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Elliott Oxton
Elliott Oxton, HVAC Mechanic
Category: HVAC
Satisfied Customers: 61
Experience:  Lead engineer at eoxtongasservice
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I have a Vitodens 100 boiler with a recurring F5 fault code

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I have a Vitodens 100 boiler with a recurring F5 fault code when it turns off or goes into rest mode. Internet search revealed it was the air or pressure-switch problem, "the infamous flap," which is a particular problem for this model (manufactured 2007). A technician was called, he opened the unit, the air chamber, lifted the flap, closed the unit and reset. He said if it continued to call him back for a replacement part. Well, I watched everything he did (turning off power, gas, opening the unit - was very easy) and did it again myself successfully, but on the 2nd try (I had read that the rubber seal gets sticky) on trying to clean the seal I broke the flap clean off. My question is - did I need this flap? I had read that it was possibly an extraneous feature that isn't quite necessary for the operation of the unit, and had caused lots of problems - do I really need it and show call the technician again?
Hi my name is ***** ***** I have worked in the plumbing and heating industry for over 18 years. I am confident I can assist you today and looking forward to helping you. Please give me a moment to review your request.
Customer: replied 4 months ago.
I have read that more current models of this type have done away with the flap. Can I go flapless, so to speak?
you are right that the new model 100s do not have this flap. But viessmann may have installed another device further down the line to replace this flap. I have not been able to find official documentation to say that this can be removed on this model.
Generally by law you should not alter the boiler as doing so could potentially cause problems and you would be the one to blame. That being said it does not seem to have caused a problem on others who have removed it.The replacement part that your technician is talking about is probably a new flap but with a different type of washer that does not become 'sticky'.So to answer your question simply:1. If you don't want to call the technician back then the boiler should continue to work with out problems. But we can't say for sure it won't cause long term issues such as causing the boiler to burn inefficiently and damage the burner itself.
2. If you are happy to call the technician I would ask him to replace the part. He may tell you off for touching the part but you will know for sure that the boiler is safe and working as the manufacturer designed. This is the option I would recommend as it is the safest option.Please let me know what you think and if you have any further questions.I have left an option for you to rate my response to you. You can do this by clicking on the star rating above. It is totally free to rate me so I am grateful for you taking a moment to do so. We can continue to talk after you have rated me so I am ready to answer any follow up questions.Thank you in advance for your feedback.Warm regards
Customer: replied 4 months ago.
I called the technician, waiting for a call back. I guess it is safer to switch the part, although more expensive of course. You reckon I could just put it back together and turn it on until the technician comes? It's cold here and we have wee ones, so heat would be nice (the unit has been shut off since noon)
I apologize but I only just got your message on my device although I see you wrote earlier.The safest option is to wait but I understand with youngsters this is not always an option.
If your technician cannot come out immediately then you could put it back together and see how it works. Make sure the case is completely shut to ensure no dangerous gases escape from the unit.If you have any other thoughts then please let me know.
Warm regards
Good day,
I see that you have left me a negative rating. I really hope that I can do something to change your rating to above a 3 star.
I'm sorry if the news that I have you was not positive in that you have had to get the technician out again. But I felt that it is the safest thing for you to do considering that you have young children. I'm very sorry that it had worked out that way.
Please can you tell me what I can do to change your rating into a 3star + rating? I definitely don't want to leave you without feeling you have received a good service from us.
Looking forward to hearing from you and doing anything else I can to help you further.
Warm regards
Customer: replied 4 months ago.
Hi Elliott - regarding option 1 that you gave me - the technician said that if I had put the unit back together, it could have caused an explosion as the flap regulates the fuel / air mixture, and if I had run the unit without the flap it could have been a disaster of epic proportions. While you did say I should call the technician, the inclusion of not calling the technician could have opened the door to calamity. Hence the two star.
Good day,
Thank you for your response. I appreciate you explaining the reasons for your rating.I believe your technician maybe trying to scare you a little by saying those things. In many lands in is illegal to even touch the inside of a boiler if you do not have a license. However the boiler would not have blown up had this part been removed. The manufacture has actually removed that part from the new models and increased the run time of the fan.However the technician did see the condition of your boiler and the damage that has been caused so he may have had another reason to tell you those things.I appreciate you explaining those things to me. It's really better to err on the side of caution which is what I will do with other requests like this.At this time I will not get any compensation for the help I have tried to give you with a 2 star rating. All your deposit will only go to the website. If there is anything I can do to change that please let me know. If not I will try and have this closed for you today.Warm regards
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