Hard water deposits on a turbine blade could cause low-reading, I would think.it appears to use an impeller for sensing flow.
Thanks for responding, Reach4.Hard water deposits on a turbine blade could cause low-reading, I would think.
Is there a symptom other than the measuring discrepancy? I would think that symptom might be to require more flow to start the WH. You might have said that, and I missed it.
Yes. The tech has been giving me excuses like "it's not a precision instrument" and "all parts have tolerances" and "inlet temp is higher in the summer", but 30% off is just way too far out of spec. Needing to pull 1 gpm to trigger the burner is way too far out of spec. Is it extremely difficult to engage Noritz in these issues? Is that why the tech is trying to convince me this is not the heater's problem?Would think 30% is way off.
Bottom line, itsy not performing as advertised you should get what you payed for.Yes. The tech has been giving me excuses like "it's not a precision instrument" and "all parts have tolerances" and "inlet temp is higher in the summer", but 30% off is just way too far out of spec. Needing to pull 1 gpm to trigger the burner is way too far out of spec. Is it extremely difficult to engage Noritz in these issues? Is that why the tech is trying to convince me this is not the heater's problem?
Yes, he went through a phone call with Noritz and reported some values from diagnostic mode, The tests passed, but it's obvious they do not measure the accuracy of the flow reading. I can show the problem clearly with a bucket and a stopwatch, but apparently that counts for very little. I don't like being a screaming obnoxious customer, but things are heading in that direction.
Nathan, I would be interested to learn your results with the replacement flow sensor.
I have considerable experience with flow sensors used in Rheem water heaters in my neighborhood, as this part is a common failure item. It is indeed a "low precision" device, very inexpensive to manufacture, and cannot be expected to give very precise or accurate measurements. In my case, the device consists of a plastic vaned impeller with an integral stainless steel shaft that spins in a plastic carrier. The impeller is magnetized, and as it rotates it generates a varying magnetic field sensed by a Hall effect pickup, that converts rotation into "pulses" per minute read by the control computer. Yours is probably similar in design.
Theoretically, each sensor would have a "pulses per gallon" calibration that the computer would use to convert the reading to "gallons per minute". But I measured pulse frequency and tried to correlate this with the computer reading, with little success.
I concluded that the computer may not need to know actual flow rate precisely, but rather needs to discriminate between "no flow" and "some flow". Some flow rate is a prerequisite to know that the entering and leaving water temperatures are indicative of actual flowing conditions, and also to ensure that the heater has some amount of water to heat. The computer can't control or anticipate the actual water flow rate, so it must primarily use leaving water temperature to control burner firing rate. If the burner turns down to its lowest firing rate and the leaving temperature exceeds setpoint the burner must turn off, regardless of flow rate.
In my experience, all flow sensor failures in my neighborhood have been due to fouling. I have cleaned several of these, and I believe the cleaned sensors will work just as well as new sensors, but I have not actually re-installed any to date. If you have a flow sensor assembly on the bench, rotate a small magnet around the sensor body and observe movement of the impeller. A clean or new impeller will respond quickly and smoothly to magnet motion. A fouled impeller may not move at all, or may move with a jerky motion.
The contaminant appears to be a black, powdery material, which I have surmised to be iron oxides or manganese dioxide or a combination of these. The particles are extremely fine, one micron or smaller, and cannot be filtered out by any practical means in a residential application. They are caused by trace amounts of elemental metals that leave the treatment plant and oxidize in the utility distribution piping. In the trace amounts that they appear in the water, the particles are entirely benign to humans. Unfortunately, the particles are "paramagnetic", that is, can be attracted by a magnet but are not magnetic themselves. So when they come upon the little magnetic impeller in our heaters, they stick on. They build up and eventually interfere with the magnetic signal or clog the impeller thrust bearing. The impeller can be cleaned with vigorous brushing, but if you do this, do not breathe the dust. The particles go into your lungs easily, but don't come out. I have found that the thrust bearing can be reamed out with a tiny drill bit.
I believe you indicated that you have a water softener, and maybe you have a filter downstream. My guess is that neither softener or filter would separate these particles, can you confirm this? A magnetic separator should work, but I have not been able to find any that have been certified for potable water use.
This is awkward, but...
It looks like you're using an ad blocker. We get it, but (1) terrylove.com can't live without ads, and (2) ad blockers can cause issues with videos and comments. If you'd like to support the site, please allow ads.If any particular ad is your REASON for blocking ads, please let us know. We might be able to do something about it. Thanks.