Sealed system switch to combi boiler

Fifitrix17

Hi

Can anyone please advise me? I've just moved house and the existing central heating (which is only 6 months old), is a "sealed system" with a cold water tank in the loft.

However, I want to do a loft conversion and so it seems I will have to switch to a combi boiler in order to get the cold water tank out of the loft. I don't need any radiators. Does anyone have an idea of how much the boiler change should cost? Thank you!

southcoastrgi

why don't you just get it moved either into a part of the roof that will still be the loft (unused room space), or can the tank not be changed to a coffin type, or the other option if you have the pressure & flow rate change the cylinder for an unvented one.

Fifitrix17

Thank you for your response. I won't pretend that I understand it, but I'll certainly raise it with the gas fitter who comes on Saturday. Cheers!

southcoastrgi

my first part i was talking about your existing roof tank not the boiler (just to save confusion), if your incoming flow rate & pressure is good enough the existing cylinder could be replaced with an unvented cylinder which would give you mains pressure hot water & no need for the roof tank, this would give you a much better performance than a combi & you keep your 6 month old boiler

Fifitrix17

Thank you so much for your helpful advice. You're a star !

reeac

Fifitrix17 wrote: »

Hi

Can anyone please advise me? I've just moved house and the existing central heating (which is only 6 months old), is a "sealed system" with a cold water tank in the loft.

However, I want to do a loft conversion and so it seems I will have to switch to a combi boiler in order to get the cold water tank out of the loft. I don't need any radiators. Does anyone have an idea of how much the boiler change should cost? Thank you!

If by "sealed system" you mean an unvented one then you don't need that cold water tank in the loft - maybe it's leftover from the previous system. If you truly have an unvented system then you should have no problem in supplying H&C to the loft conversion.

southcoastrgi

reeac wrote: »

If by "sealed system" you mean an unvented one then you don't need that cold water tank in the loft - maybe it's leftover from the previous system. If you truly have an unvented system then you should have no problem in supplying H&C to the loft conversion.

the way i read it is that the OP has a sealed system boiler with a normal vented cylinder

reeac

southcoastrgi wrote: »

the way i read it is that the OP has a sealed system boiler with a normal vented cylinder

You've lost me. The traditional system had a boiler water feed and overflow from/into the loft tank and the same arrangement for the hot tank. There are now unvented systems [we have one] where the boiler is supplied with mains water at a reduced pressure [up to 2 bars usually] with a safety valve which is connected to a tundish and thence to outside. H & C are supplied at mains pressure, hot via a coil in the tank. Are there also hybrid systems [sealed boiler/vented tank]?

southcoastrgi

you have a unvented cylinder with no large roof tank & your boiler is a system boiler which also doesn't have a roof tank (you fill the heating/boiler via a filling loop connected to the mains), you can still buy & fit open vented boilers & cylinders (which both req a roof tank a big one for the cylinder & a small one for the heating/boiler), however if i'm reading the OP correctly she has a system boiler like yourself (which means doing away with the small header tank), but they still have a vented cylinder which reqs the large tank, nothing wrong with that setup & there are thousands like it & tbh if you don't have the req pressure & flow on the incoming mains it can be the best system to fit (even now).

reeac

southcoastrgi wrote: »

you have a unvented cylinder with no large roof tank & your boiler is a system boiler which also doesn't have a roof tank (you fill the heating/boiler via a filling loop connected to the mains), you can still buy & fit open vented boilers & cylinders (which both req a roof tank a big one for the cylinder & a small one for the heating/boiler), however if i'm reading the OP correctly she has a system boiler like yourself (which means doing away with the small header tank), but they still have a vented cylinder which reqs the large tank, nothing wrong with that setup & there are thousands like it & tbh if you don't have the req pressure & flow on the incoming mains it can be the best system to fit (even now).

Right! I've owned both vented and unvented CH systems [fitted the first one myself] but never thought that there could be hybrids but can see no problem. Best solution for OP is to get the tank moved into a corner and boxed in with access door. That's assuming that they don't need H&C in the loft conversion.