Aquastat question on radiant loop

NJGator

I have a single radiant zone tied into the wet return of a GSA-125 Williamson boiler. The current high temperature Honeywell aquastat is a probe placed on a Tee about 30 inches from the boiler on a 3/4 supply line to the radiant loop heat exchanger.

The problem I seem to be experiencing is that although the boiler may contain an ample supply of hot water, the radiant supply line (which is copper) cools down quickly. On a call for heat from the radiant thermostat, the boiler burner and radiant circulator both kick on a the same time. After the circulator runs for a minute or so, the hotter water in the boiler is pulled past the aquastat and immediately turns the boiler burner off, resulting in frequent boiler short cycles.

I was considering three options to address this situation:
1. Replace the factory supplied LWCO that taps directly to the boiler with a Hydrolevel Hydrostat that handles both an LWCO and Aquastat function (like the 3000 or 3200). In speaking with Hydrolevel customer service, they insisted that their Hydrostats can not be used with steam boilers and they would not recommend a solution to me (even though I explained to him that in normal operation the probe would be below the water line). I reviewed the technical specifications and was not able to conclusively determine that the LWCO and Hydrostat functions could be operated independently.

2. Increase the supply line pipe size from 3/4 to 1-1/2 inch where the existing aquatstat taps in to the wet return (logic being that it would allow greater heat transfer from the boiler water).

3. Use a float type LWCO tapped off the sight glass fittings freeing up the existing LWCO tapping to be used with a dedicated aquastat directly into the boiler. This was the configuration before my old boiler was replaced.

4. Look for another tapping to place an aquastat directly in the boiler. Only option seems to be the right side return currently plugged.

5. Introduce a timer circuit that would bypass the aquastat until the radiant circulator has been operating for at least one minute (or similarly introduce a 1-2 minute delayed start on the boiler).

I've searched the message boards multiple times for a solution, including the following post, but came up empty handed.
https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/,

Thanks in advance for any suggestions or observations you can share.

HVACNUT

On a radiant heat demand the burner and circ come on at the same time. Once it reaches limit and the burner shuts off, does the circ continue to run? It should.
Is the circulator sized correctly?
Is the circulator off the outlet of the mixing valve?
You might need a buffer tank or a plate HX.
Pics would help.

Jellis

The aquastat on the boiler sounds like the best solution from what you are describing.
if moving the wiring is a problem Aquastats like the Honeywell L7224U can be mounted away from the well. I think you can get up to a 48" lead for the sensor. This would allow you to keep the aquastat where it is and place the sensor on the boiler.

STEVEusaPA

You can't put the sensor in the boiler. It would shut off the burner and not allow it to steam for the steam heating zones.

Jellis

@STEVEusaPA the controls would operate independently as they do now. a call for heat from the T-stat operating the steam heated zone would be seperate from the aquastat.

NJGator

Thank you for the feedback.

@HVACNUT the circulator continues to run after the aquastat interrupts the burner, as it should. The circulator has no problem delivering heat to the HX, and the radiant loop runs around 120 on the radiant side of the HX. The circulator runs off a tee on the wet return on the boiler side of the hartford loop. I'll post a pic to show more clearly.

@Jellis moving the wiring is not a problem. I am lacking an unused tapping in the boiler to place the well. Hence my question about whether I can swap the factor supplied LWCO for a dual purpose LWCO / Hydrostat. As you pointed out, the aquastat needs to be able to interrupt the radiant call for heat only, without impacting the LWCO ability to interrupt both radiant and steam call to heat.

Thanks!

HVACNUT

Stay away from a hydronic LWCO. I dont know why but Hydrolevel and MM do.
Maybe a heel tee on the return with the limit there.
We really need to see the piping. Depending on where the taps are, I'd be concerned about sending steam water and sediment into a mixing valve. Wye strainer anywhere?