Viessmann Boiler Troubleshooting
In this guide, we’ll break down common Viessmann boiler problems, the possible causes and what the error codes you see on the digital display mean.
Photo Credit: Viessmann
Every brand of boiler can be temperamental, including Viessmann models. This can unfortunately leave you struggling with a lack of hot water, low pressure or even lock-out.
In this guide, we’ll break down common Viessmann boiler problems, the possible causes and what the error codes you see on the digital display mean.
Common Viessmann boiler problems
Unfortunately, even the most well-maintained boilers can experience the odd malfunction from time to time, and Viessmann boilers are no exception.
Some common problems that Viessmann boiler owners may experience, include:
Thankfully, with a bit of troubleshooting, you will more than likely be able to determine what the problem is and whether or not you may need an experienced plumbing and heating engineer to help.
Do Viessmann boilers have a warranty?
Yes, Viessmann boilers usually come with a standard warranty of 7 years, as long as it is registered through the Viessmann website. Some Viessman boilers even have extended warranty options available for certain models.
Popular models such as the Vitodens 050-W and the Vitodens 100-W, have a standard warranty of 7 years, with extended 10-12 year warranty options available too.
You should ask your chosen installer about this when you book a survey for a replacement boiler.
How to reset a Viessmann boiler
Before you reset your Viessmann boiler, it is important you check which fault code your boiler is displaying. This is because some problems, such as lock-out, can usually be resolved by yourself, whereas others may need professional help and resetting your boiler will not be effective.
How exactly you reset your Viessmann boiler will depend on the model, since the position and appearance of the reset controls will vary. Your boilers user guide will have details on how to reset your specific model.
However, most boilers will either have a dial that should be turned or a series of buttons that should be pressed in order to reset it.
Why is my Viessmann boiler not firing up?
If your Viessmann boiler is not firing up, it could be caused by a number of problems such as:
- 1Low pressure - Your boiler could have low water or gas pressure, causing a failure to ignite.
- 2Gas supply issues - The issue may not lie with your boiler and instead, it could be an issue with your gas provider. You should check other gas appliances in your home to determine if this is the case.
- 3A tripped fuse - Boilers only require a small amount of energy to ignite, so a tripped fuse could be what is preventing your boiler from igniting.
- 4Your home is already at the right temperature - Many modern Viessmann boilers allow you to set the temperature that you want your home to be heated to. Before deciding that your boiler has an issue, you should check that your home hasn’t already reached your desired temperature.
- 5
Faulty gas valves - The gas valve controls the amount of gas that can flow into the boiler. If this is blocked or damaged, the gas cannot enter the boiler and so will fail to ignite.
Viessmann boiler firing but is no hot water
If your Viessmann boiler is firing but you’re not receiving any hot water, then it could be one of a few different reasons.
There are a few steps you should follow in order to troubleshoot the issue:
- 1If the pressure is too high, then you should bleed your radiators.
Check the boiler pressure - Low pressure can prevent the boiler from heating water. You should check the pressure gauge on your boiler and top-up the system if necessary.
- 2Check your thermostats - You should check your thermostat is working correctly. If you have smart thermostats, you should check the connection hasn’t been affected by a drop in Wi-Fi or internet connection.
- 3Check the diverter valve- The diverter valve on your boiler might be stuck in the central heating position, preventing water from reaching the pipes.
If you have checked all of the above but the issue still seems to be persisting, we highly recommend getting in touch with our team of experienced heating engineers. Our Gas Safe registered boiler repair specialists will diagnose the issue for you, helping you to get back to having hot water as soon as possible.
Fixing the pressure on a Viessmann boiler
As we’ve mentioned, if the pressure in your Viessmann boiler is too low, it can cause a variety of problems.
If you’ve checked the pressure gauge on your boiler, and you can see it is below 1.5 bars of pressure or the dial is not in the green zone, then it’s time to top-up the pressure.
To fix this, you will need to locate the filling loop, open the valves to allow water to enter the system and monitor the pressure gauge until it reaches 1.5 bars and is in the green zone. Once you’ve reached 1.5 bars, you can then close the valves and put the filling loop back.
You can find out more by reading our guide on understanding boiler pressure.
How do you find the error codes on a Viessmann boiler?
To find the error codes on a Viessmann boiler, you should look for a combination of letters and numbers on the boiler's control panel.
Some codes may be model specific, whereas others may be generic codes that all Viessmann boilers use. You should always keep your boilers user manual so you can quickly and easily find out what the error code means.
Alternatively, you could search for the error by using Viessmann’s handy fault code checker.
Viessmann boiler error codes
Listed below are some common error codes that you may see on your Viessmann boiler, however it is worth remembering that the code may differ depending on what boiler you have.
Listed below are some common error codes that you may see on your Viessmann boiler, however it is worth remembering that the code may differ depending on what boiler you have.
Error Code | System Error |
|---|---|
Fault Code 5C, 5D, 5E and 5F | Communication fault |
Fault Code 10 | Outdoor temperature sensor shorted out |
Fault Code OC | Burner blocked and insufficient power supply |
Fault Code F1 | Low water pressure |
Fault Code F2 and F4 | Flame loss during operation or no flame detected |
Fault Code A4 | Overheating detected |
Fault Code F5 | Flow temperature fault |
Fault Code D4 | Condensate pipe frozen or blocked |
