Just out of curiosity, I assume a system boiler has to work with an unvented system and a system boiler cannot be put into a vented system? (due to the lack of pressure)
System boiler on a vented tank?
- Thread starter richardindorset
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Some system boilers can run on open vented
1. As cross thread.
2. An unvented system is usually taken as referring to a hot water system which does not have an open vent over (normally) the cold water storage cistern.
3. A sealed system refers to a central heating system which is not a combination (combi) boiler system, but which has no Feed and Expansion tank.
4. Any type of controllable (gas, oil, electric) boiler can run an unvented or a vented hot water system.
5. Provided the manufacturer's instruction allow it, any type of boiler can run a sealed or an open-vented central heating system.
2. An unvented system is usually taken as referring to a hot water system which does not have an open vent over (normally) the cold water storage cistern.
3. A sealed system refers to a central heating system which is not a combination (combi) boiler system, but which has no Feed and Expansion tank.
4. Any type of controllable (gas, oil, electric) boiler can run an unvented or a vented hot water system.
5. Provided the manufacturer's instruction allow it, any type of boiler can run a sealed or an open-vented central heating system.
But must have an expansion vessel.
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Thanks Cross thread and Old Duffer!
So a quick look at a Glow Worm 30s manual (for example) mentions that the boiler likes 1.0 to 1.5bar water pressure and shuts off if the water pressure drops below 0.3bar. It flashes a warning at 0.5bar. So maybe you'd get away with a 6M head of water on a vented system? (Just put the header tank on the roof! LOL!)
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That 1.0 to 1.5 bar is the sealed system pressure. Should you really want to (and I can't quite see why you would) you could pressurise the system with something like a Rothenburger RP30 pump. It should then not need re-pressurising more than once, perhaps twice a year. In theory it shouldn't need re-pressurising at all!
But then it wouldn't be a vented system.
If the boiler gives a warning at 0.5 barg and cutoff at 0.3 barg, it would be OK in a typical 2-storey house with the header tank in the loft and the boiler on the ground floor - likely over 5m head, but might need to elevate the tank.
If not it might be possible to bypass the pressure switch, as long as the head is above the actual minimum required by the boiler.
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