1 or 2 channel programmer?

[Benji478]

Hello Everyone,

Apologies if this question has been asked before, a while ago I had an old system boiler replaced with a combi boiler that is connected to a Santon PP170b cylinder,
when the conversion was done old 2 channel programmer was retained but this has recently failed.

My question is can I replace the old 2 channel programmer with a single channel one that just controls the heating and link the DHW connections? as per a normal DHW demand combi configuration.

Basically I am asking does the combi work as normal when connected to a cylinder I.e. when I draw hot water will the combi start to replenish the tank.

Any Help or suggestions would most appreciated

David

 

[stem]

If your combi was not connected to a hot water storage cylinder a single channel programmer would be fine, that would control when the heating came on and instant hot water would be produced by the combi on demand when a tap was opened.

When there is a hot water cylinder, because it takes time to heat up, a two channel programmer is used. One channel is for the central heating and the other channel for heating up the hot water cylinder. Two channels allow them to be on at different times. For example the heating would be off all summer, but hot water is still required.

It is a bit unusual, but not unknown, to replace a system boiler with a combi boiler and then connect it to a hot water cylinder as well. Usually it's either a combi and no hot water cylinder, or a system boiler with a hot water cylinder.

 

[Benji478]

Thanks for help Stem, sorry to be a little dumb (as I am only a lowly electrician and not a plumber) and I do not understand fully how my system works, as I said earlier I have a combi connected to an unvented Santon hot water cylinder which has 2 x 2 port valves and thermostats fitted.

So my question was, can I change the wiring in the new programmer so that DHW is always on, and fit a standard heating only programmer, and allow the Santon to control the DHW and start the boiler when either the temp drops or there is demand for lots of HW?

Thanks Again for any help

David

 

[stem]

as I said earlier I have a combi connected to an unvented Santon hot water cylinder which has 2 x 2 port valves and thermostats fitted.

OK, I just wondered if you had made a mistake with 'combi boiler' and meant 'condensing boiler' but it's irrelevant really, the important thing is the presence of a hot water cylinder.

Yes you could use a single channel, I don't know why you would want to though, but it's your choice.

Would you never want to not heat the hot water cylinder? for example if you go on holiday for two weeks.... Some light sleepers also find the noise created by water being heated or the pump and boiler running, wake them if it comes on in the night.

From an installation point too, it would involve changing the wiring very slightly. When you could achieve what you want by simply swapping the two channel programmer for another two channel programmer and setting the HW to be constantly 'on', and then you still have the option of switching the HW off should you ever wish to do so.