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Brian, Plumber
Category: UK Plumbing
Satisfied Customers: 818
Experience:  16 yrs. experience as plumber, including full bathroom and kitchen installations.
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My hot water works fine when the heating is on. When the

Customer Question

My hot water works fine when the heating is on. When the heating is not on, the hot water works fine for a short while, but then the boiler shuts down with an overheat code. With the heating switched on, no hot water problems at all
JA: Sometimes plumbing issues that that you think will be really complicated end up being easy to fix. The Plumber I'm going to connect you with knows all the tricks and shortcuts. Do you plan on doing the work yourself?
Customer: Only if it is easy and safe to do, or maybe get dad to do it. He is a electrical/mechanical engineer
JA: Anything else we should know to help you best?
Customer: No, that sums up the issue
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Plumber about your situation and then connect you two.
Submitted: 4 months ago.
Category: UK Plumbing
Expert:  Brian replied 4 months ago.

Hi This sounds like its the plate heat exchanger either scaled or blocked with magnetite (black sludge)

When the heating is on the boiler has got a way of transferring the excess heat generated from the restriction in the plate heat exchanger.
When you only have hot water on the flow and or heat transfer is restricted causing an overheat. it will cool down and the process begins again.

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