Honeywell/Resideo Aquastat alternative?

t4chi

Hello all

I recently managed to fry(confirmed transformer no longer functional, also having issues with the relay not working when connected to a new transformer) my L8148-1257 aquastat while trying to install a Taco ZVC404 - though while looking around for replacement options and their cost, I'm surprised to find that this simple little board costs over $400 to replace! Is that really not that bad? Is there any alternative products to handle the job? It's my first home and my introduction to hydronic heating. The boiler is a Crown AWI128, would also be curious to know if it would be worth looking into an upgrade for the boiler as it's a bit old at this point - (would a newer model be more efficient enough to justify?) - going into the summer I was planning some other zone/heating changes as well so would like to know if an upgrade here is worth considering.

Thanks

HVACNUT

The vent damper is for efficiency only. If it was removed, and the wiring corrected, then a different aquastat could be used.

A better route would be to eliminate the damper and repipe the flue with a gas draft regulator and spill switch.

A new boiler of the same design won't be noticeably more efficient. Controls and near boiler piping could make it more efficient.

t4chi

https://forum.heatinghelp.com/discussion/comment/1800360#Comment_1800360

Thanks for the reply. I understood the vent damper to be primarily for safety - to allow exhaust out the flue, and secondarily to close when not in use to block drafts. Is that not the case?

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1800376#Comment_1800376

The damper can't block the flue if it's not there. It's sole purpose is to meet minimum efficiency requirements.

EdTheHeaterMan

Hello all

I recently managed to fry my L8148-1257 aquastat while trying to install a Taco ZVC404

That ZVC404 device is pretty easy to install, If you fried your Aquastat Relay transformer, there are some things you may need to consider. Your ability to install electrical controls is about par with my brother-in-law's ability to use an 18" Pipe wrench. After causing more damage that it was worth, He threw it in the trash to avoid the possibility of future DIY catastrophes.

though while looking around for replacement options and their cost, I'm surprised to find that this simple little board costs over $400 to replace! Is there any alternative products to handle the job?

That is the best control to keep your boiler operational. It has the ability to safely operate a Vent Damper, the circulator and the burner. If you try to design a lower cost DIY Fix, you may design a unsafe condition into the boiler control system. (based on your proven ability to follow the manufacturer's instructions above), You have a Pressure Vessel inside your home that has the ability to explode if about 10 things go wrong at the same time. If you start removing those built in safeties one at a time, then there is a greater chance of that failure happening some time later.

It's my first home and my introduction to hydronic heating. The boiler is a Crown AWI128, would also be curious to know if it would be worth looking into an upgrade for the boiler as it's a bit old at this point - (would a newer model be more efficient enough to justify?) - going into the summer I was planning some other zone/heating changes as well so would like to know if an upgrade here is worth considering.

The Crown AWI128 is a real workhorse that will last over 40 years if maintained properly. and that maintenance is not that hard. (look in the manual under maintenance). If you decide on a more efficient boiler system, the cost of the new boiler and the amount of time that nes high efficiency boiler is expected to last, you will see that the savings on tour fuel usage will not justify the new equipment.

since we can not quote actual numbers of this type of work I will just give you a hypothetical

You do not need to replace at this time since your heater can be repaired for less than $500.00 DIY if you can follow the instructions.

That leaves the entire cost of the new boiler system to be offset by the savings.

Lets say a new ultra high efficiency boiler costs $180.00 and your existing fuel bill is $10.00 per year. You would need to save 9 dollars a year for 20 years to break even. There are 2 problems with this, First is the new boiler will not save $8.00 per year and second, the boiler may not last more that 18 years, The bottom line is keep the boiler you have.

On the other hand if your boiler has failed and you must replace it, then you will need to spend $130.00 for the regular boiler and $180.00 for the better boiler. The difference is only $50.00. And since the new high efficiency can save you that in about 12 years, and the new high efficiency boiler will last 20 years, then you will have 8 more years of savings. So the bottom line is different in this case since you must spend at least $130.00 in this instance.

Although I agree with @HVACNUT more often than not, and I am not a fan of Automatic Vent Dampers, in this case I must say that you probably do not want to re-invent the wheel. The AVD will reduce your operating cost (that amount is different for each customer based on the way your house is built) and it is a factory provided part, You might be best to leave it in there and bite the bullet for the $400.00+ control

There are 2 ways to fry the transformer in the L8124 control

1. Connect 24 volts from another control (like the ZCV control) to T and TV in the L8148
2. Connect the Z terminal the the T terminal in some way.

I hope this helps with your decision process.

EdTheHeaterMan

Not recommended.  I have also replaced the transformer inside the L8148 control in the past.  I was confident in my ability to read the printed circuit board and my ability to solder the transformer wires onto that board.  You only need a 20 VA rated transformer that will fit inside the box, or you can mount the transformer outside the box and carefully run the wires thru one of the unused 1/2" conduit fitting holes.  But if you are not confident with your ability to solder to a printed circuit board, then you should spring for the new control. https://www.grainger.com/product/FUNCTIONAL-DEVICES-INC-RIB-Class-2-Transformer-120V-AC-2ETC4

EDIT: you must cut out the old transformer wire connections on this type repair.

Steamhead

If that were my boiler, I'd replace the Honeywell with either a Beckett AquaSmart or Hydrolevel HydroStat control. These offer some energy-saving features that your old one did not.

And I'd keep the damper. It not only keeps cold air from drafting thru the boiler when the burner is off, but also reduces air infiltration into the house when closed. Current-model Field dampers have replacement motor units available, so you don't have to replace the entire damper if it breaks down. Any service organization worthy of the name should stock these replacement motors.

t4chi

https://forum.heatinghelp.com/discussion/comment/1800392#Comment_1800392

I appreciate the insightful reply and edit with included picture. You're spot on about the ways to fry the transformer - this was my fault for not having rtfm well enough, and so I humbly accept the comparison to your BIL 😅

I've ordered a new L8148 and am looking forward to getting it hooked up to the ZVC correctly this time.

EdTheHeaterMan

@t4chi said:

"I appreciate the insightful reply and edit with included picture. You're spot on about the ways to fry the transformer - this was my fault for not having rtfm well enough, and so I humbly accept the comparison to your BIL 😅

I've ordered a new L8148 and am looking forward to getting it hooked up to the ZVC correctly this time."

Not gonna try for the $17.00 transformer. Good Call!