Boiler firing every time a hot tap is used?

[8-P]

Hi All

We had a new boiler installed last December.

It’s a Worcester 30Ri fwiw

Anyway, if the program is set to be producing hot water say 7am-10am and someone uses a hot tap it immediately fires up some times for a matter of seconds I assume to top the tank up. Sometimes I hear what sounds like a micro switch clicking on and off - boiler is in a cupboard in the kitchen.

Is this normal? Seems mad to fire up for a mug full of water, surely a threshold of say 20L would be more appropriate and efficient. I don’t remember the old boiler behaving in this way.

[Mr Pointy]

Is it a combi boiler which heats the hot water directly or a system boiler which heats water in a storage tank? It sounds like the behaviour of a combi boiler.

[8-P]

Mr Pointy said:

Is it a combi boiler which heats the hot water directly or a system boiler which heats water in a storage tank? It sounds like the behaviour of a combi boiler.

It’s a system boiler.

[Mr Pointy]

That doesn't sound right then as the boiler firing should be controlled by the thermostat strapped to the side of the HW tank (and the time clock of course). draining off a small amount of hot water shouldn't trigger the thermostat. Where is the thermostat strapped to the tank?

[E-bmw]

You may have done a typo as their own website calls this a "Worcester Bosch Greenstar Ri 30 kW Natural Gas Heat Only Boiler 7733600066" indicating that it is a central heating boiler only.

It goes on to say.

"This heat-only boiler is a wall-mounted natural gas unit designed to provide central heating in residential and light-commercial installations. It operates as a dedicated heating appliance delivering steady heat output while occupying minimal wall space, making it suitable for installations where a separate hot-water system is already in place."

[smokey mow]

E-bmw said:

You may have done a typo as their own website calls this a "Worcester Bosch Greenstar Ri 30 kW Natural Gas Heat Only Boiler 7733600066" indicating that it is a central heating boiler only.

It goes on to say.

"This heat-only boiler is a wall-mounted natural gas unit designed to provide central heating in residential and light-commercial installations. It operates as a dedicated heating appliance delivering steady heat output while occupying minimal wall space, making it suitable for installations where a separate hot-water system is already in place."

Heat only boilers also supply hot water. They are a type of boiler designer to work with traditional hot water cylinders.

[Sheepshanks]

Takes a load of hot water use to cause ours to fire. Doesn't do it sometimes even after a shower.

[dhutch]

If its a combi, then it will fire every time you turn on the tap, thats literally how half the boilers in the country work.

However if its a system boiler, or 'heat only' boiler, ie there is a hot water tank. Then that sounds like very strange behaviour.

A) do you have a hot water tank
B) is it currently warm to the touch
C) are you sure you don't now have a combi

[8-P]

dhutch said:

If its a combi, then it will fire every time you turn on the tap, thats literally how half the boilers in the country work.

However if its a system boiler, or 'heat only' boiler, ie there is a hot water tank. Then that sounds like very strange behaviour.

A) do you have a hot water tank
B) is it currently warm to the touch
C) are you sure you don't now have a combi

Hi All

Thanks for all the replies.

I have a Megaflo unvented cylinder in the loft so 100% not a combi boiler.

[Toyoda]

Post this on a plumbing and heating forum. Clearly most posters on here haven't got a clue.

[JoshSm]

Was the cylinder new too? Has it done this from the start?

Indirect cylinders and system boilers aren't complicated so it's most likely either a badly set thermostat right at the upper limit, a bad thermostat that just doesnt work well, a badly installed thermostat so it's not measuring correctly or some dodgy installation so the incoming cold water is somehow chilling the sensor rather than being nice and stratified at the bottom.

Either way it's unvented which makes it best left to someone competent to sort.

[Actual]

I am just wondering why your hot water heating is on all day?

My house has an oil boiler and a Megaflow unvented tank. HW is controlled by a timer which is only on 07:00 to 08:00 and then by a thermostat. I wouldn't notice if running a tap caused the boiler to fire because the HW is either legitimately heating or it is off.

Due to the current cost of oil I now heat the hot water overnight using the immersion heater and a low cost EV tariff rate.

[NerveAgent]

Actual said:

I am just wondering why your hot water heating is on all day?

My house has an oil boiler and a Megaflow unvented tank. HW is controlled by a timer which is only on 07:00 to 08:00 and then by a thermostat. I wouldn't notice if running a tap caused the boiler to fire because the HW is either legitimately heating or it is off.

Due to the current cost of oil I now heat the hot water overnight using the immersion heater and a low cost EV tariff rate.

Ours is on from 5am-10pm. It does most it’s heating at 5am, then tops up if needed. It’s such a negligible cost I wouldn't see the point in limiting it and potentially having luke warm water in the evening.

[dhutch]

NerveAgent said:

Ours is on from 5am-10pm. It does most it s heating at 5am, then tops up if needed. It s such a negligible cost I wouldn't see the point in limiting it and potentially having luke warm water in the evening.

Same