If you’re experiencing lukewarm water from your Vaillant combi boiler, it could be a sign of a faulty plate heat exchanger. This was the case with a recent repair I did on a customer’s boiler. In this blog post, I’ll walk you through the symptoms, diagnosis, and solution for this common issue.
Symptoms
The customer had been experiencing lukewarm water for a few days. They had tried turning up the temperature on the boiler, but it didn’t seem to make a difference. The radiators were working fine, but the hot water was just not hot enough.
Diagnosis
After some initial troubleshooting, I suspected that the plate heat exchanger was the culprit. The plate heat exchanger is responsible for transferring heat from the boiler to the domestic hot water. If it’s not functioning properly, it can lead to lukewarm water.
To confirm my suspicion, I checked the temperature of the water going into and coming out of the plate heat exchanger. The temperature going in was hot, but the temperature coming out was only slightly warmer than the cold water supply. This confirmed that the plate heat exchanger was not transferring heat properly.
Solution
The solution was to replace the plate heat exchanger. I ordered a new one and installed it in the boiler. Once the new plate heat exchanger was installed, I checked the temperature of the water going into and coming out of it again. This time, the temperature coming out was hot, indicating that the new plate heat exchanger was working properly.
Conclusion
If you’re experiencing lukewarm water from your Vaillant combi boiler, it’s likely a problem with the plate heat exchanger.
So please get in touch if you’re having the same issues and I’ll get it fixed for you!