12 KW Electric Boiler

[Steve 82]

The plumber at my company went ahead and fitted a 12kw electric boiler without first checking the main supply to the flat. Now I'm guessing if its only a 60a main fuse with 4 ring circuits and 1 lighting circuit, the probability is that it will blow the main fuse at 60a. I couldn't locate or get access to the supply yesterday.

Ohms law says that the boiler is capable of drawing 52a. I was thinking of putting it on a 50a circuit with a short 10mm twin and earth run of about 1 meter.

The old style mk fuseboard does have a 30ma main rcd switch, so the circuit would have rcd protection.

My other dilemma is can i still get the old style 50a mk ln5932 fuse???? Someone told me the new mks should fit ok.

I'm guessing that they may have to change to a 9kw boiler if the supply isn't 100amps???

Cheers

 

[kingeri]

Are there any other high-draw appliances in the property? (Stove, shower?)

 

[Plonker 3]

Instantaneous water heater so no diversity allowed, my calculations say that's 52 amps, so you would need a 63 amp MCB, I take it there isn't any gas or oil on the property then?

Meaning there could be a electric oven and also a shower. Sounds like you either need a smaller boiler or the DNO to put a bigger supply in.

 

[Steve 82]

Nope just 5 rings. My wholesaler just informed me mk didnt do a 50a for that board also

 

[Plonker 3]

I would be tempted to monitor the power consumption for a week and see what power they use before connecting the new load to the supply.

Regarding the lack of MCB availability you will have to install an new DB via Henley blocks then by the sounds of it.

 

[Darkwood]

Why such a large boiler?, if its new it will be well insulated is it possible to heat the tank up in off peak time so at most during the day it will just be topping heat up for a short period time.
Why has he chosen such a large tank off the electric, do you not have Gas in the premises?
How many staff do you have, ive just wired up a 6kw for the works toilets of 25 employees and it is doing a good job and keeps up with demand of them all washing off at breaks etc.

 

[Engineer54]

The plumber at my company went ahead and fitted a 12kw electric boiler without first checking the main supply to the flat. Now I'm guessing if its only a 60a main fuse with 4 ring circuits and 1 lighting circuit, the probability is that it will blow the main fuse at 60a. I couldn't locate or get access to the supply yesterday.

Ohms law says that the boiler is capable of drawing 52a. I was thinking of putting it on a 50a circuit with a short 10mm twin and earth run of about 1 meter.

The old style mk fuseboard does have a 30ma main rcd switch, so the circuit would have rcd protection.

My other dilemma is can i still get the old style 50a mk ln5932 fuse???? Someone told me the new mks should fit ok.

I'm guessing that they may have to change to a 9kw boiler if the supply isn't 100amps???

Cheers

Don't blame the Plumber, the fault is with the guy who ordered the supply and fitting of this 12KW boiler!!

You say your company and in the same sentence, your saying this is a flat, can you explain the situation your dealing with here??

 

[Guest55]

I would be tempted to monitor the power consumption for a week and see what power they use before connecting the new load to the supply.......

And whos paying for this service ?
Not needed anyway , simple diversity figures are available in the OSG.

To the OP , youre approaching this completely the wrong way , with a whopping extra 50 odd amp load you need to first assess the DNO's supply capability before worring about whether you can get mcb's or not.
If they say no to a 80 / 100 amp fuse upgrade then the boilers coming out.

 

[Darkwood]

And whos paying for this service ?
Not needed anyway , simple diversity figures are available in the OSG.

To the OP , youre approaching this completely the wrong way , with a whopping extra 50 odd amp load you need to first assess the DNO's supply capability before worring about whether you can get mcb's or not.
If they say no to a 80 / 100 amp fuse upgrade then the boilers coming out.

Bit extreme ripping it out as other options exist, economy 7, or reduction in element size, if multi-element then simply leaving 1 or 2 unconnected all will suffice with little cost if as i assume elements are standard thread size then its possible to replace them with lower kw rating.

 

[jumpin jax]

Sometimes these boilers are rated to include a back up immersion element which is rarely turned on so it may only in fact be a 9kw with a 3kw backup. As sometimes ovens are rated for every element being on. What do the manufacturers intructions say the supply needs to be?

 

[londonlec]

I wired up 2x 6KW Amptec boilers last year and the 60A aint blown yet

(no other large loads in the flat)

 

[Steve 82]

i found out the flat has a 100a supply today so that shouldn't be a problem. Will need to put a new dual rcd fusboard in though as i can't get a 50a for that old board.

it says 10-12kw on the boiler

a 50a breaker run in 10mm t+e should be ok shouldn't it, a 63a would be a bit extreme wouldn't it???

 

[Moses]

i found out the flat has a 100a supply today so that shouldn't be a problem. Will need to put a new dual rcd fusboard in though as i can't get a 50a for that old board.

it says 10-12kw on the boiler

a 50a breaker run in 10mm t+e should be ok shouldn't it, a 63a would be a bit extreme wouldn't it???

A 50A on a 10mm will be fine mate as long as all cable derating are fine.

 

[Plonker 3]

And whos paying for this service ?
Not needed anyway , simple diversity figures are available in the OSG.

All you have done is echo my comments previous. Does it matter who is paying it was a suggestion, nothing more.


As I had said in a previous post no diversity allowed for instantaneous water heaters. Unless the regs have changed since I last looked at them.

 

[Richard]

Hiya,

Fitted one last week. The trouble I found was getting hold of 10mm HR flex. Increadably expensive I think, and even that got really warm when the boiler was left running flat out (to dry the property). Also, we ended up changing the DP switch as that got really warm too. We used a Gewiss IP56 (because it looked nice) 4 way enclosure with a 100 amp main switch, which personally, I would recommend if you can.

Rich