Timer for a 4.8kw element in water cyclinder

[-AndyH-]

Hi

I'm looking for a replacement timer for our water cylinder (bottom element is 4.8kw and the booster element is 3.6 kw) but most of the timers I've found are for loads up to 3.6kw. I need one to turn on/off during the Economy 7 period for the bottom element (booster is on a switch).

Any suggestions?

Thanks

 

[securespark]

We've had almost this VERY question recently. Please search.

 

[-AndyH-]

Hi

I've searched through the forum. Unfortunately, I can't find any topics relating to timeswitches for water cyclinders with an element above 3.2 kw.

The booster element (3.2 kw) is on a fused switch as it is rarely used.

The problem is 4.8 kw main element (the existing timer has packed up)which should require, from my calculations, a timer that can take a load above 20.87 amps. Is this calculation correct?

The Horstmann timers seem to only be designed for loads up to 16 amps. My understanding is that you shouldn't use one of those timers for a load above 16 amps. Problem is, they're the only ones I can seem to find at most electrical/plumbing merchants.

Thanks

 

[ricicle]

Is this a domestic situation as 4.8kw seems a big heater for this

 

[Steve]

Think he'll need a contactor for this. All domestic timers seem to only spec up to 3.2KW.

 

[securespark]

Yeah, sorry. Missed the load.

Dom timers go no greater than 16A.

This is a commercial/industrial load?

 

[-AndyH-]

It's an Everhot water cyclinder (400 litres) for domestic use.

Something made the system unhappy (kept on blowing fuses) which caused me to investigate the problem (and I'm sure someone is going to tell me how on earth did our electrician install something like this).

The setup is this:

MCB distribution board (Federal Electric - individual circuit with a 20 amp breaker for the cylinder). Wire goes into our airing cupboard where it's connected to two 13a spur switches. One spur is wired straight to the 3.2kw booster elemnt on the cyclinder. The other spur goes to a Merlin Gerin timer which is connected to the larger 4.8kw bottom element.

Now when the circuit fused, the 13amp fuse on spur linked to the Merlin Gerin timer kept on blowing. I haven't had to reset the breaker on the MCB. The wiring itself looks a mess and to make matters worse, each time the fuse blows it is turning black.

House is only around 12 years old and we've had enough problems with it to last a lifetime

I'm still awaiting quotations to replace the cylinder with an unvented Megaflo so I don't want to spend a fortune fixing something that will hopefully be replaced within a month. At the same time, I want everything to be safe at the moment (which from the sounds of things, you experts are going to tell me it's not).

Thanks

 

[Steve]

Its safe (AFAICT), just wont work properly as it is. The bigger element draws 20.8 amps, which is why its blowing 13 amp fuses. The FCU should have been omitted altogether. A 20 amp MCB would suffice.

 

[-AndyH-]

Thanks crafty1289

We had an electrician who put in some outdoor lights linked up to a Wylex distribution board. He did a really neat job wiring everything up for us. I'll give him a call tomorrow to see if he can do something in the interim.

Out of interest, how come there are no timers designed to take loads in excess of 16a? I've searched Screwfix, RS Components, TLC Direct etc. and found nothing.

 

[JohnD]

I'm thinking about treating the 20A radial as a sub-main. Put a small CU in there, with a timer (and contactor IF necessary) and a couple of MCBs sized to suit the two loads. You may end up using industrial devices so a small MEM enclosure would be handy as it fits both domestic and industrial stuff (sorry) there is nothing domestic that should take more than 16A (an immersion heater) that you would want to put on a timer; except for space heating which is not usually installed like that in houses.

I actually prefer the mechanical timers with synchronous motors and push-out segments; because they're so easy to set even when you've lost the instruction manual. Electronic digital timers can be much more clever but not at all intuitive.

Alternatively, as it is already fused to 20A, take out the FCUs and put in 20a DP switches with neon. Much easier and cheaper.