Weil Mclain Ser. 3 manual reset lockouts on F1/2 & O1/2 temp. diff.


Old 12-28-16, 06:38 PM
Join Date: Dec 2016
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Renaldafeen you posted a picture of your weil mclain ultra installation.
Your picture clearly shows you have installed your temperature sensor for the return piping in the wrong spot. This is giving your boiler an incorrect reading. There are 2 external sensors that are shipped with the weil mclain ultra. One gets mounted to the feed manifold outside of your 2 closely spaced tees. The other gets mounted to the return manifold outside of your 2 closely spaced tees. Your feed manifold sensor is correctly located. Your return sensor is incorrectly located and mounted to the primary boiler loop. You need to move this sensor off of your primary boiler loop and relocate it to the return manifold away from your closely spaced tees. With the current configuration you are not giving the boiler the correct temperature differential between your supply temperature and your return temperature. This is what is giving you your "temperature sensor" lockout.
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Old 12-28-16, 07:01 PM
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You need to move this sensor to your return manifold outside of your 2 closely spaced tees. With this being said your installer has done you no favors by not providing you any space between your 2 closely spaced tees on your boiler loop and your first circulator branch on your return manifold. This sensor is supposed to be located in between your first circulator branch on your return manifold and your closely spaced tees on your primary boiler loop but at the same time be 6 pipe diameters away from your closely spaced tees on your primary boiler loop. judging from your picture, your installer has not given you a spot meeting these requirements to mount your sensor. This sensor is trying to deliver to the boiler a temperature reading of the water returning from your system...not a temperature of your primary boiler loop as it is currently reading. The temperature in your primary boiler loop is alot hotter than the return water coming back from your system piping.
Old 12-30-16, 10:30 AM
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andy –

This is an old thread but I think you found something that no one else noticed. I see what you are saying. In fact if you look at post #27 the devices labeled 10 on figure 14 are in fact the sensors and it clearly shows what you are saying. If you look at the picture in post #24 as you say you can see it doesn’t match the proper placement for the return sensor as depicted in figure 14 post 27. So it seems to me (I’m no expert) you are absolutely correct - the return sensor is in the wrong place.

But I just reviewed this thread again and I think the problem was that renaldafeen was getting an error message “Temperature sensors” and if you look at page 104 of the manual-


that message is supposed to mean there is something wrong with the sensor itself.

If I understand correctly the supply sensor (F) and the return sensor (O) are both dual sensors. So there is an F1 reading and an F2 reading for the supply sensor, and an O1 reading and an O2 reading for the return sensor. F1 and F2 should be close to each other and if the readings are |F1-F2| > 10 degrees then the sensor is assumed to be broken since F1 and F2 should not differ by that much. The same applies to the O1 and O2 readings.

But renaldafeen noticed that whenever he got the message “Temperature sensors” sensors F and O were showing that |F1-F2|>10 AND AT THE SAME TIME |O1-O2|>10. That doesn’t seem to make sense since why would both dual sensors (F and O) be failing at the same time.

I was just curious about where a single point of failure might be and I did find a computer chip that seemed to be used for these kinds of applications.

If I remember the sensors were connected to one side of the chip and 4 registers (R1-R4) connected to the other side of the chip, where the registers could be read by the computer via the SMBus. The chip kept these registers updated with sensor information.

I wish I would have posted the information at that time but I didn’t – and I don’t have it now. I should have saved it. But I think it was something like R1/R2 would contain information for the prime sensors (would be F1 and O1 in this case) and R3/R4 contained information from the other sensors (F2 and O2) in this case.

It seemed therefore that there could obviously be some differences internally in the chip to address and update R1/R2 vs. R3/R4. In other words, it could be something in the chip common to the path R3/R4 independent of R1/R2 that was failing.

So it just seemed to me if there were any kind of intermittent failure in that chip, including a firmware bug, such that R3/R4 were NOT actually being changed at times by the chip, but R1/R2 were, for whatever reason, that would certainly result in the kind of problem renaldafeen reported. As the computer continued to read R1/R2/R3/R4 over time, the F1 and F2 readings would drift apart as would the O1 and O2 readings AT THE SAME because R3/R4 would in effect be frozen at constant values.

Whatever it was it must have been a single point of failure for the F and O sensors. I wish renaldafeen would have posted back with whatever it turned out to be. Maybe he will someday.

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