Replacing a L8124A Aquastat with one that doesn't have a minimum temp (domestic hot water)

alansupra94

Hi heatinghelp

Thanks for the help before in determining the best way to eliminate domestic hot water from a coil in a combination AFG (just leave the coil in and leave the ends open).

Now I am trying to figure out which aquastat I should get to replace my L8124A/C/J. This aquastat has a minimum temperature that I assume is for domestic hot water. Since this is going to be baseboard water heat only, I was wondering if there is another control setup I should get instead.




Single AFG burner, single circulator pump, dual zone but that is controlled by the Nest thermostats (has two seperate ones).

Thanks!

109A_5

Hello @alansupra94,

I think I would just disable the minimum water temperature function.



I believe removing this B wire from the temperature limit switch (low limit side) would disable the minimum water temperature function. Tape and put in a safe place. No new Aquastat needed.

EdTheHeaterMan

You would also want to set the low limit to the lowest setting of 120° this way the circulator can operate at 120°. if you leave the low limit to the 140° or 160° setting then the boiler temperature must get to that temperature before the circulator pump will operate (That is a priority hot water feature that you no longer need)

The Aquastat that I would replace the L8124 with is the L7224U. That one can be set up as a cold start aquastat and is less expensive than the L8148 that is usually on the older cold start boilers of that era. That said, @109A_5 has the lower cost option. Remove the Low Limit wire from B terminal and make sure it is capped off.

HVACNUT

A little bathroom reading.

EdTheHeaterMan

@HVACNUT prefers that HydroStat over the L7224U however, I have come across more than one that has at least one problem or another. The Hydrostat with a replacement Well Adaptor can also be a low water cut off. That said, if you don't change the well adaptor and use your existing well adaptor the LWCO feature does not work so, it is about the same as the L7224U. I have also found the low limit potentiometer (the low temperature adjustment dial) were defective on more than one control and failed to maintain the desired setting. Vibration of the heating system caused it to move. I'm sure that the HydroStat folks have corrected that on the latest versions, but I have never has an issue with the L7224U control in all the years I have used it. That was my Go To replacement control for a number of oil heat (and even Gas Heat from time to time) triple aquastat relay and cold start boiler controls. Just my 2 cents!

I still believe that the L8224 you have will be just fine

HVACNUT

EdTheHeaterMan said:

@HVACNUT prefers that HydroStat over the L7224U however, I have come across more than one that has at least one problem or another. The Hydrostat with a replacement Well Adaptor can also be a low water cut off. That said, if you don't change the well adaptor and use your existing well adaptor the LWCO feature does not work so, it is about the same as the L7224U. I have also found the low limit potentiometer (the low temperature adjustment dial) were defective on more than one control and failed to maintain the desired setting. Vibration of the heating system caused it to move. I'm sure that the HydroStat folks have corrected that on the latest versions, but I have never has an issue with the L7224U control in all the years I have used it. That was my Go To replacement control for a number of oil heat (and even Gas Heat from time to time) triple aquastat relay and cold start boiler controls. Just my 2 cents! I still believe that the L8224 you have will be just fine

I wasn't trying to promote, sway, or cajole. Just putting it out there. I actually have the L7224U on my boiler as we speak. But I'm using my tankless coil. I also have a 3250 Plus with well (which the well takes about 38 seconds to replace) in the box for when an indirect was in the plans. Now when I do anything, it'll be the whole system. 
I have my WTGO-3 piped P/S with the primary circulator opening on low limit while the zone circulator(s) continue to dispell usable BTU's. Sounds silly but the boiler is from '96 and was 1 zone, split loop. I moved in in 2002 and immediately added an addition so I also added zones. For the budget, that's the best I could come up with at the time.

And I'm not aware of any of the issues you've experienced. Where they the 3250 Plus, or earlier versions? 

EdTheHeaterMan

Most likely the earlier versions. But like any new product, after you try the new thing and you have more than one bad experience, it's time to move on. In the past I could not say enough about the R72xx series of primary controls. They were the best thing since sliced bread, then they came out with the Diagnostic LCD display screen. WOW! Not to long after that Carlin came out with the 70020 ProMax with even more diagnostic features. When I retired, I had stopped stocking the Honeywell primaries and only stocked the Carlins. Once I find something I like, I try to stick with it until something better happens.

Likewise, I was a Taco man on just about everything they made. Pumps Controls Zone Valves Hydronic Specialties. Was that way for over 30 years. But looking at the Caleffi stuff, if I were still in business, I might be looking more at that stuff. Taco is Quality, Caleffi is Quality, Honeywell is Quality (not so sure about Resido since that happened just about the time I retired) The Turbo Capacitors are quality, and that Carlin primary is Quality. I look at the warranty on these things and when a company is ready to step it up to get an edge on the competition, I look harder. Taco was the first the have a 3 year warranty on Circ Pumps IIRC, Turbo Caps have a 5 year warranty, Carlin has a longer warrnaty on the primary controls. This feature talks to me.

HydroStat would need to step it up to convert me. To late for that, Im retired! But there may be others like me out there still working.

Those are the opinions of an old retired guy!

Mr. Ed

alansupra94

109A_5 said:

Hello @alansupra94,

I think I would just disable the minimum water temperature function.



I believe removing this B wire from the temperature limit switch (low limit side) would disable the minimum water temperature function. Tape and put in a safe place. No new Aquastat needed.

Awesome this looks like a pretty simple thing to do.

HVACNUT said:

A little bathroom reading.

EdTheHeaterMan said:

@HVACNUT prefers that HydroStat over the L7224U however, I have come across more than one that has at least one problem or another. The Hydrostat with a replacement Well Adaptor can also be a low water cut off. That said, if you don't change the well adaptor and use your existing well adaptor the LWCO feature does not work so, it is about the same as the L7224U. I have also found the low limit potentiometer (the low temperature adjustment dial) were defective on more than one control and failed to maintain the desired setting. Vibration of the heating system caused it to move. I'm sure that the HydroStat folks have corrected that on the latest versions, but I have never has an issue with the L7224U control in all the years I have used it. That was my Go To replacement control for a number of oil heat (and even Gas Heat from time to time) triple aquastat relay and cold start boiler controls. Just my 2 cents!

I still believe that the L8224 you have will be just fine

Thank you for posting both for me to look at.

Two options seem to be:

1. to remove the B wire from the temperature limit switch (low limit side) and tape off. Leave everything else as is.

2. Get a L7224U which may require a R7184 and some rewiring (also an outdoor switch would be nice).


It looks like the L7224U is a pretty nice unit with an optional outdoor reset (very tempting but looks to be pretty expensive ($400+) (50022037-002)

Looking at the L7224U, it seems to call for a more modern oil primary control (R7184). Currently I have an R8184G installed on the AFG Burner BUT I have a R7284 hanging out in the garage on a spare burner I got locally.

Wiring would look like this I think:



I just watched a video on the R8184G (saying it should be forbidden) but I have zero idea what this guy is talking about. He seems to just test functionality. (https://www.youtube.com/watch?v=EL8qdSoGcwk)

So the next question is do you think it is worth it for me to get a L7224U, install the spare R7284 I have in the garage and maybe snag an outdoor reset (for cheap) and bring my setup into a more modern era?

Thanks for all the help once again.

109A_5

Hello @alansupra94,
I believe that video is by @Gordo a member here. I think he likes the safety and control logic and electricity economy (ignition system) of the older and possibly newer units better as compared to the R8184. Maybe he will comment.

I wonder if Honeywell still sells the 12SN7GTA tube, the Audio folks still use them.

alansupra94

109A_5 said:

Hello @alansupra94, I believe that video is by @Gordo a member here. I think he likes the safety and control logic and electricity economy (ignition system) of the older and possibly newer units better as compared to the R8184. Maybe he will comment. I wonder if Honeywell still sells the 12SN7GTA tube, the Audio folks still use them.

Awesome I'll wait to see if he responds.

I'm leaning towards just the simple mod at this time due to simplicity. I can always replace it down the road if the setup being discussed in here is really recommended. 

The outdoor reset is definitely very interesting but I assume that can't be used with my R8184 and aquastat currently.

109A_5

Hello @alansupra94,

alansupra94 said:

Looking at the L7224U, it seems to call for a more modern oil primary control (R7184). Currently I have an R8184G installed on the AFG Burner BUT I have a R7284 hanging out in the garage on a spare burner I got locally.

Looks like the L7224U can replace a L8124A. So I would expect it to work with a R8184G. Sometimes documentation just reflects the era it was written in and the current product line. Also you may not get the all features and benefits of updated equipment.

EdTheHeaterMan

You can use the L7224U with the older design R8184G with no problem. Likewise you can use the L8124 (or L1848 for cold start boilers) with any of the newer R7284 series primary controls. If I were you and I had a free R7284 device available, I would swap that out. It is a "safer" primary safety control.

I found an old article from a 1970s trade publication that gives detailed step by step instructions on how to use a L8124 style triple aquastat relay that is designed for tankless coil boilers to replace L8148 aquastat relay on a cold start boiler.

It pretty much says that you remove the wire from the B terminal on the low side of the aquastat as mentioned above in @109A_5's original post. The next step is to remove the other two wires from the Low aquastat R & W and wire nut them together. This will complete the circuit to the circulator 100% of the time that the relay is closed on a call for heat, making it a function identical to the L8148 aquastat relay.

The following diagram will illustrate the identical circuit in each control. By eliminating the Low Limit portion of the L8124 control, the circuit is identical to the L8148 control. L1 hot feeds both the 1K1 and 1K2 relay contacts. The 1K2 contact is fed from the connected wires removed form the Low Limit R and W terminals on the L8124. The 1K2 is fed by the Jumper to terminal 3 on the L8148. All other circuits are identical.

HVACNUT

@alansurpa94, keep in mind the R8184G has been obsolete for quite some time. If it were mine, I'd be more concerned with upgrading it for safety purposes over the aquastat for penny purposes. 

STEVEusaPA

Any newer control, used or brand new, is only 'safer' if you properly check the operating and safety limits. Just wiring it up and not checking properly is stupid, dangerous and unprofessional-and not necessarily in that order.

alansupra94

EdTheHeaterMan said:

You can use the L7224U with the older design R8184G with no problem. Likewise you can use the L8124 (or L1848 for cold start boilers) with any of the newer R7284 series primary controls. If I were you and I had a free R7284 device available, I would swap that out. It is a "safer" primary safety control.

I found an old article from a 1970s trade publication that gives detailed step by step instructions on how to use a L8124 style triple aquastat relay that is designed for tankless coil boilers to replace L8148 aquastat relay on a cold start boiler.

It pretty much says that you remove the wire from the B terminal on the low side of the aquastat as mentioned above in @109A_5's original post. The next step is to remove the other two wires from the Low aquastat R & W and wire nut them together. This will complete the circuit to the circulator 100% of the time that the relay is closed on a call for heat, making it a function identical to the L8148 aquastat relay.

The following diagram will illustrate the identical circuit in each control. By eliminating the Low Limit portion of the L8124 control, the circuit is identical to the L8148 control. L1 hot feeds both the 1K1 and 1K2 relay contacts. The 1K2 contact is fed from the connected wires removed form the Low Limit R and W terminals on the L8124. The 1K2 is fed by the Jumper to terminal 3 on the L8148. All other circuits are identical.

This is perfect. I think I am going to go with this.

I think the next question is I have been reading up on bit on flue gas condensation. Is that a worry for me with a cold start heat only baseboard hydronic oil boiler? (I have a Weil-McLain WGO boiler).

I will be adding in the tigerloop I have soon as well.

HVACNUT

alansupra94 said:

This is perfect. I think I am going to go with this. I think the next question is I have been reading up on bit on flue gas condensation. Is that a worry for me with a cold start heat only baseboard hydronic oil boiler? (I have a Weil-McLain WGO boiler). 

Yes, it's a worry. But not with the 3250 Plus. Just saying. 

alansupra94

HVACNUT said:

alansupra94 said:

EdTheHeaterMan said:

This is perfect. I think I am going to go with this.

I think the next question is I have been reading up on bit on flue gas condensation. Is that a worry for me with a cold start heat only baseboard hydronic oil boiler? (I have a Weil-McLain WGO boiler). 

Yes, it's a worry. But not with the 3250 Plus. Just saying. 

I think I may lean toward the 3250 Plus because it isn't that expensive and the outdoor reset option is pretty reasonable to (wired and only ~$60). I like the features of it as well and seems simple to wire in.

I think the plan is to install the 3250 plus with outdoor reset, tigerloop and R7284. I am tempted to get a new circulator pump (possibly with freeze protection) but I don't know much about the new Taco pumps.

HVACNUT

Ask around about the Outdoor Reset. Some feel that without high water volume, i.e. a buffer tank, ODR will promote short cycling of the burner. 
Start with the Economy setting and Thermal Targeting. It could be all you need.

I'm not aware of a circulator that offers freeze protection by itself. It's usually through a control.

alansupra94

HVACNUT said:

Ask around about the Outdoor Reset. Some feel that without high water volume, i.e. a buffer tank, ODR will promote short cycling of the burner. 
Start with the Economy setting and Thermal Targeting. It could be all you need.

I'm not aware of a circulator that offers freeze protection by itself. It's usually through a control.

Okay I will start and see how it is.

As for the freeze protection, I remember seeing a friend's setup that had a taco pump and relay that basically measures water temp and moves the pump when the temperature gets below a certain point every hour.

I wasn't sure if the relay was universal or if I need to upgrade to pump to use it (like the pump is PWM or newer tech)

leonz

I have had 2 hydrostat 3250 plus units fail because the low water cut off function failed and the second units LWCO also failed for the same reason while i was watching it run and I replaced it all with a Honeywell L8124L and Bell & Gossett RB-122-E LWCO and I have had zero problems since then for the last 7 years.

I will be simpler for you to disconnect B in your current triple aquastat and tape it off.

alansupra94

leonz said:

I have had 2 hydrostat 3250 plus units fail because the low water cut off function failed and the second units LWCO also failed for the same reason while i was watching it run and I replaced it all with a Honeywell L8124L and Bell & Gossett RB-122-E LWCO and I have had zero problems since then for the last 7 years. I will be simpler for you to disconnect B in your current triple aquastat and tape it off.

I got a hydrostat 3250 plus local for cheap but mainly for it due to going to a cold start boiler. This should prevent any condescending flue (if I'm saying that right).

Did the LWCO sensor fail or part of the board? It seems like you need a special sensor to run the LWCO and I wasn't sure if I had that or if I would even use that.

leonz

Hello alansupra94,

The low water cut off function failed period went to steam and nearly boiler my boiler dry.

The single bulb that they use is what they use for both the "normal" operation and the low water cut off function.

The second 3250 plus had a mind of its own and while I was running the boiler on the oil burner to test the
3250 the unit had a mind of its own and shut the low water cut off function off while I was standing there and that is when I had enough and pulled it and returned the units to the reseller later.

If your going to keep that thing invest in a pair of Bell & Gossett direct immersion low water cut offs wiring the first unit as the first direct immersion electric control in a 3/4 tapping in the steam chest to shut the boiler down and then position the second one on the pressure side of the circulator using a 3/4 bushing in a Tee the size of the piping. Wire the first low water cut off as the VERRY FIRST electrical control connection to the boiler and then run the BX cable to the second low water cut off and then run the BX cable to the 3250 plus.

I have friends that still have had failures with these units 7 years on after I had failures with the units i was supplied with in 2015 and 2016.

I have slept very well at night with my Honeywell L8124L and the Bell & Gossett RB-122-E LWCO watching over my boiler for the last 5 years.