2000 AC/DC

CENTREX-2000-AC-DC-CNTRL-FLUSH0.gif Composting Capacity Residential Use:
AC Mode: 4-6
DC/NE Mode: 3-5

Composting Capacity Weekend/
Vacation Use:
AC Mode: 7-9
DC/NE Mode: 6-8
AC, NE, or 12 Volt
Regular Capacity


Perfect for medium to heavy seasonal or light residential use, the Centrex 2000 AC/DC allows for both a longer composting cycle, and larger waste volumes than the Centrex 1000 AC/DC. The increased surface area in the evaporation chamber coupled with the larger heating element also provides better evaporation on electric units.

When used seasonally by 7-9 adults, compost will normally only need removing annually each spring. In residential use compost will have to be extracted more frequently.

When used residentially by up to 4 adults, some compost will need to be emptied into the finishing drawer once every few months.

The Centrex 2000 AC/DC features a 370 watt thermostatically controlled heater in a sealed compartment under the unit and the standard Sun-Mar 30 watt turbo fan, with a 2" vent stack to remove the evaporate and fresh odors. This may be used when the unit is in AC operation.

For easy switching between AC and DC mode, the Centrex 2000 AC/DC requires that 2 vent stacks be installed to handle the separate venting functions. The 2" vent is in use when the AC fan is in operation, and the 4" vent is venting the unit passively when there is no power available. As an extra option, we include a 12 Volt 1.4 Watt fan with the Centrex 2000 AC/DC. You may want to install this fan if the unit is to see maximum capacity use, and you should install the 12 Volt fan if you have to put any bends in the 4" vent stack, as you will then lose the "chimney effect" advantage of a vertical stack, and will need to provide air movement with the fan.

You may just install one vent if you only plan on using one function. If, for example, you do not have 110v AC power yet but anticipate getting it in the future, you can install just the 4" vent and leave the 2" vent capped off.

The Centrex 2000 AC/DC is supplied with a 1" drain hose which should be connected to the 1" drain at the bottom of the unit. Click here for more information on handling excess liquid.

The Centrex 2000 AC/DC may be used with one or more Sealand low flush toilets, purchased separately.


The electric EXCEL, COMPACT, CENTREX 2000 A/F and Centrex 3000 A/F will evaporate all liquids, depending on use and climate (ie use over-capacity and extremely humid weather). However, other than the CENTREX 2000 A/F and 3000 A/F, where it is optional, all Central units, the Excel-NE, the Sun-Mar Mobile, and the SPACESAVER should have the overflow security drain connected.

Even though we expect the Excel, Compact, and Centrex 2000/3000 AF to evaporate all liquids in most situations, we always recommend that the overflow drain be connected if the units are being used residentially, or the units will be seeing heavy use for a short period of time (ie party, large family visits). This drain should always be connected as a security measure.

A 10 Foot 1" drain hose and stainless steel hose clamp is supplied with all Central units, non-electric units, the SpaceSaver, and all Sun-Mar Mobile units. Collect and/or treat excess liquid in an approved facility such as a recycling bed, old septic system, holding tank or drain pit.

To make a recycling bed to evaporate and transpirate the liquid without touching the environment, simply dig a bed 18" deep, and line it with plastic sheet. Bed size - normally 3-25 square feet - varies with geographic area and season. Fill it with 6" of gravel then 12" of sand and plant with grass and shrubs. Click here to open and/or download a simple guide to building your own.

Facilities for excess liquid should be installed in accordance with local regulations. In many areas, this is about 1 ft. deep and 2 ft. in diameter. Place sturdy cover (plastic, tin or wood) and a 6" mound of earth over the drain to prevent soil and surface water from settling into the gravel. See the diagram at right.

The 1" Drain hose provided with all central units, the Spacesaver, and the Excel-NE clamps on with a stainless steel hose clamp, also provided with purchase

 - - -RecyclingBed

One of the main tasks is the installation of the vent stack, which is included with all units.

The vent kits included in the shipping carton are sufficient for installation in most single story buildings. If more is needed they are normally easy to find. All vent pipes are thinwall PVC.

The drawings illustrate some of the more common vent stack configurations for central system installations:

  • Electric units with 2" stacks should have the minimum number of bends, should use 45° elbows where possible, and should not have bends totaling more than 360°.
  • 4" Non-Electric vent stacks should be installed as straight as possible. If 45° elbows are needed in a 4" vent stack then a 12 Volt fan should be included in the installation to assist airflow.
  • Merging a Sun-Mar vent with other existing vents risks interference and is not advised.
  • The diffuser included with all central units is a simple but effective device originally patented by Sun-Mar principals to aid updraft, resist winter freeze-up, and protect the vent from downdraft and weather.
  • As shown in the drawings they should be installed 2-3 feet above the peak of the roof for best performance. This prevents downdraft.
  • Vent joints within the bathroom should be siliconed, vent joints outside should be glued with CPVC glue.

Detailed Vent Stack Installation Instructions

Electric Unit (2" Diameter) Piping Installation

Piping can be installed up the inside wall; through the wall at a slight angle and up the outside wall. The choice depends on ease of installation, visibility, and (especially if the toilet is to be used consistently through a cold winter), the necessity of insulating all exposed vent pipe.

Piping and fittings are of standard 2” PVC central vacuum tubing. Additional pipe or fittings are easily available should you need them, from a building supply dealer. If you cannot find them near your location, they are available in 30” lengths directly through us.

i) Minimize the number of sharp angles as each reduces vent efficiency. If it is necessary to have angles in the vent pipe, it is recommended that 45 degree angles are used whenever possible. (90 degree elbows may be used as long as no horizontal vent results - pipe may be bracketed at a slight upwards angle to prevent this)

ii) Do not lead the vent pipe downward or horizontally at any point. This may lead to the vent pipe being blocked by condensate which would cause a urine smell in your bathroom.

iii) All connectors in the vent pipe should be sealed. Use silicone for the connection of the vent stack to the toilet in case the toilet has to be moved or you have to access the fan. PVC cement may be used in the rest of the stack installation if desired.

iv) All exposed vent pipe should be insulated with the foam insulation supplied with the toilet. This is especially important for winter or residential use.


Non-Electric Unit (4" Diameter) Piping Installation

Piping can be installed up the inside wall; through the wall at a slight angle and up the outside wall (with this configuration a 12 volt fan is necessary). The choice depends on ease of installation, visibility, and (especially if the toilet is to be used consistently through a cold winter), the necessity of insulating all exposed vent pipe.

Piping and fittings are of standard 4” PVC sewer tubing. Additional pipe or fittings are easily available should you need them, from a building supply dealer. If you cannot find them near your location, they are available in 30” lengths directly through us.

  1. The vent stack should be installed as near to vertical as possible.
  2. Silicone caulking should be used for the connection of the vent stack to the toilet because at some time the toilet may have to be moved or your may wish to install a 12 volt fan in the vent stack.
  3. The Sun-Mar 12 Volt fan is fitted inside a 10” length of 4” vent pipe for easy installation, should it be needed. It is installed by either cutting out a section of the vent immediately above the composting unit, or by raising the vent stack off of the composting unit and inserting the fan section. The fan can be used with a solar panel and 12 volt battery, or by purchasing a 12 volt adapter
    from your local hardware store and simply plugging it into the wall.
  4. If a 12 Volt fan is installed it should operate continuously, since otherwise it forms a partial blockage in the vent stack. To install, you can either use PVC connectors or a rubberized connector.
  5. All connectors in the vent pipe should be sealed.

Leading the Vent Through The Roof (All Units)

As shown in the installation, the vent stack should end about 20” above the peak of the roof so that it is less subject to downdraft. Where the piping is taken through the roof, the roof flashing provided may be used to seal the installation or if a new roof is being installed, the roof flashing should be laid underneath the new roofing material. DO NOT install horizontal sections of vent pipe to avoid leading the vent through the roof.

The Diffuser (All Units)

The diffuser provided with the unit is a simple device to be installed at the top of the vent stack with the larger pipe protruding above the smaller. The diffuser design encourages updraft, and discourages wind and weather from going down the vent stack. Unlike wind turbines, diffusers are less likely to freeze up in winter, and are more effective in calm weather.



Sun-Mar units serve as a reliable year-round facility when prepared for continuous or periodic use during the cold winter months. All units are made of fiberglass and marine grade stainless steel; so even if the compost freezes in the drum, sub-zero temperatures will cause no damage.

Winterizing Your Sealand Toilet

While the composting system will not suffer any damage due to freezing, a particular part on the Sealand low flush toilet will. This part is the water valve. You will of course not need to do this if you are keeping the bathroom heated throughout the winter. For best results, do one of the following:

  • Take off the water valve and bring it back with you, keeping it in a heated space during the cold winter months. To do this, remove the pedal cover, and then remove the valve. The toilet may be flushed with a pail of water during limited winter use.
  • Remove the brass nut on the end of the water valve. While you save the inconvenience of removing the pedal cover doing this, this action will eventually strip the threads on the valve and it will need replacement in a few years. We suggest removing the water valve entirely as recommended above.
  • Do not flush antifreeze down the toilet as recommended in the Sealand manual; this will harm your composting toilet system.


Limited Use - Central Composting System

For limited use (i.e. up to a couple of weekends a month) in cold temperatures, the unit can be used simply as a holding tank. For this, sufficient space must be available in the Bio-drum and the drum should not be rotated if it contains frozen compost. Electric units should be plugged in when in use, so that the fan eliminates all odors even though no composting is taking place. If you have a Non-Electric model or an AC/DC that you are using primarily in DC mode, you should install a 12 Volt fan to assist airflow during use in the winter months.

This advice is applicable to all planning on using the unit once a month or so in winter. If you are planning on using the unit more frequently during the winter months, please follow the advice in the section below.


Extended Winter Use

For continuous or extended use (i.e. every weekend or residential use) in winter, the composting unit will have to be kept warm (at least 55° - 60° F) so the composting activity does not stop.

  • Insulate all piping in unheated areas to avoid ice blockage including vent stacks (on all electric units), and waste inlet and drain piping where appropriate.
  • While the composting unit is not in use, energy costs can be reduced by installing a speed control on the fan so that very little cold air is being pulled in and the heater is operating less frequently. This speed control is available from our parts department.
  • If you are planning on installing a unit in a climate with extreme temperatures (ie Alaska or Northern Canada), consider installing a 3" pipe around the insulated 2" pipe to add an extra measure of insulation. Many of our customers in these areas also use heat tape or self-regulated heat cable along the length of the vent to keep ice from blocking the vent in the winter months. Contact us for additional advice if planning to install a unit under these circumstances.

What is the 12 Volt Fan?

The 12 Volt Fan is meant to accelerate airflow in all non-electric units. It comes pre-installed in an 11" piece of 4" diameter vent pipe so that it will fit inline in your vent stack. It also protects against downdraft and increases the evaporative performance of your non-electric unit by about 10 to 15% (still not enough to evaporate all liquids on an NE).

In Which Situations would I need a 12 Volt Fan?

  • If you have to put any bends in the vent stack (Sun-Mar recommends no more than two 45 elbows, even with a 12 Volt Fan installed).
  • If your cottage is subject to downdraft.

Centrex 2000 AF AC/DC

2.4 Watt 12 Volt Fan

How Do I Install the 12 Volt Fan?

Choose a section of your vent where you will easily be able to access the fan, and connect it to the battery. Cut a suitably sized section of vent stack and insert the fan into the stack, ensuring that the piece is positioned correctly so that the fan is blowing upwards (coupling will be at the bottom). Caulk both seams with silicone for the best airflow.

How Do I Power the Fan?

With DC Power:

Purchase a solar panel appropriate to the wattage of your fan (5 Watt for the 1.4 watt fan, 10 watts or above for the 2.4 watt fan). You will also require a 12 Volt battery (Sun-Mar suggests a deep cycle marine battery for best results). Connect the wires on the fan (red wire positive, blue negative) to the appropriate terminals on the battery, and the appropriate wires on the solar panel to the battery. The battery will store the charge from the solar panel, ensuring continuous operation of the fan even at night or cloudy days.

With AC Power:

Purchase a 12 Volt AC Adapter from any electronics store. Cut off the female plug. Attach the positive wire to the red wire, the negative wire to the blue wire, and secure both with small wire connectors (marrettes). Plug into wall.

12 Volt 2.4 Watt Fan

This fan increases the airflow level and is necessary for situations where there may be competing drafts, which is true in the case of the AF NE models and the AC/DC, dual-vented models.

Listed capacities refer to the amount of people, on average, using the unit per day. Do not pick a unit that is below your capacity.

Residential/Continuous (Adults/Families) 4/6 (AC use), 3/5 (DC use)
Seasonal/Vacation (Adults/Families) 7/9 (AC use), 6/8 (DC use)
Electricals must be connected while the unit is in AC use for proper operation
Maximum Amps (With Heater On) 3.3
Fan Watts (Required or Optional Hookup) 30 AC Required (electric use), 1.4 watts Optional 12 Volt Use
Heater Watts (When Thermostat switches it on) 370
Average Power Use in Watts (Heater on 1/2 time) 215
Unit Dimensions
Height/Width/Depth 27 1/2" by 44 3/4" by 26 1/2"
Vent & Drains
Vent Pipe 2" Central Vacuum Tubing (PVC Thinwall), 4" Thinwall PVC
Drains (Required or Optional Hookup) 1" Required
Weights (Lbs.) & Dimensions
Product Weight/Shipping Weight 103/124
Shipping Carton Dimensions (W by L by H) 28 1/2 " by 47" by 36"
Depth Required to Remove Drawer 44 1/2 "
Height to Top of Waste Inlet 30 1/4"
Height to center of 2" Vent 21 1/2"