A control protection (see left) slightly big but better than the geyser 20A, ignore my illegal plug tapped on left, it is my attic light/geyser circuit🤫 Hope this help. 

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14 hours ago, Gerrie said:

I would recommend installing a small 4A fuse or 4A circuit breaker in the event of a sonoff failure. I fitted a 10A control protection (see left) slightly big but better than the geyser 20A

Hi @Gerrie

 

thanks very much for the feedback, the Sonoff Pow R2 is rated at 16A should I not then rather fit a 10A circuit breaker instead of 4A? I'm concerned it will trip often if its too low and will be a pain to have to open the box all the time to flip it back up not to mention the cold shower or am I heading off in the wrong direction?

Hope I can squeeze that all into my box.

 

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33 minutes ago, Jatho said:

rather fit a 10A circuit breaker instead of 4A

The rating is for the Sonof's relay. Because the load goes through the separate relay that the Sonof's relay now trigger, the power usage for the Sonof is now very small (it would be in the milliAmps) so even the 4A is an overkill.

Also the Sonof is rated at 16A, but there is many occurrences where it goes up in flames if the current through the Sonof is that high. This is the reason for this hole setup with a separate relay.

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1 minute ago, Louisvdw said:

The rating is for the Sonof's relay. Because the load goes through the separate relay that the Sonof's relay now trigger, the power usage for the Sonof is now very small (it would be in the milliAmps) so even the 4A is an overkill.

Also the Sonof is rated at 16A, but there is many occurrences where it goes up in flames if the current through the Sonof is that high. This is the reason for this hole setup with a separate relay.

I agree. There’s no point using a sonoff pow if you are not sending the current through the POW, which in the case of a geyser, you shouldn’t. 
 

It may work for a day, a week, a month, or even a year, but there’s numerous cases of it failing so in My opinion it’s not worth the risk. 
 

you can use the sonoff basic of you have a 220V cool or even the low power devices if you are switching a low voltage 12V relay coil. 

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38 minutes ago, Jatho said:

I'm concerned it will trip often if its too low and will be a pain to have to open the box all the time to flip it back up

Hi Jatho, The small 4A cb is only to protect your sonoff control part, that will only draw milli amps and should never trip, it’s purely to protect the coil you energise and the thin control wire. Because if you have a fault on the sonoff control side or coil you can have a fire if there is only the 20A circuit breaker rated for 2.5mm wire from geyser but sonoff control might be 1mm2 wire like I done useing the pink 1mm2 wire you need to protect that thin wire aswell.

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I used a Sonoff TH16 coupled with a DS18B20 sensor and a 40a solid state relay.  The unit is installed in the roof next to my geyser.  I have removed the mechanical thermostat and installed the DS18B20 in the thermostat hole.

The Sonoff TH16 is flashed with Tasmota software, this allows static rules to be setup.  With the static rules I can ensure that the Sonoff will switch off under hard conditions, these include:

  • Should the unit loose wifi connection
  • Should the unit loose connection with the temperature unit
  • Should the temperature exceed 60 degrees

The Sonoff is connected to my Home Assitant setup and integrated into the Thermostat integration and coupled with timers.  See snapshots below:

image.thumb.png.f022a238a13fd6a5d1d15892424f63e3.png

Geyser.jpg

Sonoff Geyser.jpg

Edited by Bloubul7
Added Schematic
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11 minutes ago, Bloubul7 said:

I used a Sonoff TH16 coupled with a DS18B20 sensor and a 40a solid state relay.  The unit is installed in the roof next to my geyser.  I have removed the mechanical thermostat and installed the DS18B20 in the thermostat hole.

The Sonoff TH16 is flashed with Tasmota software, this allows static rules to be setup.  With the static rules I can ensure that the Sonoff will switch off under hard conditions, these include:

  • Should the unit loose wifi connection
  • Should the unit loose connection with the temperature unit
  • Should the temperature exceed 60 degrees

The Sonoff is connected to my Home Assitant setup and integrated into the Thermostat integration and coupled with timers.  See snapshots below:

 

 

Thanks @Bloubul7  I did think of doing it based on temp (and time) but to be honest if I stagger the geysers coming on I've got plenty of capacity to power them and in my setup I think temperature control will have only marginal savings so just not worth the extra effort and cost for me, my main goal is just to ensure the geysers aren't pulling max draw at 6:30am and smoking through Eskom power (and eating into my battery capacity in case we get load shedding).  

I have a lot of automation's based on temperature.

 

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No hassles.  I went for the addition of the temperature as it helps with reducing my costs. 

With the temperature added I have automated the main geyser reheat early mornings only if there are sufficient battery SoC remaining or if it drops below 35 degrees.  Helps to keep the long haired creatures happy.  The geyser serving the guest bathrooms will only fully heat if I have guests, when I don't have Guests then it will only heat 50 degrees and only once a day.

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1 hour ago, Bloubul7 said:

I used a Sonoff TH16 coupled with a DS18B20 sensor and a 40a solid state relay.  The unit is installed in the roof next to my geyser.  I have removed the mechanical thermostat and installed the DS18B20 in the thermostat hole.

The Sonoff TH16 is flashed with Tasmota software, this allows static rules to be setup.  With the static rules I can ensure that the Sonoff will switch off under hard conditions, these include:

  • Should the unit loose wifi connection
  • Should the unit loose connection with the temperature unit
  • Should the temperature exceed 60 degrees

I am still toying with this same idea but have one concern when replacing the thermostat with just the DS18B20 - you lose the physical 90 degree cut out of the thermostat, so if the sonoff fails closed there is some risk for a dry boiled geyser. So my current thinking for a bit of redundancy is to potentially use two sonoffs (either one physically switching the other, or as a double pole switch (one having Live, the other Neutral to the contactor/SSR). Also, in terms of operating environment, the sonoffs are rated up to 40 degree C - hot summer day easily make that in my roof space, so will likely mount just below ceiling somewhere close to the geyser. Probably overkill but Murphy knows exactly where I live..

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On 2020/09/10 at 5:15 PM, Jatho said:

 pretty tight fit in the box 🙃

Wonder how warm/hot that relay gets when powering the geyser? Bit bigger box could maybe be safer? Pic is obviously not final install position but if tempted to just toss the box ... (sounds wrong!)... next to the geyser - the closet sparky in me thinks MCB's are generally not rated/approved for any position other than vertical... 

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The key thing with geysers is to be sure they cannot overheat and create super-heated steam and then explode.

The Two safety's to prevent this are usually the Thermostat (mechanical type cutout) that wont allow the geyser to over heat, and the Pressure /  temperature valve on the geyser outlet.  With the geyser wise units they also have a mechanical cutout safety on the electronic temp sensor, as well as built inelectronic safety that will stop powering the element if there is no increase in water temp, within 1-2 hours. This prevents a faulty temp sensor / geyser overheat, and also stops one from burning out the element if the geyser runs dry.

 

check the damage a super heated geyser can do in the articles below.

 

https://kemptonexpress.co.za/95113/geyser-explosion-survivor-has-lost-everything/

http://www.durban.gov.za/City_Services/water_sanitation/Geyser_Warning/Pages/Geyser_Warning_Installation.aspx

https://kemptonexpress.co.za/94972/geyser-flies-through-the-roof-at-rhodesfield-flats/

 

Be Safe :)

 

 

 

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On 2020/09/12 at 10:08 AM, introverter said:

Wonder how warm/hot that relay gets when powering the geyser? Bit bigger box could maybe be safer? Pic is obviously not final install position but if tempted to just toss the box ... (sounds wrong!)... next to the geyser - the closet sparky in me thinks MCB's are generally not rated/approved for any position other than vertical... 

I cant imagine that it would get very hot, its rated at 40A so its running well below its threshold, I'll let it run for an hour today and then go measure the temp with a probe, I have spare temperature sensors so if I feel ambitious I could wire one up to the GPIO pins on the Sonoff and monitor the temperature inside the box.

This geyser is installed outdoors so it needs to be in an IP6X rated enclosure. 

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21 minutes ago, Barryv said:

very awesome. 

I just worried of the wire you'll use.

are you using 2.5 mm wire from the relay to the geyser?

Hi, Yes I'm using the exact same cable (gauge etc) as would be used from a DB board to Geyser between the relay and geyser, cable to and from the Sonoff is regular stranded electrical cable. 

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3 hours ago, Jatho said:

I cant imagine that it would get very hot, its rated at 40A so its running well below its threshold, I'll let it run for an hour today and then go measure the temp with a probe, 

Maybe not a bad idea. Like I said, Murphy knows where I live, so I err on the side of caution..... same reason a MTB with only half a fork makes me nervous 😉

the sonoff people also try quite hard with the basic R3 to ensure that you must be really motivated to tinker with it with that double decker PCB setup..

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8 minutes ago, Jatho said:

Hi, Yes I'm using the exact same cable (gauge etc) as would be used from a DB board to Geyser between the relay and geyser, cable to and from the Sonoff is regular stranded electrical cable. 

Nice, 

Good work!

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It is looking good well done! Here is some additional points to consider. 

  1. Ensure that the geyser will not switch on while you are on battery power unless it is not a problem and you battery bank can handle it. One way of handling it is to ensure that the contact is powered from the grid feed. Should the grid fail the contact can not close. 
  2. Have some way of monitoring your battery watts should the draw be lower than ,for example , -2000 w let it switch of the geyser. 
  3. Have a hard timer in the loop so that the geyser can only be switch automatically during day time unless you do it manually.

The assumption is made that you have a non grid tie inverter and that you need to switch between grid and solar if you have grid tie then 2 and 3 is not that important but I will look at 1 for protection of the batteries. 

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14 minutes ago, PaulF007 said:

It is looking good well done! Here is some additional points to consider. 

  1. Ensure that the geyser will not switch on while you are on battery power unless it is not a problem and you battery bank can handle it. One way of handling it is to ensure that the contact is powered from the grid feed. Should the grid fail the contact can not close. 
  2. Have some way of monitoring your battery watts should the draw be lower than ,for example , -2000 w let it switch of the geyser. 
  3. Have a hard timer in the loop so that the geyser can only be switch automatically during day time unless you do it manually.

The assumption is made that you have a non grid tie inverter and that you need to switch between grid and solar if you have grid tie then 2 and 3 is not that important but I will look at 1 for protection of the batteries. 

Thanks for the pointers, My geysers and oven are connected through a Carlo Gavazzi energy meter so when mains fails power is cut to these devices anyway, I also have other automation's that detect mains failure and cut power to things like my pool pump, toasters, kettles etc... I've got it pretty streamlined to the point where if we have load shedding during the day my batteries usually charge up to 100% because the load is that low (around 260w) I actually end up manually just switching the pool back on, I also only start things like the pool pump if mains power is available, if it isn't it waits until it is.

 

 

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Hi all, waking up this thread again, as I intend to do something similar, and would appreciate some advice/input.

Firstly, I would like to store as much energy as possible in the geyser, so the first step would be to install a tempering valve, so that I can store much hotter water in the geyser, without a scalding risk from the hot taps.  But how hot can I safely make the geyser?  I can find a lot of info on the safe minimum storage temperatures, and safe maximum outlet temperatures, but virtually nothing on safe maximum storage temperatures.  Any ideas?

Secondly, I need to add a temperature probe to the geyser.  I don't really like the idea of removing the safety of a mechanical thermostat, so I am considering using a geyserwise thermostat. Specs say it has a 90°C mechanical cut-out, and I have found one internet posting which seems to say that the included temperature probe is a DS18B20, which should be perfect.  Has anyone used one of these thermostats in a DIY project and/or can confirm that it really is a DS18B20 probe?

Thanks,

Justin

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