I'm looking to put our immersion heater on a timer. It's protected by a
16 amp fuse so I assume the timer needs to be rated the same. Many of the timers I've found so far seem to be 13 amp, even though some claim
16 amp in the headline description.
Anyone able to suggest something suitable?
And a thermostat to work with it? The current immersion heater doesn't have one.
Domestic immersion heaters are 3 kW maximum so a good quality 13 amp timer will be adequate.
The immersion heater must have a thermostat and all new ones should have a secondary safety cutout with a manual reset. The thermostat will be inside the cover of the immersion and usually slides into a pocket so it can be re placed without draining down the cylinder.
The immersion heater in my late mother's hot water tank has a thermostat, and it dates from 1960. It may just be that your thermostat was never set properly, or the setting has drifted over the years.
I'll investigate once I've plucked up enough courage to disturb the huge amount of 'stuff' in the cupboard!
Meanwhile, anyone got a recommendation for a digital timer? Or do I use a spare I have that is rated 13 amps and which I use for switching lighting when we're away?
I would need to replace the present immersion heater switch with a 13 amp socket and put a plug on the heater lead to plug it into the timer. Any problems there?
I went down the same road as you're going down, some years ago. My existing timer was just a plug-in jobbie that plugged into a socket in the airing cupboard, and the immersion heater plug plugged into that. But I was worried about the current capacity of the timer, and when it eventually packed up, I installed one of these
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mounted in one of these
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. It also needs an isolating switch, a pattress and a junction box. The Sangamo is an electronic controller, wired in, so no plug and socket arrangement, and has 16A capacity which, like you, I felt was important at the time. It's probably more sophisticated than I need, as it's used just as an on/off timer at the same fixed times overnight to take advantage of E7 electricity, but it works OK and does the job. My only reservation is that the display is microscopic and difficult to read unless you get close and have it well lit, e.g. with a torch.
As an alternative to mine, you could try these purpose-designed immersion timers, also by Sangamo
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Might be simpler to install, easier to read, and has its own case. If I'd been aware of them, I'd have gone for the PSD version, in the middle.
Google for 'immersion heat timer' there are lots of products these days. I had to replace my Smiths timer with a similar (identical) product from another supplier.
I would make sure you don't already have a thermostat. There are many products for central heating systems, but they would not be able to handle the current without using a relay.
A potential problem with plug-in types for immersion heaters is poor pin/socket contact resulting in the pins getting hot and risking a fire, due to the high current involved. With what is in effect two plugs piggybacked, you double the chance of that happening.
That is true of ours. Of course one issue after a few years was that the internal battery which was soldered in, eventually dies and the next power cut mangles the settings. Hopefully this issue has now been fixed. I have economy 7 so I have it on during the cheap hours as well, and have an over ride switch for emergencies. Brian
It's what I've had for the last couple of years, and works ok so far. With a load of something like 12 or 13 amps it may be better to use one of the older style time-switches with a synchronous motor and a mechanical switch, rather than the new-fangled things full of electronics - I've have several of these fail on much smaller loads and would be doubtful of using them for an immersion heater.
I wouldn't recommend it. It's OK for other 3kW devices like kettles which are used intermittently, but not really a good idea for immersions IMO.
I did wire up the immersion in a previous house with a plug and socket - good quality (MK) ones - but the plug got too warm for my taste and more so when the door to the cupboard was closed. I replaced it with a FSU in the end. That was for a pretty old immersion like yours which does probably pull the full 3kW. A modern one might be "eco" and draw less current.
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