aquastat on hot water boiler

[Deleted User]

are you sure you do not have a dynatherm boiler, they had a high limit clamp on aqastat on the supply piping, but the cir is turned off by either low temp aquastat or the termostat when room is satisfied,,,,,

sam_25

aquastat on hot water boiler

I have an older hydrotherm boiler which has an aquastat on the supply pipe by the boiler. When the water temp reaches the set temp on the aquastat the circulator starts. Problem I have is that the cirulator keeps running until the water temp falls to the aquastat setting, resulting in room overheating. Any advice on aquastat settings or anything I can add to stop the circulator when the boiler stops?

steveex

Set it up so that the tstat shuts the pump, relay. And keep a aq. for the high limit.

Big Ed_4

May be a little higher tech

Install a outdoor reset with a room sensor and let it follow a heat curve. Saves a few bucks on fuel and provides a nice even comfort .

Brad White_198

I agree with Ed

There is an opportunity here to do something more for not a whole lot of money. Just watch your boiler return temperature and do not set it so low that it condenses (135F return).

But I also suspect that your thermostat is not doing it's job or being allowed to.

If the room goes above setpoint and you have circulator control, your circulator should be off, period. No reason to slave it to the aquastat except as a low-limit to hold the circulator off until the boiler is warmed.

(Man, does that ever sound old-school!)

sam_25

Some more info. The room thermostat operates the boiler, no aquastat on boiler or anywhere else. It is a power pile system.

The boiler fires when the thermostat calls for heat, then when the water is at the temp set on the aquastat- the circulator pump (connected to the return pipe right next to the boiler) starts. Then the circulator stops when the water in the supply pipe reaches the temp set on the aquastat. So the circulator keeps running way after the boiler has stopped firing.

Big Ed_4

The proper basic hook up

On your system the thermostat should activate a double pole relay , one pole would turn on the burner and at the same time the second pole would send juice though the reverse aquastat to power the circulator. On a call for heat the burner will lite. The boiler will heat up an then the reverse turns on the circulator. The burner will stay on until it reaches high limit but the circ will still run. When the thermostat is satisfied the relay drops out shuting off everything and no more heat is delivied upstairs unless your system is missing a flowvalve. Which would be my guess.