Using an Isolation Relay to loop multiple Retro Dampers

With the slow down in new residential construction many contractors are looking for ways to keep sales growth moving forward.  One way they are doing this is to offer their expertise to homeowners who are looking to upgrade their existing whole house HVAC system to a zone control system.

We recently had a contractor call us and said they are retrofitting a house with our Z-300-HC zone control using it for 2 zones.  He wanted to use 9 retro dampers in zone 1 and 12 retro dampers in the current duct work on zone 2.  Being that he was an experienced contractor and knowing that Jackson System’s retro dampers uses 3.8VA each, he knew he couldn’t use a 70VA transformer to power our control panel, zone 1 and zone 2.  He called us for help.

We suggested using an Isolation Relay and a separate 120v/24v 75VA transformer for zone 2.

We walked the contractor through the following steps.  Using a Jackson Systems RY-1-HB relay(24v coil NC-C-NO contacts) we had him wire the two contacts marked 24v coil on our relay into the D and D contacts on the zone 2 terminal strip on his control board.  Next we took the common wire from our second separate transformer and wired it into the C contact on the relay.  We wired the 2nd common of the transformer into the common of the 1st retro damper of zone 2.  We then ran a wire from the NO contact on the relay into the NO contact on the 1rst Retro damper and the wire from the NC contact in the relay into the NC contact on the 1st retro damper. 
Now we are almost done.  We wire the remaining 11 dampers in zone 2 in parallel to the 1st retro damper. 

What we have accomplished is powering the zone 2 dampers with its own transformer and tying them all into the Z-300-HC control board using an Isolation Relay.  We have saved the contractor and homeowner money by not having an additional control board with a very small additional cost of a transformer, a relay and wire.

The next time you are retro fitting an existing HVAC unit remember there is usually a way to accomplish what you want that is quick, easy, and inexpensive to install on the job.

  Wiring_diagram_isolation_relay_wi_4

Updated: December 21, 2007 — 10:41 am

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