water hammer

Hi, Hope someone can help. Not been in the plumbing business very long and am stuck!

New combi (potterton Performa 24 Eco HE) fitted by another plumber to an old fully pumped system in a one floor flat, some rads are single pipe and some are run in parralel, all old system parts (cylinder etc) are still in pace but are decomissioned, 3 port valves are stil in place, whole thing is a bit of a mess.

I was called out yesterday to try to solve a water hammer which, after much investigation, is coming from the TRVs, seems to be coming on when they are shutting down, and is solved when the valve is opened up, however this just chases it to the next rad.

I adjusted the pressure in the combi which was way too high, now running at 1.5 bar, but still occurs.

All rads getting red hot.

Only thing I can think is that the plumber who fitted the combi has reversed the original flow and return, all TRVs were fitted prior to the combi installation.

Also hot water coming out scolding for 30 secs before calming down even with the thermostat at minimum.

Before I go round and change all the valves around has anyone got any other suggestions to possible cause.

Help would be much appreciated.

Sean

i would let system cool, turn off trvs, bar one, once cold turn heating back on and go round turning rads on one at a time to make sure I know which trvs need swapping and which dont

thanks mick, replaced all trvs for bi directional and now working beautifully.

Sean