Primary flow/return to heat generator, unvented cylinder????

[Maddog235]

Hi Guys, first post so be gentle.

I am by no means a plumber but i do a bit of labouring for a guy who is a plumber, now hes normally pretty good and i like to think i know quite a bit about heating systems etc, but this one has caught us both out.

Basically we are converting a system boiler with unvented cylinder in to a combi boiler system, now weve removed the tank/ old boiler etc, but there's 2 pipes that we are unsure on what to do with. The first is a pumped pipe (which has a pump on) labelled "primary flow to heat generator" and the second is "primary return to heat generator".

There is also another 2 pipes labelled "flow and return for heating" coming off the boiler is only 2 pipes (flow and return for heating i assume) we are familiar with both fully pumped and gravity systems but dont understand why there are 4 pipes in to the tank and only 2 from the boiler.

Are the 2 flows and 2 returns just linked in somewhere and therefore we just need to link them together in the tank cupboard or what?

Any advice/help will be greatfully received, thanks guys

harry

 

[WHPES]

Is there / was there a back boiler somewhere in the property?

 

[Gray0689]

The flow and returns will be 1 set was the coil pipes for hot water and 2nd would of been for the rad circuit

 

[WHPES]

I think he means he has 2 pairs of pipes going to the cylinder.

 

[Gray0689]

I think he means he has 2 pairs of pipes going to the cylinder.

Could be back boiler
What size are pipes?
Picture might help

 

[diamondgas]

My first thoughts are, "Does the system have a hot water circulation system incorporated on a 'bronze' pump? You can forget the F & R suplies to the cylinder as the combi does away with them. However the hot water in the premis may have a secondary circulation installed ... Designed to reduce the waste of 'dead legs' in pipework on larger systems...... Any help?

 

[WHPES]

Picture would help.

If there is a back boiler still connected he has to be careful!

 

[Maddog235]

Thanks for the replies so far guys.

Yeah there are 2 pairs of pipes , the central heating pair has a pumped return and the "to the heat generator" pair have a pumped flow.

Im pretty sure there has never been a back boiler but not 100% the boiler is pretty old so probably put in at build as the property is a new build style house.

How can i do away with the 2 unknown pipes? they must be connected somewhere but its not to the boiler as there is only 2 pipes coming off it, so assume they are linked in somewhere.

Cant work it out.

Also which might be related, the cylinder wouldnt drain ( i assumed it was a seized drain off) but wen i punched a hole in it and tried to syphon it i got nothing.


The little bits i did get were black, like central heating water not what you expect the hot water to look like, but again maybe thats my lack of knowledge on these systems.

the pipes in total are:

hot water to taps (complete with mixer valve connected to cold mains)
central heating flow
central heating return (pumped)
cold mains to top of tank and to mixer valve
primary flow to heat generator (pumped)??????????
primary return to heat generator ??????????????

the boiler has:
gas
return
flow

a real puzzler hey guys, although im sure theres some unvented wizzes amongst you?

 

[Maddog235]

so do you think it would be better to cap the 2 unknown pipes or to link them in i.e flow to flow, return to return?
is it possible they could be linked to the hot water system?

 

[diamondgas]

sounds like you have a thermal store unit? The Primary flow and returns are the one's connected to the old boiler and can be discarded. The Central Heating flow and returns are the ones you need to conect your combi up to along with the Hot draw-off and cold mains of course.

The cylinder/unit should have a data badge on it, find out it's details and google it may help.

Thermal store cylinders work in reverse to conventional where the coil is actually the cold mains and around it is the system water which explains the colour when you drained it.

Hope that has been of some help 🙂

 

[unguided1]

Got any pics of the Cylinder, it sounds a bit like the gledhill torrent as diamondgas says if there is a cold main going in near the top there must also be a hot outlet below it, is this also a twin coil?

 

[Maddog235]

Thanks guys, great advice, I think diamond gas and unguided are the winners.
Rang gledhill toaday they told me to link the flow to flow and return to return which seems to have done the trick as everything seemed to heat up fine and the hot water worked ok.