Question on hot water loop off steam boiler configuration

LongIslandSteamer

Hi everyone. I recently completed an extension on my house and as such the plumber that my GC hired is in the process of piping a hot water loop off of my single pipe steam system (currently running off of an approx. 7-8 year old Weil-McClain steam boiler). The radiators are all in place (baseboard) and the plumber (who doesn't seem 100% confident of his work on this) came by last week to pipe the boiler. The plan was to pipe the system the same way Dan recommends on this diagram (https://heatinghelp.com/assets/Uploads/_resampled/ResizedImage482228-hot-water-zone-off-a-steam-boiler.gif) at this link (https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler). We have a heat exchanger piped in but the plumber did not put in an aquastat which I question and he said "oh you're right". I reminded him that we need something to tell the burner to fire in order to get the water to the right temp otherwise the system will circulate cold water through the system. Now, for some reason, Dan's diagram doesnt show an aquastat but from some of the reading I've done we will need a high limit strap-on aquastat piped into a well on the boiler inlet side of the heat exchanger. Is that correct? Also, how would it be wired? The plumber is coming by tomorrow to work on this and he said he knows what to do but I've heard that story before and I want to make sure it is done right.

One other point. Last time he came and wanted to test the system without an aquastat to at least make sure it was running through the radiators properly he ran into an issue where the boiler water wasnt circulating through the heat exchanger. He determined that the circulator was piped too high on the inlet side and that he needed to lower it to get proper water flow. Does that make sense?

thanks everyone.

Jamie Hall

You can put the aquastat into the well in the heat exchanger, if there is one -- or use a strap-on type on the pipe from the boiler to the heat exchanger. It would be wired in parallel with the thermostat controlling the boiler presumably the thermostat controlling the hot water zone actually controls the two pumps.

The pipe from the boiler to the heat exchanger must come off a tap at a lower elevation than the low water cutoff on the boiler. I prefer to see the return tapped into the wet return to the boiler.

LongIslandSteamer

Jamie Hall said:

You can put the aquastat into the well in the heat exchanger, if there is one -- or use a strap-on type on the pipe from the boiler to the heat exchanger. It would be wired in parallel with the thermostat controlling the boiler presumably the thermostat controlling the hot water zone actually controls the two pumps.

The pipe from the boiler to the heat exchanger must come off a tap at a lower elevation than the low water cutoff on the boiler. I prefer to see the return tapped into the wet return to the boiler.

Hi Jamie - thank you for responding.

When you say "It would be wired in parallel with the thermostat controlling the boiler" are you referring to the primary thermostat controlling the steam zone?

If so, does that just means that the aquastat wire is wired in together with the existing boiler thermostat, essentially pigtailing two together, right?