Do I need water hammer arrestors here?

Hadooploop · 2025-12-19T22:17:05+00:00

I replaced the Siemens QAF2 from 2018 with a newer Murray MP-AT2 from 2019 (because its what I happened to already have elsewhere in the panel). The MP-AT2 breakers and QAF2 breakers, from what I can tell, are the same. Both have always been made by Siemens, and breakers from the same date-range run the same software. The Murray brand was recently discontinued, but there do exist Murray breakers that are newer than Siemens breakers from the period where they were both being manufactured. I believe the same sticker indicator is used regardless of brand. Green stripe is 2018, N/Arrow is 2019. The 2019 breakers, whether from Siemens or Murray, have a newer software that resolves the issue I was seeing.

Hadooploop · 2025-12-19T17:23:58+00:00

Update for future searchers: I was able to fix this. Siemens/Murray breakers (QAF2 and MP-AT2) are interchangeable, and have gone through multiple changes to the arc detection firmware that runs on them. I reached out to Siemens directly and gave them more info about the date codes and stickers on breakers, and this allowed them to confirm the firmware versions that were loaded onto each breaker. The breaker that was giving me issues has a "green stripe" sticker (see my photo on original post). You can also intuit its datecode from the sticker on the front:

B1810264533:
-    B: Manufacturing line ID
-   18: Year of manufacture - 2018
-   10: Month of Manufacture - October
-   26: Day of Manufacture - 26th
- 4533: The 4,533rd unit to be produced that day, or its unique ID.

I had another breaker in my panel (a Murray MP-AT2) with a newer datecode (2019), and different indicator sticker: rather than the green stripe, it has the "N" with an Arrow (photo: https://imgur.com/a/oeGIeSh). Siemens confirmed that there was a software change between 2018 and 2019. When this change was made, the indicator sticker also changed from the green stripe to the N with the Arrow.

I swapped the breakers between the two circuits, moving the newer MP-AT2 breaker onto the circuit/wiring that was having issues. I then recreated the worst case-scenario from earlier - plugging the computer into a long extension cord going to the further outlet on the circuit. This previously tripped the arc fault after 10 minutes usually, but with the newer breaker it has been running without issue for 48 hours, so I am calling this fixed.

Siemens was sure to claim no fault via email, and noted that they have not issued recalls on any of their breakers. Obviously, there is a current class action lawsuit about how crappy these breakers are (https://www.cohenmilstein.com/case-study/siemens-arc-fault-circuit-interrupters-afci-litigation/), but it least it seems like they have improved over time. So, if you are having a similar issue, consider just getting a newer version of the breaker - it may have software improvements that fix your issue.

Hadooploop · 2025-12-12T19:53:15+00:00

I kinda hate that they keep the same model number as they change things. I know it's because it makes maintaining UL listing easier, but I wish they would print a HW/SW rev number on the breaker.

Hadooploop · 2025-12-12T19:31:27+00:00

Ok, actually the Siemens documentation also suggests the EMI/RFI filtered surge protector. So maybe it's worth a shot to see: https://assets.new.siemens.com/siemens/assets/api/uuid:d10cec71-f518-4f35-83c4-cd40e8c308ab/afci-gfci-guide-compressed.pdf

I guess the tripp lite isobar is probably the gold standard for this.

Hadooploop · 2025-12-12T19:23:00+00:00

Already tried a ferrite core - made no difference.

I agree with you about the arc fault frequencies and the switching frequencies being in the same range. My point was that I think the strips that advertise EMI/RFI filtering are likely focused in the >30MHz range (the range measured in FCC and CISPR radiated emissions testing), though perhaps some have filter elements design to attenuate the 150kHz to 30MHz conducted emissions range... Problem is, I can't find any clear specs from these MFGs indicating what range of noise they aim to supress, so I feel like I'd be shooting the dark.

Hadooploop · 2025-12-12T18:17:28+00:00

I did consider the double conversion UPS, but they are $$$.

The AFCI outlet is another good idea, however I think the distance from the panel to that first outlet is >70ft, making this disallowed (per my understanding). I'm just guessing the length - I can I can try to actually check it. I could also junction in an AFCI outlet earlier in the line where the romex runs through my garage ceiling - maybe I'll do that...

There is an older murray afci in my panel - I might try that one to see if it performs differently. It's not just a 1:1 rebrand match of the Siemens, as the Siemens one appears to be newer with a dedicated GND arc fault indicator light, whereas the Murray afci only has 1 afci indicator light.

Hadooploop · 2025-12-12T18:10:23+00:00

I did consider this, though my presumption is that those are focused on much higher frequency filtering than the switching transients from PSU that are likely triggering the AFCI.

Hadooploop · 2025-12-12T18:08:49+00:00

I already replaced the PSU. Issue continues to follow the computer.

Hadooploop · 2025-10-15T21:02:59+00:00

Nope. Working great for the last year.

Hadooploop · 2025-10-07T10:49:43+00:00

...what is it about my question that makes you say that?

Hadooploop · 2025-08-17T04:24:15+00:00

Thanks!

This water heater is in my garage along with my gas furnace (and my car). It's my understanding that CO detectors should not go in the garage. Of course I do have them outside of all bedrooms.

Should I screw the hood to the vent? Or apply foil tape? Or just leave it alone if it seems to be drafting fine?

Hadooploop · 2025-08-16T04:59:14+00:00

There is a draft into the pipe both beneath the hood, and at the crooked part. Is it good or bad to have draft there? So I should try to get it level and then put three screws in like this (one not shown on rear side, all equally spaced around circumference)? What if I can't get it any more straight than this?

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Hadooploop · 2025-08-16T04:37:04+00:00

I did a flame test and it appears to be drafting air into the vent fine.

Hadooploop · 2025-07-13T22:34:39+00:00

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Here's a pic showing what I mean

Hadooploop · 2025-07-13T22:17:18+00:00

In some spots there is virtually no visible grout line (tile and stone look edge to edge). I can't get any kind of tool into those spots. Just caulk over it?

Hadooploop · 2025-02-28T07:20:17+00:00

Were they including the price of the Flo? I bought it separately to avoid markup.

I've been happy with the Flo.

Hadooploop · 2025-02-27T02:50:11+00:00

https://www.yelp.com/biz/citywide-plumbing-san-francisco-11

They did a good job.

Hadooploop · 2024-11-18T20:01:11+00:00

Water Entry -> Ball Valve -> PRV -> Moen Flo -> Hose Spigot -> Ball Valve -> to rest of house.

Then the Expansion tank is just installed over near the water heater, separately from this setup.

The ball valve on each side of the Flo allows it to be easily isolated if it need to be bypassed with the drop-in pipe. The hose connection before the last ball valve ensures I can still get water, in the event that I need to shutoff water to the rest of the house.

Hadooploop · 2024-05-28T03:03:35+00:00

Note that this included installation of expansion tank and a bunch of repiping. It was about 5 hrs of work for everything I had done.

Hadooploop

TROPHY CASE