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Posted by HeatPro on September 02, 2004 at 14:35:33:
In Reply to: Low limit; high limit + manual reset aquastat ? posted by Bob Ross on September 02, 2004 at 13:10:10:
As each boiler has its own gas valve, you need a manual reset high limit on each boiler to disconnect that burner if each boiler has a separate manifold. The 4006E has the manual reset. If you sense the water temperature outside the boiler, you do not have a manual reset control in the spirit of controlling a burner at the malfunctioning boiler and depending upon a water flow problem could burn or burst a boiler although water flow is averaging OK outside the boilers. If your control for all boilers disconnecting power to all burners is sensing within one boiler a problem can develop in one of the boilers. The problem is similar to common manifolding or individual manifolding choices.
The idea is not to have a control to satisfy the requirements, but to have controls to actually prevent a problem in a boiler from a burner attached to it.
The reason for the question is not clear. If the boilers were operating before, then adding a 4006E to each boiler or to the common manifold to disconnect its burner would be sufficient. If there were no controls before to have them operate at a temperature at all, then some other choices would be made, like 6081A's with 4006E's.
The L6190C; L6188A,B,C, and L6191A,B are room themostats, so will not satisfy the safety considerations. You are not being given safe guidance. Call Hydrotherm and find out what they usually install and recommend on commercial equipment, especially the specific make and model that you have. Their literature shows one manual L4006E high limit on the common manifold or individual manual controls on each boiler with individual manifolds.
http://www.hydrotherm.com/html/litlibrary.asp