Highflow 400 water on constant or not

19 Oct 2009
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United Kingdom
Hi Forum

I have recently moved into a property that has a Worcester 400 Highflow Electronic Series (gas-fired combination appliance).

My experience of combi boilers is that:
1. Hot Water can be set to on or off (I normally set to on all the time).
2. Heating can be set to be on, off, timer once a day or timer twice a day
(I normally set to timer twice a day).

The 400 Highflow allows hot water and heating to be set by timer i.e.
1. Hot water can be on, off, timer once a day or timer twice a day.
2. Heating can be on, off, timer once a day, timier twice a day.

My understanding (very basic) is that the boiler has a small tank of hot water (referred to as a heatbank) to help the flow of hot water.

I think....? that when you turn a tap on the boiler uses the water from the heatbank first and then maintains the temperature of the water in the heatbank after you turn the tap off?

I have noticed that if the hot water is off and you have a shower you get hot water for so long and then it gets colder but still warm - I am assuming that at this point the water in the heatbank is cooler because the pre-heated water has been consumed and the water is being heated on demand?

I therefore assume that:
With a normal combi the water is heated on demand so no cost to have hot water on all the time as only heats when demand it

With the highflow 400 the boiler constantly maintains the temperature of the water in the heatbank when hot water is on which costs money.

I currently have the hot water on timer but turn it on constant when need water outside normal timer hours.

My questions are:

Are my assumptions correct?

What are the advantages (if any) of putting the hot water on timer rather than constant?

If my assumptions are correct, how significant is the difference between water on constant and timer (in real terms)? Obviously it is easier to leave on constant but how much extra is this going to cost? If water is on all the time and not using taps how much heat is lost from the heatbank and is the cost of maintaining its temperature pennies or pounds?

Anyone have any other info advice on this boiler?

Thanks in advance
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You are roughly correct.

There is little difference in cost.

I advise my clients to set the ewater to be heated all the waking hours but off overnight.

Thats primarly to avoid noise from the boiler firing to reheat the store.

Start saving towards replacement as they are getting a bit old now. They are also susceptable to dirt in the system.


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