Gas central heating question

[FlorayG]

Why do I often hear my boiler firing late in the evening after the programmer has switched off the heating? Heating goes off at 8pm but I hear it fire right up to bedtime. What's it doing?

[Warkman58]

It could be that the temp in the house drops below your set temp, or have you set up a timed hot water demand?

[FlorayG]

My set temp for night time is seven degrees C so I hope not! And it's a hot water on demand boiler so should only fire when the hot tap runs

[SMAX]

If it is a Combi boiler then you probably have preheat switched on. This tops up the hot water heat exchanger every so often so the water heats quicker on demand.

[disneypars]

Maybe the outside temperature has dipped and it has a "frost" setting which could cause the boiler to ignite for a short period.

[FlorayG]

Originally Posted by disneypars

Maybe the outside temperature has dipped and it has a "frost" setting which could cause the boiler to ignite for a short period.

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It's not even cold enough for the heating to come on in the morning currently!

[FlorayG]

Originally Posted by SMAX

If it is a Combi boiler then you probably have preheat switched on. This tops up the hot water heat exchanger every so often so the water heats quicker on demand.

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Don't have that I don't think water takes a while to heat when tap is turned on

[SMAX]

Originally Posted by FlorayG

Don't have that I don't think water takes a while to heat when tap is turned on

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Yes the valiant does have it but it is buried in the menu. I had the same boiler and it did have the preheat turned on.

Also noticed your pressure is too low on the dial. And the heating and hot water are turned up too high. Normally 3 o'clock for both settings.

You need to pressurise the pipes using the fill loop to increase the pressure on the dial or you will end up with no heating and fault codes.

[SMAX]

Following is the explanation of Warm Start mode according to vaillant.

“ecoTEC combination boilers incorporate a warm start facility that keeps the domestic hot water heat exchanger hot, providing an instantaneous delivery of domestic hot water.” It is simply a pre-heat facility.

What this means is essentially the boiler is fired for the hot water secondary circuit so that the hot water reaches the taps much sooner than if this function was not enabled. You may hear the boiler fire up regularly throughout the day or night. If your taps are all located close to the boiler then very likely this function would not be needed and should be disabled.

myboiler/vaillant/vailla...t-mode-active/

[FlorayG]

Originally Posted by SMAX

Following is the explanation of Warm Start mode according to vaillant.

“ecoTEC combination boilers incorporate a warm start facility that keeps the domestic hot water heat exchanger hot, providing an instantaneous delivery of domestic hot water.” It is simply a pre-heat facility.

What this means is essentially the boiler is fired for the hot water secondary circuit so that the hot water reaches the taps much sooner than if this function was not enabled. You may hear the boiler fire up regularly throughout the day or night. If your taps are all located close to the boiler then very likely this function would not be needed and should be disabled.

myboiler/vaillant/vailla...t-mode-active/

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Thank you I've just dug out the very complicated instructions leaflet and yes the per-warm was on. I've figured out how to switch it off let's see what happens