Is there thermostat such that it turns the boiler off before the circulator?

A aqua stat strapped on the supply pipe and wired across the pump relay will keep the pump running after the tstat shuts the burner down, until the water cools down.

Gilmorrie said:

The residual heat in the boiler after the burner turns off, is not lost. First, the "lost" heat goes into the homes's inside space, even if it is via the boiler room, which eventially helps. And then, when there is the next call for heat, whatever heat is still in the boiler will be used for the next cycle.

Not all of it. Some of this heat is lost up the chimney, unless there is a stack damper.

I'm cheap so I find cheap ways to do things.

I would use a fan control with a single pole normally open relay and a thermodisc that will open at the desired temperature that you want the pump to stop moving water. the pump would be connected to the relay on the fan control and to the aquastat relay. Both connections must be on the same electrical panel buss. The thermodisc would be strapped on the outlet of the pump and connect to the transformer secondary on the fan control between the transformer and the relay.

The way it works--the aquastat on a call for heat would turn on the pump relay energizing the pump and when the temp of the water exiting the pump reaches the close temp of the thermodisc the thermodisc points close energizing the pump, too. As long as the power from the aquastat on the boiler and the fan control are on the same side of the buss everything will be ok.

The call for heat is satisfied, the aquastat relay opens cutting power to the pump, but the thermodisc is still closed which keeps the fan control relay supplying power to the pump. The pump continues supplying hot water until the water exiting the pump falls below the temperature that the thermodisc opens cutting power to the pump. Walla.

Of course, you can get a Taco Switching Relay like a SR501 instead of a fan control and use the thermodisc in place of the thermostat connection on the SR501. Same buss, tho.

Ya, Steve, I can see that. How would your sequential operation work? Inquiring minds want to know.

What @JUGHNE said is the best way out.

I have done this many times.Use a strap on aqustat set so that the pump will run when the water temperature is over 130 deg (you don't want to cool the boiler below that) so you need a "reverse acting aquastat" one that closes its contacts on a temperature rise

To much heat lost to the basement which does keep the basement warmer but some heat is lost up the stack while the boiler is sitting there hot.

With the aquastat wired in the thermostat will start the boiler and the circulator the thermostat will stop the boiler when the stat is satisfied and the circulator will continue to run( until the boiler cools to its setpoint (130) set on the new aqustat

HAY... @HomerJSmith
This is what @STEVEusaPA is talking about
and i think it is cheeper then a switching relay or fan center and a thermo-disc because the L6006 is rated for line voltage limit and reverse operation.



very simple to use the make on temp rise/break on temp fall contacts on the L6006C strap on Aquastat.

Can work with any circulator relay to remove heat from large mass boiler and dump it to the radiators.

You don't want to do this if you have a tankless coil making your hot water. of if your boiler is designed to maintain temperature for any other reason.

JUGHNE, very observant. The grounded conductor (white wire) is always connected. The switch is on the black wire. To use the Honeywell L6006C, the make on temp rise micro switch has to be connected to the motor black wire connection and to the 110V power into the aquastat black wire connection point, L1. Polarity is maintained.

Did I mention that I was cheap? An Aquastat is 5 times more expensive than a fan control and thermodisc. Well, maybe 4 times. But, then again labor counts. But isn't the homeowner's labor free?

Just FYI, the only way you get 110/120v IS to have a neutral. White wire, (groundED BTY) and a black hot. That hot is one leg of a 220V single phase system.
220V single phase may not need a neutral (again groundED) for operation.

To differentiate between groundED (typically white) and groundING (green or bare)......... GroundED white does carry current as return and groundING green is non current carrying safety conductor.....carries current in the event of a fault to trip the breaker.

That is the way it has been since before I was licensed in 1969.
But the next code cycle is changing the terminology, the white and green function will not change, just the wording?????