Is this Honeywell Aquastat Relay bad?

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Old 10-23-08, 10:52 PM
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Is this Honeywell Aquastat Relay bad?

I have a dual-zone hot water heating system with an oil-fired boiler. The system has a Honeywell Aquastat Relay L8124A for zone 1 and another relay control Honeywell R845A for zone 2.

I noticed I wasnít getting heat sometimes in zone 1. But if I just tap lightly on the L8124A box with the cover off the burner fires right away and I get heat. I found a picture with a description of the components in the box. It looks to me that when I lightly tap the box, according to the diagram, what I see is the ďCirculator RelayĒ doing something like chattering. That is, it seems to quickly open/close or something, with some sparking and then the burner fires and the whole cycle seems to be Ok.

Yet sometimes it will run through the cycle without having to tap the box.

All the wires seem tight in the box so Iím just assuming itís the relay. However I thought a Circulator Relay should close only after the burner runs for a while and heats up the water? It seems like the Circulator Relay closes and the burner fires at the same time when I tap the box - so I am a little confused. But I really donít know much about this stuff at all.

Is this just a typical way a relay goes bad? Will it do something like stick open/chatter ?

Iím assuming the best thing to do is just go out and buy a new L8124A control and put it in. Mine is actually an L8124A1114 according to the stamp inside the box cover. I noticed there are a whole lot of L8124A controls with different last 4-digits. For example: L8124A1015 seems to be sold in many places.

Does anyone know what the last 4-digits mean? I canít find out? I would assume any L8124A would be Ok and the last 4 digits are just a revision number or something Ė but Iím not sure.

Any thoughts would be greatly appreciated!
 
  #2  
Old 10-23-08, 11:42 PM
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The L8124 is a combination aquastat, low limit, circulator and burner control. There are several reasons why it may work intermittently and one of the reasons is the cheap relays Honeywell uses.

Depending on how it is wired it is common for the circulator and the burner to come on simultaneously.

I should know what the suffix numbers mean since I used to specify a lot of Honeywell equipment but I'm ashamed to admit that if I did once know I don't any longer.

Here's the pdf for the L8124 series:

http://customer.honeywell.com/techli...it/95-6571.pdf

Replacement is the easiest option.
 
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Old 10-24-08, 02:01 AM
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Before replacing the $200.00+ control, here is an old trick that sometimes helps out. Take a piece of light grit sandpaper, or the scratch part of a book of matches, with the power OFF, clean the contacts of any carbon from the relay in the control. Sometimes a carbon build-up is the cause of a poor connection.
 
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Old 10-24-08, 06:56 AM
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Sometimes the 4 digit code denotes a different high limit range, for example 140-220 vs 180-240.
 
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Old 10-24-08, 10:25 AM
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Thanks a lot folks!

I will try the light grit sandpaper trick hopefully tonight. Most certainly worth a try for 200+ bucks. Took a look at the above Honeywell link. Good detailed information. I think I can replace the L8124A myself. Done a fair amount of box wiring and I’m not afraid of that.

But when the tech data at the above Honeywell link talks about getting the capillary and bulb in the well with the capillary bent properly – does anyone happen to know if that is real hard to do or does it just sound harder than it really is? Is the capillary some kind of very small diameter copper tube that can be bent and coiled?

About the mystery of the 4 digits after L8124A: I did in fact believe that I came across some information online somewhere that did in fact relate those 4 digits to some limits. But I couldn’t find the information again, so I thought I just confused it up with something else. But according to oil_boiler , maybe I didn’t imagine it!

Thanks again folks for your time. You have been very helpful.
 
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Old 10-24-08, 04:23 PM
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Dad, it sounds harder than it is... you should be able to handle it no problem I think. There is a small capillary tube with a 'bulb' on the end. You just need to make sure that the bulb bottoms out in the well.

The different 'flavors' of the controls can also change the 'fixed differential' that the control operates at in addition to the temperature.

I would use this:

L7224 aquastat

to replace that.

Per this:

Honeywell replacement info

Does your boiler also provide domestic hot water to the home?
 
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Old 10-25-08, 11:36 AM
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Thanks NJ Trooper.

Your recommendation of the L7224 is very helpful. I think you read my mind. When I was trying to figure out how the burner and controls and pumps, etc. form the system (I know zero, itís tough) I had found that Honeywell says the L7224 is the replacement for the L8124A.

But looks like you can still find the L8124A out there. I was only going to use the L8124A because I figured every connection would be exactly the same and in the same position and therefore there would be no need to change wire lengths or anything like that. Not that I couldnít do that if necessary. (But looks like thereís enough extra length in my wires so they could reach anywhere in the L7224 new box anyway.) Plus I figured there would be no new variables- if I could get the bulb in the well properly the L8124A would be guaranteed to work. And it sounds like your saying the bulb placement is not a project.( Thanks.)

But I admit Ė thatís not much of a reason to stay with the old stuff. I was torn. But now I think Iíll go with the L7224. My boiler does provide hot water to the home.

Thanks again!
 
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Old 10-25-08, 03:16 PM
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The 7224 is a little different in that it doesn't use the capillary and bulb. It has a thermistor on the end of a piece of wire. But, just the same, as easy, or easier to install.

Plus, it's got blinky LEDs and a digital display to appease the electronic gadget freaks among us!
 
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Old 10-25-08, 06:17 PM
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How many gallons of oil are you using a year? You may want to consider another source of domestic hot water, and using your boiler only in the winter.
 
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Old 10-25-08, 06:27 PM
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Is it a tankless coil or indirect?
 
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Old 10-26-08, 07:20 PM
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Hi again folks!

Thanks a lot for all your time.

I do like the idea of blinky leds and the digital display. Canít help it. I see what you are saying and I can well imagine that a thermistor on the end of a piece of wire isnít that much different than the capillary and bulb. I think going with the new stuff is the right thing to do and installation differences sound minor and should just be a minor consideration.

Iím using about 800 gallons of oil per year. Iím in southeastern Pa. I believe the previous owners used about 1200 gallons per year, they were a little bit more elderly than me and probably kept the thermostat much higher than I do. I keep the thermostat very low. Sweaters work!

I have a ďNew YorkerĒ boiler with what Iíve been told is a ďsummer winter hookupĒ (I think!). And if I understand correctly (but I could be wrong) I have a tankless coil. (There is no water heater anywhere else in the house.)

I was in fact thinking that if I could work up the courage maybe someday I could install an electric water heater and somehow tee it into to the hot water supply line and not use the oil boiler to supply hot water. But leave all the connections there so that using the boiler is still an option.

Whether that scheme makes any sense at all Ė I have no idea. Sounded good when I was thinking about it Ė but I know about nothing about how these systems work.

Thanks a lot again!
 
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Old 10-26-08, 09:10 PM
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Tankless coils in the boiler are probably the least efficient ways of producing domestic hot water. In order for them to produce hot water on demand, the boiler controls must keep the boiler hot 24/7 ... when yer sleeping, when yer at work, etc ... when oil was cheap, nobody really cared... it was a quick and dirty way of making hot water.

On top of that, they really don't produce all that much hot water! You would think that for all the money you spend keeping that boiler hot, at least you could run 2-3 hot showers in a row ... nope ... ain't gonna happen.

An indirect is an efficient hot water producer. The boiler only fires up when the tank drops below setpoint, and when no hot water is being used, that's not very often, they are very well insulated.

Even an electric water heater probably makes sense economically if switching from a tankless. I wouldn't bother piping one in series with the tankless though, just install it as a standalone and let it do it's thing. Turn off the Low Limit on the 7224 and let the boiler go cold start. (there's the argument that if a boiler has spent it's life as a warm-start, it may leak when allowed to go cold due to the contraction of the sections... so keep that in mind.)

On the other hand though... if it was piped in series... and the boiler run cold start... in the summer the electric would just heat the water... in the winter when the boiler is running anyway, why not 'pre-heat' the water into the electric ? I've heard that some water heaters put a limit on how hot the water can be coming in though, but don't understand why that would be an issue. Maybe someone can comment on that.

Bottom line is that I might be willing to bet that at least 20% of your oil useage is going toward producing domestic hot water.
 
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Old 10-27-08, 01:39 PM
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Thanks NJ!

I bet your estimate about 20% of my oil is used to produce domestic hot water is very close. Last time I tracked the gallons used over the year Iím pretty sure I did in fact use somewhere around 20% (or even a little more!) of the total yearly during the warmest months when I know there was no demand for heat. That got my attention.

Oil was much much cheaper when this system was installed (in the 90ís before I moved in). Even back in 2002 when I moved in oil was way cheaper than now. I see what you are saying about how inefficient these tankless coils are.

I did not know at all about tankless and indirect. Thanks. I found a site in about a minute that indicates exactly what you are saying about the efficiency of indirect. Thanks for the info.

http://apps1.eere.energy.gov/consume.../mytopic=13020


I understand what you are saying about turning off the Low Limit on the 7224 and cold start and the consideration about boilers which have spent their life as warm start. Very interesting. I wonder how many people know that? And the other consideration about piped in series and pre-heating the water into electric. Many things to think about.

Iím determined to do something. Hope to do something before next spring. With oil so high it seems to me that some of these changes can easily pay for themselves in no time.

Thanks for your time and the valuable information!
 
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Old 11-03-08, 08:59 AM
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Hi again folks Ė

Just wanted to let you know that thanks to your help and advice I first tried the contact cleaning trick as suggested by plumbingods as worth a try before buying a new control. Good try but still had a problem.

So I went modern and got the L7224 replacement for the L8124A as suggested by NJ Trooper and installed it. Glad I did. Works great. Easy to set the High/Low limits and the differential just by pushing buttons and reading the display. And you can read out the boiler temperature, read when the circulator is on, read when the thermostat is on, etc.

Pretty good stuff. Helps a newbie like me get a picture of what goes on in the system including the limits and timing just by reading the displays over a period of time. From everyoneís inputs above, Iím starting to understand this stuff Ė well a little bit anyway. (Thatís scary, thatís when I become dangerous!)

Thank you!
 
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Old 11-03-08, 05:35 PM
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Good on ya !

Hey Dad, thanks for lettin' us know it's all good.

Nice thing about the 7224 is that you can widen the diff on the HIGH setting ... If you've got an oversized boiler, running a bigger diff will tend to lengthen the burner cycles, with more space between ... net result is the same, more or less, as to the amount of oil burned, but you may pick up a percent or so in efficiency due to the longer burns...

Let us know what you decide to do with the water heater ...
 
 

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