Aquastat assist

Renchai · December 11

I have a Utica star fire steam boiler sfh4150st with a tankless coil for domestic hot water and a hot water loop supporting a new addition. My issue is with the loop bubbling & flashing when the boiler builds a head of steam. I’m thinking of adding new aquastat that can control both high and low however I am not aware of a unit that will shut down the circulator at 200 degrees.

Appreciate the guidance

EBEBRATT-Ed · December 11

Can you post a few picture of the boiler and controls and the hot water loop connected to the boiler?

You may need a bypass pipe to mix and control the temp of the hot water loop.

109A_5 · December 11

https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

Renchai · December 11

I understand the best practice when installing a loop on a steam boiler unfortunately I did not

do the initial install. Please note the ball valve that is tied off the loop, not sure if that was a Utica best practice 25 years ago .. I have attached the requested picture

HVACNUT · December 11

Why are there Tee's above and below the circulator? The piping back to (or from) the boiler off the bull of the Tee looks like its above the water line.

109A_5 · December 12

What model is this aquastat ? It probably has a high limit. You could connect the circulator for your hot water loop to the aquastat's burner terminals. So if the boiler's water temperature is above the high limit the burner and the circulator will both be off. Probably may not even need the aquastat's burner circuit connected to the burner, since the steam zone and the DHW low limit are both active. If you actually want two different high limit temperatures (burner & circulator) you will need another aquastat.

However in the midst of winter either way may limit the available time for the hot water loop to actively work. Since you will have to wait for the boiler water to cool down enough to activate the circulator and as soon as the Steam zone calls again the water will go over the high limit. You could try it with minimal changes.

If it does not work well you may need the proper piping for the proper water blend temperature for the hot water loop.

Example Aquastats;

https://www.supplyhouse.com/Johnson-Controls-A19DAC-1C-Temperature-Control-100-240F

https://www.supplyhouse.com/Resideo-L4006A2007-High-or-Low-Limit-Aquastat-100-240-DegreeF-range-5-30-DegreeF-Adj-Differential-L4006A2007

Renchai · December 12

The aquastat model is a ra89a 1074. Looking at a line drawing it appears this is just a relay. I understand your approach but need to investigate the correct model

109A_5 · December 12

Yeah that is just a relay, I was not sure. So you would need an aquastat or change the piping (which would be better). Waiting for the boiler water to cool down may take too long when you need the heat the most.

leonz · December 12

Would a boiler mate be a better option???

Renchai · December 14

Thank you all for the input!! I will do a quick aquastat swap that will shutdown the circulator at 190. If this fails due to the length of time it takes to cool from the set point I will take the boiler mate option..I would love to better understand how this system performed without issue for 23 years before this flashing/noise problem started about a year ago slowly getting louder.

HVACNUT · December 14

https://forum.heatinghelp.com/discussion/comment/1877239#Comment_1877239

I can't comprehend the piping with the Tee's above and below the circulator if its a simple baseboard loop. And to me, the one pipe looks like its piped at steam level into the boiler. I never piped a hydronic loop off a steam boiler, but I thought supply and return should be down low on the boiler taps. A wye strainer because its piped down low. And no iron body circulator? For some reason I remember hearing that.

The current aquastat is a Honeywell L4006A, which is "open on temperature increase". I don't think the aquastat is the issue.

Follow the thermostat wire from the RA89. Does it go directly to the thermostat?

Again, I don't understand how it ever worked. You say it did. So the question is, did it work fine before the Magic Nest Common Maker?

Screenshot_20251214_111003_Samsung Internet.jpg

EBEBRATT-Ed · December 14

Both pipes should be down low. @DanHolohan also shows a method of piping both HW supply and return to a single tapping by using a DT bushing if two tapping's are not available.

What is that sensor sticking out of the RA 89A. Looks like a temp stat?

If I am not mistaken a bronze circ is the best but @ethicalpaul is running his system with an iron circ.

You need a bypass to blend the water temp so it doesn't flash when the boiler is steaming.

ethicalpaul · December 14

Yes I went with cast iron because it cost 1/3 of a bronze circulator and I keep my boiler water clean and at 9-10 ph so corrosion is reduced. My cast iron one has been going for 3-4 years I think, so far

109A_5 · December 14

https://forum.heatinghelp.com/discussion/comment/1877239#Comment_1877239

So the new addition is 23 years old ???

Something changed ? That is new information presented ?

The BoilerMate seems like the most expensive method possible. What aquastat are you swapping, I don't see one to swap. You could add an aquastat to the RA89A relay circuit.

I would not mess with the DHW (aquastat) stuff if it works OK.

109A_5 · 1:22AM

"I would love to better understand how this system performed without issue for 23 years before this flashing/noise problem started about a year ago slowly getting louder."

Has it been verified that all the air has been purged out of the hot water loop ?

Aquastat assist

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