hi,sounds like you are stoking the fire up too much,cheers

Thanks Guys - this mode of feedback is very useful.

In response to the stoking no we are a long way off from over stoking. I have connected a temp probe & controller which is set to the turn the under floor circ pump on and off at set temperatures. This way we don’t use electricity for reheating when the floor heating is on. We generally average about 65° - 70° with the fire reasonably stoked. That's the plan anyway!

What I never mentioned is that we are rural so we have a pump. I downloaded the ‘typical example...’ of wet back installations from this web site; I think that we perhaps use a PRV as opposed to an expansion tank may be an issue? Perhaps the PRV is surging water in and causing the hammer action we can hear; the header tank maybe a “smoother” fill?

What I never mentioned is that we are rural so we have a pump. I downloaded the ‘typical example...’ of wet back installations from this web site; I think that we perhaps use a PRV as opposed to an expansion tank may be an issue? Perhaps the PRV is surging water in and causing the hammer action we can hear; the header tank maybe a “smoother” fill?

no - the water hammer you hear is most likely due to 1/ insufficient rise/fall on the pipework directly out of the wetback 2/ incorrectly installed wetback ie not enough rise/fall on wetback itself - or - 3/ the fact the hwc is located above the fire and therefore a lot of head acting on the wetback resulting in steaming prior to convection taking place

hwc venting is due to expansion in system - if it is constantly discharging then there may be issue with prv or standing water level in system is incorrectly set

hi guys, my thoughts exactly Jax no one would put in that system if they were not sure of what they were doing! would they, it would be far too risky, here`s hoping,cheers

Gordon you can verify if the person was a licensed plumber by visiting www.pgdb.co.nz - under the public section you can check licences and simply enter the name of the person - you will see what licences they hold.  If they are licensed, then they should have had a certifier providing direction who should have come on site at the time of testing.  Did you see this person, if not do you know who they are?  Did you ask to see the card of the person who installed the system.  I am always in favour of going back to the installer and talking the issues through rationally - they need to remedy any problems so that you get what you asked for - a working, safe system.  If the person is a member of a professional body then you may have recourse through that.  Of course you can get a second opinion which is what it seems like you are doing, but have you gone back to the original installer?  One good place to start is to contact the manufacturer of the system and see who they recommend in your area for installations.