Gas boiler thermal store problems


19 Jan 2011
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United Kingdom

I have had a heating and hot water system linked to a wood burner and gas boiler via a thermal store. The wood burner works fine, but the gas boiler fails to heat the thermal store adequately. The gas boiler heats water for 1 -2 minutes and then cuts out for a period of several minutes before heating the water again. This is does not heat the thermal store adequately via the 15 KW heat exchanger. The installer seems confused by the problems!

Any help would really be appreciated.

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What boiler, what thermal store , what controls do you have ? a bit more info will go a long way ;)
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Reactions: GHD
The boiler is a Baxi Solo 15 HE

The store is a Newark SolarCyl Vented (96 Ltrs heated by boiler)

Control is a Drayton LP 711 limited to heating system, otherwise boiler should always maintain store at temp (50 C) but I not sure what controls this - would it be the boilers own internal systems? The boiler's water pump runs continuously until temp is reached but the boiler fires up for short periods and has long periods of not firing (pump running).

Could be a number of things - but staring at the most obvious
What setting are you running the boiler thermostat at?
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I've turned the flow thermostat up to the maximum but it appears that the boiler cuts out when the return temp warms up.
I've turned the flow thermostat up to the maximum but it appears that the boiler cuts out when the return temp warms up.
Isnt it supposed to cut out through high temperature? are you pumping water from the store through the heat exchanger?
Sounds like a circulation problem.
Could be a air lock or valve stuck in the off position even a blockage in the system.
Have a look to see if there are any hidden air vents in the cylinder cupboard that may need venting.
The auto vents are working and water is flowing so I think the valves must be opening.

The water from the boiler passes through a heat exchanger located inside the thermal store.
Baxi solo has a built in flow switch, so if no flow it wouldn't fire, so if it's firing and return is hot and up to temp, them what Onetap says would sound right.
If the store has numerous tappings for the woddburner etc, are you sure the boiler is connected to the correct connections ?

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