Honeywell L7224 Auquastat keeping burner on intermittently

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  #1  
Old 11-14-20, 10:09 AM
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Honeywell L7224 Auquastat keeping burner on intermittently

I have a Honeywell L7224 electronic aquastat that I put on my boiler about 8 years ago, the original non "electronic" aquastat failed and I decided to upgrade to this one to have more control over the boiler. It had been working great but this last month there were two instances when it seemed to keep the burner running indefinitely. To the point where the system was over pressurized and the relief valve opened. This last time boiler pressure was well above 30psi and the valve hadn't opened yet (I replaced it 5 years ago and I'll replace it again now that it has opened), The aquastat read temperatures of 280 and my mechanical gauge was way above its limit of 250. The aquastat was seemed to still be calling for the burner to be on.

I am about to replace it just for piece of mind. Do these units fail like this often? Do I potentially have something else going on? I also replaced the oil primary about 5 years ago with a Honeywell R7284u1004.

Oil fired Weil Mclain
HL 180
Hdiff 10
LL 158
Ldiff 14

Anything else I should check?
 
  #2  
Old 11-14-20, 11:13 AM
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Hi Ethan -

I replaced a Honeywell L8124 with the L7224U in 2008. But in 2012 the new L7224 failed in that sometimes it would not close the relay for the burner connections B1 – B2. It was intermittent. Maybe it was a poor solder connection but I just bit the bullet and installed another L7224U and I haven’t had any problems so far. So the new L7224 has been running from 2012 till now.

I ‘m not sure but if you look at burner status on the display I think it tells you whether the burner is running or not. I’m not absolutely sure though. If the display does not display burner running while the burner is actually running would that mean the L7224 burner relay is stuck? Seems like it would.

It seems like the L7724 must have a problem. I think it definitely should shut off on the high limit and why would it keep the burner going anyway, the low limit should have been way past satisfied or if it there was a thermostat call for heat that should have been satisfied. Just seems to me no matter how you look at it the L7224 must have been the problem – or at least part of it.

I would look at the display when the problem happens and see what the High Limit and Boiler Temperature readings are, and the Burner Status reading.

Some good boiler people here so maybe they will chime in.

My bad! Need a correction. I just checked my written record and it wasn't B1-B2 on the L7224 that was the problem. It was C1-C2. The L7224 would not turn on the circulator C1-C2. So I would never measure 120v at C1-C2 and the circulator would not run. Sorry about that.
 

Last edited by zoesdad; 11-14-20 at 02:07 PM. Reason: added "my bad ...
  #3  
Old 11-14-20, 04:32 PM
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Frequently on DIY thread is dialog on diagnosing and fixing the issue that suggests replacing defective old generation product.

Rather than just replacing the old unit it is opportunity to install new generation products with money saving features costing the same or even less.

In links below are 2 aquastats, with $5 price difference. The first can save up to 20% on fuel costs, has far more accurate and wider range of control settings with digital LCD display of menus and settings.

https://www.supplyhouse.com/Tekmar-2...iler-4150000-p price $158

https://www.supplyhouse.com/Honeywel...ronic-Aquastat price $153
 

Last edited by doughess; 11-14-20 at 05:14 PM.
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Old 11-15-20, 04:03 PM
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ethan169 might check out history on Honeywell R7284U control. Sometimes it provides useful info on system.

My favorite history message is "No Flame"

While that gives no clue as to cause of no flame, it at least say why it locked out.
 
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Old 11-15-20, 04:11 PM
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The Tekmar is only an aquastat in that it controls the burner circuit ONLY. It does not control the circulator. You still need a high limit aquastat and a circulator control much like the 7234
 
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Old 11-16-20, 09:18 AM
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Dictionary Definition of Aquastat: an automatic device for regulating the temperature of water heated by a boiler or furnace
Manufacturers of heating products create confusion when calling products “aquatats” that do several other functions beyond water temperature control.

On systems with multi function “aquastats”, when installing ODR Aquastat, burner activation is moved to OCR-A contacts.

The existing aquastat functions are left enabled, and the 24 VAC transformer used to power ODR-A.

Boiler over temperature is separate subject that when called “high limit aquastat” adds to confusion. Why not call boiler safety relief valve a pressure regulator? So is “low limit aquastat” used to deactivate circulator”

On boiler with Honeywell-l7224 when talking about "aquastat" confusion results
 

Last edited by doughess; 11-16-20 at 09:38 AM.
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Old 11-16-20, 03:22 PM
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doughess,
Dictionary terminology is one thing, reality is another.

If you could post pics of your boiler and control setup it would greatly help eliminate the confusion you are speaking of that so many of us seem to have.

Thank you for your help with this matter.
 
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Old 11-16-20, 10:26 PM
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A basis of human communication is meaning of words.

Have global experience in high technology world dealing with technical terms. That is why pointed out the issues with use of word "aquastat" in a DIY posts.

Was trying to clarify issue, not confuse it with rambling, verbose text. Confused thinking is frequently seen in posts. Try to help the novice DIYer and not focus on finding faults.

Picture of my system would not show concepts. Am not big on appearance, rather functionality, efficiency, reliability, maintainability and safety.

In one of my old posts there was a picture.
 
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Old 12-16-20, 07:54 AM
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Thank you for everyone's responses. I apologize for not responding sooner. I had typed a reply and apparently never submitted it!

Due to my hot water source using a domestic coil in my boiler, I need to get the boiler running again asap. I sourced the same "aquastat" locally (5 min before the supply store closed) and replaced it along with the other parts I needed. It's been running normally ever since, which is great.

I agree with douglas that the term aquastat could be misleading as it controls additional components like the circulator pump. While I do like more control and information from these types of controls I didn't have the luxury of time to order online. My system is plenty efficient for me at the moment so any savings on better controls would take some time to justify cost wise. I'm happy with the way the aquastat works, as long as it continues to actually work. I'm also disappointed that the pressure relief valve did not open when it should have. I'll be more diligent in purging the valve at least annually to clear out any debris.

I also replace my water pressure regulator with a functioning unit. The one old one didn't seem to adjust properly but I left it alone since I never really lost any water from the system. If the pressure relief valve would have opened releasing steam and water, that would have been a different story.

Anyway, thanks again for all the help!
 
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Old 12-17-20, 06:56 PM
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DH goes uses those sources and items that are “best buy”.

Supplyhouse.com has low prices and overnight delivery to those within 75 miles (New York City).

Often items on SH page has informative links to helpful text i.e. Install, Submittal and Literature.

The Supplyhouse.com page on Watts Auto-Air-Vents is good example. Along with link to manuals/submitall sheets, scroll down and see helpful reviews.

https://www.supplyhouse.com/Watts-05...Vent-3679000-p
 

Last edited by doughess; 12-17-20 at 07:23 PM.
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Old 12-17-20, 07:21 PM
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On boiler systems I'm a firm believer in over temperature protection. In the future look into a Honeywell L4006 high temperature limit controller. It's a basic stand alone thermostat that monitors the hot water line leaving the boiler via a strap on bulb. It can be set to open at any temperature.
 
  #12  
Old 12-17-20, 08:42 PM
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Agree on using over temperature burner shut off using separate sensor.

Use $10 eBay PID temperature +/- 1 degree F controller with LCD digital display.

One channel shuts down burner a 190F and second channel to deactivate circulator at 135F

Tiny thermocouple sensor slips in to boiler well along side existing aquastat sensor/bulb. Honeywell L4006 requires separate well.

PID can be located to easily see boiler temperature.

https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15
 

Last edited by doughess; 12-17-20 at 09:54 PM.
 

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