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Issues with & Replacement of Honeywell L8148E Aquastat

rrabih Member Posts: 38

We have a Honeywell L8148E that has started to act up and in.
We are planning to change it ourselves, but we have few questions:
- Actually, it stops sometimes and when the thermostat kicks in, sometimes it clicks sometimes no, we switch the power off-on, and it usually comes back for a cycle or two.
- the maximum temperature now is set to 180F
- To check whether the issue is coming from the relay, I did test T-TV it gives 24v, TV to W gives 24V as well. But nothing passed to the burner (B1-B2)

The reference indicated in the cover is only L8148E but while looking to buy a replacement I found many differents other sub references, (L8148E -1257, L8148E -1265,...) how could I know the one to buy (the transform is 24V when it works)?

Thanks for help


  • unclejohn
    unclejohn Member Posts: 1,736
    There should be a paper sticker on the control at the top that has the last 4 numbers.
  • HomerJSmith
    HomerJSmith Member Posts: 1,345
    I'll tell you what is wrong with it. Since you are a home owner you can do it. As a professional the liability question stops me from doing it except on my own stuff.

    You have to be careful when doing this as there is low voltage and high voltage on the circuit board, so you got to make sure they are isolated from each other. Normally it is isolated with fish paper.

    You take the circuit board out of the metal box. You mark and remove all the wires and their location on the circuit board such as TT and circulator wires and any romex or BX conduit clamps.

    The aquastat is connected on the well tube in the boiler with a screw clamp, loosen the screw clamp and gently pull the aquastat out of the boiler well. Do not damage the bulb or the tube connecting it to the board. Bend the four tabs holding the board in the metal box and gently remove the board, keeping an eye on how the fish paper is located behind the circuit board.

    Look at the solder joint on the back of the board, under magnification if need be. You are looking for cracks in the solder joints. If you find one, just re-solder that joint with a non acid solder. Reverse the procedure and re-install the aquastat.

    You just saved over $200. Or you can just buy one from

    L8148E**** That four digit number is important in getting the right one as it comes in various configurations.
  • BobC
    BobC Member Posts: 5,209
    We used to call that the black ring syndrome (looking closely you would see a very thin black line where the joint had cracked), it was usually caused by either insufficient heat during the solder operation or parts that were corroded when the soldering was done.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • rrabih
    rrabih Member Posts: 38
    edited January 2018
    Thank you for your answers, it is very helpful.
  • rrabih
    rrabih Member Posts: 38
    I actually just found the 4 digits, they are inside just above the transformer, it is L8148E 1216 - .2A THERM , 120 V 60CY CURRENT.

    I've looked to find which one I could buy and found this link:

    in which the cross reference is the product L8148E-1265.

    Thanks a lot to you all,

  • unclejohn
    unclejohn Member Posts: 1,736 your best bet.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,191
    I would never modify (solder) a safety control to save a few bucks. They are easily obtainable, and cost what they cost.
    What if the unit doesn't shut down on safety and you end up with a runaway boiler or a fire? You assume all the liability.
    Steve Minnichdelta TJellis
  • HomerJSmith
    HomerJSmith Member Posts: 1,345
    Pexuniverse is cheapest.
  • rrabih
    rrabih Member Posts: 38
    I thank HomerJsmith for the proposal to Solder the join, but for safety as STeVEUsaPa said is first for me and high, I would even call someone technician but in my area it is going to be a total of 900$ or so, and I prefer to call when it is something harder to do (Valve change or circulator change or any other professional work..) I an willing to pay 200 but not 900 for this...
    thank you all for your valuable inputs.
  • HomerJSmith
    HomerJSmith Member Posts: 1,345
    You got to be kidding me $900 to change an aquastat, it's so simple you can do it yourself in 1/2 hr at the most. You can buy this at really cheap, it comes with instructions and heat conductive compound for the bulb. Just wire it up, the same as the old one and take a picture of the wiring before you start dismantling it so you don't forget where the wires go.

    Ask your tech guy what he will charge you for the aquastat, then you will get an idea of who you are dealing with. A license isn't a license to steal. Hey, wait a minute, it is!

    Shop around for a technician and ask his hourly rate. Some technicians won't install a product that customer buys, I do, after all, it's still money in my pocket. Although, I always note on the billing that the customer provided the product.

    Do the change out yourself, if you have any mechanical ability at all.
  • rick in Alaska
    rick in Alaska Member Posts: 1,222
    Make sure it is the aquastat before you change it. Take the wires off the t-t screws on the aquastat and put a jumper across the screws. If it still doesn't work, then it is a bad aquastat. If it does work, then you need to find out where the signal is getting lost.
  • HomerJSmith
    HomerJSmith Member Posts: 1,345
    Rick of course you're right. A pair of alligator clips across the TT contacts (where the thermostat wires connect) when it doesn't work will tell you if the thermostat and wires or the aquastat is the problem. But, I've seen this so many times that I'm 99% sure that the relay solder joints have cracked because of the vibration of the relay closing over time, leads to metal fatigue of the solder joint. This creates an intermittent condition.
    rick in Alaska
  • rick in Alaska
    rick in Alaska Member Posts: 1,222
    I've seen it so many times I can close my eyes when I have the board in front of me and find the cracks. When they started shipping them out to be made, the new builders did not put enough solder on the pins, and it just took a while for the problems to show up. But, they were out of warranty by then.
  • rrabih
    rrabih Member Posts: 38
    So I did replace the Aquastat, it fixed somehow part of the issue, but not all o f it. Now at least when there's a signal sent to aquastat, it clicks and when the temp is beyond the limit (180F) it stops. this is good.

    But still one issue, let me explain:
    I have two zones, with two circulators, the circulators are controlled by Argo Control box not but the Aquastat (attached image ); the Aquastat only controls the temp limit of the water (to shut the boiler).

    What happens is that the signal is lost somewhere between the thermostat and the aquastat: I think the Argo has an issue, or may be just there is an issue in cabling because the Argo controls well the Circulators.

    In summary:
    - Zone-1: is for the hot water to use in the house.
    - Zone-2: is for the heating; there are 3 zones valves but they all share the same zone.2 in the Argo control, if one of zone valves starts (once the temp for one thermostat in house reaches the minimum) , the signal is sent to the boiler via Aquastat.

    What happens is this: the thermostat reaches the minimum temp, sends a signal to the zone valve that turns and send signal to Argo Control, which than starts the circulators and also send the signal to the Aquastat relay, if temp is less than 180F, the Aquastat sends signal to the gas valve for the boiler to starts.

    the signal is lost somewhere between Argo and the Aquastat in an intermittent way: sometimes it works sometimes not....

    Any idea?