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Advice and or help needed to install transformer 120v to 24v. Hydronic heat

Advice and or help needed to install transformer 120v to 24v. Hydronic heat

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  #1  
Old 11-24-13, 10:21 AM
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Advice and or help needed to install transformer 120v to 24v. Hydronic heat

Hello,

Thanks for all the help on here..many old posts have pre-answered questions that led me to not even needing a post at all!

I do need some help/advice on this one though.

I have a line voltage thermostat that I am planning to move. A pellet stove is going in that room so it will always be warm. As I relocate the thermostat, I want to add in the transformer to step down the line voltage to 24v (I am sure it is line voltage, its a 1950's house).

This thread has already helped, I think we are trying to achieve the same thing here: http://www.doityourself.com/forum/th...-oil-hw.html#b (as in installing a new transformer)

MY questions:If I use the Honeywell AT72D1006, how to I wire the line in? It appears that the white lead wire is 120v in (hot wire) and the black wire is 120v out (to circulator). I am looking at figure 11 in the schematic https://customer.honeywell.com/resou.../69-1641EF.pdf

Does the neutral wire to the circulator completely bypass the transformer? I just leave that hooked up as-is?

Or should I get the Honeywell R845A relay and hook it into the Honeywell L8124A aquastat? This seems like a bit more wiring. Are there any advantages to this?

My Current set-up:
I have already installed a Honeywell TL8100 for the line volatge system which has worked great. There is a hot wire that goes to it, and returns directly to the circulator. It basically just works as a switch. When the heat comes on, the furnace does not instantly kick on, it seems to wait until it is called for hot water. My house has hydronic radiant heating, which shockingly still works! The pressure holds in the system, so my boiler maintenance guy said that it probably has no (or little) leaks.

Thanks in advance, and please let me know if I need to clarify any points here.
 
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  #2  
Old 11-24-13, 10:43 AM
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It's just a transformer. Measure the line voltage that you have to find out if it is 120 volts, 208 volts or 240 volts.

If you have 240 volts, cap white and red individually and connect one of your line voltage wire to black and the other to orange.

If you have 120 volts that you wish to step down, cap red and orange.
Connect one line voltage wire to black and the other to white.

The odd thing about transformers is that sometimes common is black and sometimes it is white. I wish that it was always black. Be sure to check the side of your transformer when you get it.

The example that I posted would require you to cap black and red and use white and orange for a 240 volt application.
 
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Old 11-24-13, 10:50 AM
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The TL8100 works in the following
Hydronic applications:
Line volt circulators
24 volt circulator relays
24 volt zone valves
120 volt zone valves

Impressive stat. You are also going to need a relay or contactor.
I'd also get a NEMA3 8x8x4 junction box and some romex or saddle connectors.

The R845A doesn't give you a 24 volt common.
 
  #4  
Old 11-24-13, 06:19 PM
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Thanks Houston, I appreciate the reply! All the pictures of this transformer have only had 2 wires coming out of it, those red and orange wires in the diagram were confusing me a bit.

Do you think there is another thermostat that might allow me to not need a relay? I was considering getting an iris thermostat, and going with their whole home automation system. I was looking over the instructions but do not see a simple 2-wire installation? (would I just utilize the R and W wires?)

Do you always need a transformer and a relay to convert to low voltage?

If by any chance you know a thermostat that can be programming for short intervals (adjust the heat up for a couple mins to keep the pipes from freezing), please let me know! Perhaps there is another device that can circulate water in the pipes when an alternative heat source is being used?

Thanks!
 
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Old 11-24-13, 09:25 PM
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Do you think there is another thermostat that might allow me to not need a relay?
It would require a high voltage stat. Is moving the existing stat an option?


Do you always need a transformer and a relay to convert to low voltage?
If you want a low voltage stat to control a high voltage pump, a transformer and relay is required. A Fan Center would work if the pump is 1/3 hp or less. (It's a transformer and relay combo)
 
  #6  
Old 11-25-13, 06:51 AM
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I can go ahead and move the existing stat, I would just need to run a 120v line to the new location. I have that bug in my head that I need to update my thermostat to something from the 21st century, so I would like to install the transformer/relay to make this happen. The TL8100 is great but I might go with a nest or Iris system.

Is it better if I go with something like the R8845U or R845A? It seems like a all-in-one job? The diagrams in the honeywell instructions seem fairly easy to follow. I understand that I wouldnt have a common wire with it, but if the stat runs on batteries will I need it?

If you happen to know where a generic wiring diagram is for a transformer/relay set-up is, I would love to see it.

As much as I feel confident, I might call in a pro...But I do want to know whats involved here. If I called in an HVAC guy, how long do you think the install would take (just wiring this up, I would run the new Tstat line)? An hours labor is worth the piece of mind..
 
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