My boiler has packed in, the heat exchanger has failed and the consensus is that was due to sludge, gunk in the system, also consensus is would be better to pay a bit more and get a new boiler and guarrantee rather than getting it repaired.

My system is a regular open-vented system. The benefits of a sealed pressurized system have been explained to me and my view is I would like the central heating pressurized but not the hot water system.

The reason being I do not want the hot water system pressurized is I am concerned about additional noise from having water pipes all pressurized, and all the extra cost and hassle of having to replace the hot water cylinder.

The reason being I do want the central heating system pressurized is the system seems suspectible to air and sludge, there is a problem getting radiators high up in house working. And it makes sense to me to fill the system once, and having it continually reuse that water for the heating system.

But I am unclear whether it would be better to get a System Boiler or a Regular Boiler with kit for this purpose. System Boiler seems to only be when heating and hot water is pressurized, regular when neither is.

I understand that a regular boiler can be used with a pressurized sealed heating system via use of a external pressure balloon ectera. I am not clear whether you can use System Boiler if you are only going to use it for heating water used in the central heating system and not for directly heating hot water.

I am not sure if you can use a System boiler in a non-pressurized system. i.e if a System boiler is installed, and then we find pipes are too leaky or mains pressure not enough would that then mean System Boiler was no use or could it be used liked a regular Boiler ?

  • I was in the boiler business for 40 ears and am having a hard time understanding your question. Here in the USA we almost always, install pressurized hot water heating systems. I do not understand the terms you are using, "system boiler' or "regular boiler". You also said that your system is a regular open-vented system. We had systems we call open or vented long before I started in the profession; (the expansion tank was an open and vented tank, mounted at the high point of the system with a drain line that ran to the basement). Sometimes, it is hard to explain what we each see when different
    – d.george
    Nov 30 '18 at 12:04

What do you mean by "hot water system"? The hot water that comes out of your taps? That will either be mains pressure (combi-boiler or system boiler), gravity fed (your current tank system) or boosted by a pump (in areas where mains pressure is low).

I've only heard the central heating system referred to as presurrised. That said, there does need to be some pressure in the pipes that go to your taps or you wouldn't get any water. Too much pressure and it will shoot out and splash. Too little pressure and it will dribble. My amateur understanding is that nobody wants a gravity system these days. I suppose higher pressure means higher flow rate and maybe more noise, but that's only when the taps are running and shouldn't be dramatic. You can get water hammer arrestors and pressure limiters if it's a problem. We get more noise from our central heating pipes expanding than the taps.

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