what defines a "3-wire" hot water system?


  #1  
Old 01-06-06, 08:29 AM
X
Member
Thread Starter
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
what defines a "3-wire" hot water system?

While I'm becoming a heating expert (chasing an air problem in another thread for over a month; as of today I think we're getting closer to solving it...), here's a question about my zone valves and thermostats.

I have Taco 571 zone valves. They have three wires on the terminal block. Looking at the Taco info sheet on this valve, two wires (1 and 2) go to the thermostat, and two wires (2 and 3) go to the circulator relay. Very straightforward.

But, is this a three-wire system or a two-wire system?

For a battery-powered programmable thermostat, it would appear that many models are specifically "not for three-wire systems."

Thanks for insight.
 
  #2  
Old 01-06-06, 04:04 PM
Grady's Avatar
Forum Topic Moderator
Join Date: Jan 2005
Location: Delaware, The First State
Posts: 12,682
Received 41 Upvotes on 39 Posts
2 or 3 wires

Some zone valves need power to both open & close. These would require three wires going to the thermostat. On some thermostats when using heat motor zone valves, such as the Taco 571, you need to add a resistor. If your stat says nothing in the instructions about a resistor & is capable of handling a load of at least 1.5 amps, you should be OK.
 
  #3  
Old 01-09-06, 09:33 AM
X
Member
Thread Starter
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
Gotcha. Thanks.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: