Tankless coil question

If the coil becomes coated with scale. You won't get much hot water.

It also has to be sized right. Has it ever worked as expected?

Cheers!

have the coil cleaned, usually ultrasonic does a good job and see if that helps, also make sure boiler is set at proper temp( 170 to 180), if set too low it wont make enough hot water, if all that doesnt give you enough you can set up a storage tank with a circulator and aguastat to give you 40 or 50 gallons of hot water to draw from as the coil keeps up..or put a separate water heater in all together..

Ayuh,.... When I ditched the electric water heater, 'n went to the coil in the boiler, I had to put a flow reducer in-line with it,....

At full flow, 3/4" water line, that water moves to fast, 'n don't heat,....
A 3 gallon a minute flow reducer cured it, 'n I now have unlimited hot water,...

I had one of these on my homes original boiler. Never worked for us after we bought the house. Worked fine for the little old lady who lived there alone. My wife and i along with a, at the time, young daughter could never have enough hot water. I disconnected it and put in a standard 40 gal water heater untill I had time to upgrade the heating plant. Once that was dome, I zoned a 50 gallon boiler mate to the new boiler and never looked back. My, now, teen age daughter could not run that thing out of hot water no matter how hard she tried.