Hot Water Mystery

[mrsparks]

I'm hoping someone can shed light on this mystery for me. My son has moved into a rental flat and, not being very savvy with central heating controllers, I'm trying to help him understand how it works. And I'm trying to help him remotely which is making it very difficult. His flat has a combi boiler and a Vaillant VRT360 thermostat/programmer. I've downloaded the manual for the VRT360 but I'm a bit stumped also. He says that the thermostat/programmer has been in the OFF position since moving in a few weeks ago - presumably set that way by the previous tenant or the landlord. The flat is relatively warm so he's not needed heating during that time. However, he says that whenever he's run the hot water - shower, sink, etc - that hot water has been available. I don't have a combi boiler myself so I'm not entirely familiar with the setup, but my understanding is that combi boilers deliver hot water on demand and there's no hot water cylinder. So, I'm failing to understand how he has hot water when the thermostat/programmer has been OFF the whole time. I'm also struggling to understand why you'd even need to program on/off times for the hot water when it's on demand anyway - but that's another story. Can someone please explain how it's possible he has hot water with the thermostat/programmer OFF? Thanks.

 

[Aire]

On a combi, the thermostat/programmer only controls the heating. You are right that a combi delivers hot water on demand. Its controlled by a flow switch within the boiler which is activated when a tap or shower is used.

 

[mrsparks]

On a combi, the thermostat/programmer only controls the heating. You are right that a combi delivers hot water on demand. Its controlled by a flow switch within the boiler which is activated when a tap or shower is used.

That's brilliant. Thanks for your help.