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Posted by Brett Anderson on February 29, 2004 at 19:17:59:
I have a new Weil Mclein Ultra 230 boiler.
It's going into an existing hot water heat system with 2 zones and a 40+ year old boiler.
The old system used a boiler that didn't have a thermostat input. That is, the boiler simply maintained heat, and when a thermostat requested heat, it switched on a zone pump via a relay.
The new system requires a thermostat input to the boiler, but there's only an input for one thermostat. As each tstat is hooked to a relay, I can't simply feed both into the same set of terminals on the boiler, or when one tstat kicks in, feedback will trigger both zone relays.
I've tried the obvious, diodes, but can't get good results. I'm not exactly electrically illiterate, given that I'm a professional BMW technician that specializes in customizing the cars, which involves lots of DC electrical wizardry.
Still can't seem to get this simple system running right.
Would appreciate a link to a wiring diagram. The new boiler also has a circulator control circuit, which I'm not using right now (which has it's own associated problems.)
Thanks
Brett Anderson