Gravity primary system to a C Plan...?

[Mike2007]

Another awkward question to add to this tricky problem! If the CH is calling and the HW is satisfied then boiler and pump start.
What if the pump then breaks leaving no pumping at all with boiler still working!
In the new C Plan there would be an un-opened valve in the return/expansion primary pipe.....boiler still running and going to overheat!
Is this still a practical solution considering all possibilities?

 

[Terrywookfit]

Thats what the boiler stat is there for!!
The cold feed and expansion pipes are not isolated by the valve!!

 

[bhm1712]

sorry to bring this post back to the surface, but i found it useful,

in this scenario is it correct to say that if CH is on, then the cylinder stat is irrelevant and the hot water will go over the setpoint, but in the case of just hot water being on, the cylinder stat will control the temp?