Honeywell Aquastat L8148b Relay Question

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Old 01-09-14, 08:11 PM
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Question Honeywell Aquastat L8148b Relay Question

I'm helping a friend attempt to replace the Aquastat Relay on their boiler heating system. The model is L8148B, and I found in other threads and online that the replacement is the L8148J1009. Only problem is, I don't know if they have a 24VAC gas valve or not, how can I find out? Would there be a label saying 24VAC? Guessing yes but I haven't seen their setup yet so i'm unsure, but my guess is that it is probably 24VAC since that seemed very common. NJTrooper has responded to 2 other threads on the topic so I'm hoping he can chime in

I read the instruction manual on replacing the Aquastat relay in the Honeywell documents found here:
http://s3.pexsupply.com/manuals/1350..._PROD_FILE.pdf
One part I am uncertain about is this:
If old well is unsuitable for new installation, remove it and proceed
with instructions for new installation. If old well is suitable,
use it and a 124904 immersion well adapter (ordered
separately from form 68-0040, Wells and Fittings for
Temperature Controllers) for the installation. (If the well
clamp fits directly over the flange of the existing well
spud, adapter use is not necessary.) The adapter has a
flange at the wide end that fits into the well clamp and is
slotted lengthwise to accommodate both the capillary
tube and the short length of tube extending from the bulb"


Does this mean that we must also get the well adapter, or is this only if the old one is no suitable? I want to be sure we have all the parts ready to go IF we need these other adapters or what not. If the machine is old should I anticipate also needing to replace that well piece also? And if so, do I need to drain the system beforehand? I know I don't have to drain if its just the aquastat relay and probe, but guessing the well would require draining.

In relation to the terminals and wiring, I am guessing I will follow the existing schematic of wire location, and put them onto the new location, correct? I saw both schematics and they look similar with only a few minor variations (New one having more options). Must I break out a multimeter or will I be ok following old schematic and simply replacing to the new location?

He was told by a handyman that the aquastat relay is the problem in this system for the symptoms he is experiencing. I guess he has to keep manually turning it on or resetting it every morning to get it to fire, or something about the heat not rising over 70 degrees. None the less, he ordered the replacement Aquastat relay and i'm planning to go help install it this weekend and was hoping for some advice.

Help is much appreciated!
 

Last edited by handyfrank; 01-09-14 at 08:29 PM.
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  #2  
Old 01-09-14, 08:34 PM
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Chances are 99.99% that you won't have to change the immersion well.

I don't know if they have a 24VAC gas valve or not, how can I find out? Would there be a label saying 24VAC?
Should be markings on the gas valve... model number of gas valve, look up spec on internet.

What's the make model of boiler? That would be the most telling, as long as manual is on-line can look in there.

He was told by a handyman that the aquastat relay is the problem in this system for the symptoms he is experiencing
Sounds scary........................ not that some 'handymen' don't know what they are doing... but there's a helluva lot of boiler techs that can't troubleshoot a bad aquastat!
 
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Old 01-09-14, 08:51 PM
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I'm sure you'll hear from Trooper but in the meantime the 8148J can be used for 24v or millivolt gas valves.
If he has natural gas, then he has one of those systems.
It's most likely 24v unless it's a real old system. It should say it on the gas valve or get the name and model number.
 
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Old 01-09-14, 09:22 PM
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Thanks for the replies,
The system is definitely old (I'd guess 30 years). So if he has a 12V gas valve, is there a different aquastat, or does that mean the gas valve also needs to be changed out to a 24V? Hoping its a 24VAC so its one less thing to deal with. Is a millivolt the other option to a 24V valve? I am going to plan to try to get the info off of it and Google it, or hopefully just see the small 24VAC sticker right on it.

NJ Trooper, happy to hear that it is a 99% chance that extra piece doesn't need to be changed. So does that mean all we need is the new Aquastat and no other parts or adapters?

I'm unsure of the boiler make/model, but am going to look at that also and see what I can find.

Do the symptoms I mentioned sound like an Aquastat problem? I sure hope so
 
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Old 01-10-14, 05:41 AM
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if he has a 12V gas valve
I can't recall ever having seen a 12V gas valve. There ARE 120VAC valves though, but very rarely seen. Perhaps you meant to type 120?

Is a millivolt the other option to a 24V valve?
Millivolt is not 24V at all... millivolt gas valves are actually powered by the voltage that is generated by the pilot flame heating the "ThermoPILE" ... which is not to be confused with a "ThermoCOUPLE". The thermopile is literally a 'pile' of thermocouples in a single package wired in series to produce a higher voltage.

So does that mean all we need is the new Aquastat and no other parts or adapters?
As long as the a'stat is actually the troublemaker, probably so.

Do the symptoms I mentioned sound like an Aquastat problem?
Based on this:

I guess he has to keep manually turning it on or resetting it every morning to get it to fire, or something about the heat not rising over 70 degrees.
I would not be able to draw ANY conclusion without further testing. These are two very different symptoms and very non-conclusive as to the a'stat being at fault. Not saying it CAN'T be the a'stat, just saying that it's not conclusive that it IS.
 
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Old 01-10-14, 08:48 AM
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Thanks for the extra info. Yes, I meant 120V, sorry.

So I went over and got more info. The gas valve is a VS820 A 1013 which I read is 750 mV, not 24VAC. I called a supplier who sells the Aquastat L8148J replacement and he said that it will work with this gas valve also. So is 750mV mean it is a millivolt model?

For some extra info, the Aquastat is L8148B 1015, and then also says 120V, 60CY, and 2A Therm Current. The boiler system is a Utica model PGB125A.

Any extra info you can add will be great
 
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Old 01-10-14, 09:09 AM
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Hi Frank,

So is 750mV mean it is a millivolt model?
Yes, " mV " is the abbreviation for millivolt. Wire the new aquastat accordingly and pay strict attention to the 'jumpers' inside.

Note from a'stat manual:

FOR POWERPILEŽ (MILLIVOLTAGE) GAS
VALVES, REMOVE JUMPER TP-Z AND WIRE BURNER
B1-B2. JUMPER Z-W REMAINS IN POSITION
.

Were you able to obtain any clarification of the exact symptoms of the problem?
 
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Old 01-10-14, 12:30 PM
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Thanks for the extra info. Good tip on the PowerPile notes, thanks for pointing that out again.

Nope, I asked his son and he said his dad said the machine would cut out, and he would have to keep raising the temperature, and I think it would keep resetting. Not very clear so I'm unsure, but I think they want to attempt replacing the Aquastat anyways now that they got it, so i'm going to lend a hand. Fingers crossed.

What are some other common problems that go wrong with old boilers?
 
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Old 01-10-14, 01:07 PM
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What are some other common problems that go wrong with old boilers?
Actually too many to even begin to list...

Do you know if the system is 'zoned' or not? Multiple thermostats in the home, with electric zone valves at the boiler...

I can understand if having already purchased the replacement going ahead and installing it.

It could well be the problem. Without being able to clearly understand the problem they were having, there's really no way to speculate on a cause.
 
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Old 01-10-14, 01:42 PM
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It is definitely a single zone, and I think only 1 thermostat in a smaller sized apartment.

Agreed on now really being able to pin point without clear symptoms. I'll be back and let you know how I make out. Thanks again.
 
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Old 01-14-14, 10:18 AM
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Thanks again for all the help. We changed it out Saturday morning, wire by wire, and it hasn't shown the problem ever since! Success!

The only wires that took some thinking were the Thermostat wires, and that jumper which was already in the default location. $150 part, less than an hour of going slow, and the problem is fixed. Good deal in my book
 
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Old 01-14-14, 12:42 PM
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Good job Frank! Glad it all worked out and thanks for letting us know.

Millivolt systems, since they run on very low voltage, are susceptible to 'dirty' switching contacts. That may have been the case there.

Good Luck!
 
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