Can't think how I could plumb this let alone fix

[PAULY1985]

Went to a job last week two outher plumbers had moved the boiler,owner complaining heating coming on with hot water.after inspecting I noticed primary flow and returne were crossed over at the cylinder this is an s plan system with no primary towel rail cercit or bypass.i fixed this and all seemed to be ok,got the call today samething happening went back sure enough same problem.it seems that the return from the cylinder is heating the rads but how is it circulating when the heating two port is def shut,no bypass or towel rail cercit it doesn't seem possible,I'm going back to start lifting floors any suggestions on how it could be circulating would be appreciated.

 

[lame plumber]

coz youve cocked up the pipework, got the bypass in wrong place etc etc

 

[PAULY1985]

Not me i got called because the outher plumbers did a runner,no bypass visible on the system.

 

[lame plumber]

you state you fixed the issue by changing the pipework, but that hasnt fixed the problem, so theres a cock up somewhere still, and your work hasnt solved it

 

[PAULY1985]

The pipe work was crossed over a quick fire up and feel of the pipe work proved that.after I corrected this I fired it again primary flow got hot both motorised valves opened and closed with the thermostats everything seemed fine,how ever it seems to happen after hot waters been on for 30 minutes or so when its returning to the boiler,what I can't see is how its circulating when the heating two port is closed.

 

[kris]

It depends where theyve teed in the return from the cylinder, you should always go as close to the boiler as possible or you risk this happening, a bypass wouldntve made the slightest difference if the returns in wrong place pauly, youl have to check pipework and re-pipe the faulty part

 

[kris]

2 pipes come from the boiler , which then turns into 4, the 2 for the cylinder , 1 is the 2 port on the flow , where is the return from the cylinder go / or where is it teed into ?

 

[PAULY1985]

Thanks kris iv not come across this befor,I'm aware of the three tee rule when plumbing these systems it's still baffling me how this is circulating through the heating.

 

[PAULY1985]

I'll have to get the floors up to see that kris iv only had a few hours there I'm not looking forward to tomorrow I can see a late one

 

[Billy Bob Bob]

last t to domestics rule not followed there is your issue

 

[kris]

Or it might be possible if someone (not saying you) has done a bit of diy by installing a radiator in the house and teed the pipes into the wrong place as the reason the rads are heating up is because the primary return has become entangled if u like with the sec flow n ret, OR could the motorised valve maybe not fully closing , Id use my temperature gauges to measure the temps of the pipoes this will tell you where its slipping through, ( other side of zone valve or return)

 

[PAULY1985]

Thanks for the replies guys,I'm sure the heating motorised valve is closing fully,and that this is a pipe work issue all your posts have been a great help,the thought of the furniture I have to move tomorrow is making my back ack

 

[dmheat]

Considering the boiler being moved seems to coincide with this issue.

Is it a system boiler by any chance? If yes, I'd say they've reversed the f&r connections on it and it's pumping the wrong way? Seems a bit of a coincidence that they moved the boiler and then the coil was heating up in reverse? Why would they have swapped the cylinder f&r pipes if just moving a boiler?....just my thoughts.

Failing that, sounds like reverse circulation, hw return should be the last tee on return before the boiler.