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I have two different blowers in the house (one a 300 cfm multi-port ventilator, the other a 600 cfm cooktop downdraft blower). I also have a low-voltage motorized damper in the fresh air supply duct. I would like to have the damper open when EITHER of the two blowers are turned on. I think that I will need a couple magnetic coil relays to make this work, but am unsure if the relay coils should be wired in PARALLEL with the blower motors, or in SERIES with the blower motors. If the answer is PARALLEL, as I suspect, then do you think that the warranty on the downdraft blower (Dacor model CABP3) would be voided, since the on/off switch is integrated into the unit and I would have to tap in between the motor and the on/off switch?
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Yes, you are correct, parallel. And I don't know about the warranty but things like this usually void warranties. I don't know your blower but many hvac devices have screw terminals on the circuit board for external controls.
You may not have to creat your own relay circuit. Alot of unusual HVAC controlls are already available. I've never seen what you need but that sure doesn't mean a good supplier couldn't find it. Check out Grainger or McMaster-Carr as a starting point.
McMaster-Carr
Grainger
*Chris:This is off-topic, but what did you do about the delaminated floor sheathing?i Stillsnowed in,Matt
*Nothing yet. Still waiting for the furnace & electricity to be hooked up so I can dry the house out for a week, then I'll reevaluate the situation.
*Series is definitely wrong, you would be putting the entire supply current through the relay coil. I wouldn't tap into the blower either. A couple of suggestions: Use one or more "sail switches" that have a vane in the duct and activate when there's air moving; or look into the bazillion X10 modules out there for a possible solution, esp. something that would sense the current draw of the blower without interfering with it.
*An interesting source for DIY relays and controllers for the home is http://www.smarthome.comI don't know if your downdraft blower is wired into a box, or plugged into an outlet, but you can buy "switched plug outlets" which sense current through one outlet to switch on another. I know Sears sells one brand and by now there should be a few models on the market. They're more specifically designed for plugging in tools and such. You plug the box into the wall, your saw into the master outlet, and your shop vac into the slave outlet. Every time you turn on the saw, the box senses the current draw and automatically switches on the shop vac. You might be able to "modify" a plug in unit. I think there are also similar devices designed for hardwiring as well. Maybe not an elegant or cheaper solution, but worth investigating.A HVAC supplier can probably get you something much more built for the job, but unless you know a plumber AND a specific part number you're in for a frustrating experience. These guys don't cater to DIYers and they won't hesitate to let you know where they think "non-tradesmen" sit in the world.
* Chris Maybe this will help. I couldn't find their national website, but this San Diego site might get you some info. We use them for some parts here in FLA. and they're pretty decent most of the time. Johnstone Supply Scott