Veissmann Vitodens 100 - combi help

[Turbo-G]

Hi all,
First post

I have the aforementioned boiler fitted, and currently quite disappointed by the central heating output....

Running it at the maximum setting (6) for heating, the temperature reading on the LCD never really gets above 50 degrees (usually sitting at around 46 deg).

Subsequently the rads around the house never really kick out much heat (warmest room in House struggles to get above 19 degrees on the room stat), with all rads on max setting.

Hot water seems fine, on the max setting when running the water you tend to see the boiler top out around 66 degrees - and it runs constantly.

Curiously the burn rate / firing rate indicator on the LCD is always on the lowest burn for central heating, but switches to full burn when hot water is running...

Does this indicate a problem somewhere in the heating system, and possibly explain the low heat output?

For info, the boiler has been installed only a couple of years, and has been serviced. No air in the (13) rads, and no blockages that we’re aware of.

Thanks in advance for the support

 

[Phill Peck]

Hi all,
First post

I have the aforementioned boiler fitted, and currently quite disappointed by the central heating output....

Running it at the maximum setting (6) for heating, the temperature reading on the LCD never really gets above 50 degrees (usually sitting at around 46 deg).

Subsequently the rads around the house never really kick out much heat (warmest room in House struggles to get above 19 degrees on the room stat), with all rads on max setting.

Hot water seems fine, on the max setting when running the water you tend to see the boiler top out around 66 degrees - and it runs constantly.

Curiously the burn rate / firing rate indicator on the LCD is always on the lowest burn for central heating, but switches to full burn when hot water is running...

Does this indicate a problem somewhere in the heating system, and possibly explain the low heat output?

For info, the boiler has been installed only a couple of years, and has been serviced. No air in the (13) rads, and no blockages that we’re aware of.

Thanks in advance for the support

Has it always been this way or worse this year?

Was the system powerflushed when the boiler went in?

When you say serviced....does someone wave an analyser at it or do they service it?

 

[Turbo-G]

Thanks for the reply - it had a proper service as far as I’m aware. It’s also had a heat exchanger sensor replaced last year.

It seems to have gotten worse although can’t recall it ever being great.

Tell me more about power flushing? Is this something that should be done during installation?

Most of the system seems to be microbore 8mm copper piping too unfortunately, from the original central heating install a few decades back - which possibly doesn’t help?!

 

[Phill Peck]

The system needs to be cleaned.
Usually this is done with a powerflushing machine and chemicals.
Although that’s not the only way.

Your boiler will have rubber hoses. If the system was very clean they will be starting to block.
It is an easy job to sort for those familiar with the boiler.
What area are you in?

 

[Turbo-G]

Just tried putting it into ‘service’ mode, the temperature has reached 70+degrees, and the burner is showing highest output - which it doesn’t during normal operation.

That being said, does that indicate the fault is in the boiler itself (perhaps board issue) as opposed to a blockage in the system?

 

[Phill Peck]

Probably a circulation issue.

What area are you in.
Get in someone who knows Viessmann boilers well. Where are you in the country I may be able to put you in touch with someone.

 

[Turbo-G]

Tamworth area.

The rads have got lovely and hot whilst in ‘serv’ mode - reading on LCD is 77 deg currently.

 

[Phill Peck]

Your boiler should still be under warranty.
Have you asked Viessmann to attend?

It does seem odd it would run ok in service mode.

Do you have weather compensation?

 

[Wally©]

If you have weather compensation your boiler's heating curve needs to be adjusted upwards...

Check the manual on how to do that...or the video below...

Best to to this with increments of 1...