How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Andrew Smith Your Own Question
Andrew Smith
Andrew Smith, HVAC Technician
Category: HVAC
Satisfied Customers: 3644
Experience:  Heating and Controls engineer
46681511
Type Your HVAC Question Here...
Andrew Smith is online now

My Vaillant 428 bangs when achieved set temperature or switching

Customer Question

My Vaillant 428 bangs when achieved set temperature or switching off
Submitted: 3 years ago.
Category: HVAC
Expert:  canuck the pro replied 3 years ago.

canuck the pro :

Hi, my name is Mike and I have been in the home improvement and repair field for 20 years. I will be glad to help you today. I am sorry you are having troubles with your system. Let's work it out. Would you please tell me what your current system pressure is?

JACUSTOMER-r174m535- :

This not a combo boiler

JACUSTOMER-r174m535- :

Sorry I mean combi boiler

JACUSTOMER-r174m535- :

An ecoTEC plus hung open vent condensing boiler

canuck the pro :

I am sorry for my delayed response. I will still be away for several more hours so I will opt out so other experts can help when I am away. If no other expert has responded I will opt back in. Sorry about that. Mike.

Expert:  Andrew Smith replied 3 years ago.
How does it perform normally - are you getting kettling from the appliance when running?
Do you have the approximate age?
Customer: replied 3 years ago.

No, I do not have any kettling, no problem with hot water, on and off, just 'heating ' bangs when system is switching off ! No other problems

Customer: replied 3 years ago.
Relist: Incomplete answer.
Expert:  Andrew Smith replied 3 years ago.
Does the heating still take the normal amount of time to heat, or is it getting longer?
Customer: replied 3 years ago.

No problem with achieving temperature, just bangs when achieved

Expert:  Andrew Smith replied 3 years ago.
I wonder if it is not modulating?
Is there a viewing window on your model?
If so can you see if the flames get smaller when the system is hot?
Customer: replied 3 years ago.

I am sorry for delays in replying, 'working!'


Unfortunately there is no window. The boiler is approaching 5 years old.


Heating takes normal time to heat, it is not taking any longer.

Expert:  Andrew Smith replied 3 years ago.
Ok, I suggest we just monitor for the next 24 hours