wiring in 6kW electric boiler

[Tom]

My electrician has connected a 6kW electric boiler for us so we can start to get some heat through the screed. He has put in a temporary consumer unit, and then a 10mm twin and earth cable to the boiler - however this goes via a fused 13A socket. We have yet to fire up the boiler as we are missing a part, naturally, but I'm wondering if the 13A fuse is man for the job - if I = W/V then the max current draw at full throttle (6kW) would be 25 amps! Am I wrong?

[joe90]

8 minutes ago, Tom said:

but I'm wondering if the 13A fuse is man for the job

NO ITS NOT, is he a proper electrician??

[ProDave]

Show us a picture of what he has done.  Some electric boilers want 2 feeds, a high rating one for the heating elements and a lower one for the controls.

[Tom]

Haven't got as picture unfortunately and am at work now, but it's essentially just the 10mm twin/earth going from the consumer unit in to the 13A fused socket (with an on/off switch) then a slightly thinner cable going to the boiler. 

Def sure it only needs one power in. 

Does it definitely need a fuse? Would it not be protected by the RCD in the consumer unit?

[joe90]

23 minutes ago, ProDave said:

Show us a picture of what he has done.  Some electric boilers want 2 feeds, a high rating one for the heating elements and a lower one for the controls.

But the lower one would not need a 10mm cable surely?

[ProDave]

IF there are 2 cables one would need to be large for the heaters.  Post some pictures when you are home.

[Tom]

OK, just spoke to the electrician. Seems like his worker used the 13A fused switch just as a temporary thing to get power to it to test the boiler, and was waiting on a 50A double pole switch which he didn't receive in time. So just left it like that. Good of him to tell me. It's on an RCBO in the consumer unit, so he says I don't need the fuse and just a switch will suffice. Though TBH why he bothered with a switch anyway is beyond me. It's only a few meters away from the consumer unit and can easily be isolated from there.

Anyway, is he right saying I don't need the fuse?

[ProDave]

It's good practice to have an obvious local switch to isolate it for maintenance.

 

This will be on it's own circuit so the rcbo is all the "fusing" in needs.

 

Don't try turning it on until he has fitted the correct switch.

[joe90]

6 minutes ago, ProDave said:

It's good practice to have an obvious local switch to isolate it for maintenance.

 

This will be on it's own circuit so the rcbo is all the "fusing" in needs.

Same as a cooker switch 👍

[Tom]

9 minutes ago, ProDave said:

Don't try turning it on until he has fitted the correct switch.

 

So definitely not twist the wires together and wrap with electrical tape?

[Tom]

30 minutes ago, joe90 said:

Same as a cooker switch 👍

Ah, of course

[Tom]

6 minutes ago, Tom said:

 

So definitely not twist the wires together and wrap with electrical tape?

Will get one of these tomorrow and do it myself: https://www.toolstation.com/bg-45a-low-profile-dp-switch/p51324

 

I wonder how much off the £800 I was charged for this the electrician will give me?

[ProDave]

Please tell me the electrician did not charge you £800 just to connect the electric boiler?

[Tom]

Hmmm, also included pulling through about 15m of armoured cable and connecting to our existing supply.

Still seemed a bit steep tbh, especially as they haven't actually finished the job and then effed off for Christmas. Though TBH I'm fed up with the whole process now, just seem to be surrounded the whole time by f@ckwits and just want it all finished. To top it all I am paying 12.5% to a project manager who just seems to be a glorified email/WhatsApp forwarding service.

[Tom]

So, this is the wiring. I've put in the 45A switch myself. All fired up and seems to be working.

[SteamyTea]

1 minute ago, Tom said:

All fired up and seems to be working.

Did you do an earth continuity check?

[Tom]

At full flow the inbuilt pump goes at about 14l/min, which means white a low flow through each of the 11 loops (barely registering on the flow meters). Should I wire up the manifold pump? Is it a matter of just putting a 13A plug on it?

[Tom]

Just now, SteamyTea said:

Did you do an earth continuity check?

Ummmm....

Well, I wired the earth's in to the socket!

[JohnMo]

The pump is there to pull flow through the mixer, the boiler pump will not do that.

[Tom]

All seems to be working without it, just only at 14l/min

[JohnMo]

Why ask the question if it's all ok

[Tom]

Um, because it's only pumping at 14l/min, as I said!

[Tom]

The boiler is set at 25 degrees, so I could increase the temperature, wire up the manifold pump and rely on the mixer to set the temp?

[Temp]

The manifold loop pump is needed to circulate water around the floor loops.

 

I suspect without it the return temperature to the boiler might be too high causing it to switch on and off so not delivering 6kW continuously. 

 

The pump will eventually be controlled by the room stats and wiring centre which will also open the appropriate actuators. If you want to run the pump without control I would remove the actuator heads so the loops are all on. 

 

Turn the  mixer down to control the flow temperature. Turn it up gradually to dry the screed. Don't rush it or you will get cracks. Might get them anyway. 

Edited December 24, 2023 by Temp

[Tom]

Thanks @Temp, is it just a matter of putting a 13A plug on the pump wires and plugging in? Happy Christmas by the way!