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floaters
floaters

Posted: Sun Apr 29, 2012 1:19pm

Post Subject: morco water heater D-61B

temp adjusting knob is turned to hot,main burner comes on then goes out , with a pulse motion then reignites.water goes from hot to luke warm .new pump fitted as told water pressure problem.pipes cleaned out and flushed .then new morco fitted, still the same?.costing a lot of money now .gas pressure does not have a problem? can not think of any think else.please help if you can .cheers

Tony-B
Tony-B

Posted: Sun Apr 29, 2012 2:27pm

Post Subject: morco water heater D-61B

I think the pulse motion is in time with the water pump turning itself on and off. I have no experience of the Morco and think I have seen some less that glowing comments from experienced plumbers/engineers. All this type of heater use a diaphragm with inlet water pressure on one side and outlet water pressure on the other with a flow restrictor in between. The flow restrictor may be the temperature knob. The idea is that the inlet will always be under a relatively high pressure and when a tap is turned on the outlet will be under a lower pressure so the diaphragm is pushed up, opening the gas valve. So if the pressure on both sides equalises the diaphragm will drop and the gas be turned off. Often this is a case of scale in the heat exchanger or loose scale blocking the water ways but as you say you have fitted a new Morco this should not be the case here. We come down to insufficient pressure difference across the diaphragm. The manual on the Morco site says the water pressure should be between 1 and 10 bar so with most water pumps operating at between 2 and 3 bar cut out pressure and a cut in of perhaps half that straight forward pressure may not be the problem - but please check the specs. for your pump. I suspect your domestic water pipe feeding the boiler may either be too small or have a restriction in it like a service valve. This would cause the inlet pressure to be less than the pump outlet pressure when a tap is open and possibly worse still if a hot and cold tap is open. On the other hand something may be restricting the outlet plumbing so pressure in the outlet side of the diaphragm is not as low as it should be when a tap is open. So we come back to undersized plumbing or a restriction like a non-full flow service valve. An accumulator will help to extend the time the pressure pulses are present but I very much doubt one would solve your problem. If you have fitted one of the expensive delivery sensing water pumps that alters its speed according to the delivery required I fear it may be delivering well under one bar into your plumbing system. I will now show my prejudice by saying that my experience with a variety of such heaters on the hire fleet has convinced me that I would never have one. If I needed gas water heating I would use a calorifier and probably an Alde (long tall one) boiler or a Trumatic. Sorry not to be much help. Tony Brooks

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