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Old February 11th 19, 06:25 PM posted to uk.d-i-y
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Default System boiler or conventional when replacing combi

On 11/02/2019 18:05, The Natural Philosopher wrote:
On 11/02/2019 17:45, Chris B wrote:
On 11/02/2019 16:50, The Natural Philosopher wrote:
On 11/02/2019 16:46, Fredxx wrote:
On 11/02/2019 14:44, Darksyphon wrote:
Large extension added to my 3 bed property. Combi has been a pain
in the arse
and now won't cut it with 2 main bathrooms.

My question is should I go for a system boiler with an unvented
cylinder or
get a conventional boiler and have pressurised ch and again an
unvented hot
water cylinder?

Plumbing in the extension hasn't started yet and I plan to put the
unvented
cylinder in the gurage.

My plans were for the system boiler but I met a plumber who said to go
conventional.

A system boiler implies a conventional system. You have a choice of
unvented, vented or thermal store.

I went for the thermal store as the cylinder isn't pressurised so
doesn't need inspection and testing while still having high pressure
hot water.

TBH I suppose I just did the first inspection and test of my
pressurised cylinder in 16 years after replacing all the pressure
bits... :-)

Personally I'd still go for a pressurised system

Thermal store almost as good.


Can depend on location.* Thermal store in old house suffered from
major scale up in the small bore pipes that run through the thermal
store to provide HW.* Filling a bath ended up being so slow that water
was cooling down faster than hot water being supplied.* Just barely
acceptable for shower or washing up.* Probably worse than a combi. A
Water softener may have helped but there wasn't one fitted,

I think anyone who doesn’t fit a water softener in a hard area in a
property they expect to inhabit for a decade or more is a numpty


Well technically it had one of these chemical cartridge type softeners

https://www.amazon.co.uk/PERMUTIT-IN.../dp/B01MSJSKOT

But I don't think the cartridge had ever been changed since the kitchen
had been refitted. (Carpenters had made it impossible to change without
removing one of the kitchen units)



The damage done to shower fitments especially is massive. Not to mention
the internals of a complex hot water system

I think IF you are going to upgrade a DHW system fitting a softener is
probably step 1. Even a combi will scale up eventually.




--
Chris B (News)

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Old February 11th 19, 07:44 PM posted to uk.d-i-y
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Default System boiler or conventional when replacing combi

replying to Tim+, Darksyphon wrote:
Thanks for the replys. The only thing I'm wondering is if I need the central
heating side pressurised too? I like the idea of not having any tanks. But
that means more gear....another pressure vessel. Just wondering if the extra
reliability of a conventional boiler is worth having to add all the things
seperatly that are now inside system boilers. I'm not bothered about the cost
just want the best system that is reliable. Not looked into Thermal stores.
Will have a read

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for full context, visit https://www.homeownershub.com/uk-diy...i-1345914-.htm


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Old February 11th 19, 09:29 PM posted to uk.d-i-y
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Default System boiler or conventional when replacing combi

On 11/02/2019 19:44, Darksyphon wrote:
replying to Tim+, Darksyphon wrote:
Thanks for the replys. The only thing I'm wondering is if I need the
central
heating side pressurised too? I like the idea of not having any tanks. But
that means more gear....another pressure vessel. Just wondering if the
extra
reliability of a conventional boiler is worth having to add all the things
seperatly that are now inside system boilers. I'm not bothered about the
cost
just want the best system that is reliable. Not looked into Thermal stores.
Will have a read

reliability is more about implementation than design.



--
“Some people like to travel by train because it combines the slowness of
a car with the cramped public exposure of 
an airplane.”

Dennis Miller

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Old February 12th 19, 02:52 AM posted to uk.d-i-y
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Default System boiler or conventional when replacing combi

On 11/02/2019 14:44, Darksyphon wrote:
Large extension added to my 3 bed property. Combi has been a pain in the
arse
and now won't cut it with 2 main bathrooms.

My question is should I go for a system boiler with an unvented cylinder or
get a conventional boiler and have pressurised ch and again an unvented hot
water cylinder?

Plumbing in the extension hasn't started yet and I plan to put the unvented
cylinder in the gurage.

My plans were for the system boiler but I met a plumber who said to go
conventional.


If converting from a combi, system boiler makes sense since your won't
already have a separate pump or the separate paraphernalia associated
with a sealed system (since they are all in the combi).




--
Cheers,

John.

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| John Rumm - john(at)internode(dot)co(dot)uk |
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Old February 12th 19, 03:01 AM posted to uk.d-i-y
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Posts: 22,632
Default System boiler or conventional when replacing combi

On 11/02/2019 19:44, Darksyphon wrote:
replying to Tim+, Darksyphon wrote:
Thanks for the replys. The only thing I'm wondering is if I need the
central
heating side pressurised too? I like the idea of not having any tanks. But
that means more gear....another pressure vessel. Just wondering if the
extra
reliability of a conventional boiler is worth having to add all the things
seperatly that are now inside system boilers. I'm not bothered about the
cost


Ultimately you will have the same major components, its just the
location of them that changes.

Note however you may be able to implement more sophisticated controls
with the system boiler, to give things like split temperature
operation[1] or weather compensation[2], which are harder to do with
heating only boiler usually.

just want the best system that is reliable. Not looked into Thermal stores.
Will have a read


http://wiki.diyfaq.org.uk/index.php/...and_Heat_Banks

http://wiki.diyfaq.org.uk/index.php/DIY_Heat_Bank


[1] Split temp allows you to run lower flow temps through the heating
(for greater condensing efficiency) when its not desperately cold
outside, but still run high temperatures when reheating the cylinder.

[2] Weather compensation makes the flow temperature automatically adjust
to the outside temperature, and sometimes also the heat loss
characteristics of the building and sometimes also the size of the
difference between the actual internal temperature and the target temp
set on the room stat. So it runs hotter water through the rads on colder
days, or when it needs to heat the place more quickly.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/


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