If you have problems with your Worcester combi boiler where the hot water is going cold, this is a common issue with Worcester boilers with the main issue. The main causes are a blockage in the hot water heat exchanger and a faulty diverter valve. But there can be other causes. Here, we look at the most common reasons.
Combi boiler hot water goes cold reasons
A combi boiler’s hot water can go cold if any of these occur: A scaled-up heat exchanger inside the boiler that is blocked so water cannot be heated, water flow is too slow or even too fast so isn’t heated up, the pressure relief valve is set too low or it could even be the shower thermostat isn’t working.
Fixes for a Worcester combi boiler not providing any hot water
Scaled up heat exchanger
A blocked up heat exchanger, partially or fully with scale, will cause hot and cold water problems. The boiler will struggle to reach temperature and will be more likely to overheat, which can lead to component breakdown.
If caught early, the plate heat exchanger can be removed and cleaned out. Otherwise, if completely blocked, it will need to be replaced, and that isn’t exactly cheap.
Leaking flow turbine
A common cause of intermittent hot water for Worcester boilers is a leaking flow turbine, which up to now has been made from plastic rather than brass. These are prone to pinhole leaks and affect the temperature of the water. If the leak gets severe, you will see a fault on the boiler display. This will usually need to be repaired by an engineer.
Troubleshooting tips when a Worcester boiler stops heating water properly
Slow water flow
Another possibility is that there’s an issue with the water flow rate – if it’s too low, the boiler will struggle to heat up properly and will keep cycling on and off. Again, this is something that an engineer will be able to help you with.
Water flow is too fast
On the other hand, if the water is running through the boiler too fast, the system doesn’t get the chance to heat the water up enough.
The boiler engineer will be able to adjust the valve after doing the necessary checks to adjust the flow rate through the boiler. Slowing the water rate will heat it up much better.
Faulty shower control thermostat
If your hot water suddenly starts going cold or lukewarm, check whether it is only at the one outlet or with multiple. Water being lukewarm or tepid at just one outlet, usually the shower, indicates a faulty thermostat on the shower. Check with a nearby hot tap to make sure.
Preheated water in the boiler
Worcester combi boilers, taking water directly from the mains to heat up, will always have some hot water in the boiler, whether preheated or not. So when a tap is turned on, you will get one or two seconds of hot water, then cold water coming through the pipes before the boiler plays catch up and delivers heated water.
Worcester boiler fault codes explained for troubleshooting
Pressure relief valve
If your boiler is cycling on and off frequently, it could be due to a number of reasons. One possibility is that the pressure relief valve (PRV) is set too low. This can cause Worcester boilers to overheat and trip the safety switch, leading to the boiler shutting down.
Cost of Worcester boiler models and installation
If you think this might be the case, you should call in a Gas Safe registered engineer to take a look.
Hometree provides engineers that give customers peace of mind with home care packages for your Worcester boiler, central heating, plumbing, drains and home electrics all at an affordable monthly or annual cost. Click here to see why we recommend Hometree for home care cover.
Summary
Worcester combi boilers may give cold water instead of hot for these reasons:
- A scaled-up heat exchanger.
- The water flow is too fast.
- Slow water flow.
- Leaking flow turbine.
- A faulty shower control thermostat.
- Preheated water in the boiler.
- A failing pressure relief valve.
Related Articles: