can i use old 1" and 1 1/4" gravity pipes when converting to fully pumped?

[rolysatch]

hi

i've got a pumped central heating/gravity hot water system. if i was attempting to convert it to a fully pumped S plan system - as you can tell i'm a diyer - can i use the old 1 1/4" flow and 1" return of the gravity system for my pumped hot water or should i take this all out and replace it with 22mm?

any advice appreciated

​

 

[kozak1968]

I am guessing it is iron pipework which is quite old, would be best to replace.

 

[SimonG]

If it's copper, leave it. Although you will be heating a greater volume of water. Depends how much you are wanting to spend.

 

[erpkid]

I would use new and weigh in the old. If imperial sizes you don't need the hassle and old copper is worth a mint. If iron you need this sort of hassle even less.

 

[rolysatch]

thanks for the reply's, yes its all old copper, it wouldn't be a huge amount of work to change the pipes as i was going to fit a new hot water cylinder anyway, and i didn't think about the scrap value of the old pipes which would offset the price of new anyway so maybe i'll change them.

i can get my head around the wiring side no problem with the help of diagrams, as far as the plumbing, is it literally a case of me just splitting the output from the boiler after the pump, fitting the two zone valves and putting in a bypass valve and everything else stays the same? my current pump is a grundfos 15-50 is that adequate to pump the heating and hot water or would i need something more powerful?

my biggest problem i'm trying to figure out is the boiler expansion pipe comes off the hot water as it enters the hot water cylinder which also feeds a bathroom radiator from the loft before going into the expansion tank. from what i've read the expansion pipe needs to be before the pump on a pumped system, so would i have to have a new seperate expansion pipe now, before the pump, and could i still run my bathroom rafiator off it? (i might be getting confused at this pount so correct me if i am)

 

[Dotty]

draw a picture mate, and put it up for us to look at for you.

 

[rolysatch]

ok don't laugh at my "engineering drawing" but it will give you an idea of what i think i have, obviously the radiators on the heating circuitr aren't plumbed in like that but it should give you a roungh idea of what i've got. as you can see i think the radiator in the bathroom runs off the hot water heating circuit.

 

[rolysatch]

so with the help of my drawing:

is it literally a case of me just splitting the output from the boiler after the pump, fitting the two zone valves and putting in a bypass valve and everything else stays the same? my current pump is a grundfos 15-50 is that adequate to pump the heating and hot water or would i need something more powerful?

my biggest problem i'm trying to figure out is the boiler expansion pipe comes off the hot water as it enters the hot water cylinder which also feeds a bathroom radiator from the loft before going into the expansion tank. from what i've read the expansion pipe needs to be before the pump on a pumped system, so would i have to have a new seperate expansion pipe now, before the pump, and could i still run my bathroom rafiator off it? (i might be getting confused at this pount so correct me if i am)

 

[stevetheplumber]

you need to investigate the positioning of cold feed and vent in relation to the pump as the pump will have to go on the flow now where does the cold feed go now you havent shown it on drawing which i assume is the existing set up

 

[secret squirrel]

You could combine the cold feed and vent but agree with steve you need to find the cold feed and it is imperative they're in the correct place.

 

[rolysatch]

i'll have to see if i can trace it back from the header tank in the loft, the boiler and pump etc are all downstairs in an outside cupboard but i only have one return pipe coming through the wall so the cold feed must join up with the radiator return somewhere else in the house but the cold feed is not in the same room as the boiler and pump etc. does that help?

 

[M77]

Hi rolysatch, you would have to run a cold feed and vent pipe from the f/e tank and connect this in before the pump. Don't know how hard this would be? Although you have mentioned replacing the current pipe work to the cylinder so this could be done at the same time.
If not would it be easier to move the pump and valves up near to the cylinder then reconnect the htg there? You could also reconnect the bathroom rad into the htg if didn't want it to be off the hot water circs.
Hard to picture without being there but hope this helps.
Just make sure you connect the feed and vent correctly (no more than 150mm apart, before the pump. Or you could use a 'air sep'.)

 

[rolysatch]

So when you say that they shouldn't be more than 150mm apart, i understand this where they are plumbed in but dies it matter if there course deviates from each other a bit on the way up to the F&E tank or do they have to run parralel no more than 150mm apart all the way up?

Also when ever i see the vent pipe on a diagram it always shows it going straight up vertically to the expansion tank (is that just for the diagram and reality is different?), mine would have to take a bit of a windy route - but always going upwards or horizontal - does this matter?

and finally i've got some very long runs from the boiler to tanks in the loft, what are everyones feelings on using pushfit type pipe instead of copper to help keep the cost down, i could use compression fittings with it if this was considered safer?

 

[M77]

Just 150mm where they connect before pump, Vent can be either vertical or horizontal.
And I wouldn't personally use push fit although there's nothing to say you can't. That's why I wondered about the possibility of moving the s plan up to the cylinder, that would shorten your feed and vent runs.
Presume you have rads on the first floor, not just the bathroom?.

 

[secret squirrel]

Love this post started off giving the impression you had a good idea of what your doing, can I use 1" pipes for this to, HOW do I do this.

Brilliant.

Before you start moaning at me yes, this is a site for free advice blah blah blah, my comment is not meant as an insult just amused me.

Genuinely, good luck with your project.:20: (really like this smiley, I am going to use it soooo much more)

 

[Dannyparty92]

That's a heat leak radiator roly used on gravity hot water to help circulation without it the water in the boiler would get to a high temperature.

 

[rolysatch]

Just 150mm where they connect before pump, Vent can be either vertical or horizontal.
And I wouldn't personally use push fit although there's nothing to say you can't. That's why I wondered about the possibility of moving the s plan up to the cylinder, that would shorten your feed and vent runs.
Presume you have rads on the first floor, not just the bathroom?.

hi thanks for the advice, yeah its maybe a good idea, we haven't got a very big airing cupboard and i'm fitting a shower pump so i'm going to have even less room but i'm sure i could squeeze it in there somehow. yes i have rads on the first floor as well and i'll steer clear of the pushfit then. thanks again

 

[rolysatch]

Love this post started off giving the impression you had a good idea of what your doing, can I use 1" pipes for this to, HOW do I do this.

Brilliant.

Before you start moaning at me yes, this is a site for free advice blah blah blah, my comment is not meant as an insult just amused me.

Genuinely, good luck with your project.:20: (really like this smiley, I am going to use it soooo much more)

lol no offence taken, the fact i gave the impression i knew what i was doing wasn't deliberate. i have a much better idea now though thanks to everyone's advice. to be honest when the gas valve and pcb on our boiler packed up recently i got a quote for a new boiler to be fitted, but money is tight at the moment and with quotes at £4k+ i just got it repaired. and i figured if i can convert it to an s plan myself i'll have a much more efficient system and when i do decide to upgrade to a new boiler hopefully it will be a relatively straightforward (and hence cheaper) install for the heating engineer.

 

[rolysatch]

That's a heat leak radiator roly used on gravity hot water to help circulation without it the water in the boiler would get to a high temperature.

understood, i think i would like to leave it on the hot water heating system as you get nice dry and warm towels even when the heating isn't on.

 

[Kev the gas]

What is the make of the existing boiler?

Old floor standing boilers had sometimes 8 different flow and return tappings, all dependent on whether the system was gravity /fully pumped.

The return positions will be the most crucial, back circulation being the least of the problems you encounter.

It has been known for only part of the heat exchanger to circulate/heat up the water when old boilers are updated without the correct tappings been used.

Might be a good idea to leave well alone as it has worked so well for this number of years !

 

[rolysatch]

oh i didn't realise, i don't think the boiler is as old as the pipework, it's a potterton kingfisher mf rs70.

 

[M77]

If there's little room in the cylinder cupboard, maybe be put a y plan in, give you a bit extra room as well as a little more efficient.

 

[Dannyparty92]

Control over heating and hot water independently plus you don't need a bypass.

 

[Kev the gas]

oh i didn't realise, i don't think the boiler is as old as the pipework, it's a potterton kingfisher mf rs70.

You will not be able to carry out the works completely yourself.

Alterations inside the boiler have to be carried out to convert to fully pumped, from gravity. This work involves opening the combustion chamber which is illegal to do unless Gas Safe Registered.


Regards
Kev.

 

[M77]

You will not be able to carry out the works completely yourself.

Alterations inside the boiler have to be carried out to convert to fully pumped, from gravity. This work involves opening the combustion chamber which is illegal to do unless Gas Safe Registered.


Regards
Kev.

What alterations inside the boiler would have to be made?? Sorry if I'm missing something obvious.

 

[PlumbBobBob]

one thing i don't think anyone has mentioned yet(only skimmed) the two vents are going to the wrong tanks.

 

[rolysatch]

If there's little room in the cylinder cupboard, maybe be put a y plan in, give you a bit extra room as well as a little more efficient.

yes that maybe a good solution

 

[rolysatch]

You will not be able to carry out the works completely yourself.

Alterations inside the boiler have to be carried out to convert to fully pumped, from gravity. This work involves opening the combustion chamber which is illegal to do unless Gas Safe Registered.


Regards
Kev.

oh i didn't realisethe boiler would have to be modified, i certainly wouldn't touch that.

 

[rolysatch]

one thing i don't think anyone has mentioned yet(only skimmed) the two vents are going to the wrong tanks.

hi steve, that's just me rushing the drawing late at night, it is actually plumbed in the correct way, but well spotted.

 

[PlumbBobBob]

glad to hear it lol

 

[Dannyparty92]

What boiler alterations would need to be made? Like check if the current boiler had a high limit stat?