Adjusting Primary - secondary valves

greg_7

I have noticed that my boiler's secondary pump and piping will occasionally act strange, usually on very cold days.

What happens is that the secondary (boiler) pump will only circulate hot water around the boiler and the bypass pipe and none will be injected into the rest of the system.

Then the boiler cycles on and off due to the high limit aquastat and the house gets chilly.

This is a gravity conversion.

I can correct the situation by shutting off the bypass. Then the hot water shoots into the system, gurgling and rumbling. Then I slowly open the bypass to temper the return water and it works as it should.

The physics of this intrigue me. It's sort of like vapor lock on a carburator.

Any ideas?

Unknown

Can you show a picture

of how the boiler piping connects to the system?

Noel

http://www.heatinghelp.com/heating_howcome1.cfm