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Fredxx[_4_] Fredxx[_4_] is offline
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Default New Cylinder needed for system boiler fitting?

On 12/06/2021 19:14, Roger Mills wrote:
On 12/06/2021 18:15, jkn wrote:
Hi All
Â*Â*Â*Â* I am musing about finally replacing our anciente back boiler
(Baxi Bermuda, part of a Plan C system dating back ... quite a bit)

One possibility I am considering is having a system boiler fitted
rather than a combi. On question - would it be necessary/advisable to
replace the cylinder at the same time, or could this be kept?

Thanks & Regards
J^n


I would say that it wouldn't be strictly necessary, but it would be
highly advisable.

The cylinder will almost certainly be the indirect type with a separate
coil inside through which the primary water from the boiler flows.
Whilst would work with a system boiler, it may not work very well. If is
was installed in Baxi Bermuda days it is pretty old and will likely be
scaled up unless you are in a soft water area. Also, it's unlikely to
have a fast recovery coil inside so the domestic hot water won't be
heated anything like as fast as it would be with a new cylinder.
Finally, all recent cylinders are covered with foam insulation which is
likely to be better than fitting a loose jacket round it.

I'm assuming that you plan to alter the pipework and controls in order
to make it a fully pumped system? Modern low volume boilers just won't
work with gravity circulation HW systems like the old cast iron lumps
did. Unless the pump maintains the flow until the boiler has cooled a
bit after each firing cycle, it will overheat and trip out due to the
residual heat.


The OP could consider S-plan. And if an issue to minimise alteration of
pipework, the OP could have separate pumps for CH and DWH with
non-return valves.