Remeha Avanta 18v boiler very slow

[SlimD]

I've been putting in some new rads on a y-plan system. Came to running the system and it was incredibly slow to heat up. At first I thought it was something i'd done but after numerous checks it became evident that it was the boiler. Flow and return gave 15.5 degree difference and flow temp gradually rose to about 55 C but really slow to rise. I tried running it on full load but that would only run for a few seconds before restarting, then it'd run for a few seconds, restart, run, restart, etc...(although that did heat system up faster). I tried upping the setting for the flow temp but itmade no difference and never seemed to fire up like you'd expect. Almost like it's running on minimum. Customer said it's always been like that.

Can anyone shed any light on why it's so slow to heat the system up or for that matter has anyone ever heard of these boilers before? I know I havene't.
Cheers.

 

[Pitty]

We use remeha in most of our property's and I always find the 15,18 V/H slow to heat up.

 

[SlimD]

We use remeha in most of our property's and I always find the 15,18 V/H slow to heat up.

So there's nothing actually wrong with it then. It's just VERY slow?

 

[Pitty]

Either that or the system/rads are very dirty ?

 

[SlimD]

Either that or the system/rads are very dirty ?

Just put in a load of new rads and both new and old heat up at same rate, slowly so I guess it's just those boilers then.