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Use MQTT WiFi relay to control 3.6kw storage heater?


(Ruraldev) #1

Could I use the MQTT WiFi relay to control power to a 3.6kw storage heater, I’m thinking of replacing a device I have which diverts excess power from my wind turbine to a storage heater (connected to power 24 hours a day).

I wasn’t sure if as it’s 16amp that using it for a 3.6kw heater would be pushing it too far.

Thanks in advance.

Gordon


(Robert Wall) #2

Is your heater 3.6 kW at 230 V or 240 V?

Depending on which it is, at maximum UK line voltage (254 V), it’s either very close to the rating or over it. It should be OK, but I think I would advise you to slave up and use it in the coil circuit of much beefier contactor. A 25 A one (with a 230 V coil) will cost about the same money as the WiFi relay, but there’s much less chance of having to replace it due to contact burn.


(Ruraldev) #3

I’ll check on the voltage but might be worth just taking the safer route.
Thanks for respsponding.
Gordon


(Moojuiceuk) #4

If it is a “dumb” storage heater with no electronics inside then I can’t see an issue- but I would aim for any power switching device to be higher rated than 16A, as you will want to have some margin and tollerance.

If the storage heater has inbuilt electronics, this could prove to be an issue. What is the model of the storage heater? (This is my line of work…)


(Ruraldev) #5

I’m not at the premises at the moment but I’m pretty sure it’s a Dimplex XLS probably actually 3.4kw


(Moojuiceuk) #6

Ahh right. If it is an XLS, then there are no “electronics” inside. Just a limit stat, safety cut-out and dual sensing room thermostat. If it is the 3.4kW model, bear in mind that a “full charge” is based on 7 hours @ 3.4kW = 23.8kWh of electricity (hence XLS24N). If you are going to really benefit, then your turbine needs to me producing a fairly significant kWh per day to make feeding into the heater worth the effort.

What sort of capacity does the turbine have and were you just looking to charge only when producing >3400 watts?


(Ruraldev) #7

It’s a 6kw turbine but what I am trying to solve is the current device uses excess power and works fine but when it’s very cold and calm the over ride only lasts for 2 hours so I was thinking of having the ability to use the excess power but if the temperature is below a certain level then it imports from the grid to charge.

Should add most of the day we use almost no power as it’s just a garage and office


(Moojuiceuk) #8

That’s certainly do-able. You might want to add in additional rules to cap the hours of charge taken from the grid when wind production is low, especially if on an Economy tariff. Last thing you want to be doing is accidentally charging when falling back over to peak-rate.

Disclaimer It goes without saying that any electrical works should be carried out by qualified personel and charging the heater from anything other than a traditional off-peak grid supply will void warranty etc etc). Be careful!


(Ruraldev) #9

It’s on peak rate all the time unfortunately but once it’s charged it switches off anyway.

It’s been on the diverter device since new and seems to work fine, appears to just use any power it can get access to without complaining.

Thanks for your help.

Big project this year is new garage with 120kw of PV, 6 X Tesla Powerwalls and 3 electric minibuses!


(Moojuiceuk) #10

Sounds like a right mission! Maybe you should document it on here, or YouTube?


(Ruraldev) #11

I manage a charity and we are just waiting for the final piece of the funding jigsaw, 80% chance it will go ahead and it’ll be well documented as it’s really a demonstration project.

When it kicks off I’ll post a link to the website for anyone interested in it.