Cental heating not circulating.
My system is about 30 years old its has for most of it’s life had fernox inhibitor but perhaps only two lots over this time scale. No other problems in this time scale.
It is a Y plan system pump flow to 3 port valve (diverter) extra 2 port zone valve in the flow to control upstairs rads via separate room stat.
I noticed about a week ago that the upstairs rads where only getting warm and ground floor cold. I shut off the first floor by closing the first floor zone valve then some of the ground floor rads got warm ie those nearest to the flow pipe.
The domestic HW flow and return are working OK.
The system is 22mm main runs with 15mm off the rads.
The system is DHW priority.
I have drained the system, changed the pump for a new one, stripped down the 3 port valve (working ok) purged the system of air but still no circulation on rads circuits upstairs or down.
I notice if the 3 port valve is held on the latch ie mid position with the DHW calling for heat with the upstairs zone valve open the upstairs rads get hot, but if I then set the system to CH the 22mm flow pipes to up and down circuits get hot but only until the boiler stat shut off the boiler, the nearest rads to the flow main pipe are luck warm but go cold after the boiler shuts down. Boiler only cycles when the water in the flow / return and in it cools.
ANY Ideas please.
Don’t take this as the answer just a thought, could it be magnetite (iron oxide, black water) blockage , soft water area no lime scale, if so do 22mm pipes generally totally block with magnetite. I ask this because it looks like the return 22mm pipes from the up and down circuits are the problem. HOW do I get it out?
Just one point when draining the system down the run off water was clear clean water!
My system is about 30 years old its has for most of it’s life had fernox inhibitor but perhaps only two lots over this time scale. No other problems in this time scale.
It is a Y plan system pump flow to 3 port valve (diverter) extra 2 port zone valve in the flow to control upstairs rads via separate room stat.
I noticed about a week ago that the upstairs rads where only getting warm and ground floor cold. I shut off the first floor by closing the first floor zone valve then some of the ground floor rads got warm ie those nearest to the flow pipe.
The domestic HW flow and return are working OK.
The system is 22mm main runs with 15mm off the rads.
The system is DHW priority.
I have drained the system, changed the pump for a new one, stripped down the 3 port valve (working ok) purged the system of air but still no circulation on rads circuits upstairs or down.
I notice if the 3 port valve is held on the latch ie mid position with the DHW calling for heat with the upstairs zone valve open the upstairs rads get hot, but if I then set the system to CH the 22mm flow pipes to up and down circuits get hot but only until the boiler stat shut off the boiler, the nearest rads to the flow main pipe are luck warm but go cold after the boiler shuts down. Boiler only cycles when the water in the flow / return and in it cools.
ANY Ideas please.
Don’t take this as the answer just a thought, could it be magnetite (iron oxide, black water) blockage , soft water area no lime scale, if so do 22mm pipes generally totally block with magnetite. I ask this because it looks like the return 22mm pipes from the up and down circuits are the problem. HOW do I get it out?
Just one point when draining the system down the run off water was clear clean water!