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I can wire up a 13 amp plug, my joinery skills are pretty good and armed with my debit card off I went to my local electrical store to buy a skirting board fan heater with the intention of installing it myself. One look at the paperwork and I replaced the heater on the shelf and aborted the quest.The directions said that the heater had to be installed by a qualified tradesman with the use of a double poll isolating switch. I would never breech legal regulations but I would like the forum to satisfy my curiosity by providing answers to the following questions.
a) Why can't I just plug it into a 13amp socket
b) What is a double poll isolating switch and what is its purpose
c) Would installing it create disruption to my decor
d) What would a sensible price be for a tradesman to charge to install the heater.
I would be grateful for the answers to any of these qustions.
Regards Oldalex01

Part P is law but the regulations are not but can be used in a court of law to show work was at fault. So when I quote the regulations that does not mean they must be followed in all cases.

The regulations say over 2kW and fixed needs a dedicated circuit i.e. not from the ring final so heavy items even if not built in are not portable so for example washing machine, tumble drier, dish washer and immersion heater should all be on their own dedicated circuit. In real terms only the latter is always on dedicated circuit.

The problem is the 13A plug was modified from original design with bits of plastic on the pins to protect fingers. A fuse produces heat and this heat has to be got rid of and since less is now transferred into the socket when a plug especially white one is taking maximum current for a long time it tends to over heat. A kettle may take 13A but not for long.

Second problem is the ring final can be overloaded and so large current using devices are normally put on their own circuit.

In the case of your heater instead of a plug you would use a fused connection unit (FCU) which can get rid of the heat better and using a switched FCU it would have a double pole isolator that is the switch. If it did have a dedicated supply with a 10A or 16A MCB in the consumer unit (fuse board) then just a double pole switch (Isolator) would be required as used with a cooker often red in colour.

Reason for double pole rather than simple on and off is neutral is regarded as live. The phase wire is called line and is also live. But often one is allowed not to switch the neutral it depends on supply type. We have TN and TT earth systems with TT we use an earth rod and you need a linked switch which switches both neutral and line but with a TN system where earth is supplies by electric company you don't need double pole but it is normally used anyway.

So to recap under 2kW you could plug in. From 2kW to 3kW you would use a FCU should be dedicated circuit but would depend on what is already in use. Over 3kW no option dedicated circuit like used for cooker or shower.

I have a fan heater in my house a Myson these can be skirting mounted and although fan is electric heat is from central heating water.

Hi Oldalex01

Before we go anywhere with this, please let us know which heater it was you were thinking of. There are times when makers instructions are rather dubious, being translated from country of origin.

Hi proptech,

Many thanks for your response. I should tell you that these events took place some time ago so I am afraid I have not got the precise details of the particular model I was referring to. I do know that it was B and Q that I was in when I was looking at them.
My questions were put solely to satisfy my curiosity and the terms "double polar isolating switch" and "wired directly into the mains" made me freeze.
I would install one myself if I could do so without a breach( I must be more careful with my spelling) of the law. That seems unlikely
Regards Oldalex01

ericmark wrote:Part P is law but the regulations are not but can be used in a court of law to show work was at fault. So when I quote the regulations that does not mean they must be followed in all cases.

The regulations say over 2kW and fixed needs a dedicated circuit i.e. not from the ring final so heavy items even if not built in are not portable so for example washing machine, tumble drier, dish washer and immersion heater should all be on their own dedicated circuit. In real terms only the latter is always on dedicated circuit.

The problem is the 13A plug was modified from original design with bits of plastic on the pins to protect fingers. A fuse produces heat and this heat has to be got rid of and since less is now transferred into the socket when a plug especially white one is taking maximum current for a long time it tends to over heat. A kettle may take 13A but not for long.

Second problem is the ring final can be overloaded and so large current using devices are normally put on their own circuit.

In the case of your heater instead of a plug you would use a fused connection unit (FCU) which can get rid of the heat better and using a switched FCU it would have a double pole isolator that is the switch. If it did have a dedicated supply with a 10A or 16A MCB in the consumer unit (fuse board) then just a double pole switch (Isolator) would be required as used with a cooker often red in colour.

Reason for double pole rather than simple on and off is neutral is regarded as live. The phase wire is called line and is also live. But often one is allowed not to switch the neutral it depends on supply type. We have TN and TT earth systems with TT we use an earth rod and you need a linked switch which switches both neutral and line but with a TN system where earth is supplies by electric company you don't need double pole but it is normally used anyway.

So to recap under 2kW you could plug in. From 2kW to 3kW you would use a FCU should be dedicated circuit but would depend on what is already in use. Over 3kW no option dedicated circuit like used for cooker or shower.

I have a fan heater in my house a Myson these can be skirting mounted and although fan is electric heat is from central heating water.

Hi ericmark
Many thanks for your comprehensive response.

I can understand a lot of what you say but certainly not all of it. My fault- not yours. It is for me, a hypothetical question because I wanted to satisfy my curiosity as to what is a double pole isolating switch and what would be involved in the installation of such a heater. I have come to the conclusion that such a task would be beyond my limited electrical capabilities.

Regards Oldalex01

I looked at the B&Q web site and there is a "Plinth Heater" listed it looks like a standard fan heater with two heat settings and likely 1 and 2 kW but strangely no details are given. Tried Screwfix as same company they show a Winterwarm WWFH20 Plinth Fan Heater 2kW which does not have switched heat output but does have thermostatic control at least on that site they do tell you more about it and in spite of having thermostatic control is cheaper.

With the Screwfix model which does seem better than B&Q model I would not be worried about plugging it in. But the B&Q one just simply does not have the information required to know how it would need to be supplied. To be frank with so little info give I would not buy it either.

I have looked at pictures on internet and the B&Q heater looks like:-

Consort Heatstream Electric Plinth Heater - Black
Consort Black Finish Heatstream Slimline Electric Plinth Heater available in 2kW or 3kW Models

Provides instant heat where space is at a premium and discreet yet effective heating is required. Cleverly concealed in the "kick space" beneath counters, displays and kitchen units, stairwells and fitted furniture, these heaters are suitable for both commercial and domestic environments. They require a minimum kick space height of only 100mm thereby offering increased installation options. The standard range features an on-off kick-switch that Consort pioneered to eliminate stooping - whilst the wireless controlled models have no switches on the heater (model requires a CZC1 controller, not included).
2kW or 3kW models
Variable heat settings
Cool blow function
Connects to 13A fused spur unit
Easy installation and maintenance
Illuminated kick switch on/off operation (on standard models)
Optional wireless control
Please note: Wireless models require a CZC1 controller (not included). See above
Fan only setting for air circulation in warm weather
Minimum kick space height of only 100mm
Automatic safety cut-out
Fitted with 2.2m of supply cable
Also available in Brown, Gilt, Stainless Steel or White

As you can see there is both a 2kW and 3kW model I would not be worried wiring 2kW to a 13A plug but although the 3kW is still within the limits of a 13A plug it's right on the edge and prolonged use could cause the plug to over heat so I would want to connect to a FCU which can better get rid of the heat from a fuse.