Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Buderus G115 heating up radiators periodically even on summer setting

WarmInNorway Member Posts: 3
We are sweltering in Norway right now, Oslo area. I set the Buderus G115 to “summer” (been doing this for years and have checked and all is correct) which is supposed to only heat up our water for faucets, bath/shower, and no house heating. It does say on Wednesday’s it will circulate water through the system at noon, for a few minutes.
But we first noticed one evening, I heard the slight knocking as it warmed up, and it was eight p.m., and then also in the morning. We even have the thermostat also set to 15 deg. Celsius, but the thermostat is supposed to be ignored in summer setting. One smaller, longer radiator is noticeably warm couple of times a day. We have only one zone, it’s not multiple, but so weird that the other radiator is not warm.
We are up at 30 deg Celsius, and the radiator warming up is not helping, also the cost.

Every hear of this problem before? I see the LED with the parasol icon, is on, the panel says summer (and I have no temp set on it either but did briefly try 17 degrees, but it still happens).


  • GW
    GW Member Posts: 4,556
    Seems like you’re moving heat out of the boiler when your water heater kicks in
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
    HVACNUT Member Posts: 4,622
    You probably have 2 circulators.
    When the boiler heats for domestic hot water, hot water is also migrating to the heat zone. Enough to get to the first rad anyway.
    There should be valves you can close on the heat zone for now.
    There should be a flow check, either by itself, or in the circulator, that is not seated properly and allowing water to bypass without the circulator being on.
  • WarmInNorway
    WarmInNorway Member Posts: 3
    Thanks to both of you for the help! One consideration, it does mention even in summer mode, on wed. It will “circulate” water in the heating system only for a few minutes. Think it said it was to keep the pumps from drying out. But if I close off the radiators, will it still be able to keep the pumps from drying out? Even if there is no place to pump water through? If all radiators are closed off?
    HVACNUT Member Posts: 4,622
    Yes, you can shut off the radiators instead.
    Pump exercising.
    Do you plan on doing the repair yourself? If it's an internal flow check in the circulator, and the circulator has isolation valves, then it's fairly easy to replace.
  • psb75
    psb75 Member Posts: 571
    You may be talking about "ghost flow" i.e. hot water from the domestic hot water zone "drifting" to places it is not needed, like the central heating zone in summer. That is where check valves can help. But it IS also good to have circulators "exercise" in the off season--but not necessarily to move heat. Some boilers do this.
  • WarmInNorway
    WarmInNorway Member Posts: 3
    Tua is agin so much. I’m doing a little experiment, I closed all registers valves at the register except one. The weird thing was the living room, long thinner radiator, seemed to be the only one heating up but I know for sure we don’t have zones. Just one closed circuit, so I want to first see if the dining room larger radiator now warms up, if so will close that too and just figure the living room one used up the heat?
    Anyway, it’s a solution. Thanks!