Vaillant ecoTec plus 837 issue: Radiators slow to heat up

Cheers. Thats really useful

The radiators are new (fitted with the boiler). All double panel with double convectors ranging in size from 1200 to 1600.

My aim is to heat the place as quickly and cheaply as possible. It's a second home so stands empty and cool most of the time which is an additional problem.

Should changing those settings cause the pressure to rise. It's now over the 3 limit

Adam90 said:

Should changing those settings cause the pressure to rise. It's now over the 3 limit

Click to expand...

No changing those settings are not the problem. Look in the faq at the top of the page look at boiler pressure problems, the bit that talks of expansion issues , should help you out.

Pressure shouldn't rise much at all and certainly no more than 0.5 bar.


Undersized, poorly adjusted expansion vessel.


Further confirmation of an a7se of an installer.


Quickly isn't necessarily cheap. . Heat is a luxury. . If you want it warm it will cost bucks.

If it's a second home, then running costs shouldn't be an issue. And sympathy will be very limited.

Program the controller never to drop below 14 degrees and then damp and freezing will not be an issue.

Adam90 did you ever find a solution for this? I have exactly the same problem with a Vaillant ecotec plus 831 and Vaillant VRT 350f wireless programmable thermostat. The symptoms are exactly as you describe. Very slow heating. from cold. Sometimes if I switch off and on off and on again it bursts into life, the radiators heat up quickly, the flow temperature reaches the target level and the burner then modulates to maintain it correctly. But when the heating comes on from cold the burner usually stays low so it takes about 45 minutes to get up to temperature.