Storage Heater 24hr Supply

[Dave Liquorice]

OK so half dead storage heater is going to be replaced, nice though heatpumps are that ain't going to happen anytime soon.

May as well try and have something that might save a bit of energy and be controllable, not just a heap of hot rocks in a corner... The Quantum range from (Dimplex/Creda/Heatstore) fits the bill but requires a 24 hr supply as well as the off peak. The 24 hr supply is to run the electronics and fan but also a boost heater of 1 kW or so. In the fullness of time there could be 4 such heaters installed.

The required 24 hr supply(s) will be new circuit(s) so fall under

17th regs and as they will be buried in walls less than 50 mm deep need RCD protection.

Current CU is split load, I'm thinking that a 32 A RCBO in the unprotected side provides:

The 24 hr supply to the heaters via a ring in 2.5 mm^2 T&E. (Ample capacity, ring 7 kW, load 4 kW, maybe). Discrimination in the event of a fault v using the protected side which already has two rings on it (kitchen and sockets). RCD protection for the regs.

Individual isolation will be provided by a 20 A DP switched connection unit at each appliance.

What have I missed?

[spuorgelgoog]

In most cases the peak supply to the heaters can be spurred from an adjacent socket on the ordinary socket circuit through a FCU.

The off-peak supply should be 20A switch not FCU because the load often exceeds 13A.

Owain

[Dave Liquorice]

Except this 24 hr supply is also a 1 kW boost per heater. Worst case is an extra 4 kW onto a single ring on top of the ordinary load on that ring. OK even then the load will probably only be 5 kW (heavy loads in the kitchen are on their own ring) but the 4 kW is "hidden", say a base load of 1kW, some one comes along with 2 kW fan heater, after all the boosts are on so it must be flippin cold...

The discrimination is a factor as well, don't want the heater control electronics depowered due to a fault on ring main whilst away for a few days mid winter. One would lose daytime heat and maybe overnight heat and charging if the off peak doesn't power up the electronics when it appears. Will have to look at the circuit diagram...

Tell that to the "professional" who installed the heaters in the first place. Biggest heater is 3 kW, so in theory fine for a 13 A fuse. Switches started to fail due to brick/plaster dust, replaced like for like ie a SFCU and reputable brand:

Engaged brain and immediatly replaced all SFCU's on the heaters with

20 A DP switches...

[Brian-Gaff]

That is what the fitters of mine said, but these are not the posh ones, these are the basic hot rocks and the timer under the stairs type.

The only snag with storage heaters is the old one of a cold night and a warm day. Or I suppose the other way around! Brian

[Dave Liquorice]

The old one is a pile of hot rocks and bimetal strip operated damper to let more heat out directly from the core as it cools down. Fully charged the thing is too hot to touch.

These Quantum things are "high heat retention storage heaters" and the only ones in the market to meet BS EN 60531, I've yet to investigate what that really means.

The marketing gives the impression that the casing only gets warm the insulation "uses insulation material with almost the lowest theoretically possible thermal conductivity", most of the insulation is microporous silca. The net says that has a thermal conductivity around 0.02 W/m/K with the core at 500 C (apparently) I think that works out at < 50 W leakage.

Only when the time switch is wrong, ATM it's about right.