Viessmann Vitodens. Hot weather, no hot water

[frogisland]

We had this problem for a few days last year, but has appeared again. During these warmer temperatures that we are currently experiencing our boiler stops heating the hot water. Upto a couple of days ago when it was cooler it was working fine, and if as last year as soon as it cools off again it will be back to normal working.

Conventional condensing boiler (not combi), it does have the outside weather compensating sensor.

Anyone any ideas - I'll look into getting an engineer in over the next week, but suggestions might help point him in the right direction if these problems have been experienced previously.

JP

 

[ShaunCorbs]

sounds like weather comp is holding the boiler off

@townfanjon

 

[townfanjon]

I gather you mean a system boiler along with a cylinder?

 

[frogisland]

Yes, thanks

 

[townfanjon]

Have you any idea if its a “four pipe “ system boiler .
Perhaps post a pic

 

[frogisland]

2-pipe i think, with diverter valve and pump in loft

 

[townfanjon]

2-pipe i think, with diverter valve and pump in loft

Pumps should be in the boiler if it is a system boiler !!! Need a pic if you aren’t sure .
Probably a daft question in this heat lol , does the heating work

 

[frogisland]

Vitodens 100-w 35kw. 2x 22mm pipes to boiler; flow to pump to valve, plus a return.

Yes, heating working, just checked.

Might add that the hot water heats OK when set to come on in the early hours when it's much cooler outside.

Thanks for your patience

 

[ShaunCorbs]

100w open vent

 

[townfanjon]

If you turn the cylinder stat up does the boiler fire ?
Has it always been ok since the installation?