Replace flash timer with Drayton wiser 1

[Abyone]

Hi

I have a Flash Immersat timer which control my conventional gas boiler on off.
There is one thermostat in my system which shuts off the rads when it is switched, but if timer is on, the heating remains on to heat the hot water cylinder. Basically the only thing that switches on or off the boiler is the timer switch and if the boiler is on hot water cylinder always gets heated.

Anyway, I want to replace the flash timer with a Drayton wiser controller so I can control it remotely.

My current wiring is shown in the photo, I have no idea what all the wires are.

From L-R on the Flash timer the terminals are Lin Nin Nout Lout.

The Drayton wiring is as per instruction manual.

Could I get some advice on how to wire the Drayton.

Thanks.

 

[stem]

At the moment, If I've understood you correctly, it sounds like you have a timer that when it switches 'on', the boiler comes 'on', and a room thermostat that I guess operates a central heating pump and circulates water around the radiators. When the thermostat switches 'off' the pump goes off and the heating stops. However, the the separate timeswitch allows the boiler to still run thus providing hot water only.

If that's the case, there are currently two separate devices each controlling two separate things. Move to Wiser and you only have one device, which contains both the time control and room temperature control in the same unit, so the thermostat will turn off both the heating and the boiler.

So, that means no hot water, unless the heating was actually running as well (i.e. room thermostat calling for heat). You might get away with it in the winter if the heating was running long enough to heat the hot water; maybe struggle in mild weather when the heating not running for very long periods; but no hot water at all in the summer. Unless you don't mind having the radiators on in hot weather as well.

As it stands, Wiser is not suitable for your system, and I guess you would likely need some modification to the existing plumbing arrangement before you can incorporate it.

If I've misunderstood how your existing system works, then please feel free to correct me.

More information about this can be found on the Drayton Wiser website here.

 

[Abyone]

Thanks for your detailed reply.

I am not sure exactly if you are right or not, but that is because I am not 100% sure myself how it works.

When the thermostat switches 'off' the pump goes off and the heating stops

This bit I am not sure about, what would drive the heating loop through the hot water tank if the pump switches off ?
My thinking was that the thermostat just switched a valve that opened or closed the radiator circuit. But as I said I am not 100% sure.

However, the the separate timeswitch allows the boiler to still run thus providing hot water only.

Just to be clear there is only one switch - currently the flash timer controls on or off the boiler.
When it is off then system is completely off. When it is on it heats the hot water tank and if the thermostat isnt activated then the rads get hot too.

Does that help or is that what you understood ?

 

[stem]

In the past, heating systems worked like the diagram below, and I suspect from your description that you may have this arrangement.

When the boiler is 'on' water circulates naturally through the hot water cylinder by what is often referred to as 'gravity circulation' warm water rises and cooler water falls. Then when heating is required the pump starts and water is pumped through the radiators. One clue as to whether or not you have this system is the 4 water pipes connected to the boiler. [2 x flow and 2 x return]

This is the type of system Wiser is not suitable for.

There are several other ways that may be possible, as you say. There maybe a motorised valve or two somewhere, but the controls you have would suggest it's unlikely, and even if there were, with the controls you have it would require a rewire of the existing system not just replacing a timeswitch to use Wiser. You would also need the Two Channel Wiser as it includes Hot Water control. [The One Channel is primarily for Combi boilers that don't have a hot water cylinder connected to them]

So to progress any further, you need to ascertain exactly the type of system that you have installed.

 

[Abyone]

I will check and confirm.

But one thing confuses me.

If my current flash switch goes on and off at set times why wouldn't the Drayton perform the same task ?

All i need is a switch that turns on and off when I want it to, nothing more than that.
The only difference is I want to control it remotely via app. But everything else is the same.

Edit : my system definitely has a motorised valve, and the valve closes when the thermostat temperature is reached

 

[Rodders53]

Pics of the HW cylinder (any thermostat on it?) pipework and this motorised valve would help.

 

[stem]

If you do have the layout I originally suspected then:

Now
Timeswitch turns the boiler on/off
Room thermostat turns the pump on/off
Result: Boiler can run without the pump running

With Wiser
Only one device that turns both boiler and pump on/off
Result: Boiler and pump will both have to operate together, you can't have the boiler on without the pump as well

My system definitely has a motorised valve, and the valve closes when the thermostat temperature is reached

OK, from what you say it would appear that the motorised valve is only on the heating circuit, if so, it could be that water is pumped from the boiler to the hot water cylinder and the radiators, and the motorised valve switches off the heating leaving the pump to just circulate water around the hot water cylinder. Unfortunately if that is the case that doesn't change the unsuitability of the Wiser.

Now
Timeswitch turns the boiler and pump on/off
Room thermostat opens/closed motorised valve
Result: Boiler can run without the motorised valve being open and the heating on

With Wiser
Only one device that turns both boiler and pump on/off and opens and closes motorised valve
Result: Boiler will be on and motorised valve open together, you can't have the boiler on without the motorised valve open as well

However, if there is a thermostat on the hot water cylinder and a motorised valve controlling the hot water system heating somehow, that's different to a single motorised valve just controlling the central heating.

So still more clarification is required I'm afraid.

 

[Abyone]

So still more clarification is required I'm afraid.

Thanks for your help, I'll get some photos and get back in a few days.

 

[Abyone]

So still more clarification is required I'm afraid.

I finally got around to taking some photos Hopefully they help.
There seems to be only one supply and return water to the boiler but let me know what you see

 

[stem]

Looks like it is fully pumped and that there's a motorised valve probably for the central heating, but the hot water is controlled by a tapstat or similar device, rather like a thermostatic radiator valve that regulates the temperature of the hot water.

I don't think it changes the issue with the controls though. So as you described it earlier and from the photos, it appears that the timeswitch turns the boiler and pump on and off together and heats the hot water. But the Room thermostat opens the motorised valve and starts the central heating.

So you still won't be able to replacing timer ans thermostat with a one channel Wiser, the whole system [boiler/pump/motorised valve] will all go on and off together, without the possibility of running the boiler for hot water without central heating.

It shouldn't be too difficult to add a second motorised valve and cylinder thermostat for the hot water and convert it to what is known as an S-Plan. The controls would need completely rewiring though.

 

[Abyone]

don't think it changes the issue with the controls though. So as you described it earlier and from the photos, it appears that the timeswitch turns the boiler and pump on and off together and heats the hot water. But the Room thermostat opens the motorised valve and starts the central heating

Thanks but just to tease this out.

The room thermostat doesn't do anything except open and close the motorised valve which serves the rads.
The boiler only fires up when the time switch is active and is off when the time switch is off.

If that's the case I don't see why the Drayton is any different except instead of a rotary 24hr switch it would be programmable.

What am I missing, why do you say the Drayton won't work.

 

[stem]

So I'll tell you again for the 3rd time.

Now
Timeswitch turns the boiler and pump on/off
Room thermostat opens/closed motorised valve
Result: Boiler can run and heat the hot water without the motorised valve being open and the heating on.

With Wiser
Only one device that turns both boiler and pump on/off and opens and closes motorised valve
Result: Boiler and pump will be on and motorised valve open all together, you can't have the boiler on without the motorised valve open as well

You could use a Dual Channel Hive, because it has a function that can be selected to allow separate control of the boiler and pump from the motorised valve. Wiser doesn't have this function, but some rewiring would still be required, It wouldn't be a straight swap.

 

[Abyone]

So I'll tell you again for the 3rd time.

Thanks for your patience but you haven't explained why. Sure you are telling me the different scenarios now and with wiser but I was looking for the why so I can understand.

With Wiser
Only one device that turns both boiler and pump on/off and opens and closes motorised valve
Result: Boiler and pump will be on and motorised valve open all together, you can't have the boiler on without the motorised valve open as well

Why are you saying with wiser only one device? Why can't I keep my existing thermostat with the wiser -
If the thermostat only talks to the valve why is the wiser incompatible?

Or have I got it wrong and my thermostat is doing more than opening and closing the valve and needs to communicate with the wiser also?

 

[stem]

The Wiser contains both time and temperature control in a single unit and is designed to replace the timeswitch and the room thermostat.
Perhaps the following sketch will explain better than words.

The Wiser should be permanently powered and not connected via another timeswitch that turns the power to it on and off. It maybe possible to rewire it so that the Wiser is permanently powered but it's a bodge, because the Wiser could open the motorised valve when the timeswitch was off, so you would have to make sure that the existing timeswitch corresponds to the same times as the Wiser and remote control via the Wiser app won't work properly as it won't allow you to change the existing timeswitch settings.

You have an antiquated and inefficient system and are trying to fit 'state of the art' controls to a something not designed for it. The Wiser website states that: Wiser is not compatible for systems that lack water cylinder thermostats, and motorised valves.

The proper way to do it would be to add another motorised valve and a cylinder thermostat for the hot water, it will then become what is known as an S-Plan and a two channel Wiser can be used to give separate control of the hot water and heating. Here's the wiring diagram from Wiser from this type of system.

 

[BlueLoo]

Hmm.

I have the full wiser system on a fully trvd system with CH and HW.

My system used to be Splan.

I now have only one motorised valve where i used to have 3.

(I actually reused a mv to replace the bypass but thats a different story).

I bought a 3channel wiser kit. I only needed a 2channel.

Hw channel goes to the HW MV, (and then to the SL)
Ch goes straight to the boiler SL.

On CH only, the HW valve remains closed.
On HW, the HW valve is open but all the rads are closed (trvs shut down by the app).

In the OPs case, you can switch the logic of the MV. (I did this by rotating the motor plate 90deg)

But you need to trv all the rads.

So, HW on- Mv opens, HW satisfied. CH (rad valves remain shut by app).

Ch on, MV closed, Rad valves open as instructed by app.

Ch hw on, MV open, Rad valves open as required.

Requires some tinkering with bypasses and wiring but 100% works perfectly.

(Not suggesting this is for the OP but it's an example where wiser works with just one mv to control Ch/Hw)