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Posted by HeatPro on January 18, 2006 at 15:49:49:
In Reply to: Re: Ergomax and boiler wiring and settings posted by Dave on January 18, 2006 at 15:32:42:
The T475A would be added to the boiler high limit circuit as a switch to control the max boiler temperature.
The 8888 and the 8889 are Honeywell's version of the SR504 to extend the AQ475 control over more zone valves or circulators. Nor do you need a Tekmar to just keep the boiler water from getting too hot for the weather. These devices are "magic" to folks looking for a "better way," thus more expensive - like getting a Hummer to carry garden tools to the back yard. Using an electronic outdoor reset at 4 times the cost won't make it do any more than what you have with the simpler T475A - with no electronics to fail.
As you already have an SR504 controlling all, you don't need the more expensive AQ475 nor an 8888. Just adding a T475A or Beckett HeatManager to the boiler would be sufficient.