Central Heating layout incorrect

[alan999]

Hi
Has anyone ever come across a boiler that should be pressurised with a filling loop but instead is linked up to a header tank in the loft.

The boiler - a Ferroli Tempra 12 perhaps 10 years old - still works though not too well. Of course cannot be pressurised anywhere near to where it should be. I'm thinking that fitting a filling loop at this late stage of its life could lead to all sorts of complications.

I wondered if anyone had any thoughts.

 

[ChrisOxford]

Hi Alan,

Why do you think the system should be pressurised? And why do you think the pressure's too low?

I don't know your boiler, but MY boiler's manual gives 3 options:

(1) Sealed system pressurised by mains water via a stop cock, filling loop and non-return valve.

(2) Sealed system pressurised by water from a tank ("make up vessel") via a stop cock and non-return valve. The make up vessel is mounted at least a foot above the highest point on the system, which means that the appropriate pressure(see below) can be achieved.

(3) Open (non-pressurised) system connected to a feed & expansion tank, achieved by removing the automatic air vent and connecting the feed/vent pipe from the tank instead.

Note that the boiler's water-to-water (secondary) heat exhanger is fed directly from the mains irrespective of whether the primary is sealed or open.

The appropriate pressure ("system design pressure") for my boiler is defined as the static head of the system in bar, + 0.3 bar. Roughly 1 bar is typical.

As 0.3 bar is equivalent to about 10 feet of water, I fail to see how option (2) can work either

Maybe the clever professionals can tell us the answer

Hope that helps a bit.

 

[alan999]

Thanks Chris
I checked the manual and it says 1.0 bar pressure required - must not fall below 0.5 bar. Interestingly the boiler has a low pressure warning light which remains off.
Theres only 6 radiators on the system which struggled to warm up last winter. While the boiler probably needs a service and the system probably needs a flush the pressure issue seems the logical one to tackle first.
Incidently the boiler is room sealed and the hot water comes from a cylinder in the airing cupboard which the boiler heats. There is no mains water in the vicinity of the boiler.

 

[ChrisOxford]

Sorry, had it in my head that you had a combi for some reason

 

[Boilerman2]

As long as the static head of your open system is great enough to overcome any low pressure switch, then all is fine - this arrangement is not as rare as you would imagine, the reason the boiler is not too reliable is due to the name badge on the front IMHO!!

if you do sealk the system and fit a filling loop do not forget a 10 litre expansion vessel and a 3.0 bar safety valve if there is not one on the boiler, if the built-in vessel is still fitted to the boiler check the air charge before sealing
Sealing the system however should not be necesary

 

[kevindgas]

there have been a few boilers over the years that worked ok on low pressure including a few combi's

the problem with the tempra, F24, F30 and the Modena 80 & 102 is they all use components that are not top quality, the most common problems i have found is the plastic venturi's, the thermistors, the overheat stats & fairly often the PCB settings (which can be a pain to set!)

replace the venturi, check and replace if necessary the thermistors and the stat and it should go again!

 

[misterdubya]

Sorry, had it in my head that you had a combi for some reason

Its a system boiler. I still see a few old Worcesters (Combi's) that use a header tank.