Immersion wiring thru timeclock & thermostat

[GtScot]

Hi. I am wiring an immersion heater to be used in conjuction with a solar cylinder (i.e. to supplement the solar thermal panels when necessary).
There is a fused spur and I propose to take the wiring to a time clock (which I assume wires just like a switch) and then to a thermostat - to switch the immersion ON when the temperature is low enough (wiring it so that set temperature CLOSES the circuit). Presumably, the immersion heater itself will switch off when target temperature is reached.
I'd be most grateful if someone could confirm, or otherwise, that what I am proposing is correct.
Thank you!

 

[ban-all-sheds]

Hi. I am wiring an immersion heater to be used in conjuction with a solar cylinder (i.e. to supplement the solar thermal panels when necessary).

So that'll be most of the time then.

There is a fused spur and I propose to take the wiring to a time clock

Why? Are there times when you'll be happy to turn a hot tap on and not get hot water out of it?

(which I assume wires just like a switch) and then to a thermostat - to switch the immersion ON when the temperature is low enough (wiring it so that set temperature CLOSES the circuit). Presumably, the immersion heater itself will switch off when target temperature is reached.
I'd be most grateful if someone could confirm, or otherwise, that what I am proposing is correct.
Thank you!

Plan B:

A regular immersion heater with an integral thermostat which will do what it needs to do as and when to keep your stored hot water hot.

 

[GtScot]

Hi, thanks for that. The solar panels are really effective and deliver a good level of hot water. The immersion on the time clock is for when there is very high demand on hot water (it's a holiday let sleeping 6) and no input from solar - i.e. mainly early morning.
Does that answer your queries?

 

[EFLImpudence]

to switch the immersion ON when the temperature is low enough

When you say that - do you mean the temperature of the water, or the weather?

 

[GtScot]

Hi. Yes, the temperature of the water. It is for DHW only.

 

[EFLImpudence]

There is a fused spur and I propose to take the wiring to a time clock (which I assume wires just like a switch)

Yes, it just switches the live.

and then to a thermostat - to switch the immersion ON when the temperature is low

You don't need a thermostat.

The immersion has an integral thermostat which turns it off when the water is hot enough and consequently on, if the timer is calling, when it's not.

 

[ban-all-sheds]

I'd suggest you don't need a timeswitch either, unless you've got a 2-tariff supply.

I'd suggest that if I was renting a holiday property I'd want the water coming out of the hot taps to be hot at any time of day.

 

[GtScot]

Firstly, thank you both for your replies.
The thermostat: the immersion is half way up the cylinder while the proposed thermostat is at the top. The idea of the 2nd thermostat is to prevent the immersion coming on until the temperature has dropped to the prescribed level.
ban-all-sheds - I am trying to achieve the constant hot water as cheaply as possible. The solar works very well. If I don't have a timeswitch the immersion will do the work of the solar which will then be wasted.
The immersion is very much an emergency back-up (as there is also a solid fuel stove contributing to the system - when it's on).

 

[EFLImpudence]

The thermostat: the immersion is half way up the cylinder while the proposed thermostat is at the top.

Not the best position for the thermostat. It should be one third the way up the cylinder.

Single immersion heaters are normally and should be at the bottom.

The idea of the 2nd thermostat is to prevent the immersion coming on until the temperature has dropped to the prescribed level.

I can't see how what you are trying to achieve is possible.

In effect, what you want is for the immersion to remain off, regardless of temperature, if the solar is going to heat the water.

Or to wire the immersion so that it cannot operate when the solar is working.
Although the water may already be hot from the last time the immersion heated it when the solar starts.

ban-all-sheds - I am trying to achieve the constant hot water as cheaply as possible. The solar works very well. If I don't have a timeswitch the immersion will do the work of the solar which will then be wasted.
The immersion is very much an emergency back-up (as there is also a solid fuel stove contributing to the system - when it's on).

A simple on/off switch operated in conjunction with the human brain would seem the best way.


In reply to an earlier post - even with the immersion back-up the system will not satisfy the demand of six people in a row.
Which ever way it is done, you only have one tank of hot water followed by at least two hours before the water is hot again.

 

[GtScot]

Thanks for that. Yes, the switch and brain system is the one in use currently. The only problem with it is the brain.
The principal problem that I am trying to overcome is heavy use of water first thing in the morning depleting hot water before solar is effective. I take your point that the thermostat should be further down the cylinder (particularly when there is a timeswitch). The other point, however, is that the property is regularly either unoccupied or in low occupancy and residual heat overnight is more than adequate to avoid the use of the immersion - subject to my 'low' temperature thermostat.
My original query was not actually about the theory, it was about the mechanics of achieving what I was planning. So, so far, I am happy about the timeswitch, agree the thermostat should move down the cylinder, still believe that the thermostat needs to dictate the 'start' temperature - and then get slightly lost about the type of thermostat and how I should wire it. I have a thermostat here that may be more appropriate. It has connections for "adjuster" (could I possibly use this to close the circuit and switch the immersion on when the temperature drops to, say, 35 degrees?) and a "limiter". Could I use that for the 'switch off' temperature?
I do not understand the wiring diagram as it shows the Live going thru' both switches, then both terminals 1 & 2 of the second switch connect to (separate) boxes marked "U" and then to the Neutral. I would have thought the Live should continue thru' the switch connection which is "ON" to the immersion???
Sorry if this is 'going on a bit' but grateful for your advice.

 

[EFLImpudence]

The only problem with it is the brain.
The principal problem that I am trying to overcome is heavy use of water first thing in the morning depleting hot water before solar is effective.

Then all you want is a 'normal' set up where the timer switches on the immersion from, say, 5am to 8am or whatever time you choose.
The immersion will switch itself off when the water reaches set temperature - usually 60°C,

I take your point that the thermostat should be further down the cylinder (particularly when there is a timeswitch). The other point, however, is that the property is regularly either unoccupied or in low occupancy and residual heat overnight is more than adequate to avoid the use of the immersion - subject to my 'low' temperature thermostat.

I am assuming you mean the 'low' temp. is to turn on the immersion because it is not hot enough rather than you only want the water to be heated to 50°C.

There is no point having a 'low' temperature thermostat because if it is timed to come on then you want it hot (60)

My original query was not actually about the theory, it was about the mechanics of achieving what I was planning. So, so far, I am happy about the timeswitch, agree the thermostat should move down the cylinder, still believe that the thermostat needs to dictate the 'start' temperature -

As above - no need if you want it hot it does not matter how 'cool' it is.

and then get slightly lost about the type of thermostat and how I should wire it. I have a thermostat here that may be more appropriate. It has connections for "adjuster" (could I possibly use this to close the circuit and switch the immersion on when the temperature drops to, say, 35 degrees?) and a "limiter". Could I use that for the 'switch off' temperature?

As above - the integral immersion thermostat will already be on - waiting for the timer to send the power.

I do not understand the wiring diagram as it shows the Live going thru' both switches, then both terminals 1 & 2 of the second switch connect to (separate) boxes marked "U" and then to the Neutral. I would have thought the Live should continue thru' the switch connection which is "ON" to the immersion???

Not quite understanding that but it (the live) will.
Can you post a picture of the diagram?

 

[GtScot]

You are quite correct, of course; thank you for persisting until the penny dropped! My logic was totally wrong in wanting a low temp switch on.
Finally realising that, as you say, I do not need an additional thermostat and any flexibility on water temperature could be achieved by altering the setting in the immersion.
Partly to make sure that I could upload an image, I attach below a copy of the instructions, including the basic wiring diagram at Fig 7, for the thermostat I mentioned earlier. I would welcome your comments.
Thank you again.

View media item 49567

 

[EFLImpudence]

It's just an electrical way of drawing it mainly indicating that all neutrals are connected together and that both L & N carry on and go elsewhere.

The supply live to 'C' (on the left) and the outgoing live to '1' or '2' (on the right).

The '1' on the left being for the manual switch.

The 'U's are two separate loads (or a choice) the lives of which would be connected to '1' or '2' (on the right) depending on how they were to work, i.e. call for heat or cold.


Just to point out that this model would be no good for a normal domestic cylinder as drilling and threading are needed.
Normal cylinder thermostats just strap on to the cylinder with what is a piece of curtain wire.

 

[GtScot]

Great. Thanks for that. Yes, the cylinder is a solar one with pockets for the thermostats.
How do I "thank you"?

 

[RF Lighting]

You just press the button