HELP! Buderus GB 142-45 Problem

[richg]

Folks, this one is bleeding me out of cash, time and energy and some advice would be very much appreciated.

Buderus GB 142-45 installed September 2009. Three zones controlled by zone valves, individual Honeywell thermostats and an AM10 module. The circulator pump had been wired directly to the boiler with no relay switch. While having some routine plumbing work done, a Buderus-certified plumber said that the pump was wired incorrectly and a relay switch was needed. OK, fine, I paid to have him install one. All hell broke loose.

The boiler starts and runs fine after power has been turned off and then turned on. However, after the initial heat cycle and the three zones have come up to temp, the boiler will not respond to heat calls from any of the thermostats. The zone valves open in response to a heat call but the boiler will not respond and no error codes are flashed. The relay switch was replaced and the AM10 was disconnected to see if either of those were the problem. Nope, same thing.

I'm more than a bit ticked off that this boiler worked perfectly for 10 years and is now malfunctioning after it was supposedly "fixed". The tech is certified for Buderus boilers but he has no idea what is going on. It takes 30 minutes minimum to get through to Buderus tech support. Any advice would be VERY much appreciated, thanks.

 

[richg]

PS< I have no idea why my location is showing as TExas. I'm in northern NJ.

 

[Sponsor]

 

[Dana]

The first question that come to mind is why such a ridiculously large boiler? That's enough boiler to heat an uninsulated 10,000' house in northern NJ! Even the minimum modulated output of that boiler is above the design heat load of my house (at +5F).

The second question is what is the type & amount of radiation, zone by zone?

According to pages 6 & 7 of the manual for the AM 10 a pump relay is necessary. It's not clear how it was wired & working without it (or maybe that was without the AM10?) Even if you already have, bury yourself in the manual for awhile and check how the whole system is configured relative to how it was previously (if possible.)

Is it just a single pump, pumping the system direct, or is there a primary pump (for the boiler) and a second pump driving the radiation flows, with the loops intersecting at a hydraulic separator. Are the zones valves controlled by a zone controller (if so, which?).

Does the system run correctly for at least one cycle if you cycle off the power for 10 seconds and turn it all back on?

 

[Dana]

BTW: While you're at it, check to make sure yours isn't one of the GB142s recalled for fire safety issues:

The recalled Buderus GB142 is a gas-fired, wall-hung boiler. The boilers are white and designed to be mounted on walls. The black control drawer in the bottom center of the front of the boiler is marked "Buderus GB 142." Boilers with a green sticker inside the control drawer are not included. The model numbers included in the recall are 142/24, 142/30, 142/45 and 142/60. Only models with date codes of 7246 through 7256 are included in the recall. The model number and date code are located on a label on the bottom left side of the boiler.

 

[richg]

The first question that come to mind is why such a ridiculously large boiler? That's enough boiler to heat an uninsulated 10,000' house in northern NJ! Even the minimum modulated output of that boiler is above the design heat load of my house (at +5F).

The second question is what is the type & amount of radiation, zone by zone?

According to pages 6 & 7 of the manual for the AM 10 a pump relay is necessary. It's not clear how it was wired & working without it (or maybe that was without the AM10?) Even if you already have, bury yourself in the manual for awhile and check how the whole system is configured relative to how it was previously (if possible.)

Is it just a single pump, pumping the system direct, or is there a primary pump (for the boiler) and a second pump driving the radiation flows, with the loops intersecting at a hydraulic separator. Are the zones valves controlled by a zone controller (if so, which?).

Does the system run correctly for at least one cycle if you cycle off the power for 10 seconds and turn it all back on?

Howdy:

Thanks for your note. In reply:

-I had first purchased the GB142-24; installer said that was too small based on his heat calculation.
-There is a pump on the manifold and a second one downstream of the manifold and before the zone valves; the second one is where he put the relay switch
-Hot water baseboard
-there are three zones with separate thermostats and zone valves. The zone valves are wired in parallel (I think?)
-System would run correctly for one heat call if you turned it off and then back on. Once the heat call(s) were initially satisfied, the boiler would not refire when another heat call was sent.

Bosch instructed me to jump the WA terminal; I did that and the boiler fired right up and is now working fine. It is not modulating as the water temp rockets up to 195 every time but at least it's responding to heat calls, firing and pumping. Feedback was that it is likely an AM10 module that is sensitive to voltage changes or the boiler transformer is going bad. The plumber said that they no longer install AM10 modules and I could get by without it. This thing is 10 years old, probably has only another 4-7 years of life in it and I'm out a forkload of money, all in the name of taking a 2" piece of 14ga wire and jumping the WA terminal. That being said, if you have any thoughts as to what the problem might be I'd be interested as I'd rather fix it right than go with a half-buttock approach. Thanks again.

Rich

 

[WorthFlorida]

What brand of a zone controller are you using? The TACO brand has a set of contacts for each zone circulator, and one set for the boiler to activate regardless of which zone calls for heat. After that it's up to the Buderus to respond.

I worked on my brother Buderus and TACO controller where he had several issues. It was the same with his (installed around 2007). The first time it fires up the temp did go to 195F but after that it regulated the temperature. What I think happens is the unit learns how long it take to get the temperature to the MAX temp. The circulator turns on the the temp drops down to maybe 140 degrees (trying to recall) then it fires up the boiler if the system is still calling for heat. I also believe he has the outside air temp sensor. His log home is in Mt Snow, VT.

His TACO unit, the 24 volt transformer went bad. I replaced it and he had wiring in an additional thermostat incorrectly. The Buderus problem was his Kohler whole house generator. When it went to power back up the voltage regulator in the generator was putting out 137 volts per leg. This over voltage error out the Buderus and took a power cycle to the Buderus for it to reset itself until the power was lost again. Kind of common in the VT mountains. This went on for years and he was ready to throw out the Buderus since he lived 230 miles away and always had to call a neighbor to reset it so his pipes won't freeze. I found the overvoltage by using a UPC Battery Backup unit trying to save the Buderus but the line voltage report from the UPC device listed the line voltage and the UPC would not trip to battery back up either.

 

[Dana]

How much baseboard is there, broken down zone by zone? (You probably don't even have enough radiation to run it at condensing temps, ergo the rocketing up to the high-limit quickly on zone calls with the jumper in place.)

How did the installer calculate the load?

No zone controller between the thermostats and zone valves? (Typically a zone controller is what calls the boiler & circulator when any zone is calling for heat.)

I'll mull over the AM10 manual a bit as time allows, see if something springs to mind.

Even the GB142-24 would be about 2x oversized for the design heat load of my place at my local +5F 99% outside design temperature (comparable to western or northwestern NJ design temps (Phillipburg's design temp is +6F) , and enough boiler for 19 out of 20 houses. Even though it's water under the bridge, you might find a fuel-use load calculation interesting as well as running some numbers on the zone radiation and it's output at condensing temps relative to the minimum firing rate output of the boiler. This will be important to already have solid confidence in when seeking out the replacement boiler.

I suspect the installer either ran an idiot's rule of thumb calculation along the lines of:

"Lessee, 40 BTU per square foot times 2800 square feet of house is 112,ooo BTU, so the next size up from there is..."

...or they measured up ~200 feet of baseboard in the house, multiplied by 600 (which is about what fin-tube baseboard emits at an entering water temp of 195F, average water temp of 180-185F) for a total of 120,000 BTU/hr, then picked a boiler that would deliver at least that much. Both are really common yet tottully rong, ways of sizing a boiler, and it ruins the potential efficiency & comfort when sizing a modulating condensing boiler by those methods.

 

[richg]

Gents,

Thanks for your replies as I very much appreciate your advice. Here's what we've got:

-I went to a well-known plumbing supply web site, looked up "zone valve controller" and a Taco ZVC403-4 came up as one make/model. There is no zone valve controller on my system. The zone valves are Honeywell with two red wires and two yellow wires. One yellow and one red wire is connected to wires from the individual thermostats and the others are wired in common. Should I get a zone valve controller?

-Heat load calculation: I have to be blunt and can not speak ill of those who have passed away.....the plumber who said I need the 142-45 instead of the 142-24 was a neighbor....it was September of 2009, the depths of the Great Recession, he had very little work and was struggling to put food on his plate. I felt bad for him and gave him the job despite concerns about his ability to correctly install and set up a complicated system. The house only had electric baseboard prior to the GB142-45 and needed baseboard and associated lines installed. He did outstanding work on the baseboard, manifold connections etc but said he had no idea how to program the GB142. He did go over his heat load calculation with me and it seemed to make sense but please keep in mind I am a lay person, not an HVAC expert. The installer has since passed away.

-The WA jumper was removed and wires gong to the relay switch were removed from the X terminals and are now wired in common to the T posts. It is pretty cold right now and the boiler has been operating normally for the first time since the relay switch disaster started. The AM10 lights up when there is a heat call but goes dark when there is no heat call. The theories put forth by Bosch and the local plumbing tech about what the relay switch problem might be:

1. Zone valves going bad
2. AM10 is sensitive to voltage fluctuations or is going bad
3. Boiler transformer is crapping out

Bosch said that if the boiler operates normally with the WA plug jumped, that means that the issue is not within the boiler but with an exterior component. I do have a brand-new AM10 module sitting in a box but am reluctant to install it because it cost me $300.00 and it is unclear if that is even the issue. The boiler did not work when the AM10 was bypassed so it stands to my twisted reason that it is not the AM10. If anyone has any ideas, I'm all ears. Thanks and stay warm.

Rich

PS: here are pics of the manifold and zone valves. The PVC condensate piping was yellow and discolored when he installed it. I will clean up the wiring this weekend. The spare wires you see next to the zone valves are the old ionization sensor and igniter. Those were replaced 12/16/2019 but obviously were not the problem

 

[richg]

The plumber talked to Buderus tech support and they conveyed something they would not tell a homeowner: "The installation manual contains an error which they never acknowledged. The manual says power wires for the relay are pulled off the pump circuit but it should say to take power off L1 and L2 off of the boiler circuit and then use X X on the relay to tell the boiler to fire. L1 and L2 from the relay should be put on L1 and L2 on the boiler."

Here is L1 and L2 on the relay switch....can anyone point out L1 and L2 on the boiler? The boiler is working fine but it is lighting much more often than it used to when the AM10 was connected and this has me concerned about propane usage. Thanks!