Gledhill/Rayburn question

4 Jul 2008
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United Kingdom
We have a system thats been in a while and uses a Geldhill Boilermate II thermal store with an oil fired Rayburn Nouvelle.

My question is concerning the almost permanent running of the boiler pump. We only switch on the Rayburn boiler when we need instant hot water or central heating, othewise its off because it will just keep firing to heat the thermal store and waste an awful lot of oil. The problem is down to the setting of the thermal store dial on the front of the boilermate. If we have it set anywhere slightly above summer to winter, the neon light is always lit and the boiler pump continually runs. If we turn if right down to summer, it works as expected and the boiler pump cuts out after the 5 minute overrun. However given the Rayburn cooker is permanently on, there is always low background heating of water in the boiler pump circuit, enough to gradually heat the store for evening hot water and showers etc. The problem is that if the boiler pump is off, the hot water often gets to boiling point as it won't circulate well enough. The only way I've found of preventing this is to turn up the boilermate dial until the neon comes on, which then starts the pump. But its then running almost permanently.

Am I misunderstanding something we should be doing, or should there be somekind of additional thermostat to ensure the pump starts if the pipes in the Rayburn get to a certain temperature?
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Having studied the wiring logic, I'm thinking if I fit a pipe thermostat to the boiler flow pipe fairly close to the Rayburn, I could wire this up to provide live to the boiler pump if the pipe reaches a certain temp. This should ensure if the boiler was turned off, and the missus was cooking on high (which usually causes a boiling water sound in the flow pipes), all the heat into the pipes should flow into the thermal store.

Anyone know of any drawbacks to this?
Would it be a high limit pipe thermostat that I need?
should work but your store temp will obviously be very high sometimes.

i dont think the gledhill is well suited for a rayburn hence the issues.
What size pipework is off the rayburn? Is it designed to run the heat store via gravity?

You may need a heat leak radiator installed to dissapate the excess heat produced from the rayburn.
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So far, we don't seem to have suffered store temps too high (been using it for 5 years). Usually the water gets used before its too hot. Sometimes the CH comes on by itself so I'm assuming there is something in the system set to dissapate the heat, although I can't see anything in the wiring logic doing that. I know it has the 40 hour few second blip, but sometimes it does come on for longer, enough to heat a few rads.

Yeah I tend to agree, not the best pairing (BM2 and Rayburn), but they were in when we bought the property. Both have there good points, but the bad one is its very expensive to run, hence why I'm trying to improve.

The rayburn has 28mm pipes for the flow and return. I'm not sure about the gravity part, but there is a Grundfos 15/50 on the return, so I'm assuming it can't be gravity. What would the setup look like if setup via gravity?

Seems such a waste to fit a dissapating rad for the excess heat, then later fire the boiler to heat the store.

My brother is an electronics whizz who has fixed both the PCBs over the years with the usual buzzing failures, resistor failures etc. Costs a few pence to fix. I think I might get him to build a new PCB to replace the existing ones and control the heat dissapation issue. He said they are so badly designed, it would be easy to improve the whole setup.

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