Some time ago I said how important flow rate was with these heaters as many use a 7 litres a min pump and a L5 this will give you luke warm water. A l 10 will boil that water and even burst the boiler if its not turned.One needs a flow rate higher so one can turn the controller to suit the boiler or a higher boiler rate and tone down the boiler flame.One needs to balance.Some ass told me at the time I did not know what I was talking about.But many have paid the price of not matching boiler and pump. Flow rate is very important in these cases.Dont think if your boiler works well it is not a problem its just luck the two match.
With a L10 they will work well but can overheat, the thermostat will cut out and will switch off the boiler if its reaches a dangerous heat.If not the brass fittings of the heater will burst or hoses burst.In the case of the L10 Chinese unit these brass fittings E.G.( PRESSURE valves) are very thin and not of even thickness and not consistent.SO ONE UNIT IS GOOD AND ONE NOT SO GOOD.