Cycling on head pressure

[Geofridgee]

I have an air conditioning unit that comes on automatically at seven am and every now and then in the colder months will go out on LP causing the lockout relay to hold the unit out. The unit is a package unit which has no head pressure control. Will fitting some way of regulating the head pressure solve this problem ? The mornings have been getting as cold as 1 degree celsius.

[Brian_UK]

A head pressure control could ease the problem but have you identified the problem itself?

Does the unit start and go straight into low pressure or does it run for some time before the LP switch operates?

[Geofridgee]

I have not actually been there when it has happened. It has tripped twice in the last month but when I have gone out to reset it the pressures have looked ok.

[mcjo tech]

If the a/c is programmed to activate in the early hours and is not dependent on load conditions then a low ambient control may be required. This will turn off the outdoor fan and increase the discharge pressure and thus keep the suction pressure up so as to not trip the low pressure switch. Also if the low pressure switch is manual reset you may want to consider modifying to an automatic reset low pressure control or re-programming the thermostat to a later start time based on temperature load conditions.

[old gas bottle]

has is got a fan speed contoler on ? if not try that,or set the LP just over 0 psi just to see if it stops it before spending on it. happy days.