04-03-2016, 11:46 AM
"Don't know if yours is a sealed system combi boiler (as opposed to an open vented) condensing boiler. ..."
There's a common confusion here.
All modern boilers are condensing, whether combi or otherwise. All combi systems are sealed and pressurised. Other systems can be pressurised or with header tank, depending on how you wish to design the system. It's recommended to pressurise a new system as it gives cleaner water conditions. No area of water exposed to air in the header tank. Also if, like me, you have a loft conversion, getting the header tank high enough isn't easy. I managed it on the original installation but it was a pretty fine margin between working OK and overpumping into the header tank. That was a very good reason to change to pressurised when I changed the boiler.
When I fitted my boiler in 2011 I changed the system from header tank to pressurised. I bought a so-called system boiler which has all the necessary bits built in. Pump, pressure gauge, bypass, expansion vessel etc. Except for the filler loop which I had to buy separately and fit externally. I'm glad I did pressurise it, as a system with header tank has an unlimited amount of water available. Mind you, a system with header tnak runs at much lower pressure so the hose might not have split in the first place.
The part that has failed on my system is item 002 on p94 of this document. It connects the primary flow from the main combustion unit to the rest of the water system.
http://www.viessmann-us.com/content/dam/...1bc_is.pdf
It looks like a bit of rather thin car radiator hose. IMHO it's not up to the job and should be replaced by something with a flexible metal jacket. Just like the hose used to connect the expansion vessel to the rest of the system.
I pressurise my system to 1 bar when cold. It goes up to about 2 bar when hot. The overpressure valve should open at about 3 bar.
There's a common confusion here.
All modern boilers are condensing, whether combi or otherwise. All combi systems are sealed and pressurised. Other systems can be pressurised or with header tank, depending on how you wish to design the system. It's recommended to pressurise a new system as it gives cleaner water conditions. No area of water exposed to air in the header tank. Also if, like me, you have a loft conversion, getting the header tank high enough isn't easy. I managed it on the original installation but it was a pretty fine margin between working OK and overpumping into the header tank. That was a very good reason to change to pressurised when I changed the boiler.
When I fitted my boiler in 2011 I changed the system from header tank to pressurised. I bought a so-called system boiler which has all the necessary bits built in. Pump, pressure gauge, bypass, expansion vessel etc. Except for the filler loop which I had to buy separately and fit externally. I'm glad I did pressurise it, as a system with header tank has an unlimited amount of water available. Mind you, a system with header tnak runs at much lower pressure so the hose might not have split in the first place.
The part that has failed on my system is item 002 on p94 of this document. It connects the primary flow from the main combustion unit to the rest of the water system.
http://www.viessmann-us.com/content/dam/...1bc_is.pdf
It looks like a bit of rather thin car radiator hose. IMHO it's not up to the job and should be replaced by something with a flexible metal jacket. Just like the hose used to connect the expansion vessel to the rest of the system.
I pressurise my system to 1 bar when cold. It goes up to about 2 bar when hot. The overpressure valve should open at about 3 bar.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
