Priming of Hot Water System

[Jim_374360080]

I have an intermittent fault on a Bailey Arizona. Sometimes (1 in 4) the hot water system will not prime. When it is primed it works well. To prime it I have to empty and refill up to three times. So far I have replaced the pump, the filter and the non return valve in the Truma heater outlet bend(where I can hear the air surging) I have also fitted a non-return valve above the main filter. I have checked for inlet leaks and have connected the new pump directly to the inlet pipe in the aquaroll as I suspected the water inlet connection on the side of the van. Any further suggestions would be appreciated Thanks Jim

 

[alaintaylor]

Not sure I can help, but I note you have fitted a non-return valve above the filter - does this mean you have two non return valves in the same pipe run? If so you have isolated a section of pipe which may cause problems being unable to drain down or release trapped air (hot water for example needs to expand and contract freely as it heats and cools). There shouldn't be a need for multiple non-return valves.

 

[JTQ]

Jim, My thoughts,

First its a big volume to fill either 10 or 14 litres depending on model so that's nearly half an Aquaroll so its going to take some time. If its restricted for some reason as Alan suggests then its going to take a fair bit longer.

If that's not the answer then it points to some other restriction.

My money is on a non return valve sticking closed. There should be one to stop the boiler back feeding into the cold supply and that's the one I would target.

More systematically:

If you first get the cold running then switch over a tap to hot you know that the pump itself is primed and not air locked. With the pump primed you have as much pressure being developed as possible so it ought to fill.

Next I would open all hot taps as that presents the least resistance and overcomes a fault in an individual tap.

Failing all that I would break into the system to put the boiler outlet into a bucket via a piece of hose then switch on. If it still does not "prime" then the problem is "up stream" of the bucket. So its put the bucket just before the boiler and try again. Using this technique you ought to identify where the problem is.

Hope it helps, don't kick over the full bucket in excitement when it works!

 

[Jim_374360080]

Alan

Many thanks for trying to help

No this is the only non return valve

Since writing I have backflushed every circuit by putting a piece of flexible in the tap outlets and blowing back. Some debris was found. I have filled it six times and been able to prime it each time -so fingers crossed

Kind Regards

Jim

 

[Jim_374360080]

JTC

Many thanks for your response

Please see my response to Alan above

I think that your point about timing is very relevant 10 litres and some impatience could have been another cause

I also found that a quick lift of the drain **** speeds up the clearance of air which is present even after priming

Hopefully I will be OK but grateful for your help and I will keep all your other points for the next failure

Kind Regards

Jim