Honeywell L7224U Sensor Probe 50001464

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Old 05-08-16, 01:40 PM
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Honeywell L7224U Sensor Probe 50001464

Well, if you have to have a Heating problem, May is a good month to have one.

I've been relying on my L7224U Aquastat since around 2006 with very few problems . . . . so far. Whatever issues came up, I've discussed on this Forum.

Mid-day today we were just making Hot Water until the temperature dropped, and thermostatic call for heat should have occurred (and would have been appreciated). The Boiler was running to maintain the Low Limit only, and I had an Error Code 1 flashing periodically - Sensor Fault, Check Sensor

I read that this may be due to "'corrosion" . . . . but corrosion where ?

I touched nothing . . . . but AFTER the indoor temperature dropped 2 degrees below the normal Cut-In temperature, the Boiler Cut-In; and we've been heated up to our normal Cut-Out Temperature.

So it must have fixed itself ? I think not !

Now I wonder "How long has this Error 1 been appearing and correcting itself ?"

Is the Sensor Bulb leaking ? or fatigued ?

Are the contacts in the Modular 3 Prong Plug (female) what gets corroded ?

Are there any serviceable aspects to the Sensor 50001464 ?

Should I just clean the Modular Plug ?

I'm prepared to just order a new 50001464 and a small batch of Thermal Grease or Heat Conductive Compound to install a new Sensor in the Boiler Well; but wondered if others have encountered this problem ?

Is 10 or 12 years a "normal" life expectancy for a Honeywell Sensor 50001464 ?

I'm glad that this is happening in May . . . . and even happier that I was able to watch it at Mid-Day !

Any help or personal observations will be appreciated !
 
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Old 05-09-16, 07:59 AM
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Vermont-

I have the L7224 also. This is my second, the first only lasted a few years and the relay stopped working. I didnít look for a soldering defect on the board but rather just got another L7224U.

Iím pretty sure I remember that NJT would repeatedly say donít use the thermal compound unless you have to. I didnít use the paste as the bulb seemed to fit snugly in the well and I havenít had any problems.

If you used the thermal compound I wonder if it has a limited lifespan. If you didnít use thermal compound could there have been some in the well from a previous installation that has broken down? Maybe just a long shot.

I would try to clean the well thoroughly (however you do that, lol) and clean the bulb and try to make sure the bulb is in the well snugly. If you still have the problem I would try some new thermal compound. Then if you still have the problem I would then order a new bulb.

As you point out, there isnít much you can do there, and what in the world are they talking about when they say ďcorrosionĒ ? I guess they must mean the surface of the well. But that doesnít sound right. I wonder if they mean the surface of the well inside the boiler. Maybe that can happen. That would seem to make some sense. But that would be a bummer since you would have to install a new well.

Would be nice if there was a way to check the heat transfer through the well, because I can see worst case. You buy a new bulb and still have the problem. Then is it the well or is it a bad L7224U?

Maybe one of the pros would know how to check the heat transfer efficiency through the well. Hopefully it isnít necessary.
 
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Old 05-09-16, 09:46 AM
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Thanks for bumping my questions back up to active . . . . and for reading !

I haven't scrutinized it recently; but I think my Boiler's "well" is ĺ" or ⅞" in diameter and maybe 4" deep, so putting the Sensor Bulb (which is only about ⅜") without using some kind of thermal grease doesn't seem like there'd be a reliable contact or heat transfer ? My John Wood Boiler must date from the 1950s and modern boilers must have teeny tiny wells.

I also think that if my well was corroding, then I'd be experiencing leakage (under pressure) from the well. All of my experience with these Sensors was with the L8124 Aquastat, and the integral Bulb connected with copper tubing. I haven't looked at an L7224 Sensor up close and personal since that day in 2006(?) that I inserted this one in my "well". I do recall that I didn't clean the well out thoroughly in 2006; but scraped what ever loose and caked material out of it that came easily, made sure I had a clear path to the bottom, and supplemented it with the new Heat Conductive Compound that Honeywell supplied with the original L7224 at that time . . . . and no problems in 10 years.

Watching the digital readouts of the Boiler Temperature's activity, as an entertaining past-time during the quiet times, led me to believe I had real good contact and fast responsive readings that the Controller used to manage the System exactly as I had programmed (?) it to function.

Today, I can report that this System is operating "normal" and responding immediately to fluctuations in temperature . . . . not waiting 2į or more beyond a set point to take an action. I'm used to trusting these automated or mechanical processes to behave in a highly predictable manner (unlike Human Beans), and the erratic behavior I witnessed yesterday shatters my confidence (a little).

After a couple days of consistent behavior, I'm going to detach the Sensor's Modular Plug from the L7224, and examine the prongs to see if there's any corrosion (or moisture) there. Not knowing what the life expectancy is for these probes is, I guess I'll prepare for a replacement of the Sensor . 50001464 (less than $15,00) before Winter (and I'll keep the old one for reference).

Thanks for thinking about this (I knew you were a fellow L7224U User) so I expected that if anyone had something to offer, you'd be it.

One thing about these Digital Aquastats like the L7224 is that our local Service people shy away from them in preference to the older analog units that they seem to think gives them more control. I don't know if that is common elsewhere in the US; but around here, there aren't many technicians who I can speak with about these digital units.
 
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Old 05-09-16, 12:39 PM
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IMHO Vermont that sounds like a good plan.

I'm used to trusting these automated or mechanical processes to behave in a highly predictable manner (unlike Human Beans), and the erratic behavior I witnessed yesterday shatters my confidence (a little).
Isnít that the truth! When these things disappear on their own that doesnít give you a warm fuzzy. But it sounds like you are on top of it.

Good luck!!
 
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Old 05-10-16, 06:12 PM
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You can clean the inside of the well with a copper fitting brush. Hopefully that heat conductive compound hasn't turned to concrete. If I have anywhere near a good fit between the well & bulb or sensor, I don't use the stuff.
 
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Old 06-09-16, 08:04 AM
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I just ordered a new Sensor Probe.

Since the beginning of May, my L7224U has been behaving normally; but really it has been asked to do is control the creation of Hot Water.

Today, we awoke to outside temperatures of 38įF to 40įF, and indoors we had a nippy 61įF, so I thought this would be a good time to check and see if my Sensor Probe was still acting up.

So I reluctantly turned the Thermostat to "Heat" . . . . and sure enough, nothing !

I went down to the basement and as expected, the L7224U was showing Error #1 again, just as it had displayed in early May; indicating "Sensor Error". Physical things don't usually fix themselves, so this isn't a surprise . . . . if they do fix themselves, it's usually just for a short period of time - just long enough to lull you into some level of complacency.

Still, I dickered with the Boiler for a bit, turned the Emergency Switch on and off a few times, thinking that there might be a Re-Set function that would overcome this Error, and I even dis-connected the Probe's Connector in the L7224U looking for a bit of corrosion . . . . but none appeared.

I got the Boiler to activate the Circulator finally, and we got heat for a few cycles; but it's not reliable. I sure am glad it's June, and not February.

So I ordered a new Sensor Probe 50001464 from Boiler Geeks . . . . only $14.50.

I'll fiddle with this some more in the Fall; so I have something else to think about between now and then . . . . like I needed that ?
 
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Old 06-10-16, 12:55 PM
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Don't wait until fall to fiddle with the sensor. As soon as you get it, check it out.
 
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Old 10-10-16, 02:21 PM
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For those who are interested, I did get around to promptly replacing my Sensor today . . . . like they always say, "No point in doing today that which you can put of until tomorrow !"

Removing the old sensor wasn't as easy as I expected; part of the bulb remained at the bottom of the well. Here's a picture of the new sensor next to what I initially pulled out of the well:

[ATTACH=CONFIG]71735[/ATTACH]

The leads came out directly, without a struggle, so I don't I was responsible for separating them from the bulb in extracting the device; a progressively poor connection (corroding) to the thermistor was probably my problem from the beginning.

Here's a close-up of the ends, old and new (sorry about the focus):

[ATTACH=CONFIG]71736[/ATTACH]

So then I had to decide whether to retrieve the bulb from the bottom of the 7" or 8" well . . . . and how ?

I tried a variety of methods; but wound using a lag bolt and partially threading it into the bulb . . . . I think the thermistor is still at the bottom of the well, but not occupying much of the available space. Here's the corroded remains of the chintzy old bulb that I was able to retrieve . . . . I think the new bulb is of an improved design, with a rounded nose:

[ATTACH=CONFIG]71737[/ATTACH]

If you're wondering whether I used a new application of thermal grease when installing the new probe, I did apply about a teaspoon towards the end as I inserted it. I'm hoping that I won't be involved in replacing this sensor the next time around.

So that task is completed with plenty of time to spare !.
 
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Last edited by Vermont; 10-10-16 at 03:19 PM.
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Old 10-10-16, 09:36 PM
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a progressively poor connection (corroding) to the thermistor was probably my problem from the beginning.
You asked in your first post about corrosion. Seems you found it.
 
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Old 10-10-16, 10:03 PM
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Looks like the silver conductive compound on the end of that probe. Hardens like concrete. I never use it. Might drill out or leave alone or new well.
 
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Old 10-11-16, 03:43 AM
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I just use the same thermal grease (heat conductive compound) that Honeywell supplies with the L7224U . . . . it ought to have been engineered to inhibit corrosion of the components ?

And it ought not harden like cement either ?

My well is about ĺ" and the sensor probe is about only ⅜" so I guess I'll get a stiff brush to clean out the well and rig up a tiny attachment to my boiler vacuum so I can get all the debris out of the well "soon", and also see what readings I achieve without any compound.

I suppose I could also write Honeywell and ask if they have a better pliable heat conductor in the pipeline?

It's not a perfect world, is it ?
 
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Old 10-11-16, 07:53 PM
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Far from perfect, maybe what keeps it interesting.Ever fix your vent?
 
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Old 10-12-16, 03:46 AM
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Originally Posted by guyold
Ever fix your vent?
I guess I did . . . . cuz I don't think I currently have any that need fix'in . . . . but which Vent was that ?

I bought a new Taco Universal Flo-Chek valve; but never installed it after those few licks with a rubber mallet (suggested by my Wife) seem to have done the trick for the past few years.

If you could mention which Vent, I'll go check. Most of what I've done on the hydronic system has been successful up til now; but I'm always on edge, waiting for the other shoe to drop.
 
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Old 10-12-16, 06:14 PM
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I must have been thinking of something else.No sense dropping the shoe early,might as well enjoy the Fall.Nice on the check valve.
 
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