Retrofit Warm Weather Shutdown to System

BigRob

So I have a Knight mod con that has outdoor reset and warm weather shutdown, but I use a taco pump controller to accommodate a high amp pump and two groups of zones. I can activate the ODR/WWSD (warm weather shutdown), but the T-stats still activate the pumps of the taco pump controller. I don't want to use outdoor reset- only want the WWSD. Any ideas, all?

Robert O'Brien

Set point at low outdoor the same as high outdoor.

Ironman

I could probably draw it easier than explaining it, but here goes:
1. Using a 120v relay, connect its coil to the “system” pump terminals on the boiler
2. Remove the factory jumper between “ZR” and “ZC” on the terminals of the Taco panel
3. Route the “ZR” and “ZC” terminals through the “NO” (normally open) contacts of the relay.
This will cause the pumps to only be energized when the boiler fires for space heating.
If you have an indirect tank pump connected to the Taco panel, it will need to be moved to the boiler’s “DHW” terminals.
This should take care of the electrical side, but you’ll have to program the WWSD in the boiler to do what you want. That may also involve changing the ODR curve, but I can’t understand why you’d wanna do that. You’re gonna loose probably 15-20% in fuel savings.

BigRob

Robert, thank you for the screen shots. I will give it a try.

Ironman, thank you! I had the idea of using the relay control from the Lochinvar pump contacts, but the ZR and ZC part was the missing link for me. I didn't know the ZR/ZC jumper powers the pump relay 120V circuit. Maybe I'll look into using the ODR curve. The radiators are piped right off a SEP4 so they get whatever temp the boiler is set to. I haven't used different Lochinvar zones for different supply temps because there aren't that many radiators, they are not used often, no outdoor sensor, no one complains, and I didn't want to deal with it. Right now I send 120F to 10k sqft of thin slab radiant flooring divided into 12 zones. Surface temp is about 80F by the time the heat gets to the surface of the floor. Each zone is a condo with a zone valve. If I ever have to change out our DHW tank I will probably transition the rads to that boiler. The long term plan is to install convectors to replace the radiators. The DHW pump is switched by a Functional Devices brand interposing relay since the pump draws over 1.8A. The Functional Devices relays are cool- I like the integrated nipple. I wish there was a regular plastic J box with a nipple.

https://www.amazon.com/dp/B000LEUJU6?psc=1&smid=A37ZI4YLTC1W3E&ref_=chk_typ_imgToDp

I looked at the Taco wiring examples but gave up. The traditional boiler lingo is too vague- wish they just provided a circuit diagram. Maybe I missed it.