"John Rumm" wrote in message
...
John Stumbles wrote:

thus a bypass is needed for an S-plan system but not Y-plan (where the
3-way
mid-position valve provides a path via the HW cylinder)

Could you not still get into a problem situation though with Y plan?

If there was no call for heat from the cylinder stat, but there was from
the room stat, the 3 port valve would have switched to the heating only
position and eliminated the path through the cylinder. Meanwhile if
there were TRVs on all rads (including the one in the room with the
stat), then they could all close off but leaving the main stat calling
for heat and no path through the CH circuit.

Yep you are right



_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account