Central heating comes on when I run a bath

[Geometer]

I moved into my (privately rented, gas-fired CH) flat 2 years ago. For some reason, whenever I run a bath, the shower, or the washing machine, the central heating comes on. Apparently without activating the boiler.

It's not a problem particularly, although it's a bit annoying in the summer, to have all that superfluous heat belting out. I'm just baffled as to why it should be set up like this (I understand the last tenant installed the shower over the bath himself, so I'm presuming it's down to him), and hoping someone can shed light on the puzzle.

Is it common practice? Is it something I should be concerned about?

Geometer

 

[ChrisOxford]

This is bizarre and doesn't really make sense!

By "central heating comes on", do you mean that the radiators get warm?

Do you have a hot water cylinder (big cylindrical tank with foam insulation) or is it a combi boiler (no hot water cylinder, boiler fires up as soon as you turn hot taps on).

Most modern washing machines are cold-fill only, in other words, are only connected to a cold water supply via a blue hose, so operating the washing machine shouldn't affect your hot water supply at all.

From the info you've given us I suspect that you have a combi boiler and that it makes the radiators feel slightly warm after you've run a hot tap, because combis often use the radiators to cool down the primary heat exchanger when the hot water demand stops. When you switch the hot taps off, can you still hear the boiler's pump running for a minute or so afterwards?

Tell us more!

 

[45yearsagasman]

Tell us the boiler make and model.

 

[scatmanjohn]

This is bizarre and doesn't really make sense

Is it? Quite common in my experience.

Most modern washing machines are cold-fill only, in other words, are only connected to a cold water supply via a blue hose, so operating the washing machine shouldn't affect your hot water supply at all.

But the OP never said he had a modern washing machine.

From the info you've given us I suspect that you have a combi boiler

I agree.

and that it makes the radiators feel slightly warm after you've run a hot tap, because combis often use the radiators to cool down the primary heat exchanger when the hot water demand stops. When you switch the hot taps off, can you still hear the boiler's pump running for a minute or so afterwards?

I disagree.


OP ....Your diverter valve is almost certainly passing.

 

[ChrisOxford]

Can't work out how to delete double post, sorry

 

[ChrisOxford]

OP ....Your diverter valve is almost certainly passing.

I agree

That makes a lot of sense.

 

[Geometer]

By "central heating comes on", do you mean that the radiators get warm?

Yes, that's a more accurate description. Only, they don't get warm, they get hot - as hot as they would be if the CH was on.

Do you have a hot water cylinder (big cylindrical tank with foam insulation) or is it a combi boiler (no hot water cylinder, boiler fires up as soon as you turn hot taps on).

Combi. Worcester 24CDi.

Most modern washing machines are cold-fill only, in other words, are only connected to a cold water supply via a blue hose, so operating the washing machine shouldn't affect your hot water supply at all.

Yes, cold-fill WM, Zanussi Aqualux.

From the info you've given us I suspect that you have a combi boiler and that it makes the radiators feel slightly warm after you've run a hot tap, because combis often use the radiators to cool down the primary heat exchanger when the hot water demand stops. When you switch the hot taps off, can you still hear the boiler's pump running for a minute or so afterwards?

This is the odd thing - the rads only heat up when the WM, the shower, or the hot tap to the bath are used, not the hot taps to kitchen or bathroom sinks; and the boiler doesn't come on at all.

 

[Geometer]

OP ....Your diverter valve is almost certainly passing.

I don't know what that means, but it doesn't sound good

Is this something I should bring to the attention of my landlord? Is it an easy fix?

Thanks for the replies

 

[scatmanjohn]

Yep..tell the landlord the boiler is faulty.

Whoever comes to fix won't be very pleased when they see which boiler you have.

The diverter on a 24 CDi is one of the worst jobs in boiler repair land

 

[Geometer]

Oh, teriffic.
OK I'll get on to my landlord asap.

Many thanks to all,
Geometer