Boiler link up

[Hampelmann]

For years, I have been running a solid fuel boiler and an oil boiler in parallel on an open system.
The oil boiler had two flow and two return connections with one set used for the pumped heating and the other for gravity hot water.
There were no valves in the system, other than thermostatic radiator valves.
I have now changed the oil boiler to a unit that has two returns but only one flow connection.
With both boilers working the hot water seems to work satisfactorily.
When the solid fuel boiler is off the gravity hot water only seems to work once the solid fuel boiler has sucked enough heat to get the gravity flowing.
During the warm up period there seems to be some reverse flow to the
hot water cylinder via the hot return from the radiators and up the gravity return.
Would a dumball valve in the gravity return work or would that be dangerous?
I have fitted a room stat, which was not there on the old system and despite the inefficient link up I should save some money with the new system.
If I can't get it to work satisfactorily, I will look at either fitting an equalizer or do away with the solid fuel boiler and convert to a closed system, but this only next year.
What do you think?.

 

[Best]

Sounds very hard to understand by your description. I personally am happy with twin coil cylinder system using one way valves ONLY on pumped pipes. Do not think of doing this with gravity pipes. A neutraliser another option. What you want is a system that heats properly without one circuit heating another but safety is first consideration. Take a look at solid fuel link up plans. A job, planning & any work for experienced man only.

 

[Hampelmann]

Thanks. I'll take your advice and leave gravity pipes untouched.