Buderus GB142 control question?

Dave_22

Hello. I have a question regarding the Buderus GB142 series boilers. I have an issue using the analog in house thermostat (can't remember the model #). I woke this morning 3 degrees under the thermostat setpoint. When i checked the boiler, it was running at 135 with a 115 return temp. I have the space heat dial on the boiler turned up to 190 yet the boiler runs like it just wants to maintain a 20 degree delta. My guess is it's just terrible programming of it's control system.I would think it should raise the water temp as the in house temp begins to drop under thermostat setting. I believe when I tried outdoor reset it did the same thing. Can anyone confirm this is the nature of the beast? Or is there a way to make it work correctly? Thanks.

GW

You may have the AM10 control tucked inside the housing. Pop off the cover and look for another control inside. It’s white and has 3 or 4 buttons. You can probably google the thing and adjust it easily.

GW

This is it

Dave_22

Thanks Gary. I do have the AM10 but have it disconnected and am using the RC10 room controller. I believe each controller would not reach the maximum water temp. I'd have to check again but I believe that's the whole reason I disconnected the AM10. With the RC10, i could be 5 degrees under setpoint and the boiler is only running along at 135 degree supply. temp.

Dave_22

This is right out of the AM10 manual " The boiler
fires, runs and modulates based on the
information received from the AM10, and
the delta temperature between supply and
return". I suspect that the statement about the delta temp is what keeps it running up to the outdoor reset temp. The only thing I can think is that my house is under-radiated. It's just not possible it seems for the boiler to ramp all the way and maintain a delta T of 20 degrees, which seems what the boiler tries to maintain above all else.

Noel

It's possible that the maximum firing rate is reduced. Check it by pressing the wrench button and the chimney sweep button at the same time. If it isn't reduced, the display will read L - - . If it is limited, it will read "L" and a number that represents the maximum % firing rate allowed. Raise it with the chimney sweep button.

GW

I don’t have any troubleshooting experience with the RC10. I never took a iking towards them and only tried that control once in 2005 or so. You could simply take off the RC10 and move the wires to the normal thermostat terminals and install a basic thermostat if the RC10 isn’t cooperating

Dave_22

Just for some feedback on this thread. I tried both a normal thermostat with the outdoor reset and then the RC10 indoor thermostat. Both control methods had the same results in that they wouldn't increase the water temperature any higher if there was a 20 degree delta T across the burner. Even know the outdoor reset controller displayed 160 for a setpoint, the boiler would only go to 135. With the RC10 controller, it didn't care if it was 5 degrees under setpoint, the boiler would stop ramping up once the delta T was approx 20 degrees. I really think the boilers internal programming keeps it from ramping higher when the delta T is 20 degrees.

GW

Your control may possibly be locked out at 135 max temp. I would need to dig into the manual to explain how to raise it. So you have a manual? Read what Noel said above

Noel

It does limit the firing rate based on Delta T, and the blending in the header with properly sized pumps and correct speed choices on the pumps usually only makes it be an issue at startup of large water volume systems. The maximum reduction of firing rate happens at 20° CELSIUS, and reduces from there.

Dave_22

GW said:

Your control may possibly be locked out at 135 max temp. I would need to dig into the manual to explain how to raise it. So you have a manual? Read what Noel said above

I did check. There is no minimum set. The display shows "L--".

Noel said:

It does limit the firing rate based on Delta T, and the blending in the header with properly sized pumps and correct speed choices on the pumps usually only makes it be an issue at startup of large water volume systems. The maximum reduction of firing rate happens at 20° CELSIUS, and reduces from there.

I turned the boilers circ pump up to high as I figured it would have less of a delta T with higher flow (it was on medium). I have a Taco 007 as a circ pump to 6 zones that have panel radiators with TRV's. I have the TRV's removed in the zone that the RC-10 thermostat is mounted in. Any suggestions as what to do to make this thing get more heat to the zones? Bigger secondary pump maybe?

Noel

What size is the boiler? What BTUH do you need to deliver to the zone? How many GPM does the pump move that's in there now? Are all of the sensors in the boiler accurate?

Dave_22

Noel said:

What size is the boiler? What BTUH do you need to deliver to the zone? How many GPM does the pump move that's in there now? Are all of the sensors in the boiler accurate?

GB142-24

I "believe" the design was 70,000btu @ 10F outside temp. Not sure how to figure out what the GPM is that the pump is actually moving? Especially with TRV's regulating. The boilers digital temp matches the outlet temp gauge and the inlet temp gauge shows anywhere from a 12-20 DT from the boiler outlet. I can only assume all the other sensors are working but haven't verified.