We have a Munchkin condensing boiler configured for natural gas that, with routine maintenance, ran reliably for three years. One morning, it stopped heating, and the controller display showed a code of F13.
The code on the display meant that the blower in this boiler wasn't spinning fast enough to safely open the gas valve and begin ignition. The problem was that, according to the diagnostics display on the controller, it actually was spinning at least 200RPM faster than the lowest speed for ignition. If I reset the controller, it would begin ignition, heat the water, satisfy the demand, and then shut down with that mysterious error code again. Sometimes, it would inexplicably shut down before demand was met.
I decided that I needed to make sure all the sensors were working as they should. One by one, I tested them to make sure the controller responded appropriately. The controller reacted pretty much as I would have expected. While doing this, I noticed that many key parts weren't made by Munchkin. The blower was made by EBM Pabst of Germany; the gas solenoid was made by Dungs of Denmark; the controller was made by S.I.T. Controls of Italy; the rest was apparently assembled in the US. This thing reminded me of the Tower of Babel story in the Bible.
EBM Pabst has a website with lots of data about its blowers. I had presumed that the blower was under some sort of control because, when I unplugged it while powered up, it went to full speed. From EBM Pabst, I found out that if I grounded the PWM speed control line, it should stop and go to a standby mode. I tried that, and the blower didn't shut down. Now I had reason to spend hundreds on a new blower. After replacing the blower and checking for leaks, I put it to the test. Everything worked properly again.
Looking back, I have to wonder whether the folks at S.I.T. Controls considered this failure mode. The F13 code was being triggered because the blower speed was free-running, not because it was under-speed, as the error code documentation suggested. The controller also wasn't consistent about why or how it tripped, leaving everyone wondering what the controller was balking at.
I give EBM Pabst low marks for quality control. S.I.T. Controls gets failing marks for erratic firmware behavior, and poor Internet presence, besides. However, Munchkin completely flunked because of its manual.
Despite detailed performance data, the boiler manuals did not have a Control Narrative section. The Control Narrative explains in gory detail exactly what the automation does in response to all stimuli in every automation state that it could have. It is a key deliverable to clients. As a registered controls engineer myself, I wouldn't dream of designing a potentially dangerous device such as a gas boiler without explicit documentation of this sort.
Without that narrative, even experienced, reputable service firms have little idea what the unit is supposed to be doing, why an error code might be there, or what tests one might use to diagnose it. It is not enough to failsafe on devices like this. Customers or their designated repair firms deserve a reasonable explanation of what kept a device from working.
This entry was submitted by Jacob Brodsky and edited by Rob Spiegel.
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The error code indicated there was a problem with the blower. You changed the blower and solved the problem much like any service man would do. So it would appear that the error code in fact worked.
If you were a real do-it-yourselfer, you would have fixed the blower - probably a simple connection problem as 95% of electronic problems are these days.
Easy for me to say.
By the way in our neck of the woods, the law states that only certified and licensed gas service personel are allowed to service gas appliances.
At least your boiler had a manual, although it did not provide the answers you were seeking. I am daily infuriated by CAD programs that come without manuals. These are not cheap give aways like those free things I used to run across, but even thousands per seat does not come with a manual. They come with a web address for a fixed amount of time and then a, charge-by-th-hour service to answer questions I used to be able to find in the operator's manuals that came with AutoCad, or whatever program was the flavor of the day at wherever I was working.
Then add the fact that the help at the other end of the line can neither speak nor understand English.
That is far too often the case. There have been a number of threads recently about component substitutions causing failures. I also blame high turnaround. It seems that three years has become the normal tenure, instead of working until retirement. It seems that as soon as a product is out the door, that the product's designers, and all of their knowledge, are out the door too. The next thing you know Purchasing starts to complain about the sourcing on a component, and Senior Management pressures Engineering to accommodate the change without the time (read as cost) required to fully understand the change.
I worked for one organization that allowed Manufacturing Engineering to specify changes on a design without the approval of Product Development. Worse yet, Manufacturing Engineering didn't even have a EE on staff, so they just followed the recommendations of Purchasing. Purchasing even routed contested ECNs during lunch if one of the primary signatures was against their change. I know it sounds like the premise for a sitcom, but they actually made medical devices.
As an OLD Motorola alumnus, I'm exceptionally familar with the "M" seires parts. There's a legit reason for this: these parts have their own proprietary specs, and are SELECTIONS from the parent product line. The spec differences are (usually) narrow range of beta, and (often) leakage current, noise figure, etc. The "generic' replacement part (like NTE) will mostly work, but design margins may be violated and therefore performance degraded. In my 13 "batwing" years I probably set up several dozen of these P/Ns myself. So of course if you characterize a specific M9706, it will fit all the parameters of the MPSA64; however, the reverse is NOT true for other MPSA64s! Given your comment on "proprietary unit" I'm surprised that you didn't recognize that those "M" parts were too!
There is another side to this story that has not been brought up. I've worked in various industries for OEM suppliers and been on numerous system integration teams. For at least the past decade I've seen far too many OEM customers go with suppliers who had never worked on any component like that required for the system, and who subsequently screwed up the programs so severely that they had to be delayed (to the point of missing market windows in some cases!) or cancelled. The reason for the bad sourcing decision? Low bidder, without regard for qualifications! Perhaps DN needs a new blog series called "Managed by Morons."
I wonder how many times we have inadvertently installed fake parts into our systems. It is embarrassing to find a good design failing for no good reason. We suspect many things- circuit boards, wiring, etc. without thinking that little IC or transistor could actually have been defective to begin with. Unnerving, at least.
The error code was confusing. The blower appeared to be under some sort of control because when I unplugged the control lines it went to full speed (as it was supposed to). The service technicians wanted to replace both the controller at the blower to the tune of close to $1k. They lacked any diagnostics to isolate which was broken.
The bottom line: was it not working because the controller was defective, a sensor was defective, or the blower was defective? I do not like to replace parts without knowing with some certainty that it was actually defective.
Yes, I know, from a labor and overall cost perspective, given the lack of information on what the embedded system was supposed to do, their approach is cheaper.
Papst had a name for producing quality stuff so to read of your bad experience is disappointing.
I recently removed two Papst fans from a junked UPS. They had been working for years but still ran smooth as silk. You can't say that about the average PC fan....
Papst also produced an outer-rotor motor which was used in some high-end tape recorders. Weird things, the outer case turned and the spindle stayed still and was attached to a mounting plate.
I would have to agree with you Curmudgeon. The only way that such diagrams would be included is by regulation.
I also have to say that there were parts of this Munchkin manual that had to have been written with an attorney breathing down the neck of the technical writer. The first chapters of the installation manual were so littered with bold face large type warnings of dire consequences that it made reading the rest of the manual far more difficult than it had to be.
This is what I call the "Step Ladder Warning Disease." If you plaster too many cautions, warnings, and bold faced admonitions in a manual, few will read it and most of the public will continue to do the stupid things outlined in the warnings. Frankly, I have seen pilot operation handbooks (for aircraft), and even firearm manuals with fewer warnings than this monstrosity.
The solution is to undestand that this is indeed a gas boiler. Yes, natural gas can be explosive. There is also heat and condensate involved here. If an installer didn't know that, it is very unlikely a bold faced warning will teach them anything.
Attorneys need to understand that writing a manual that people will actually read and comprehend is an art form. The more they inject liability disclaimers in to the manual, the less likely it will be that anyone will be motivated to read the silly thing.
Some day I would like to see a conference between technical writers, engineers, and attorneys on how to build a better manual, because the state of the art right now isn't serving anyone well.
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