Baxi Combi 80E. hot water not constant

17 Nov 2011
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United Kingdom
Hi there... I have a baxi combi 80eco boiler. I seem to be having a problem with the hotwater.. where it is not constant. The water goes hot and cold and then hot again.. in a cycle.. Can anyone help me/shed any light on what maybe be causing this problem?
Thanks in advance guys :)
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This is most often a blocked secondary heat exchanger.

But it can be other causes as well!

This is most often a blocked secondary heat exchanger.

But it can be other causes as well!


Is there another name for the secondary heat exchanger.. as I cannot find it in the baxi manual? I can see the primary heat exchanger but no secondary.
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Can the Plate Heat Exchanger be cleaned/unblocked or do i need to get a new one?
I am having the same issues again, is it likely to be needed to clean or replace DHW plate heat exchange again? I need fit a new one in dec 2011?
Is this a common problem/part that needs to be cleaned or replaced every so often?
Thanks for help guys.
If your plate hex has blocked up again on the primary side ,its a consequence of the condition of your central heating water. You would have been well advised ,several years ago when you had the problem ,to have your central heating system cleaned / flushed ,and a filter fitted. And Inhibitor added when topped up.
even if it is the hot water that is affected.. the heating part seems to be working fine?
Yes ,the water channel's in the plate heat exchanger ,that gives you domestic hot tap water ,are very narrow. And thus block quite easily .The sludge that collects there is being pumped around your central heating system and is essentially as a result of corrosion ,and is largely magnetite.The fitting of a magnetic filter onto your central heating return pipework helps to trap those particles before they enter your boiler.
Getting what done ? System flush and mag filter supplied and fitted and a new HEX ? Prices vary quite a bit , depending on location and who you use. Best get 3 quotes from reputable company's ,preferably recommended by people you know if possible.
I can do the Dhw heat plate exchange myself as i have done that before not a difficult job. Is fitting the filter and a system flush similiar level jobs?
Fitting a filter and BASIC flushing should be within your capability then. But chemical power flushing is really a job for a professional with the kit ,and would achieve better results. Is your pipework to radiators small bore , 10 mm ,or less ? If so it is debateable whether or not power flushing would be as successful as you would wish.

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