can anybody explain the tech.....gravity HW pumped CH boiler

[bhm1712]

as in the title,

im just wondering how exactly the heat exchanger in a gravity HW boiler is, with 4 tappings - HW primary and CH secondary pipes

i know that the gravity side utilises the fact that hot water will expand and rise, creating flow through the pipes, and that the CH side relies on the pump to do this, but my question is,

if the heat exchanger is basically seperate for each side, how does the filling loop which is on the HW primaries also fill the CH side? is the heat exchanger common to both? if so why doesnt the pump have an effect on the HW side?

might sound like a daft question but i just wonder for my own knowledge

 

[fitz1]

what filling loop

 

[bhm1712]

the filler pipe from the header tank.....i may have worded it wrong as in a sealed system but i meant the fill pipe

 

[adlplumbing]

are u asking how does f & e tank works?

 

[bhm1712]

no im not, im asking about the boiler

i want to know about the setup of the heat exchanger, the way it is made, as i cant understand how the filler pipe tops up both the CH and HW if it enters the system in the HW primaries, which i believe are seperate completely from the CH pipework. i just dont know how it all works....... i know the science behing head pressure and how the f&e tank actually works..d

 

[fitz1]

two pipes from h/x to coil in cylinder and two pipes to heating. the water is the same in both . h/x is a box full of water, basically.

 

[bhm1712]

ok i see, so explain one more thing if you can please?

when the CH is on being pumped around, and the HW valve is open ( C plan) how come the pump does not force any water through the HW pipes too?

 

[adlplumbing]

right i am not sure what you are on about but here is stab in the dark
boiler heats up what via primary heat exchanger above the boiler

the flow water goes to three port on y plan then depending on the requirement that moves the water either central heating or hot water or both

and f and e tank operates as filling loop

i hope this helps

 

[fitz1]

on the heating side the pump pulls heat out and pushes cooler water in therefore causing circulation. on a gravity system the pipes have no choice but to circulate unless airlocked.

 

[bhm1712]

not really, your not reading my original question.....im asking about a Gravity HW and pumped CH which is neither Y or S plan,

i know what a heat exchanger is, and where it is located

i was merely enquiring about the way the whole thing works because as i understand it, the HW and CH pipes all connect to the H/X which as fitz1 has explained is basically a box full of water common to both CH and HW

if this is the case, then my question is, how come when the CH pump is running and the HW is on, that the pump does not force water through the HW pipes. my initial thoughts were that the H/X must be split into 2 parts.However then i couldnt understand how the filling pipe tops up the CH and HW when it enters the system on the HW primary

 

[adlplumbing]

if u are talking about annuls i think that how spelt inside a cylinder then it simply an air bubble and it can be blowen out at which point u have to drain down several times and refill

 

[bhm1712]

adlplumbing, no disrespect but you really are not following this thread at all.......are you really a plumber who knows about CH?

 

[adlplumbing]

yes but not 100% sure what you on about

 

[fitz1]

http://www.deals4homes.co.uk/images/centheat1.gif

 

[bhm1712]

is this basically how the H/X is?