Vitodens 100 DHW Priority

Marie_Ange1

Hi, since my plumber serviced our boiler, our DHW loses temperature when the heating kicks in. He first thought it had to do with crud in some pipes, then to do with the thermostat setting on the shower (although we told him that it happens on all taps). It only happened since the service, so I wonderd whether he has changed a particular setting.

Any ideas?

Alan (California Radiant) Forbes

Can you be more specific? Is the DHW not as hot? Is there less DHW available?

Larry Weingarten

Hi, Can you give us photos of the equipment? It would be nice to see how flow is controlled.

Yours, Larry

Marie_Ange1

When the heating kicks in the DHW will go hot and cold, on and off.

GGross

Can you take some pictures of the system as piped? I'm assuming this is a combi, are you absolutely sure the only time the DHW goes hot-cold-hot-cold is when there is a call for heat or is there just always a call for heat and it is a coincidence? Combi units will sometimes experience flow issues, or the little flow sensor can get debris stuck, or the heat exchanger can become scaled (the little flat plate one not the big round one), all of these issues are regular service issues that would cause your issue. As far as I know there is no way to disable DHW priority on those combis unless you turn the DHW off entirely. There is also a diverting valve inside the unit which disables all heating water flow until DHW is satisfied.

GW

shower only? If yes, it's not a water production issue, it's a shower valve issue

such a simple question you pose, but so many variables.