I HAVE A HALSTEAD ACER HIGH BOILER AND IT IT IS SAYING LOCK OUT ON THE BOILER WHAT CAN I DO TO FIX IT

This may explain things about the heater
http://freeboilermanuals.com/pdf/halstead/AceHE_installation.pdf

You can download a manual here. http://www.onlineboilermanuals.com/ManualsLibrary/Halstead

Probably a waterlogged expansion tank. The tank provides a springy air cushion for the water to push against as it expands, and the air pushes back as the water contracts. This scheme minimizes the pressure change that would otherwise be caused by expansion and contraction of the water, giving the water somplace to go when it expands. If the air cushion is gone ... big pressure swings.

Whining = pump bearings
Pressure reduction = pressure relief valve diaphragm either perished of gunged up - look for water coming out of the overflow pipe from the valve
leak in ch system look at all joints

sounds basic, but make sure the electrode is in the pilot flame
check the overheat thermostat is not jammed on
disconnect and join wires together for temporary override check and run boiler.

fan, blockage, board, microswitch,

next time it turns off let it cool and clean with a cotton swab with rubbing alcohol after brushing.

perhaps the aquastat is ending a power surge to the primary, blowing it, id repl aquastat

I know of no limitations on the temperature of the inlet water for any boiler. The warmer the water, the less energy it will take to heat it to desired temp and the colder the water, the more energy it will take. Extreme temps over an extended amout of time in either direction can stress a unit and could possibly, only possibly reduce service time.

Hi I am thinking what your tryig to say is the air pressure switch?
you can check this switch to see if the boiler works by removing one of the sensing tubes from it & by sucking on or blowing as this willactivate the switch you dont have to do it very hard, just gently as you will hear the switch clicking, if the boiler does fire when you click, in order for it to continue to ignite you may have to fold over the tube, when you release it the boiler should stop.if it does work then you will have to change the air pressure switch, but remember this can only be done by a Corgi Engineer

Kindly

Richie