Aquastat assist

Renchai

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

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

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

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

Renchai

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

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

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

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

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

Would a boiler mate be a better option???