Hi,

Thanks very much for looking at the diagram and responding. A picture is worth 1000 words in this case. Yes I agree with what you say, and its obvious to me now that the pulse valve was there for a good reason. I wish it had been obvious to the plumber who did the replacement work for me.  I have done some research into the available pulse valves on the market, and came up with a phone number that I have since called and spoken to a guy who is making the valves near where I live in Kerikeri.  He has some first hand experience with the original installer of the system, and what he says ties in with your thoughts.

I am going to invest in one and get it installed. I will get back on the site and report on the outcome!

Murray

Very good diagram , The tempering valve is not the problem what confuses me straight away is that your flow is running into your open vent above the body of water in the tank (should be about 300mm above the return, as the hot water has no more space to rise it cant contribute to the circulation) This explains why they used a pulse valve. Also part of the problem is that your solar is on the same circuit this is bound to disrupt the natural circulation.

The greater the vertical height of a circulation system , the greater will be the circulating pressure. The greater the difference in temperature between the "hotter" rising flow and the "cooler" falling return, the greater the circulation pressure. Also the simpler and shorter the circulation system the smaller the loss of circulating pressure due to friction.  The amount of bends you have are too many and not swept enough and having a 20mm pipe does not help the cause at all. Sorry but looking at this I think without reconfiguring the system thermal circulation is impossible. If you don't llike the noise of the pulse valve I would suggest a thermostat triggering a pump, I know it defeats the purpose of a wetback using an electrical solution also this needs to be installed correctly as it can push water through the vent if not done properly. If it was my place I would redo the wetback or put up with the pulse valve. Hope this helps some what.. 

Thank you Victor s. That's a useful thing to know. How would I measure it though? I've had the council check my meter and they weren't particularly alarmed by our usage. I bet we'd be losing at least that amount if I didn't run around like a headless chook trying to prevent it though. We are first off the village water supply and other people can't get water if we waste it, so I've been desperately trying to avoid inconveniencing them.

I'll have a word with my water usage contact in the council and let her know this fact. I'll give her the latest reading and see if there's a spike.  Very useful. Thanks

When you say "service call" - do you mean from the council or from the installer?

Funny you should say that Jax, because I watched that earlier and they were talking about human rights and how violated their rights and caused them to suffer and how they felt intimidated on the day they were raided.

I lost my house and business and can assure you I felt very violated, stressed and intimidated, its been four years of shit from these goons......and Williamson won't even talk to me.....

Hi and thanks for your reply. Sorry its taken me a while to get back to you...

The piping from the cylinder down to the wetback is the same as was installed for the 3Kw " Pulse Valve " model I took out. Its 20mm but it is smaller than the tubing ends that stick out of the new 3kw wetback, which are 25mm.

The plumber had to do some squashing ( not a professional plumbing term, but thats what he did ), to get it to where he could weld one to the other. Could this reduction in pipe sizes be the cause of the problem?

I crawled into the roof space to check: the tempering valve is connected between the top of cylinder outlet ( H ) and the cold water supply ( C ) and outputs to the hot water taps in the house. I guess this is to cool the water if it gets too hot at the top of the cylinder. So, no its not in the wetback side of things. My apologies for throwing that one in.

Yes the wetback up-pipe goes to the top of the cylinder where it is open vented through a standpipe on the roof, which is lagged and sleeved, and is about 3 m high. The cold water down to the wetback comes directly out of the cylinder a few inches above the base of the cylinder, which is my experience of where it should come from.

The wierd thing is that when you light the fire from cold, you get  gradual heating of the riser side, while the down pipe stays cold, or cool anyway...then after fifteen or twenty minutes there is usually a succession of gurgles and burps, and some rattling of the whole set-up, after which it settles down but both pipes appear to be rising. Eventually there is very little difference between the riser and the down-pipe as far as temperature are concerned, but there is little or no boosting of the water in the cylinder when you go to take a shower.

I would love to get this sorted out....so any input would be gladly received. I have installed a couple of systems before, myself, and they have worked fine. One included a temperature controlled pump to do the circulating as there was a distance of several metres horizontally and with no rise to the cylinder. But this one is a straightforward setup and should work without issues.

Is it possible that I should instal a non return in the downpipe...to replace the pulse valve that was in the existing system before I decided to change the wetback?  ( And wish I hadnt!! )...I was told that its bad plumbing practice to instal any kind of restricting valve in a wetback system, in case it fails.

Cheers

Murray