UK Immersion heater timer

[wunatey]

Hi
I have a Horstmann e7bx water heater boost controller for my immersion heater which I want to replace with a timeguard trtd7n timer which is suitable for dual element ,the only problem is that the new timer has only got 5 connections and old one has 10,is this possible or do I have to get another timer with the 10 connections?
Thanks

 

[EricMark]

Just to add my two pennies worth, I can heat whole tank with oil, or top of tank only with electric, in my case from solar panels.

Using the oil, I would heat the tank 4 times a week for 20 minutes a time in the summer, and this would give me hot water, not super hot, every day, the tank would stay hot for around three days, so little point in a timer for the tank, but huge reason for the pipe work boiler to tank, as not only the hot coil gets hot, but all the pipe work too, so 20kW boiler, so used around 25 kWh per week.

When solar fitted also fitted an iboost+ so it has a sensor, so turns on immersion only when exporting, and it has a display to tell me how much I have used, so it tells me around 2.5 kWh used per week, but it only heats top of tank, this will last around a day, if we have bad weather, in summer, we can end up with it not running on the odd day, hot water the next day until sun comes up, is not really hot enough, so limit is around a day for cylinder to retain heat.

So unless your using off-peak, or solar, there is simply no point in having a timer on the immersion heater, it would cost me around 70p per week to heat DHW with an immersion heater, and using a timer might if lucky save 5p a week, simply not worth the cost of a timer to save that much.

 

[brianmoooore]

.......as not only the hot coil gets hot, but all the pipe work too, so 20kW boiler, so used around 25 kWh per week.

This is an often missed point with oil boilers which tend to be remotely sited from the HW cylinder, but I have a bathroom towel rail on the primary circuit. When the oil boiler switches off, a valve closes and isolates the cylinder coil, but the pipework, boiler contents and towel rail form a thermosyphon, which keeps towels dry and the bathroom heated for more than two hours afterwards.