Upgrade from Gravity Fed Hot air system to CH Boiler and Rad

[cello33]

Hi All first post on this subject, just after a few pointers plese...

Like the title says I have upgrded from a old hot air gravity system that has never worked properly to a Condensing GLow worm boiler. Have plumbed in the hot water circuit (indirect) and this functions ok, no pump so it takes a long while to heat the DHW up but is loads better then the old system.

Now I am about to plumb the downstairs rads in and currently have mountd them in the right places. Next comes the actual plumbing that looks pretty striaght forward, well at least before it gets back to the boiler!

I have a pump and about to get a 3way valve and wondered if I need to reposition where the cold circuit feeds the system?

CUrrently its on the return of the copper tank, effectively dragging cold water behind it into the boiler as the hot water gets lifted out of the boiler by capilary action ( i think) . There is a expansion pipe on the copper tank inlet , so any excess hot water (blockage) has an escape path into the header tank. Looking at some diagrams the cold feed needs to be between the pump and the boiler on the flow out - does this need to be like this or do you think having the cold water feed on the return it will function OK???

ALso regarding the use of plastic / copper pipe , which would be better? I like the look of copper and will be using some of the excess 22mm to make the connections to the pump but wondered if I could use plastic on some of the feeds/returns to the rads to cut the cost a bit?

There seems to be loads of pushfit/comp connections to make the routing of the pipes easy enough although I may need to get the pipe benders/blow torch out to complete the pipe work near the boiler as I will need a awful lot of 90 deg/ t pieces to feed all the down stairs radioators which go off in three separate directions from a central point (concrete floor)

Thanks

 

[Biggles..]

Modern boiler aren't really designed for gravity hot water....might need a rethink.

 

[cello33]

May have not described my situation clearly, I plan to install a pump on the outlet of the boiler and wondered if the mains cold feed is OK on the return pipe?

Not sure if this is method will just take longer to initially feed/fill the system and then function OK.

ALso do I need a bypass as I dont plan to shut off any of the radiators. Not sure how to balance the radiators if I get tht far (!) , I guess I just switch all the radiators to max and throttle the hot ones near the pump to allow the distant ones to receive the same amount of hot water/temp (Four rads in total)

Cheers

 

[theheatinghelper]

pump on the outlet ???

 

[cello33]

Thats hot water flow outlet from the boiler.

Its a heating only condensor boiler, hence the use of a 3wayValve.

Cold water header tank connects to the return pipe at the base of the copper cylinder which then feeds back into the boiler return.

 

[theheatinghelper]

Id get some on to give you a quote, it sounds like you are a beginner, you want to fit a pump on the hot water out let yet its a heat only boiler, I take it you mean primary flow to the three port, If you serious about it I would by the readers digest book of diy , its got everything u need to know in there minus gas work

 

[cello33]

Aye a beginner but a sensible one, hence the questions. Sorry my terminology sucks I agree! Will pick up the book , thanks for the tip.

Still interested to know from an expert if the cold water feed from the header tank connected to the outlet of the copper cylinder which then returns to the boiler would still be suitable if I install a pump on the boiler primary flow out? THis would then connect to a 3wv which I too need to install.

Thanks for your patience

 

[theheatinghelper]

the out let from the copper cylinder should be the hot draw off , this comes out of the top of the cylinder , it should have a tee on it that goes downwards to your hot supplies and upwards to the cold water storage tank and over the top to be used as an expansion pipe , this tank will also feed the cylinder aswell ,the bottom entry.
you then have a boiler with a flow pipe and a return pipe, the flow pipe runs to the three port but before this an open vent pipe is took off the flow then a cold feed pipe from the small expansion tank then the pump then the 3 port which then splits to the heating circit and the cylinder, the circit then heads off to the rads and the cylinder, remember the return from the cylinder needs a lockshield valve to be cut down and it must be the last tee back to the boiler
try to have trv`s on your bedroom rads as a minimum requirement and place your room stat usually in the hall not near a rad

hope this helps

 

[cello33]

Thanks for that, It sounds close to what I have.

I neglected to state that I have two tanks in the loft and four pipes feeding into the cylinder. I worked out the Hot DHW supply so did not mention these but...

From top to Bottom of the cylinder..

1) DHW out, Direct to hot taps - no vent.
2) Heating circuit (from boiler) Hot water in and T Piece to vent feeding the small header- catch/expansion tank
3) Heating Circuit Out plus T which comes from the expansion header tank (feeding water into the system)
4) Cold water in from the large header tnk in the loft.

The system is old 70's vented one I think but there again it never really worked! Last years winter almost did for me, hence why I am changing it.

Does the above tie in with your thinking - I think it's slightly different.

Cheers

 

[hansthebear]

no vent on dhw?

 

[cello33]

Sorry talking Borrocks - just had a look , t piece out of Hot DHW from cylinder which leads up to the large header tank - its vented!

Looks like i need to move the vent from the heating element feed into the cylinder to the point pre 3wv but after the pump.


thanks for your help