lights dim when ch boiler starts up

[runci21]

just had a 12 kw aztec electric boiler fitted today and when it kicks in the lights dim and when it cuts out lights get brighter again .
do i need a bigger incoming supply/meter/fuseboard ??????

 

[davy_owen_88]

A bigger supply cable is most probably needed. Did an electrician fit it for you? Did he not check the tails/service fuse and offer you any advice?

 

[runci21]

yes qualified heating engineers fitted system , main fuse was 60A he upgraded to 80A lights used to dip slightly before but worse with the higher load

 

[davy_owen_88]

Heating engineers upgraded your service fuse?

 

[securespark]

 

[runci21]

getting scottish power out to do a load test ,might need a 3 phase meter

 

[festa]

HMMM ....
Runci21,is your electricity supplied via a T.T,(overhead mains cables coming into your property)?

 

[runci21]

yes it is , its an old property on a farm

 

[festa]

After chatting to a friend who works for my local DNO, (united utilities), he told me the supply nature of the T.T system can give the consumer dips in current,causing the symptoms you describe and it is just one of those things with the T.T.

Yes get onto your supplier and get an engineer out to seek his advice on uprating your main fuse/cut out.
Im getting a sneaky feeling that if he was to test for voltage/current he `might` get lower than average results.

 

[bernardgreen]

From the Aztec data sheet......

Important
The electrical supply requirements:-
The 2 kW boilers and 6 kW boilers meet the requirements of EN 61000-3.3.

The 9 kW and 11 kW boiler must be installed in premises having a service supply of > 100A per phase.

The 12 kW boiler must be installed in premises having a system impedance of not more than 0.1939 + J 0.1939V.

So it would seem that the 80 amp fuse is not adequate and possibly the supply will have to be upgraded. It may be worth running this from its own single circuit CU with tails via Henley blocks direct to the meter to reduce the effect of the impedances in the CU for the rest of the house.

 

[Lectrician]

After chatting to a friend who works for my local DNO, (united utilities), he told me the supply nature of the T.T system can give the consumer dips in current,causing the symptoms you describe and it is just one of those things with the T.T.

Nonsence.

An overhead TT supply will predominantly be fed by a length of cable from a small pole mounted tranny - It is this small tranny that has a limited capacity, and high impedance, causing voltage dips on high loads. Long network runs will also give very similar effects. It has nothing to do with earthing system types.

 

[Lectrician]

From the Aztec data sheet......

Important
The electrical supply requirements:-
The 2 kW boilers and 6 kW boilers meet the requirements of EN 61000-3.3.

The 9 kW and 11 kW boiler must be installed in premises having a service supply of > 100A per phase.

The 12 kW boiler must be installed in premises having a system impedance of not more than 0.1939 + J 0.1939V.

So it would seem that the 80 amp fuse is not adequate and possibly the supply will have to be upgraded. It may be worth running this from its own single circuit CU with tails via Henley blocks direct to the meter to reduce the effect of the impedances in the CU for the rest of the house.

These lecky boilers must be fed from a switch fuse, or one gang CU - the instructions comment on this. They make a huge point of saying the MCB must not sit adjacent others etc.

 

[festa]

Nonsence.

Squeeze me mr LECTRICIAN ...
Did i say it had anything to do with the earthing? ...NOPE
I asked was his supply a T.T...quite straight forward really.

 

[RF Lighting]

Plenty of underground urban TT supplies round here.

Like Lectrician says, Earthing type has nothing to do with it.

TT does not automatically make it a small pole fed supply with a long LV run.

 

[davy_owen_88]

the supply nature of the T.T system can give the consumer dips in current,causing the symptoms you describe and it is just one of those things with the T.T.

You are assuming a TT supply means an overhead supply. It does not. The term TT defines the earthing type, and has nothing to do with the route the supply cable takes. Hence Lectricians response.

Davy