The discriminating buyers of these large homes want the assurance that their installer is the best in the business so you don't want to find any "screw-ups" when you finish the job. Hopefully the hints that follow will eliminate most installation pitfalls, provide you the confidence to design a system properly, chose a power unit with adequate power, and overcome obstacles inherent in larger projects.
Don't put valves behind doors without considering if the door will be in the way of the cleaning pattern. Inlets in the center of a large wall might be blocked by furniture so attempt to locate them near doorways. Make sure you will be able to reach patios, balconies, garages, and even pool rooms. Locate the garage inlet close to the large garage door so the client does not need to pull his boat or motor home into the garage to clean it.Always try to reach the hallways from inlets that are outside the bedrooms. You don't want the maid to have to disturb anyone in a bedroom to vacuum outside the bedroom. Often, large homes will require separate inlets for each bedroom. (I've installed a seven-inlet master suite!)
Consider providing a shorter hose for cleaning major traffic areas. Often, a 20-foot hose will reach all the traffic areas if inlets are properly placed. If needed, many manufacturers offer a 35-foot hose option. The 'Vac Pan' is another unique option for the kitchen and mud room which allow quick cleaning by sweeping debris with a broom to a floor level inlet that activates with the flip of the toe.If possible, locate the main power unit in a mechanical room but consider the noise that it emits. Don't mount it on a wall that backs up to an office or bedroom! A few manufacturers offer extremely quiet power unit, which can be located within the home if necessary. If the unit requires an exhaust, make sure it won't be an excessive distance that would cause backpressure and overheating. It also would be wise to coordinate your efforts with the decorator, structural engineer, electrician and the HVAC contractor to avoid mistakes and clarify any ambiguities.
Also consider your altitude factor. If the home will be located in the mountains at the 8000-foot elevation, the air is much thinner. This increases your cubic feet per minute (CFM) but reduced your water-lift (sealed suction.) This might reduce the size home that would require the larger powered power unit.
The industry has wholly embraced inlet valves that contain low Voltage and high Voltage for operating the electric power brush. Make sure the electrician knows to connect these to his circuits. Electric power brushes have far superior cleaning power than air tools.Shear-paneled walls will require double plaster guards to insure being found once plastering is completed. Make sure you understand load-bearings on TJI's before drilling them and never cut into the top or bottom support. To circumvent second floor walls that are directly above steel I-beams, consider jogging the pipe in the adjacent room if you know there will be a cabinet or shoe rack covering the pipe.
An often-missed vacuum pipe chaseway is in the pocket of the I-beam. Naturally you cannot drill the steel beam but this makes an excellent collector to reduce the need to drill all the joists in a large room. If you must run underground, don't use schedule 40 pipe but rather incase the vacuum tubing in three-inch irrigation pipe. The fittings and low Voltage wire fit smoothly inside and provide crush protection as well as a vapor barrier.Find out what type of wall textures will be applied and coordinate with the wallpaper, sponge painter, or mirror contractor. Certain types of valves are better for wallpapering. You really don't need to locate any "clean-out" points if the system is properly installed.
Make sure the electrician has provided the proper power voltage and amperage. The larger units require 10 Gauge wire with a 30 AMP, 110 volt receptacle; or a 20 AMP, 240 volt receptacle.All the pre-planning in the world cannot accommodate each job so establish a policy ahead of time on dealing with change orders. Plan on making a few extra trips out to the job on a large home but be encouraged that central vacs have the least amount of call-backs of all the home electronics. Most contractors price the job per inlet plus finish equipment. Don't short-change the client - throw in an extra hose and tool set and a separate garage kit. Make sure your attachments are of the highest grade possible and you will only hear from the client with referrals.