What size hose should I run on my air Compressor?
You don't mention how many CFM your new compressor is rated at or what you will be using it for. Most air tools have a maximum rated pressure if they are expected to last for a reasonable period of time. Just because the compressor is capable of producing 175 PSI it may not be the best thing to always have the pressure switch set this high. By keeping the pressure down to around 125 PSI it is much easier on the compressor and makes the system more efficient. The use of a pressure regulator to control the pressure reaching your tools should be used at all times along with a water seperator and lubricator. As far as air line size, this is determined by the consumption rate of the tool, length of the air line and number and capacity of connectors used.
If you are running really long air lines it is helpful to start out with larger line and use a smaller, more flexable, line for the last ten feet near the tool. I have a 5 gallon surge tank I put at the end of the large supply line from the compressor when using large nail guns. By hooking onto this surge tank with a 20 foot 1/4" whip hose I don't experiance the line loss problem often encountered with these tools.
Contrary to what many folks believe smaller lines do not increase pressure. This is determined by the pressure applied to the line by the supply source. Smaller lines will, however, result in lower operating pressure at the tool if they do not have the capacity to supply the flow required.
A larger air tank, such as yours, will give longer run periods between compressor cycles but will not increase the total output of the system. If you need really long run times then running higher pressures at the tank will allow more draw down but will also require more time to build back to full pressure. Another problem with the higher pressures, if the system is being used heavily, can be the buildup of excessive heat. Higher pressures could require the addition of a cooler in the line between the compressor and the tank in some situations.
A connection between the water seperator and tool lubricator is a good idea for use when airing up tires, blowing off parts or sandblasting. No need for oil in the air for many jobs.
If your unit is not equipped with a head unloader and automatic tank moisture drain consider adding these.
Hope this helps some.