7kw electric shower - 4mm2 too risky?

[Yonny24]

There is a way of detecting when the shower is switched on and then switching off large loads until the shower is turned off - a shower priority unit. This would work well if the shower and some of the ufh were supplied by the same LN pair. It would not matter that the ifh was off for a little while. Something like this:

Garo Priority Shower Board 6 Amp IP40 1 Row - https://www.meteorelectrical.com/distribution-control/consumer-units-accessories-1/garo-priority-shower-board-choose-priority.html

thanks was just editing my previous post to implement a smart switch of some kind so both can never be on at the same time! Good idea!
I'll look into this as I really don't want to have to pay for a new installation and monthly costs for extra power to the CU.

Would certainly want the UFH to switch off and not the shower if my wife is washing her hair!! lol

So this kind of unit would be installed in the main CU downstairs, one output feeding the UFH and the other the shower which would need to be cabled through to the upstairs CU?

 

[marconi]

I will wait to hear about the cost of upgrading the supply capacity to your home. It seems you are at that point now and would be useful should you wish to add ev car charger. Aircon etc in future.

The shower priority units contain a 40A rcbo ( rcd and Mcb combined) suitable for a shower so in terms of cost to you not much more and indeed might be less than buying the components separately..

Could use with 6mm2 cable. For 4 mm2 would need extra 32A mcb. Getting ahead of myself - sorry !

 

[Yonny24]

I will wait to hear about the cost of upgrading the supply capacity to your home.

The shower priority units contain a 40A rcbo ( rcd and Mcb combined) suitable for a shower so in terms of cost to you not much more and indeed might be less than buying the components separately .

I won't go ahead with increasing the costs of the monthly kwh - my other half does not want to spend any more money, especially during these hard times.

So some kind of smart switching device.

There is some talk here about using a combination of contactors that only allow one on at a time. How is this achieved?

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This smart shower unit is not available here and will be too expensive to send over with all the taxes and shipping etc

I will be able to program this through automation easily with the wifi switches I use anyway - shower contactor on -> UFH contactor off.

 

[marconi]

thanks was just editing my previous post to implement a smart switch of some kind so both can never be on at the same time! Good idea!
I'll look into this as I really don't want to have to pay for a new installation and monthly costs for extra power to the CU.

Would certainly want the UFH to switch off and not the shower if my wife is washing her hair!! lol

So this kind of unit would be installed in the main CU downstairs, one output feeding the UFH and the other the shower which would need to be cabled through to the upstairs CU?

Yes but that is my quick answer. Which is easiest panel to wire shower to ?

you have the idea now. Just need to study whether shower and ufh power supply sharing can be implemented only at c63 or if it also could be done at c40

 

[Yonny24]

Yes but that is my quick answer. Which is easiest panel to wire shower to ?

you have the idea now. Just need to study whether shower and ufh power supply sharing can be implemented only at c63 or if it also could be done at c40

ah my mistake - was thinking I had a C40 downstairs not a C63.
Much easier to wire it to the upper floor C40.

It will be fairly easier for me to program an automation to switch OFF the downstairs UFH if ON when the shower is turned ON through the contactor. Just a smart scene within the smart switches. Very easy.

Unless there is a physical way of doing this with contactors wired in a specific configuration.

 

[marconi]

I will work you up a scheme but that will be tomorrow.

Time for a glass of Spanish wine for me before doing a salad for when my wife returns home from outpatient appointment in very hot London 30C. I am sat in our aircon home at a nice 18C.

 

[Yonny24]

I will work you up a scheme but that will be tomorrow.

Time for a glass of Spanish wine for me before doing a salad for when my wife returns home from outpatient appointment in very hot London 30C. I am sat in our aircon home at a nice 18C.

Salud! I enjoy a nice merlot from local vineyards here in Uruguay.
Yes my daily meeting with my team in Lichfield today said it was quite warm and most wanted to go to the office where there is AC!
Here 30c would be pleasantly warm for a summer day.

 

[Yonny24]

The only RCBO ratings I have found here are 25a or 40a.
Only other option is an RCD and CB of 32A - 2 units.

 

[marconi]

Which make of home automation technology (hat) do you use in your home? I want to look up if there are any hat relays or contactors or sockets.

 

[Yonny24]

Which make of home automation technology (hat) do you use in your home? I want to look up if there are any hat relays or contactors or sockets.

I have a mix of Tuya and Sonoff switches. I do know TUYA make some RCD and CB with smart tech but they are way overpriced for me.

 

[marconi]

I have had a look at SONOFF products and thought about a scheme which senses the current drawn by the shower to turn off the ground floor UFH via the home automation network. I do not like it because it relies on wifi connectivity and a fast response by the hat network and logic. I envisage a short period because of data transmission delays when both the shower and the ground floor ufh could/would be on and exceeding the capacity of your circuit breakers and cabling albeit only briefly perhaps but I think maybe long enough for breakers to trip. And forgive me for saying this but we ie you would have to build it which I am not easy with. It is not tried and tested.

The tried and tested way is a shower priority unit made by a reputable company like GARO for many years and giving reliable safe service in the UK and I assume elsewhere too. The device would switch between the shower and the UFH on the same floor as the shower via the C40. Thus it would be easy to install because all the connections are at the upper board's location.

Could you take a look at this example and if you read to the end you will see that one version of the priority board has a timer function which may be useful to you to stop overly long showers.

https://www.garo.co.uk/docs/2020/info/shower boards info sheet.pdf

 

[Yonny24]

I have had a look at SONOFF products and thought about a scheme which senses the current drawn by the shower to turn off the ground floor UFH via the home automation network. I do not like it because it relies on wifi connectivity and a fast response by the hat network and logic. I envisage a short period because of data transmission delays when both the shower and the ground floor ufh could/would be on and exceeding the capacity of your circuit breakers and cabling albeit only briefly perhaps but I think maybe long enough for breakers to trip. And forgive me for saying this but we ie you would have to build it which I am not easy with. It is not tried and tested.

The tried and tested way is a shower priority unit made by a reputable company like GARO for many years and giving reliable safe service in the UK and I assume elsewhere too. The device would switch between the shower and the UFH on the same floor as the shower via the C40. Thus it would be easy to install because all the connections are at the upper board's location.

Could you take a look at this example and if you read to the end you will see that one version of the priority board has a timer function which may be useful to you to stop overly long showers.

https://www.garo.co.uk/docs/2020/info/shower boards info sheet.pdf

Hi Marconi,

I have all of my sonoff devices on lan mode also using a customized integration - GitHub - AlexxIT/SonoffLAN: Control Sonoff Devices with eWeLink (original) firmware over LAN and/or Cloud from Home Assistant - https://github.com/AlexxIT/SonoffLAN, also some flashed with tasmota using mqtt messaging protocol which is highly reliable and almost instant - far better than wifi and the stock firmware by sonoff.
Many of my automations are also done with node-red.
Mqtt messaging between the devices would not be an issue or even the sonofflan imo.

Relying on the sonoff/ewelink cloud would obviously not be a good idea - I have nearly all of my devices controlled locally.

Thanks

 

[marconi]

Most if not all of what you have written is not at all familiar to me. If we were dealing with low wattage stuff I would not be cautious. It is because we are dealing with several kW/ tens of Amps that I am acting trepidatiously. Perhaps you could give me your critique on the priority shower unit?

By nature I like simplicity albeit my earlier working life was spent working with highly complex equipment which was necessarily so to do what what it did!

 

[Yonny24]

Most if not all of what you have written is not at all familiar to me. If we were dealing with low wattage stuff I would not be cautious. It is because we are dealing with several kW/ tens of Amps that I am acting trepidatiously. Perhaps you could give me your critique on the priority shower unit?

By nature I like simplicity albeit my earlier working life was spent working with highly complex equipment which was necessarily so to do what what it did!

The model

GM6-PS​

certainly sounds like the ideal solution but unfortunately, these are not available here and haven't located any in USA.

I work in IT and am confident a failsafe automation can be implemented here to switch off the UFH if the shower contactor is to be switched on. Probably in nodered - it will check if the UFH is off and will never allow the shower to be turned on if the UFH is not off.

Thanks

 

[marconi]

Yes, we would need a tellback that the ufh is off before allowing the shower power. I will send you the idea with some sonoff components and a couple of current sensors for us to discuss further. If you bought the components we could trial it before installing the shower to make sure it works and safely.