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Microcentral Systems

Microcentral Systems

This was introduced to interface the Honeywell systems to PC's since the PC were becoming increasingly more powerful. The down line controllers were called the Excel Plus controllers and were very solid and reliable. The database was programmed off-line with special software applications.

The controllers were net worked together via a proprietary bus called the L1 bus and you could have up to 29 controllers per bus. Each controller could support a maximum of 64 HVAC points but there were also other controllers that could support fewer points. The controllers were fully programmable and were capable of doing DDC control and any other application whatsoever.

The front end was text based and used the concurrent DOS environment from Digital Research. This operating system allowed 4 separate windows and each window could run a different Honeywell or other application. The system had quite an impressive system of reports available and you could also program custom reports.

The system supported a maximum of 16 buses. So it could run a large campus pretty easily. Later a fire alarm system was also introduced, the FS90/FS90 Plus. This fire alarm system could be run alongside the HVAC interface and so one could have an integrated Fire Alarm/HVAC system under one platform.

The PC communicated with the field buses via a gateway. Several types of gateways were provided. The gateway models differed based on the number and type of ports supported and whether the gateway was wall-mounted or PC mounted. There was also a single channel gateway for the economically minded applications.

The front end was capable of annunciating alarms both from the HVAC and fire alarm side. The alarms are of many different types and are capable of  meeting or exceeding the demands of the customers. All down line controllers were fully capable of running stand alone even in the case of the front end failure. Extensive training was provided for field personnel.

CITS has all information on this system and all of its documentation and other tools used to install, service and support this system. CITS can also repair all hardware for this system and has stock for all of its parts. CITS can provide all services for this system including training and re-programming it from scratch. This system was later ported to various PC interfaces like the DPC (Delta Professional Computer) and to this day there are still some of these systems out there. CITS can also support the PC front-ends that this Excel system was ported to. This system was also ported to another Honeywell front end called the Graphic Central. CITS has all service and support capability for this system and many others also.


CITS Advisory 1


All parts for this system are now obsolete and hence the current stock is not cheap. But CITS has in stock every item for this system. Parts available for this system are searchable on this website. All items are available immediately. The prices are subject to change without notice for understandable reasons.


CITS Advisory 2


It may appear to that the cost of some to these items is pretty expensive in some absolute sense but CITS advises that even at the current prices the items are well worth the value since otherwise you will be looking at replacing the system or upgrading it or you will end up using a lot of time searching for the items. CITS recommends immediate attention to your system and offers repair/replacement for every item in this system in short order. This way you can save tens of thousands of dollars. Please, remember that even migrating just one air handler can cost over 20 thousand dollars, if not more. This is because all programs will have to rewritten and new hardware/wiring installed and new front end used. Please call a CITS engineer to get more information and a recommended path for your migration. Please use a safe and economical approach for your site.

In the final analysis, use the current system, repair/service it as long as necessary and produce the money for the replacement for the long run.

Always use a safe and economical approach and not just what is technically available. Because the latter may be exciting but may not be justifiable for your business.

Thank you


This page describes the Microcentral Systems. Although not much 
in use, there probably are still some systems out there that were 
not upgraded and may still need help.

Riaz Hussain, Automation Systems Specialist

I can answer your questions and I can find/configure a solution for you!

Call Me NOW (651)442-9044!

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