Honeywell ST9400C- hot water preheat turns on heating

dk3

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Hi all. Moved in to rented property recently. Got to grips with preset timings on heating, no probs. Hot water timings are seperate but didn't use them as water was perfectly hot without preheat. Recently hot water has not been great so began to use the preheat, however it heats the rads also even though the heating is defo in off setting. Any suggestions, some setting or other I can sort myself or bigger issue? Thanks for any help.
 
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We need more information!

For a start, what boiler do you have (make and exact model)?
 
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Read the manual and set the programmer for independant heating and hot water (Fully pumped setting) -assuming you have a fully pumped system of course!! ;)
 

dk3

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Thanks. Boiler is Valliant Ecotec plus 615
 
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The 615 is a system boiler, so you must have a separate Hot Water cylinder.

There will be either one 3-port (left pic) or two 2-port (right pic) motorized valves. They will be near the HW cylinder. Which do you have?
View media item 5946 View media item 11762
I don't understand what you mean by "pre-heat".
 

dk3

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Thanks. The valve is a Monsoon 2 port. The controls have a timer for heating and hot water, photo attached. I assume the hot water control is to preheat it in advance of using it, however we have not used it before and now it is heating the rads on that setting. Valve was changed 2 weeks ago.
 
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Right I think I understand what you are trying to say

You moved in and you set up the right hand side of the programmer to control the central heating
you did not set up the left hand side of the programmer that controls the hotwater and left it off because you actually were getting hot water anyway and therefore thought that the hot water side of the programmer was some sort of "preheat" function
yes?

It's not, it actually controls the hotwater so either the hot water was getting heated via immersion or there is a wiring/component fault
you will have two valves if they are 2 ports, its likely that the one that was changed was the cylinder one (that was passing), did the hot water go off after this was changed and do you know why it was changed?

Matt
 
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The valve is a Monsoon 2 port.
The name "Monsoon" is normally associated with shower pumps. Can you post a pic of your valve?

As matt1e says, the HW controls on the left control when the water in the cylinder is heated, it's not a preheat.

Is there an electrical cable going from a switch on the wall to the top of the HW cylinder? If so this is the electric immersion heater. There is no need to have this turned on as your cylinder can be heated from the boiler (It's cheaper ;)) It's there as a standby if the boiler goes wrong. Turn it off at the wall switch.

As for setting the hot water times, just remember that it will take about an hour to reheat a cold cylinder. It's most likely best to start heating the cylinder about an hour before the central heating comes on in the morning. "Topping up" the cylinder during the day will depend on your lifestyle and hot water requirements.
 

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