What is a Bypass valve for?

the_amazing_raisin

Bypassing stuff obviously 🤣

So there's a valve on my heating system which I'm trying to figure out

It's got a red plastic cap on it, and is placed between the flow and return lines to the heat pump, after the buffer tank but before the zone valves

The master tradesman that is Google tells me it's an automatic bypass valve. Here's one that looks similar

My guess is that it's for when the heat pump is defrosting from the buffer. The zone valves close off and the flow is then directed through the bypass so it sends the warm water in the buffer to the heat pump to defrost it

Is that even remotely close to the truth, or am I miles off?

How is it triggered, is it when the pressure goes above a certain level or something else?

10-10-20

I just found out myself, so here's my knowledge on it.

It's to bypass the heating loop in the case of a situation where all valves close off and the pump is still pushing water - or in the case of gas, in case the burner is still lighting and the water then becomes static. Rather than have the pump go into an overload/overpressure/cavitation, the bypass opens and allows the flow to route into the return, bringing the system back into a flowing state and dissipating excess heat from the heating coil.

Points out of 10 from a plumber? 😆