How Does My Open Vented Gravity fed System Work

rainbow123 · 21 Aug 2014

Hi i am a plumbing enthusiast (not a plumber) i have a genuine interest in how things work mainly in case things break iv a good genuine knowledge of how to or what needs to be repaired. iv recently moved propertys and the new house has what i believe to be a open vented gravity fed back boiler heating system (very old). When i look in the cupboard to the side of the boiler in the kitchen there are 5 pipes. 1 is i believe the gas pipe to the boiler, 2 will be the hot water flow and returns and 2 will be the ch flow and return. there is a grunfos pump on 1 of the pipes which if im right in thinking will be the ch flow pipe.

Am i right in thinking that the hot water flow and return to the boiler simply goes upto the cylinder and back down to the boiler heating the water in the cylinder.

And the ch flow and return is pumped by the grunfos pump around the house and back to the boiler??? ????????

kbdiy · 21 Aug 2014

In a word - yes - exactly as you said. Back boiler relies on heated water rising to heat the cylinder then falling back to the boiler as it cools by virtue of losing heat to the cylinder - thermo-syphon principle.

rainbow123 · 21 Aug 2014

ok so the hot water doesnt need to be umped? also how come when the hot water comes on does the ch flow pipe become warm ie making a select few of the rediators slightly warm ???????????

kbdiy · 21 Aug 2014

Basic back boiler setup - no pump used for the hot water circuit. Not the most efficient way by today's standards but the back boilers are not particularly controllable so not really any way to control a pump, if one were to be fitted.

As for the central heating getting warm, this is possible due to the same principle as for the hot water circuit. Heated water rises so may induce some circulation in the central heating too.

rainbow123 · 21 Aug 2014

ok thats logical, so the ch flow and return dont go to the cylinder or have anything to do with it, they simple go from the back boiler and back to the back boiler.

kbdiy · 21 Aug 2014

Quite so. Usually piped from opposing sides of the back boiler to reduce the possibility of inducing circulation in the other circuit. The setup is about as basic as you can get in terms of heating systems these days.

rainbow123 · 21 Aug 2014

ok so what is the difference from a direct and indirect system as i believe i have indirect system

Terry lambert · 21 Aug 2014

A direct system would be your cylinder being heated by an immersion heater, indirect by your boiler

rainbow123 · 21 Aug 2014

my cylinder has a immersion in the top of it tho even tho it says indirect on the fromt of the cylinder??

Terry lambert · 21 Aug 2014

Your cylinder is Indirect, heated by the boiler but has an immersion as an emergency back up.

Direct would just use immersions

gasanstuff · 21 Aug 2014

Direct has immersion heater
Indirect has a coil and immersion heater

rainbow123 · 21 Aug 2014

ow right so the immersion is a back up got you brilliant now im getting somewhere. i cant work out if i should rip it out and put a combi in instead. thoughts ??????

flameport · 21 Aug 2014

rainbow123 said:
i cant work out if i should rip it out and put a combi in instead. thoughts ??????

If you only have one bathroom, only use one hot water outlet at a time, don't mind having no hot water at all when the boiler breaks and want your bath to fill much more slowly than it does now, then by all means get a combination boiler.

Otherwise, keep what you have and when it breaks beyond repair get a proper replacement boiler.

Nige F · 22 Aug 2014

gasanstuff said:
Direct has immersion heater
Indirect has a coil and immersion heater

Not quite; we had a copper cylinder with no immersion and no c/h coil - only way to get hot water was light a fire or boil a kettle

well it was a 1950 council house

stardanny · 22 Aug 2014

rainbow123 said:
ok so the hot water doesnt need to be umped? also how come when the hot water comes on does the ch flow pipe become warm ie making a select few of the rediators slightly warm ???????????

Probably missing the Non return valve or anti-gravity valve or stuck open if one is fitted.

Daniel

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

How Does My Open Vented Gravity fed System Work

Similar threads