Vaillant Ecotech Plus system boiler firing rarely

[DavidC99]

Hi,

My 38kw ecotech plus is failing to heat the house. It's currently 12 degrees indoors so pretty cold, however the radiators do feel warmish. Some are hot, others tepid.

I swapped one of the tepid radiators for a new one thinking it was sludged up (which it was), but it hasn't made any difference. The new radiator is also tepid.

If I stand in front of the boiler I can hear the external pump running and the display says the internal pump is running. When the system asks for heat, the boiler fires up and the flow temperature rapidly climbs from around 40 degrees to around 70 (it's set at 75) at which point the burner sounds like it cuts out. The pump continues to run and the flow temperature quickly drops to around 50 degrees, before dropping towards 40 over the course of 3-5 minutes. The boiler doesn't fire in this time. After this period the cycle repeats: the boiler fires and the temperature rapidly climbs before it cuts out again

The are no error codes (I got one f22/3 when I first refilled the system but resetting and bleeding the radiators fixed that). That time it fired, stopped, fired, stopped in quick succession.

I would guess there's an airlock or blockage somewhere, but there's no error and the boiler seems happy to go around this loop constantly. I've tried setting d0 to a low number to reduce the output but it makes no difference.

I'm confused about why the radiators are mostly getting hot, some too hot to keep your hand on if the pump isn't working, or it's blocked.

I've also tried adjusting the lockshields on the radiators to both open and close them more, but it seems to make no difference.

Anyone have any ideas, or do I need an engineer to figure it out?

Oh, and the motorized valves do seem to be opening and closing. Having the hot water valve manually open doesn't appear to prevent the boiler cutting out, but there does appear to be hot water. Very odd.

Help!

 

[CBW]

Probably best with an engineer tbh, sounds like a circulation issue or a restriction

 

[DavidC99]

Fair enough. I figured it was something blocked, but really hard to diagnose what or where.

 

[DavidC99]

To answer my own question, I had two plumbers out who were basically useless, so I decided to remove the pump (the hot water didn't work either so it had to be downstream from the pump). It was full of debris. I removed the debris from the impeller with a small allen key and pit some x800 in the system.

It now works nicely and all the radiators are getting nice and hot. If the plumbers had had their way I'd have a new boiler and a powerflush on order.

 

[BlueLoo]

To answer my own question, I had two plumbers out who were basically useless, so I decided to remove the pump (the hot water didn't work either so it had to be downstream from the pump). It was full of debris. I removed the debris from the impeller with a small allen key and pit some x800 in the system.

It now works nicely and all the radiators are getting nice and hot. If the plumbers had had their way I'd have a new boiler and a powerflush on order.

"Plumbers".

Do more harm than good half the time.

Don't leave that cleaner in the system. It's very strong. Make sure to flush it out and use inhibitor.
Take the opportunity to clean the rads out of you can. Take em off and hose them out.

You might see if you have a filter installed. If not, they are not hard to fit. I'm not convinced they do much to well installed and maintained systems but they won't do any harm.

 

[DavidC99]

It has a magnetic filter which is slowly catching additional debris. I'm taking the x800 out and putting some x100 in today. Thanks for the reminder.

I'm loath to do any more with the rads since every valve I touch seems to start to leak at the spindle, but that's another story.

 

[Johntheo5]

Set d.00 to something like 15kw, it can allways be increased/decreased if required.

 

[DavidC99]

It's now at 20kw and it seems to be working absolutely fine, thanks