I found a 12 amp relay, would  a Sonoff Basic hooked to the 12 amp relay be ok for a 2 kW geyser, ie 9 amps.

1 hour ago, Tariq said:

I found a 12 amp relay, would  a Sonoff Basic hooked to the 12 amp relay be ok for a 2 kW geyser, ie 9 amps.

It will work, one thing to keep in mind is every time it switches on their is a small spark that switching spark is a big contributor to what eventually destroy’s the contact, the bigger that contact the longer it normally last. I would rather install a relay with at least double the load current rating to get a longer life out of the relay.

If you have a look at the Amp rating of your Geyser's Circuit Breaker in the db you'll see it's at least 20 Amp, if not 30 Amp so a Power Relay like this, switched on/off by the Sonoff BASICR3 for instance (using 220V to drive the VCoil,  is, I would suggest a minimum requirement.

Although I'd prefer a 3P Contactor to switch Live and Neutral.

You can look at the CBI Astute wifi switches. Rated for 30A Resistive and they have power monitoring built in. And if you really brave, I made a tutorial to make it work with Tasmota (albeit a little involved). They R350'ish at Builders (stock is limited) or R550 at LiteGlow.

Hi,

 

I'm late to this thread but with the same ambition - which is to be able to manage when my geyser runs via software control.

I have any number of Sonoff smart switches - my thought was to use that to switch the coil side of a contactor and actually switch the geyser with the contactor.

Am I supposed to switch both live and neutral - there is already a 2 pole isolator switch.

The other part of this is to be able to measure the water temperature in the geyser.  What options to do that?  Again - easy to hook up a probe and get a reading back - but how to get the probe into (or near enough) the water?

 

 

4 hours ago, Elbow said:

Hi,

The other part of this is to be able to measure the water temperature in the geyser.  What options to do that?  Again - easy to hook up a probe and get a reading back - but how to get the probe into (or near enough) the water?

If you replace the thermostatic switch with a contactor you can insert the sonoff temp probe into it's place (someone else mentioned they done it that way).

If you keep the thermostatic switch you can stick it to the plate on the side. I have measured other stuff this way. Removed the cover of temp probe (depending on what probe you have) and then glue it to the side of the removable plate. Tape some insulation over the probe to ensure a more accurate reading.

I still need to do this with mine at some point. As it is I want to change the 3kW element for a 2kW one.

I'm playing catch up with all you clever folk. A question I can't seem to get clarity on, what is the difference between a contactor and a relay?

3 hours ago, Speedster said:

I'm playing catch up with all you clever folk. A question I can't seem to get clarity on, what is the difference between a contactor and a relay?

Good question! A contactor is a large relay normally with 4 contacts and is used to switch motors, heaters or any heavy current device. To mount usually clips onto a Din rail.

A relay is normally smaller and is often installed directly onto a PCB. It has fewer contacts but will have NC and NO as standard..

On 2019/07/20 at 8:50 AM, Ernie said:

I'm sure this has been covered somewhere but I can't find it. Is it safe to put a 100L geyser with a 2kW element on a 16A Sonoff switch? What would the surge power be for this element?

Its simple P = I x E

Power = Current x Voltage or
2000  =    ?         X 240

           =   8.3 Amp and always allow for 20% extra as power can have a high surge of 15% and then 5% variance on equipment.  20% rule of thumb make it safe and working well.

 

57 minutes ago, Richard Mackay said:

Good question! A contactor is a large relay normally with 4 contacts and is used to switch motors, heaters or any heavy current device. To mount usually clips onto a Din rail.

A relay is normally smaller and is often installed directly onto a PCB. It has fewer contacts but will have NC and NO as standard..

In the industry a contactor is known more for heavy current. 100Amps  normally ins switch gear etc... heavy gear

A relay is 15amps and smaller and most often used in electronics or where a small switch used to switch egg a geyser.

And for your car starter its called a solenoid referring to the electrical device generating the flux and closing the contact.  Cars use anything from 600 - 3000 amps in +/- 20  - 50 mS to start turning the engine

The workings are the same for all 3. The load the difference  In a "switch" yard a relay of 48V switched a contactor of 11KV 1000Amps.....

I currently use the CBI Astute which can do 30A for geyser type loads. So far it works fine on a 4kW and 3kW geyser. Going to look at replacing the elements with smaller ones.

This makes sense ... copied and pasted.

 

Contactors are typically built for and used in 3-phase applications where a relay is more commonly used in single phase applications. A contactor joins 2 poles together, without a common circuit between them, while a relay has a common contact that connects to a neutral position. Additionally, contactors are commonly rated for up to 1000V, while relays are usually rated to only 250V.

On 2020/11/14 at 2:52 PM, gbyleveldt said:

You can look at the CBI Astute wifi switches. Rated for 30A Resistive and they have power monitoring built in. And if you really brave, I made a tutorial to make it work with Tasmota (albeit a little involved). They R350'ish at Builders (stock is limited) or R550 at LiteGlow.

Please share the link to your tutorial. 

Edited March 7, 20215 yr by Tim003

I suppose I've just been lucky then? 

I have a 3kw 150L geyser connected in line, running now for over 2 years! 

I do however think I read somewhere there are newer Pow R2 and older ones... And that the older ones perform better. 

Good day everyone 

I'm a Newbie here, I've noticed that some users use the sonoff th16 with a relay/contactor. Just some advice the neutral of the sonoff in and out is one connection and not switched by the sonoff device. There's no need to use two relays or switching contacts. Just connect the neutral in of the sonoff th16 to the same connector point of the geyser neutral main supply in and neutral of the element. Only the live should run through the sonoff and relay/contactor there's no need to run the neutral through a relay or contactor. 

Edited September 1, 20214 yr by Louwrens Coetzee
More information

I have seen same images on this thread  of some  ungracefull  failure of sonoff devices.  While I am not squeaky clean myself when it comes to the rigour required for electrical safety and protection , I can see some serious harm and fire hazard this little device can cause.

I get the feeling that we tend to rely on the db circuit breaker. In reality the CB is only matched to the building wire size, and offers protection to the wire itself not burning or catching fire. 

 

The consumer load must always look after itself in this regards and in the case of electronics , suitable faster blower fuses needs to be introduced. That terminal block that sonoff employes is bad bad news, causes dry joints and subsequently cause of burn.  The relay contacts also will not be protected by CB , as it is substantially lower rated than say the 35a of the CB. If it is a must to use the sonoff, then those clipon terminals must be somehow replaced with screens and a load matching fuse of 16a be introduced.

 

Just my 2 cents

On 2021/07/10 at 2:23 PM, Atmosphere said:

I suppose I've just been lucky then? 

I have a 3kw 150L geyser connected in line, running now for over 2 years! 

I do however think I read somewhere there are newer Pow R2 and older ones... And that the older ones perform better. 

Exact same experience as mine. Have a Gen1 POW Sonoff running for well over 2 years on my geyser with a 3kW element. Zero issues.

Edited September 2, 20214 yr by JoeyhZA

14 hours ago, Louwrens Coetzee said:

Only the live should run through the sonoff and relay/contactor there's no need to run the neutral through a relay or contactor. 

On my own geysers I prefer to switch both live and neutral through a double pole relay rated 25A, this relay is controlled by a Sonoff, the 25A relay takes the geyser load of about 9A while the Sonoff load is only the relay coil of about 20mA. In this case the Sonoff should last many years because it’s just for control and not power loads. Using a double pole contact to also switch neutral will make fault finding easier should their be a earth to neutral fault on the geyser element. If you don’t have a double pole switch you might have difficulty resetting the earth leakage on a neutral geyser faults. Just my thought on geyser control.

8 hours ago, JoeyhZA said:

Exact same experience as mine. Have a Gen1 POW Sonoff running for well over 2 years on my geyser with a 3kW element. Zero issues.

Also have a POW2 sonoff running a 3kW element.  Burnt the previous one and learned why they burn.  Fixed my mistakes and the new one is working fine. 

But there are better cheaper equipment now for this purpose.

I use these 72A Ewelink Breakers that are Sonoff compatible and run 3kw load through them without any issues.

They also measure the current and you can set min/max current, power and voltage cutouts. 

They integrate with Home Assistant using the Sonoff Lan plugin without any issues.

They are not flashable with Tasmota as far as I am aware.

You can buy them either at Banggood Link or locally from the Robofactory Link

 

9 hours ago, Gerrie said:

On my own geysers I prefer to switch both live and neutral through a double pole relay rated 25A, this relay is controlled by a Sonoff, the 25A relay takes the geyser load of about 9A while the Sonoff load is only the relay coil of about 20mA. In this case the Sonoff should last many years because it’s just for control and not power loads. Using a double pole contact to also switch neutral will make fault finding easier should their be a earth to neutral fault on the geyser element. If you don’t have a double pole switch you might have difficulty resetting the earth leakage on a neutral geyser faults. Just my thought on geyser control.

There is a double pole version of the ewelink breaker as well 

 

I see that they are also selling on Bidorbuy at pretty good prices. 

Me, myself and my shadow will not draw more than 4A long periods or 6A short term on the small terminals of the older Sonoffs.

CBI also have a pretty good smart isolator switch that will replace the one you have to have by law on your geyser.

Measures your power consumption runs on the Tuya platform so will integrate into Home Assistant etc.

https://www.builders.co.za/Electrical/Plugs%2C-Sockets-%26-Switches/Smart-Electrical/CBI-ASTUTE-SMART-ISOLATOR/p/000000000000751913