Boiler with 2 zones and 2 air handlers

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Old 09-27-14, 10:00 AM
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Boiler with 2 zones and 2 air handlers

Good Morning. Let me start off by saying I might use the wrong terminology here as I am new to HVAC, but am fairly mechanical. I just replaced a ductless system in my home with 2 separate ducted systems. One for upstairs, one for downstairs. I was able to wire up the air conditioning no problem and it worked great all year, now I am getting ready to hook up the heat and I have a few questions. With the old ductless system, my boiler received the signal from the thermostats, and turned on the circulators, and sent the hot water to small Honeywell Zone valves that opened and sent that water to the unit that was calling for it. Now that I am changed over to forced air, Im assuming I need a new set of controls for this. I have done some research on zoning and the controls needed for that, and see that I can get a Taco boiler control that will handle 3 zones. That seems pretty straight forward, my question is, what tells the air handler to come on? Do I need another control for the air handler (Hydro Air Control)? Or is there something is the regular boiler control or zone valve that will tell the air handler to come on?

Thanks in advance for your help.

Brian
 
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Old 09-27-14, 10:38 AM
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Hi Brian, no problem with the terminology, we can usually figure out the meaning, welcome to the forum.

Let's start be telling us makes and models of the equipment.
 
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Old 09-27-14, 12:59 PM
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Great, thanks for the quick response, and I am a quick learner, so I hope you can help me out. For the unstairs unit, I have a 36HBXB-HW air handler. I know there is a word for it, but this unit has the heating coil built in to it. I have run 3/4 water line for inlet and return up to the unit.

For the downstairs unit, I have a AFP24A1A. On that unit, I installed a heating coil when I did the duct work. I also ran 3/4 water lines to that unit. I jumped the boiler and the circulator pump and turned the fan on downstairs for testing purposes and to make sure I had no leaks, and it worked great.

I have a Munchkin boiler that runs off Natural Gas.

Please let me know if you need any other information to help out.

Thanks again for taking the time to look at my issue.

Brian
 
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Old 09-27-14, 02:35 PM
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Your thermostats... they are heating/cooling jobs, right?

And you want the same thermostat to control the heating as the cooling, yes? (I don't see why you wouldn't, just asking so we're 100% clear on everything!)

How are you zoning the two hot water coils? By zone valves? or individual pumps?
 
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Old 09-27-14, 02:44 PM
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I just looked at FirstCo website... and the install manual has ZERO wiring information in it.

Did you get a wiring diagram with the air handlers? can you scan or photograph it in a readable format ?

I see that the handlers have pumps built in to them... at least the hbxb does, haven't looked at the other yet.

I just did a search on the second model number you posted and nada, zip, zilch, nogotz.

Any more info on that one?
 
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Old 09-27-14, 03:06 PM
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Yes sir. The thermostats are both heating and cooling.

The same thermostat will control heating and cooling. I have one thermostat upstairs, and one downstairs.

I have not done any zoning yet, and would like your input as how best to zone them. I have an understanding of how zone valves and pumps operate, just not sure if one is better than the other?

Thanks
Brian
 
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Old 09-27-14, 03:11 PM
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I think I have a diagram for the FirstCo. I will check. It makes sense to me that the other one has a pump in it, when I hooked up the water lines (feed and return), without a zone valve, just to make sure it was not leaking, it would not circulate thru that coil.
 
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Old 09-27-14, 03:17 PM
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Here a link to the manual for the AFPB24A1. Let me know if that works.

Wiring Diagram - Fedders AFPB24B1 Instruction Manual [Page 10]

Page 10
 
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Old 09-27-14, 03:25 PM
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Here is the wiring diagram for the other air handler.

http://www.firstco.com/getattachment...-hw714-(2).pdf

Page 4
 
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Old 09-27-14, 03:46 PM
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It sure would be easy if both air handlers were the FirstCo, wouldn't it?!

First off, do you have the water lines already connected to the boiler? If so, how so?

You'll need a circulator pump for the Fedders, but if I'm reading the FirstCo correctly, there's a pump inside.
 
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Old 09-27-14, 03:57 PM
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In the Fedders diagram there is a "4 circuit female heat control receptacle..."

I'm guessing that's a Molex connector?

You are probably going to have to tap into those wires. Looks like the easiest way.

The wires on pins 2 and 3 of that connector would be suitable for energizing a 24VAC relay coil.

That relay could be used to send signal to the boiler to fire up, and another set of contacts on that relay could be used to power the circulator pump.

The blowers in both units should operate on a call for heat as well as cooling.

The HBXB has " T T " connections which can go directly to the T T input of the Munchkin, along with the wires from one set of the contacts on the relay you will have to add to the Fedders.
 
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Old 09-28-14, 05:07 AM
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Good Morning,

Thanks for the responses. I sure wish the other one was a FirstCo, it is a really nice air handler. Unfortunately I was on a tight budget, and purchased all of the equipment used.
 
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Old 09-28-14, 05:17 AM
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Good Morning again,

I do have that connector and I think it is a Molex. It would be easy to tap into.

What you say makes sense to me, and I will try to hook it up that way and let you know.

So I really dont need zone valves or zone valve control because the FirstCo has a pump built in, and I can use the other pump on the boiler to circulate for the Fedders heating coil. My question is, when the FirstCo calls for heat, wont it circulate through the Fedders air handler as will without zone valves?

Thanks
Brian
 
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Old 09-28-14, 10:07 AM
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Hi Brian, yes, the piping is important.

With two pumped zones you will need 'flow check valves' on each heating loop to prevent it's pump from moving water through the other.

If the pump at the boiler is on piping that is common to both loops, it needs to be moved from that location to only pump to the Fedders.

The zoning can be done without zone valves since both loops have individual pumps. The correct wiring will perform the zoning.

I'll have more suggestions on the wiring later...
 
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Old 09-28-14, 10:18 AM
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Awesome, that makes perfect sense, and sounds fairly simple. I will have some time next week to hook all this up and give it a try. Check Valves can be fairly simple Im assuming, just 3/4 that can be purchased at any hardware store? Is there any way you can send me a simple drawing of the piping of the check valves to each heating coil coming off the boiler? I cant wrap my head around that?

Thanks
Brian
 
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Old 09-28-14, 10:40 AM
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Something like this:

219-4 - Taco 219-4 - 3/4" CxC Horizontal (Bronze) Taco Flo-Chek

Which you may be able to get at HD or Lowes...

Did you run 3/4" copper? ( I hope... 3/4" PEX is smaller ID and may not support the heat load )

How much of the boiler piping are you planning on re-doing?
 
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Old 09-28-14, 10:52 AM
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UH OH. I ran pex. I can upgrade to 1 inch Pex if you think that will make a difference.

I am ready to repipe whatever is necessary on the boiler. I have the skills to solder if needed.

I will check out the diagram.

Thanks
Brian
 
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Old 09-28-14, 11:42 AM
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Im still having trouble coming up with plumbing diagram that will work. Would the external circulators work as check valves when not energized?
 
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Old 09-28-14, 12:23 PM
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I can upgrade to 1 inch Pex if you think that will make a difference.
I can't make your decisions of course, that's completely up to you. I do feel that 1" pex would be a better choice at least for the hbxb being that it's rated at 62K BTUH (which you probably don't need that much anyway...). I didn't look at the BTU spec on the Fedders but if it's greater than 40K then the 1" would be a better choice there as well.

Would the external circulators work as check valves when not energized?
Only if they have " INTERNAL FLOW CHECKS " installed in them.
 
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