[Mrmotofy]

I'm trying to pinpoint a weird issue with my boiler overheating bypassing the HiLimit cuz the control reads a lower temperature and continues to fire.

I've contacted Dunkirk tech support for the XEB-3 and he suggested replace the well, but was stumped and not sure what to say. He had no real good ideas and apologized. Only other suggestion was switch back to original aquastat, sorry $200 every 3 yrs is not gonna happen. Especially with the known history on em.

Contacted Hydrolevel the control manufacturer and they politely consistently informed me it was dangerous and should be looked at by a licensed plumber cuz it was a really dangerous situation blah blah. But he was stumped, so he checked with his head engineer and was also stumped. Suggested try to find someone local, but agreed it might be hard and expensive to find someone knowledgeable enough. Also found it confusing nothing was consistent but was random. But agreed must be system related due to 2 different aquastats doing same thing.

So I'm left to deal with it. I want to verify all the wiring is correct so that's why I need the diagram. I've seen a lot of em but none quite match what I have.

Essentially the old 8148a aquastat died again after only 3yrs...those dumb relays again. So the Honeywell 7224 seems to be a universal replacement. Great, install it, everything is fine for a couple weeks, then boiler started overheating randomly. After being shutdown for a while restore power and it's back to normal for a day...or 3days and a random overheat. Find out the control is consistently reading abnormal low temp when actual temp is 250deg and overheating. So control keeps firing boiler attempting to heat up. Now remember this is a random occurrence. Sometimes it's during a call for heat, sometimes it's just heating back up. Can be hours, or a day or two. So the control seems to be malfunctioning as in getting wrong temp. Temp probe is all the way in well, zone valves seem ok opening and closing correctly, flow is ok, Circ pump is ok, no other piping/pump changes etc, boiler fires up perfect and shuts down fine and normal most of the time. Aquastat must be bad.

Return Aquastat and get a Hydrolevel 3150, install it no problem. Runs great for a few hours then same thing. Temp reads abnormal low and boiler overheats. Power down for a while to cool down and back on and everything is fine again till it randomly does it again. In normal operation the control temp and analog gauge on boiler is only a few degrees different. But when malfunctioning control said 153 deg but boiler was at 250ish. I decided to pull the well out to inspect for mineral deposits etc and verify size if replacement is needed. Reinstall and refill and everything is all good till a random overheat after a few hours of normal operation.

So clearly something is going on and neither tech support had any useful suggestions. I'd also like to add an overtemp limit switch likely in the 120v line to boiler transformer.

 

[TarheelTerp]

and should be looked at by a licensed plumber cuz ....

cuz they have insurance and usually a clue.

Generally... HVAC = refrigeration components & controls
Generally... BOILER = plumbing & heating contractor

Who did the install and initial commissioning?
Start there.

 

[Mrmotofy]

cuz they have insurance and usually a clue.

Who did the install and initial commissioning?
Start there.

Since the Boiler manufacturer and control manufacturer didn't have a clue. It's not gonna be an easy one. Or a cheap fix going through techs till ya find one that actually knows something. On top of that it's only randomly malfunctioning. It's darn near impossible to fix something when it's not broken.



I didn't post on a diy page how do I find a contractor. If I was looking for one I wouldn't be here trying to find a solution. My home is insured and we can work on anything in the home as a homeowner. Now if you have nothing else useful to add kindly move on and have a happy new year. :vs_cool:

 

[TarheelTerp]

Since the Boiler manufacturer and control manufacturer didn't have a clue.

Don't sell them short. They got all the clues they need.
Just like everyone else reading your posts here does.

 

[Mrmotofy]

Don't sell them short. They got all the clues they need.
Just like everyone else reading your posts here does.

I didn't sell them short, they told me. I don't know what to tell you, there's clearly something going on there but I don't know what it is or how to tell you to proceed. Other than the one guy says call someone local.

They said they don't know I'm just relaying it. So what's your point?

I'm looking for someone who claims they know and wants to help and we'll go from there.

 

[TarheelTerp]

I'm looking for someone who claims they know and wants to help and we'll go from there.

Again... Who did the install and initial commissioning?

 

[Mrmotofy]

Again... Who did the install and initial commissioning?

A local company installed it in 04. There was some idiots that owned the house before I did and butchered all kinds of stuff and may have messed with the wiring but I don't know for sure. It doesn't seem like a pro would have done the wiring the way some of it is. So I figure I'll start from scratch and check everything. I have my opinions on the way some of it should be but I'd prefer to see how a third party would do it.

 

[surferdude2]

I think what everyone is saying is, it will take someone eyeballing the installation of the limit control to determine why it isn't sensing the correct temperature. I can only guess that there is some crud in the heat well or perhaps it could use some heat sink compound... just guessing. I'll bet any competent heating/plumbing contractor could cut right to the chase and fix it. It's dangerous as you have been told and people are smart to not try to fix it remotely, as you are finding out.

I'm just going on what you have posted... if the limit control isn't sensing the temperature overrun, then it has three possibilities, 1. poor contact between the sensor and the heated surface, 2. defective control, 3. shorted wiring.

Thermal grease <<<<<<<< read that and get some.

There may even be other possibilities. If it worked before and doesn't now, then something failed. Look for the failed item.

SD2

 

[Mrmotofy]

I'm just going on what you have posted... if the limit control isn't sensing the temperature overrun, then it has three possibilities, 1. poor contact between the sensor and the heated surface, 2. defective control, 3. shorted wiring.

Thermal grease <<<<<<<< read that and get some.


There may even be other possibilities. If it worked before and doesn't now, then something failed. Look for the failed item.

SD2

I know nobody knows me but I'm aware of pressurized heated vessels. I'm aware of the dangers, I'm aware of what might happen. I've been trying to solve the issue with different controls for a while. I can monitor it remotely and shut it down although house is occupied most of the time and everyone knows what the sound is and how to shut it down. The blow off valve operates as needed. I'm almost able to automate the shutdown with a limit switch, the first ones I tried were cheap inconsistent junk. I'm really surprised there isn't a limit switch installed on the boiler itself, but I guess maybe would be hard with the varied conditions of use.

Both new electronic aquastats are spec'd as a replacement for what was there. In theory they should work. I know that, the boiler tech support knows that. The Hydrolevel guy questioned the model I have till his engineer said don't worry it's fine.

I'm aware of thermal grease/paste etc. The instructions state specifically Don't use thermal transfer grease, this one is designed for the Electrowell with low water cutoff, which is disabled on control. Hydrolevel verified they will work in a standard immersion well. But many areas require the low water cutoff. I have an autofill valve so low water is very unlikely. But it does appear to be working fine and accurately at 10-12psi it's rated for.

I'm aware of the flow chart for temp readings. The control is new, and operates the same as a similar control but different brand. These 2 are electronic though, the original was the old analog style with mechanical relay etc. The temp probe is fully inserted, well is clean etc as it's never had any grease/paste in it. The Dunkirk guy said if there was air in the lines the opposite readings would be happening as in it would read too hot and shutdown. So he seems to think it's not air bubbles in the line. But It's been flushed 2x now just to make sure and well has been removed inspected and reinstalled(was virtually spotless) as I suspected.

It works correctly most of the time, the temp reading is consistent with the boiler mechanical gauge until the control temp reading is randomly and intermittently reading low and it continues to fire the boiler even though it's actually overheating. I also verified temp of the fitting well is installed into, with a IR thermometer and mechanical boiler gauge reads pretty accurate. 2 different brand newer style electronic controls are acting the same and weird which rules out the controls failing. But why is the question and what is the solution?

That's what led me to the wiring possibility and needing suggestions on what is actually correct to compare it to with my specific components. Some commenters said they had a bad Neutral on the transformer going to the house blowing boards out. Power company repaired and no problem since. Another guy said he disconnected control from the main power and plugged into a UPS and never a problem afterwards. Hinting at other power issues going on.

The other main issue is it's so intermittent, it's near impossible to know if anything is fixed except with time. So I could have 5 guys checking it billing me hundreds each time and nobody knowing if the problem is actually fixed.

 

[surferdude2]

The instructions read as follows (bolded text by me:
IMPORTANT
Best thermal response is obtained with a well
that snugly fits the sensor. Insert the sensor
until it rests against the bottom of the well.
Use a well of correct length and bend the wiring, if necessary, to hold the bulb against the
bottom of the well.
If the well is not a snug fit on the sensor, use
the heat-conductive compound (furnished
with TRADELINE®
models) as follows: Fold the
plastic bag of compound lengthwise and twist
it gently. Then snip off end of bag and work the
open end of the bag all the way into the well.
Slowly pull out the bag while squeezing it
firmly to distribute compound evenly in the
well. Bend the wiring, if necessary, to hold the
sensor against the bottom of the well and to
hold outer end of the sensor in firm contact
with the side of the well. See Fig. 2. Wipe
excess compound from the outer end of the
well.

Red markup is mine:

 

[Mrmotofy]

The instructions read as follows (bolded text by me:
IMPORTANT
Best thermal response is obtained with a well
that snugly fits the sensor. Insert the sensor
until it rests against the bottom of the well.
Use a well of correct length and bend the wiring, if necessary, to hold the bulb against the
bottom of the well.

The instructions specifically say Don't use heat grease. I presume it's likely cuz it causes interference with the conductivity of the sensor to the well for Low Water...but don't know for sure. Top paragraph last line-after Note
The well is a pretty standard 3"
That still wouldn't explain why it reads accurate temp most of the time. It seems like if the temp sensing was poor it would be poor all the time and sometimes high and low etc. The probe has a small wire like paper clip that compresses in the well therefore keeping probe in contact with opposite side of the well. The previous Honeywell control had no such wire but also read temp and responded the same way. Leading me to believe poor contact isn't the cause.
At this time the control reads 175 and gauge reads like 168ish, close enough to be normal in my opinion of a digital vs mechanical. The last time it malfunctioned the control said 150, the gauge said 260ish.

I also used an IR thermometer to read temp on housing well is screwed into and gauge seems to read about dead on at all times, I trust it not the control.

 

[surferdude2]

I think we can agree that the control is working as it should based on the input data it is getting. The thermistor is the first point of measurement and proper contact is of the utmost importance.

This type of device is normally much more responsive and accurate than a simple capillary tube thermostat.

There are only two possibilities that I can see. Either the thermistor isn't in proper contact with the heat well surface or the control electronics are defective.

Given that the problem is intermittent in nature, it would seem to point to something related to thermal expansion at the heat well contact or temperature failure of some discrete electronic component in the control. I suspect the latter but would want to verify that the thermistor and its proper installation was beyond doubt.

Now... given that you have changed back and forth between a capillary and a thermistor type of control and have experienced the same exact issue (taking your word for that) then we can then suspect that the heat well has some sort of problem that is fooling these controls.

I recommend extreme measures to make sure the well is absolutely clean down to bare metal. A drill powered brush might be the method.

I can't imagine that the heat well would be located in such a position that it's being subject to temperature stratification in the boiler when the circulator pump is not running. You have indicated that the surface temperature near the well seems accurate and high enough to trip the control off yet the digital display doesn't track that same temperature. That pretty well shoots down the stratification theory.

Another thing that you should perform, just to cover all bases, is to purge the entire system of any possible air entrapment. Likely you already have but I had to mention it.

If after all these steps, none of it help, I'd suggest getting a new control since that one isn't controlling.

SD2

 

[Mrmotofy]

I think we can agree that the control is working as it should based on the input data it is getting. The thermistor is the first point of measurement and proper contact is of the utmost importance.

This type of device is normally much more responsive and accurate than a simple capillary tube thermostat.

There are only two possibilities that I can see. Either the thermistor isn't in proper contact with the heat well surface or the control electronics are defective.

Given that the problem is intermittent in nature, it would seem to point to something related to thermal expansion at the heat well contact or temperature failure of some discrete electronic component in the control. I suspect the latter but would want to verify that the thermistor and its proper installation was beyond doubt.

Now... given that you have changed back and forth between a capillary and a thermistor type of control and have experienced the same exact issue (taking your word for that) then we can then suspect that the heat well has some sort of problem that is fooling these controls.

I recommend extreme measures to make sure the well is absolutely clean down to bare metal. A drill powered brush might be the method.

I can't imagine that the heat well would be located in such a position that it's being subject to temperature stratification in the boiler when the circulator pump is not running. You have indicated that the surface temperature near the well seems accurate and high enough to trip the control off yet the digital display doesn't track that same temperature. That pretty well shoots down the stratification theory.

Another thing that you should perform, just to cover all bases, is to purge the entire system of any possible air entrapment. Likely you already have but I had to mention it.

If after all these steps, none of it help, I'd suggest getting a new control since that one isn't controlling.

SD2

The previous control used temporarily before being swapped with the current was also a thermistor, the one before that was 3yrs old and failed from a relay starting the whole thing was the old capillary tube analog style. Both newer electronic thermistor types have been operating the same way. They have been different brands and models but both newer electronic style. So I'm lead to believe it's not the controls malfunctioning but system related. Which was also affirmed by the Dunkirk tech and the Hydrolevel tech.

While possible it's the contact in the well, I also find that hard to believe cuz it's pretty easy to install it, the new one has the wire holding it to the other side of well. The sensor is installed fully and seems right. While that is the obvious cause it seems improbable with the numerous times it's been removed and replaced, Also both controls were doing it.

I also did drain and refill the system 2x to try and eliminate air bubbles. There's a Spirovent that removes air automatically. The Dunkirk guy said if there were air bubbles the temp would be spiking and causing shutdown. Also leading me to believe that's not it. There's also an autofill valve that appears to be working and holding steady 10-12psi it's rated at. The air bubbles was one of my first guesses and audible for a while after refilling and running.

I could attempt to find a brush long enough to reach inside...But not convinced that's the cause. Since most of the time it works and reads perfect. The internal sensor is sooooo simple it seems improbable. But I find it more probable that something else could be influencing the reading/control. But I don't know what. Being all electronic they are more sensitive to external influences than the old kind. Which is why I was thinking to look over the wiring with a magnifying glass and verify everything.

It's been running perfect for 48hrs now and I haven't touched it since it overheated last and I shut it down. I'm beginning to worry.

 

[surferdude2]

Sometimes putting data together from different time frames leads to the wrong conclusion but I don't think that is the case here unless you don't agree with the following statement:

I was basing my diagnosis of the poor heat well contact on the fact that you stated about using the IR tool and it showed the higher temperature while the control displayed the lower one. That seemed to me like the control wasn't getting proper input from the thermistor.

That just gets me hung on it being the thermistor contact. There could be some gunk in there that is affecting the response. But let's consider another possibility.

Perhaps a very slow seepage of water that evaporates and cools the thermistor. A tiny crack or erosion of the heat well could cause that. I would suspect a crack more than an erosion since it the problem is intermittent and a crack would be more dynamic than an erosion hole.

So, there a new possibility for you to consider. Installing a new heat well would be the fix.

 

[Mrmotofy]

So, there a new possibility for you to consider. Installing a new heat well would be the fix.

I'm not ruling anything out completely. I'm also trying to balance probability. But I do have a hard time believing a crack/leak could cause a 100deg temp differential. I'm leaning towards putting a new well in just so I could rule that out, and it's a cheap option. I'm sure it's had a few cycles in the presumably 15yrs it's been in there.

For the most part yes I agree with your different time frames data theory for the most part. But backtracking to see what's changed that may have caused an issue. The only thing is the control, both new controls acted the same way making me wonder if there's some kind of force influencing the operation. Maybe it's coincidence, or maybe there's a force there that's not obvious I don't know. 3 days now and it's been flawless.

 

[beenthere]

First, I'd probably just get a new analog control and put it in.

It may very well be a grounding problem. Since the control uses the grounding for LWCO operation. And since your using a standard well instead of the one for LWCO operation. A grounding issue in your home may be interfering with the controls operation.

Is your home on a well? Was there any other electrical work done at your home in the last year?

 

[Mrmotofy]

First, I'd probably just get a new analog control and put it in.

It may very well be a grounding problem. Since the control uses the grounding for LWCO operation. And since your using a standard well instead of the one for LWCO operation. A grounding issue in your home may be interfering with the controls operation.

Is your home on a well? Was there any other electrical work done at your home in the last year?

They said on both controls it replaces the old analog. This model has LWCO disabled and manual and confirmed with control tech they work for regular immersion wells. Nope city water, and no electrical done recently.


I've been wondering if there was some kind of interference from something, but not sure how I could find out



It "should" work as a replacement for old control

 

[beenthere]

It should. So either you have to check your home for ground issues. Or install an analog control.

 

[Mrmotofy]

It should. So either you have to check your home for ground issues. Or install an analog control.

As far as I can tell the Home ground system is fine. Using the little plug in testers everything verifies as grounded and wired correctly. I connected a receptacle to the line of boiler feed and tested with the plug in tester, everything tests perfectly. Using a multimeter one gets 120v from Hot to Neutral and hot to ground/metal case. It's grounded as much as one can reasonably test that I know of. I have numerous other computers and UPS devices(Computer battery backup) plugged in around house that would also indicate a wiring fault, which don't. I have all the normal GFCI's around the house that would also indicate a fault, they don't.

As an update everything ran fine for about a week, then late one night it overheated and has multiple times since. It makes no sense.

I finally got a new well and installed it so I could rule that out. It ran perfect for about 6hrs then began random overheats again. What could possibly cause the temp to read low, and why is it not consistent?

 

[beenthere]

Did you check to see if there was a voltage reading between ground and neutral at the boiler.