Question what is the temperature setting of the boiler?

With the pump running backward it should not cause any temperature problems but only some efficiency issues.

What make and model is the boiler?

The question is, did your aquastat really malfunction and need to be replaced or was its malfunction caused by the reversed circulator and did not need replacing at all?

The incorrect placing of the circulator could cause the boiler temperature to spike just like an engine block without a working water pump but at what temperature does an auto cutoff switch at the boiler activate, assuming there is one and that itâÂÂs not defective?

I believe Steve53 to be completely wrong on this issue. When a circulator is installed in reverse it is trying to pump towards the âÂÂpoint of zero pressure changeâ that is at the expansion tank. Reversing the flow towards the expansion tank cannot increase pressure and cause flow - even if the size of the circulator were to be increased! The only pressure in the system is basically the static pressure as when everything is off. When the circulator is turned on, in reverse mode, you have no pressure change on the expansion tank side of the system (the direction that youâÂÂre now pumping towards) because the circulator is incapable of creating a pressure change on this side - but it does create a pressure drop on the other side (now the suction side). A gauge reading taken on outlet side of the pump will not register a change but a gauge reading taken on the suction side of the pump would now show a pressure drop where we would normally want to create a pressure increase.

Pressure at the peak or highest point of the system will be zero or close to it, as no pressure or head has been created. Problems created within the system might be air noise or if system pressure at this point goes negative, it may draw air into the system via the air elimination devices, if there are any. Another problem that might be created is air that is trapped and kept in solution may also appear due to pressure drop causing noise and possibly air lock.

Someone that is well versed and completely up to date on their hydronic heating theory, including all modern hydronics for peak efficiency, should be servicing your system.

IMO

SR

Why do you believe the first aquastat failed, if you replaced it and the boiler temp still spiked?