domestic hot water too hot

tallents

Homeowner here with a Buderus Logimax GB 142-45 unit with a Buderus



S-120 hot water tank connected. System has "outside" control so



regulates itself depending on outside temperature.







Heating set on auto, hot water set on 120. However when weather gets



cold domestic hot water temperature over rides setting and becomes very



hot.







What to do/ check?

Paul48

I&O Manual

Go back and recheck all connections, and settings. Make sure you understand each. I'll state the obvious.......something's not right. Approach it as though you are starting over.

tallents

domestic hot water too hot

one reply i received was a question of check valves. I can see no check valves on the line running from boiler to tank and I don't believe the circulator pump has a built in one. I am thinking this might be the issue

Gordan

You need a thermostatic mixing valve

The DHW outlet of the indirect should have a thermostatic mixing valve installed to temper down the tank water to a safe temperature, regardless of what's in the tank. This is a safety issue.



Apart from that, yes, if you're missing check valves where you need check valves, it is very possible that the space heating circulator could circulate water through the indirect during a space heating call.

tallents

domestic hot water too hot

Thanks planning to check all this tomorrow. Do I really need a second regulator on the feed side of hot water tank?

Looks like we might just switch out the circulator with one that has a built in regulator rather than add check valves as we can't identify the pecks that the contractors plumber used and he will not call me back!

Thanks again for your input and i will post results

heatpro02920

When was this installed

Is this a new problem or has it done it from when it was installed? I would like to see a picture of the piping. Do you have a check valve in you primary pump? Did you wire the dhw pump to the ps terminals not pz and the sensor to the fw terminals? I have installed many you are also using the am10 mod? I'm very curious

tallents

domestic hot water too hot

Yes this has done this from the get go, we are now in our second heating season. Re wiring I have no idea but will try to check tomorrow and will post shot of pex set up etc.



Thanks for your interest

Gordan

The second check

One check valve is enough to prevent forced circulation. The second check is to prevent gravity circulation either to, or from, the indirect, which can happen out of either end. Due to buoyancy hot water rises in pipes. This could result in DHW overheating or, more likely, could result in your space heating getting warm (and wasting energy) even outside the heating season.



I only have a single check on mine, but I use a heat trap, which is a piping arrangement that would force hot water to go downward by itself (something that it's not inclined to do.) A heat trap won't prevent forced circulation, though, which is why you need at least one check valve.