Replace Broken Switchmaster 300 to Control HW/CH Separately

[bozallen]

Please excuse my lack of knowlegde about my own HW and CH system. Hopefully someone will be able to give me some answers though.

I currently have a Switchmaster 300 timer. It switches on and off the HW and CH at the same time. All or nothing! This looks to be connected to two 13amp sockets.

One is definately connected to it. It's next to the Switchmaster, and has the boiler plugged into it. Another, just below my kitchen work top under the boiler, wih a pump plugged into it.

Last night the Switchmaster clock stopped turning, so a replacement is required. Can I replace it with a digital model and is it possible to separate the operation of CH and HW?

 

[D_Hailsham]

Sounds a Heath Robinson set-up, so changing to separate operation may be difficult. However, you will have to provide much more info before you get a sensible reply

Make/Model of boiler
Is there a hot water cylinder?
Does it have a thermostat on the side?
How many motorized valves?

 

[bozallen]

The boiler is a Pottinger Flamingo 20 30, located downstairs on the wall of my kitchen.

There is a cylinder in the airing cupboard upstairs, almost directly above the boiler. I'm pretty sure it hasn't got a thermostat.

There are no motorized valves on the radiators. I had radiator thermostats fitted as it was obviously getting v hot in the summer when I wanted hot water.

 

[D_Hailsham]

You probably have a semi-pumped system; aka gravity hot water, pumped heating. You can tell by the number of water pipes connected to the boiler - it will be four (2 x 28mm; 2 x 22mm). If you have a fully pumped system you would only have two (22mm). The 28mm pipes will connect to the hot water cylinder, which will get heated by "gravity" circulation. The 22mm pipes will connect to the central heating, which will be pumped circulation.

In the winter, both CH and HW are required, which is OK as the water will circulate in both circuits. In the summer, only HW is required, which is done by turning the pump off, which then acts as a closed valve. However you can still get "reverse circulation" - the water travels the wrong way round the radiator circuit. This is controlled by placing a gravity valve in the circuit.

If you want independent control over CH and HW there are two options:

1. Convert to fully pumped. This will involve re-piping the HW circuit and adding a cylinder thermostat and one or two motorized valves.

2. Convert to a C Plan system. This involves the installation of a valve in the gravity HW circuit which is controlled by a thermostat on the HW cylinder.

Option 2 will be the cheaper, but you will need advice from an installer as your current system wiring will be virtually impossible to decipher over the internet.

 

[bozallen]

There's actually 3 water pipes coming off the boiler and a gas pipe.

Boiler bottom right pipe enters second pic top far left, and furthest right of the boiler goes to the top of the red pump in the second one.

The two pipes to the far right in the first pic are the same as the 1 in the second on the far right, the second is behind that wooden batton.

Is it not possible to just not run the pump when you dont want radiators?

 

[D_Hailsham]

There's actually 3 water pipes coming off the boiler and a gas pipe.

The installer has provided a single flow (at the top) instead of separate flows for HW and CH.

It would have been better to provide one picture showing the complete wall! Does the horizontal pipe at the bottom of picture 2 change direction behind the piece of wood and become the right hand pipe in the first picture?

Is it not possible to just not run the pump when you dont want radiators?

That's what I said! "In the summer, only HW is required, which is done by turning the pump off, which then acts as a closed valve."

 

[bozallen]

Sorry about 2 pics. There's a kitchen worktop in between and I couldnt get far enough back to get it all in 1. My kitchen is v small!

Does the horizontal pipe at the bottom of picture 2 change direction behind the piece of wood and become the right hand pipe in the first picture?

Yes. It connects with a T peice. Those 2 pipes go down through the floorboards too.

So would a 2 channel controller be appropriate, switching the boiler and pump for CH and just the boiler for HW or should I just isolate the pump supply in the summer?

 

[D_Hailsham]

Sorry about 2 pics. There's a kitchen worktop in between and I couldnt get far enough back to get it all in 1. My kitchen is v small!

Fair enough!

It connects with a T peice. Those 2 pipes go down through the floorboards too.

Is this what the pipework looks like?

Untitled

• D_Hailsham
• 2 May 2009
• 1

So would a 2 channel controller be appropriate, switching the boiler and pump for CH and just the boiler for HW or should I just isolate the pump supply in the summer?

Changing to a 2 channel timer would be a big rewiring job, so I would leave that until you replace the boiler. It might be better to just unplug the pump in the summer (try it out first!).

 

[bozallen]

Yes, your diagram is spot on!

I'll do as you suggest and stick with single channel operation for now.

I've got money set aside for a new boiler but it seems a waste to change while this one is going so strong! Would this boiler be original to the house? 1980.