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[tinfoilhat2020]

So the past few days I noticed the boiler cycling more often than normal....SP is 175-185. I was in the yard and noticed it come on 10 min after shutting down...I said hmm that odd so I checked boiler gauge and it was at 182....I checked aquastat on back (ranco) and it was 174....then it instantly jumped to 183. Then shut off at 185 like it should.....I watched it for the past few days and noticed this happen again once or twice. Not consuming any more wood than normal...pumps are all working...house and building are up to temp as it should b....so this morning I notice my inside bbg temp is at 190( I knew the boiler temp was probably closer to 200 bc the BBQ temp on the pex has always read a bit lower...) So I run out to the boiler....boiler gauge is at 196..go to the back and aquastat is at 176....I crap fans down, go back to check aquastat again and its at 197 ....hmmmmmmmmmmmm what the hek? Could the probe be getting flase readings? Could the flow in the boiler be making a cold spot? I have dual pumps hooked up, one for shop and one for house. BG nrf-22 and BG NRF- 36  (on 2nd speed). They seem to be working fine...and like I said everything is getting heat....the aquastat just seems to be jumping around a bit.....ANU THOUGHTS?? Thanks guys

[mlappin]

Have a spare aqua stat?

I’d think if it had a cold spot it wouldn’t instantly jump up in temp when the cold spot dissipated unless said cold spot instantly disappeared.

And since you said this has only happened the last few days I’m guessing a bad sensor.

[tinfoilhat2020]

Mlappin...I have the original one that came on the boiler I'm going to hook up...Honeywell mechanical

[tinfoilhat2020]

So weird it works fine for a while then seems to have a mind of its own on a cycle every so often

[RSI]

Is there any chance the water is low enough that the the aquatat could be out of the water?
If you had a honeywell aquastat, I am guessing the well is around 7/16" ID. Could the probe be making poor contact with the inside the well?

[tinfoilhat2020]

Turns out that temp of be sensor is junk.....contact in the well is fine...I put the sensor in a cut of hot water and the temperatures were jumping all over the place...what a piece of junk....this is the 3rd Ranco I've been thru in 3 months! I guess I'll try and Johnson A19

[mlappin]

Weird, still using the same one I installed on the waste oil boiler last year.

Usually I get the junk.

[tinfoilhat2020]

I have returned 3 of them thru amazon so far this year...I mean its not costing me any more $$$...but I just want something to hook up so I do t have to mess with it anymore

[RSI]

Has the same thing happened to all of them or was it a different problem each time? They are usually real reliable.

[tinfoilhat2020]

First one didn't even work, 2nd one the temp probe was pinched and didn't get and accurate reading....those were sent back right away....simple exchanges on amazon...the third one worked good for 2 montha until now

[ambonci]

I also have a ranco on my boiler and I noticed a few weeks ago the probe was cracked.  its just a year old.  is you probe cracked at all?  Not to hijack your thread but will a cracked probe cause a false reading?  So for hijacking but both having ranco issues.  Good diagnosis by the way!!!!!

[tinfoilhat2020]

I ordered a Johnson A419....they are refunding me for my ranco. Hopefully I have better luck there. Probe didn't appear to be cracked

[RSI]

I also have a ranco on my boiler and I noticed a few weeks ago the probe was cracked.  its just a year old.  is you probe cracked at all?  Not to hijack your thread but will a cracked probe cause a false reading?  So for hijacking but both having ranco issues.  Good diagnosis by the way!!!!!

The crack shouldn't hurt it unless it breaks the sensor or wire inside. You probably want to keep it dry though.

[RSI]

First one didn't even work, 2nd one the temp probe was pinched and didn't get and accurate reading....those were sent back right away....simple exchanges on amazon...the third one worked good for 2 montha until now

Sounds almost like Amazon got a bad batch of them.

[doow14]

How much was it to buy one from amazon,might be they are getting iffy units to sell cheap.I think I paid about 80 bucks 6 years ago from McMaster carr.I have seen rancos on ebay for 20 or 30 dollars.might get one for a backup.