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Two source water heating

Postby » Tue Aug 26, 2008 8:44 am

I heat my domestic hot water from 2 sources - an open fired high output back boiler and oil heating boiler. The back boiler feed is gravity with 28mm pipe and the CH boiler feed is pumped. How can I stop the pumped feed going round the back boiler when the open fire is not lit. The system as it is works fine but I fear I am wasting heat in these circumstances. (By the way, I know about the Dunsley neutraliser but don't want to use one of these). Thanks. Dave
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Simply Build It

Postby plumbbob » Tue Aug 26, 2008 5:39 pm

For safety reasons you cannot interfere with the backboiler feeds so the logical solution is to convert the oil boiler hot water circuit to a gravity feed.

The problem is of course the cost of materials and installation would possibly negate any saving made by reducing the hot water flow through the back boiler.

What about fitting a gate valve in the pumped DHW circuit and set to just open so as to restrict the flow through the cylinder coil thereby reducing the possibility of water circulating around the back boiler? Turn the pump speed down?
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