Help request for Buderus GA124 with Logamatic R2107 installed 2005

pej2000

I have a Buderus GA124 with Logamatic R2107. It's been working well since the house was built in 2005. This week I noticed temps dropping in the house. The house is radiant floor heat only (circuit #2). There are no error messages on the R2107. The settings look correct and it is reading the outside temperature correctly. Domestic hot water is working fine.

I did have an HVAC guy out yesterday who didn't know the system but was able to point out components to me, release air from the lines and switch it into manual mode which brought the house back up to temperature.

When I Switch back to Automatic the boiler temp starts dropping and the mixing valve appears on the R2107 to rapidly turn on and off every 5 seconds.....that is the R2107 shows a 'down triangle' for 5 seconds and I hear a click, then it clicks and goes away.

I guess I'm trying to figure out how to diagnose the problem....could it be the R2107, the mixing valve or some other component/sensor.

The mixing valve looks like it was originally mounted a bit weird with the red arrow not aligned with the blue/red dial indicator. On that I understand the dial can be manually adjusted, but is it also adjusted by the R2107 to determine the water temp?

I like my local guy a lot but I want to help with the leg work figuring this out as there are very few systems like this where we are in New Mexico and the original installer is no longer here. Any suggestions appreciated.

pej2000

better picture below

pej2000

Also messing with mixing valve I am surprised by how far I can turn it? I expected it to only go maybe 90-180 degrees, but I can turn it several times 360. At some point either direction I water suddenly rushes or stops. How do you determine the proper setting?

pedmec

Can you take a picture of the model #? My guess is its a floating type valve and the clicking that your hearing is the controller positioning the valve to maintain the target temperature.

pej2000

pej2000

This sticker is on the top of the valve. I don't see how to pull the whole thing off to look at the back. Thanks !

pej2000

In Automatic now for a couple of hours. The high and low temps on the mixing valve were both at 120, even with no demand currently. So I turned it all the way to the right (about 5-10 turns) till I hit the stop. Now guessing temps will go down and then I can gradually adjust up as needed. But still don't understand if this is the right process or if in Automatic it would adjust itself.

Brent H.

Are you using a FM241 module in the Logamatic R2107 to control the radiant?

pej2000

Interesting question. I opened up the R2107 and yes there is an FM241 board in there wired to the mixing valve. I'm learning quite a lot in this process. Wish I knew what it all meant. LOL

pej2000

So here's a question. It's a warmish day (44F), so right now there are now zones requesting heat. But I see that the mixing system still shows high and low temps of 120F (despite my manually turning the dial all the way to cold side on mixing valve). Also the GrundFos pump on the mixing system is running continuously. Is that normal? The R2107 is still set to Automatic.

Brent H.

I’m not sure about the circulator running all the time as my R2107 is only used for baseboard heat, no radiant on my system. The FM241 is designed to control the mixing valve to achieve a temperature determined by the outdoor temperature sensor and a reset curve. You may want to do a bit of reading in the R2107 service manual to understand how the curve works:

s3.supplyhouse.com/product_files/R2107-Install.pdf

The older manual I have for mine contains an example wiring diagram for that mixing valve.



Hope this helps a bit. One of the pros on here may be able to offer more insight.

Big Ed_4

Correct , the fM241 is used for the pump station . A remote 24 volt transformer powers the valve in the pump station . Normally you would see the valve moving back and forth to dial in I would check the transformer . No error messages will pop up when the valve loses its power .

Brent H.

@Big Ed_4 What determines when the FM241 turns on the pump if the room sensor isn’t used?

pej2000

Thanks for the responses. I have read up on the Ref temp curve, so I'm comfortable with that bit. And I guess I'm understanding that the FM241 should adjust the dial based on the outdoor temp and Ref Temp Curve settings. So I won't worry about manually setting it unless I find I have to put the R2107 back into Manual. There must be a temperature sensor in the mixing valve that feeds back to the FM241? I suppose that could be the problem that started all this.

Just now I see that there are no zones demanding heat and the recycling pump is now off and temps have dropped, so that seems appropriate. Probably should open a window and see if we what it does when there is demand.

Big Ed_4

The circulator will run at a constant unless the outdoor temperture rises above the heat set point .

The room sensor tweaks the heat curve program only

Brent H.

It looks like the temperature sensor is mounted to the pipe just above the red temperature gauge. Likely underneath the pipe insulation and zip ties. Looks like a small black cable comes from there.

Big Ed_4

That supply temperture sensor could be off , you will need to OHM it out and check he chart if it is bad .

Do you have 24 volts to the FM241 ?

pej2000

I'm learning more and more....but I still feel pretty lost.

I did find the supply temperature connection to the FM241, disconnected and measured the impedance at 8kohm which looks good based on the handy chart in the service manual.

Then I tried measuring voltages on the FM241. I looked for 24v at the 41, 43 and 44 connectors but only got zero (AC).
Initially there was 120v alt at 61, 63 but that went to zero at some point, I don't know why. R2107 was in Auto at the time.
I tried to create demand in one of the zones by turning up the temperature, but the Taco zone board wouldn't activate.

Then I switched the R2107 back into manual mode and the appropriate Taco zone light turned on.
And now there is 26v AC at the FM241 #41 and 120v at the 61,63.
61,63 appears to power both the Taco board and the Pump at the mixing station.

So it seems like the R2107 is capable of providing power to the Taco board in Manual but is choosing not to in Automatic suggesting some Logic error. The outside temp now is 20F (as reported by R2107) and WWSD is set to a conservative 70F. What other reason could it have to not power the Taco board or pump?

Hopefully I'm not just making things worse. All your suggestions much appreciated.

At one point I did see a DHW ERR, but I turned the system off and on and it hasn't come back...

pej2000

One last effort before going to bed. I checked for air in the lines as I had seen my HVAC guy do. There's a manual valve and one that's supposed to be automatic. A small amount of air did come out and then clean water. I don't know if that is of any significance. The system remained silent.

Brent H.

Take a look at section 8.8 of the application guide. I think it is fairly close to your setup and may provide some insight into how it should operate.

https://bosch-thermotechnology.us/us/media/country_pool/documents/download-buderus-products/buderus-manuals/logamatic_2107_controls_applications_manual_06.2018_us.pdf

Big Ed_4

To check the pump station transformer voltage and the out put from the board you need to use one of the meters leads to the common . The wire nut with the the blue and white wire . Input 41 and wire nut to check the transformer . terminals 42 ,43 to the wire nut to check output.

Power to the taco board will come from the main board . It will not supply power until the boiler reaches 120* ..

Swithing to manual will bypass the hot water sensor and just let the indirect circulator run . You need to throttle down the boiler temperture dial as to not super heat the hot water .Switching to manual is temporary option until the problem is corrected .

So your having problems with heat on heat circuit 1 too ? I would call tech support 603-552-1100 durning the week and let them trouble shoot the main control . If bad control , order the FM board for the radiant too .

pej2000

This morning the boiler temp is 137 and power is on to the Taco board and FM241. Thanks Ed. My system only uses circuit 2, I gather because it is floor radiant only, no baseboard heating.

Checking voltages according to Big Ed suggestions. I get 26v at 41input. And 0v at 43 output; 26v at 44output. Note that the 43, 44 wire colors are reversed based on wiring diagrams suggesting 43 is too close and 44 to open. Seems like this could be a wiring error, but I won't mess with it, since things were basically working before.

61,63 voltage is constant now at 122v.

There is intermittent clicking again from the R2107 accompanied by changes in the up/down triangle on the panel indicating the mixing valve opening or closing. Associated brief voltage change at 43,44

Right now the mixing panel has outbound and inbound temps around 120F/118F. There's only one room asking for heat so that seems appropriate. I'm not sure anymore what to say the symptom is. I guess I can watch that room to make sure it is heating. Luckily we have some colder days coming.

many thanks for all the help. I've been looking at the application manual which is very helpful.
I'm looking forward to talking to Buderus/Bosch tomorrow. I definitely want to be confidently using Automatic mode. The one day in Manual overheated a couple of rooms. I do have DHW Aquastat turned down I'm a little surprised that when you turn it to Aut/190 there's no 'click' to say you are in Auto mode.

I wish I knew enough to double check all the wiring and operation for the whole system...like should 43,44 really be reversed?

Obviously still a lot I don't understand.

pej2000

I do have one point of understanding I'd like to double check. It looks to me like my (nonBuderus) thermostats have no direct control over the system. They just tell the taco board they need heat and the board signals a valve to open. The boiler/furnace/R2107/mixer just work to keep the water available to the valves at an appropriate temperature based on the reference curves and outside temps.

So it could be that the boiler/furnace/R2107/mixer are working fine and the problem is actually upstream (like air in the line?).

Big Ed_4

Is the valve in the pump station moving on its own ? if not it may be a bad power head ..

Big Ed_4

Call Buderus Monday , They would like a tech there on site during the call . Best to call and ask for their Knowledge , They are great up there . Have paper and a pencil ready to take down the part numbers if any.

pej2000

Thanks for that clue Ed. I wasn't sure if I should see the valve moving and I haven't yet. I put a mark on the position just now so I can watch for a change.
I'll definitely call tomorrow, hopefully with tech on site.

Just as a matter of keeping notes:
a few hours ago the Taco was powered, boiler temp 110, OA 48, mixing temps ~100, pump on....only one zone requesting heat, temps seem reasonable for OA

just now Taco has no power, boiler temp 127, OA 50 , mixing temps 120, pump is going, living room digital thermostat off; surprised at the high boiler temp unless that just reflects DHW production at the time. Mixing temps seem high for OA points to possible mixing valve problem.

pej2000

Big progress (I hope) with phone call to Buderus. Of course I had a contractor with me to make sure they would take my call, but he had never seen a system like this. Thanks to all your help I was able to sound somewhat informed while talking to the tech. It looks like the signal from the R2107 to the DHW Aquastat was not giving enough voltage (the voltage was actually dropping while I measured it). Shorting the Aquastat fired up the boiler proving the Aquastat worked and that (apparently) the R2107 needs to be replaced (ouch).

The theory is that the system would decide it needed to make DHW, go into that mode, never fire the boiler and eventually time out. Time spent not making DWH but stuck in that mode was time spent not heating the house. Oddly, the whole thing was somehow intermittent as we never totally lost hot water in the house. I think maybe the time out in DHW mode would send it back to try again and sometimes the boiler would light.

Anyway I've ordered a replacement R2107 with overnight shipping. Hopefully I'll be installing the new one tomorrow night and everything will behave and this is the correct solution. Need to make sure I have all the settings written down.

Again many thanks for all your comments and suggestions. This was a very helpful, educational and encouraging experience. I'll post again if this isn't the solution. I'm just glad I'm interested and motivated enough to dig into these problems myself. I have no idea what you would out here in the woods if you needed someone with time and expertise to figure all this out.

pej2000

So now I have installed the new R2107. It is ready to power on.

But one question. I unfortunately took at the tie off the Sensor Bundle which goes into the boiler well. This consists of one thermistor, two capillaries and a spacer (according to the manual), there is also a rectangular piece of copper. I can put them together and get them into the boiler well. The problem is I'm not sure how they were arranged. Does it matter?

Big Ed_4

Replace the well with the new one (I seen a few leak ) , spay a tad of penetrating oil and push each one all the way down with a screw driver ..