Timer for hot water cylinder

Dazzler13

Hi all. First post. Handy enough with electrical stuff.
I want to put a timer in for my hot water cylinder. All posts I’ve seen are for changing out the switch and connecting to cylinder. Is there any reason that I couldn’t just put the timer in before the switch and that would control the power.

DublinDilbert

Dazzler13 wrote: »

Hi all. First post. Handy enough with electrical stuff.
I want to put a timer in for my hot water cylinder. All posts I’ve seen are for changing out the switch and connecting to cylinder. Is there any reason that I couldn’t just put the timer in before the switch and that would control the power.

If any post recommends removing the switch, they are wrong. The switch should always stay and the timer fitted before it.

Dazzler13

DublinDilbert wrote: »

If any post recommends removing the switch, they are wrong. The switch should always stay and the timer fitted before it.

That’s what I was thinking. Makes more sense to have the timer control the power to the switch and therefore the tank than after it. ðŸ‘ðŸ‘

alan4cult

The switch should be before the timer as the timer is only switching the live. The switch is double pole.

If you want to isolate both the timer and the appliance you need the switch first.

RebelButtMunch

I've a timer before the switch. Switch left 'on'. Works a treat.

coylemj

What makes the most sense is a two channel timer, that would allow you to remove the switch. But there doesn't apear to be any timer on the market that allows you full control over both the sink and bath elements. All of the two channel timers out there restrict the bath element 'on' times to Economy 7 off-peak periods.

So you really have no choice but to keep the switch and put the timer between the switch and the mains feed. You then manually set the switch to sink or bath, leave the On/Off switch permanently on and the timer will look after the power feed.

DublinDilbert

alan4cult wrote: »

The switch should be before the timer as the timer is only switching the live. The switch is double pole.

If you want to isolate both the timer and the appliance you need the switch first.

But there is two lives (bath and sink) coming from a standard emersion switch, which live are you going to out the timer into?

DublinDilbert

coylemj wrote: »

What makes the most sense is a two channel timer, that would allow you to remove the switch. But there doesn't apear to be any timer on the market that allows you full control over both the sink and bath elements. All of the two channel timers out there restrict the bath element 'on' times to Economy 7 off-peak periods.

So you really have no choice but to keep the switch and put the timer between the switch and the mains feed. You then manually set the switch to sink or bath, leave the On/Off switch permanently on and the timer will look after the power feed.

Yes you won't get a two chanel timer capable is switching that load.

alan4cult

DublinDilbert wrote: »

But there is two lives (bath and sink) coming from a standard emersion switch, which live are you going to out the timer into?

The timer should be switching the live after the double pole switch on the immersion.

2011

ormally the timer is wired upstream of the switch. That way the timer switches power on to the switch when requried and teh switch determines which element the power is applied to. This is the best solution IMHO.


If the timer is downstream of the switch then a 2 channel timer is required, one channel for the sink element and one for the bath element. It is harder to get a two channel timer that is suitably rated but not impossible (Sonoff do one). The other option is to use a timer that is not rated for the full immersion current and get it to swicth two contactors that are rated accordingly. A lot of hassel for very little in return. An inetrlock to ensure that both elements can't be powered at the same time woudl be an important consideration

DublinDilbert

alan4cult wrote: »

The timer should be switching the live after the double pole switch on the immersion.

Which live should it switch, the bath live or the sink live?

alan4cult

DublinDilbert wrote: »

Which live should it switch, the bath live or the sink live?

It switches the common terminal to the bath sink circuit.

Incoming live and neutral to the double pole switch segment. You then timer switch the live out (after the double pole). The output of the timer then enters the bath sink segment common terminal.

This solution ensures the entire circuit (including the timer) can be isolated.

DublinDilbert

Yes if there's a link that can be removed, i've seen some switches which don't have that link as it is internal to the switch.

alan4cult

DublinDilbert wrote: »

Yes if there's a link that can be removed, i've seen some switches which don't have that link as it is internal to the switch.

Yes you are correct. If there is no link then you need the timer switch upstream.

Wateryway

I have an Alexa switch. You can get her to do boost timer etc and even turn on remotely. Switch costb 40-50 euro.

vurstflavor

Most timer s need electric all the time to keep correct time so will not work after switch . Make sure timer has enough amps to run immersion

alan4cult

vurstflavor wrote: »

Most timer s need electric all the time to keep correct time so will not work after switch . Make sure timer has enough amps to run immersion

The switch is on all the time. As it would be if the timer was upstream.
The function of a downstream timer is complete isolation of the circuit if for example the timer fails.

Newuser2

alan4cult wrote: »

The switch is on all the time. As it would be if the timer was upstream.
The function of a downstream timer is complete isolation of the circuit if for example the timer fails.

Timers don't provide isolation to the immersion heater

They can in theory but isolation of domestic appliances is Double Pole

Newuser2

Timers are control devices

Immersion Switches are control plus isolation

alan4cult

Newuser2 wrote: »

Timers don't provide isolation to the immersion heater

They can in theory but isolation of domestic appliances is Double Pole

I never said a timer provides isolation to the immersion.

The double pole switch provides the isolation to the immersion. When the timer is downstream the double pole switch provides isolation to both the immersion and the timer.

Newuser2

There's 4 types of switching:

Control

Isolation

Emergency Switching

Switching off for mechanical maintenance

2011

Newuser2 wrote: »

There's 4 types of switching:

Control

Isolation

Emergency Switching

Switching off for mechanical maintenance

I would have thought that it would be more like this:

1) Control switching
2) Isolation switch that can be used for any type of maintenance (mechanical, electrical etc...).
3) Emergency shutdown (often a mushroom type push button).

I think that some very simple tasks can be made far more complicated than they need to be.

Newuser2

2011 wrote: »

I would have thought that it would be more like this:

1) Control switching
2) Isolation switch that can be used for any type of maintenance (mechanical, electrical etc...).
3) Emergency shutdown (often a mushroom type push button).

I think that some very simple tasks can be made far more complicated than they need to be.

That's simpler alright