Unvented cylinder and heating issue?

[macka09]

Hi all. At a job today there's a regular boiler feeding an unvented cylinder, heating, hot water and UFH. For some reason the flow to the UFH was cold whilst the return was getting hot. So we swapped over the pipework hoping that was the fix. Unfortunately it wasnt. The set up has three 2 port valves which seem to work fine when the stats are operated. Anyway after swapping the flow and return from the boiler we wasn't getting much heat in the rads. Maybe the return was backing up? Any of you lads got any ideas what to look for tomorrow???

 

[AWheating]

probably a circulation issue with the controls/ valves on the pipework to the under floor manifold or on the manifold itself.

if it has been working correctly before i dont think the pipework would be crossed over.

 

[macka09]

I don't think it has been working since installation a couple of months now.

 

[AWheating]

prob wired wrong.

 

[macka09]

Thought as much.

 

[macka09]

Let me get this right. The lever arm on the motorised valves should automatically move to open when you operate the stat. But should locate in the auto position when not being used???

 

[AWheating]

when stat turns off/ reaches temp the valve should return to the closed position which shuts the boiler off. Very important on the supply to the cylinder especially. normally closed valves. bypass important.

 

[macka09]

The heating and wiring intrigue me unfortunately I don't get to work on it as often as I would like.
Also went to a house today with an S plan system with 2 heating zones and the DHW. For some reason when only the DHW was switched on via the programmer the heating kicked in ??? Replaced the 2 port valve and upstairs stat but still the heating comes on when only the DHW is called for

 

[Chalked]

Is it a regular boiler with a separate pump?
have come across before where installer has connected the f&r into the mains before the pump.

 

[AWheating]

Also went to a house today with an S plan system with 2 heating zones and the DHW. For some reason when only the DHW was switched on via the programmer the heating kicked in ??? Replaced the 2 port valve and upstairs stat but still the heating comes on when only the DHW is called for

could even be not enough core's run to clock so sparks bodged it up.

clock should put power to the stat which puts power to valve which moves and puts power to switch live to boiler and pump. if turning on the hot water opens the heating valves then its wired wrong. Sometimes its easier to just take it all apart and rewire them instead of trying to figure out whats wrong.