Rads heat up when hot water on

[herbystaines]

Just a quickie.

I have an s plan system, the 2 port for the heating circuits is not passing,
when i have demand for hot water only, all upstairs rads heat up.

The auto bypass is located incorrectly i.e tee's off before the valve (ok)
but tee's back into the cyl return not primary return.(not ok)

Does anyone think this may cause the flow to channel trough to the heating circuit? can't tell how anything is connected to the primary return as under tiles then ply!!

Suppose i could prove if cycling the wrong way by first turning the heating on and checking which is the flow pipe, then allow to cool, turn on hot water and see if other pipe (return) heats up first??

Any other ideas anyone?? would be very greatful.

 

[lightning]

might be piped up wrong upstairs. no c/h pipe should be teed after the cylinder return ,other wise you might get reverse circulation

 

[herbystaines]

No telling what has gone on with pipework. customer doesnt want the floor up. hay ho

 

[MIGEM]

Under tiles and plywood?
It might be easier to take the ceiling down in the room below, should you need to get to the pipes; just a thought.

Tiles? in the bathroom? Nice new bathroom? Nice new towel warmer? Fed off the primary pipe work so that it is also on when only a demand for hot water? Connections in the wrong place? Reverse flow?
Is the heat just convecting or is the water flowing to the radiators?

Edited: Isolate the bypass, if you think it is that....?