Boiler faults on hot water only: isolating the DHW circuit
A fault that appears only when you open a tap is a gift to a diagnostic engineer. Heating works, so the burner, pump and gas side are broadly healthy.
Faults that appear on hot water only: the short technical version
Under a hot water demand the boiler fires at high rate almost instantly, which stresses ignition, gas supply and heat transfer harder than heating does. Weak gas supply, a scaled plate exchanger or a diverter valve stuck part-way will show up here and nowhere else. That means the diagnosis targets a short list rather than the whole appliance.
Faults that appear on hot water only: engineer's shortlist
- High-rate firing exposes marginal gas supply first
- Scale reduces transfer and drives overheat cut-outs
- Part-stuck diverters give heat to both circuits weakly
- Flow turbines can under-report and confuse modulation
- Note whether the fault needs a hot tap or any tap
Where we deal with this
Published business details
- Based at 24 Bristol Road, Radstock, BA3 3EE
- Telephone enquiries: 07516 118198
- Opening hours: Monday to Friday, 8:30am to 5:00pm
Straight answers on faults that appear on hot water only
The honest position: Tell the engineer exactly what triggers it. On hot-water-only faults, that detail is most of the diagnosis.
Call Jamie Crawford Heating on 07516 118198 during the published weekday opening hours.
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Services that cover this
Questions we get asked
- Does this mean the boiler is on its way out?
- Not necessarily. Hot-water-only faults are usually component level and repairable.
- Should I turn the hot water off in the meantime?
- You can keep using heating. Avoid repeatedly triggering a fault that locks the whole appliance out.
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