20A DP or FCU for 1.5kW storage heaters

[KevinH]

Done a few EICR's recently and having a blonde moment regarding storage heaters.

All storage heaters in the property are rated at 1.5kw and fed by 1.5mm HR flex, circuits are individually fed in 2.5mm T&E by individual 16A MCB's.
All perfectly normal, except that each one is isolated locally by a 20A DP. I'm sure in the past I've been told by "old timers" that any appliance less than 3kw should be isolated by an FCU, or am I thinking of something else? I get the whole discrimination thing, but is there actually anything wrong with the way this installation is done? ie replace all DP's with FCU's? What's the thought on fault codes for this? I don't think there's a problem as the flex can handle over 16A (clipped direct) but I keep hearing the old timers voice, so maybe a few more voices might drown it out!

 

[telectrix]

cables are protected by the 16A MCBs. no need for a further point of failure, i.e. FCU.

 

[Dustydazzler]

20amp switch or FCU really doesn't make any difference Imo

I have seen quite a few manufactures instructions call for a FCU so I guess if you are to follow the MI then a FCU should be used

But as Tel points out you are then adding a second fuse into the circuit for no real reason

 

[James]

Let’s face it, 99% of the time, a 16A mcb will trip before a 13A fuse anyway.

 

[Risteard]

My opinion is that a DP switch should be used with storage heaters, and never an FCU as the fuse/carrier will heat up and potentially become brittle/damaged from being energised for eight hours at a time.

 

[Dustydazzler]

My opinion is that a DP switch should be used with storage heaters, and never an FCU as the fuse/carrier will heat up and potentially become brittle/damaged from being energised for eight hours at a time.

I agree and why I favour a 20a switch for immersion heaters as well

 

[brianmoooore]

My opinion is that a DP switch should be used with storage heaters, and never an FCU as the fuse/carrier will heat up and potentially become brittle/damaged from being energised for eight hours at a time.

Totally agree, but at 1.5kW, nothing is going to heat up either way.

 

[littlespark]

No guarantee the 1.5kW heater stays at a 1.5kW though for the time the circuit is in.

Homeowners have a habit of moving things around to fit their furniture in.

20A dp switch for storage, immersion heaters and single point spurs from grid switches….
13A SFCU for panel heaters and anything else.

 

[Ray Pooley]

Done a few EICR's recently and having a blonde moment regarding storage heaters.

All storage heaters in the property are rated at 1.5kw and fed by 1.5mm HR flex, circuits are individually fed in 2.5mm T&E by individual 16A MCB's.
All perfectly normal, except that each one is isolated locally by a 20A DP. I'm sure in the past I've been told by "old timers" that any appliance less than 3kw should be isolated by an FCU, or am I thinking of something else? I get the whole discrimination thing, but is there actually anything wrong with the way this installation is done? ie replace all DP's with FCU's? What's the thought on fault codes for this? I don't think there's a problem as the flex can handle over 16A (clipped direct) but I keep hearing the old timers voice, so maybe a few more voices might drown it out!

Although not essential I think you might as well fit an FCU for isolation purposes. For example I have a B16 MCB serving the central heating system. This goes to the junction box that delivers power to the separate electrical components. The boiler itself requires a 3A fuse. So the isolation switch is a FCU with a 3A fuse. Similar for zone valves and hot water tank element. All downstream of the junction box of course. It's not like it's a cost impediment.

 

[KevinH]

Thank you all for your answers.
The general majority seems to favour leaving the storage heaters on the 20A DP's so I think I will go with that as it will keep the customer happy with a clean bill of health on the EICR, I will sleep better knowing all is ok, and it means I don't need to do a return trip to replace accessories. Everyone's happy!