Connecting AC to Hydronic System
We have a hydronic boiler system for heat. I tried turning on the AC and it wouldn't turn on.
Found a cut hanging wire to the side of the air handler which is the wire running to the AC condenser, so someone previously cut/disconnected the AC.
I'm trying to figure out how to connect the condenser back into the system again.
It seems that the original fan relay/board failed and they created a workaround using a new 24V transformer and RIB relay to power the fan whenever the heat turns on.
Since I have a hydronic boiler system for heat, do I need a separate 24V transformer for the AC? Or can I use the existing 24V transformer/RIB relay?
If so, my current thinking is:
24V transformer -> Rc (thermostat)
White (condenser) -> Y (thermostat)
Red (condesnser) -> Common (transformer)
But if I have to use a separate 24V transformer, how do I get the air handler's fan to turn on when the AC kicks in?
Comments
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Doesn't the air handler have a transformer and relay to control the blower? G and Y and Rc from the t-stat should connect to the air handler and the contactor in the condenser should connect to Y and C in the air handler.
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Or do you have a hydroair coil in the air handler? Old systems g on the t-stat called the blower on high which is what you need for ac and y was just a junction point to connect the t-stat and condenser contactor. In newer systems y turns the blower on high, so you'd need a second relay for y if you don't have a control in the air handler to do a high blower call with g or y.
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What happened? Did this system ever work before? Or did you just buy this place?
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I've included a picture of the air handler's original wiring diagram. However, it appears that the previous fan relay may have failed so someone installed a RIB relay to control the fan motor.
I believe we have a hydroair coil in the air handler. Our boiler heats water which then gets circulated using a circulator pump to the air handler.
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Pretty sure this is the original 24V transformer and, fan relay board, and terminal board which are no longer being utilized.
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We bought this home and moved in the Fall and never had to run the AC. So I only found out this past week that it wasn't working.
At first, I found out I wasn't receiving 24V to the condenser. Turns out… the wire to the condenser was cut and just hanging outside the air handler not connected to anything.
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Every part in that control box is easily replaceable and a standard part.
What is what you've labeled T-T? normally it is a control to a boiler that turns the boiler on when you short the terminals. Is it controlling a relay that shorts t-t in your case?(you need to make sure this is correct)
the easiest way to add cooling to what you have is probably to add a second relay that is controlled by y from the t-stat, use that relay to power the cooling speed of the blower, and connect the condenser contactor between c and y at the air handler.
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Ok so the T-T terminals are from a single zone switching relay (Taco SR501).
What type of relay would you recommend for the cooling side?
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what controls the taco zone control?
that t-t is designed to control a boiler when the zone is calling, it closes t-t on a heat call or a valve end switch depending on how it is set up.
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Hmm I'm not entirely sure what else controls the taco switch relay. There is a triple aqustat at each boiler, I've included some additional pictures of the setup.
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why are there 2 boilers?
t-t is an output from the zone control. there normally is a thermostat connected to it that controls it. without a heat call to the zone control, the circuit you drew will not energize the relay.looking at the manual r-w/t-t on the sr-501 is a dry contact input, you close a switch between them to close that relay. it makes no sense where you have it drawn
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Not sure why the original installers/homeowners had 2 boilers put in place. The one on the left was installed 1-2 years ago. They are connected in series and provide hydronic heating to 7 zones (air handlers).
Yeah now that I'm thinking about it, I definitely missed a connection in my drawing as I didn't include the triple aquastat. Will confirm when I get home later, thank you
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OK looking at this system, I can come up with several ways top make this work. If the RIB relay is the RIB2401D, I might use this configuration
As you can see from the bottom left addition of a thermostat, and condensing unit all you need to add is the blue an yellow wire from the air handlet to the outdoor unit to make the air conditioner work.
The fan relay for the cooling side will be operated by way of the green wire from the thermostat to the air handler. It is unlikely that the fan relay has failed. The RIB was added for the heat to operate the fan, since the Green wire is not powered on a call for heat.
But it appears that you have the RIBU1C which only has one set of contacts. that may be why the additional transformer is there. I will need to look closely at the wires to make sense of them on your system.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Hey Ed thanks for putting that together, really appreciate it. There is currently a RIB24P in place with the additional transformer. I'm adding a few more pictures. Please let me know if there is anything in specific you need to see.
In regards to the end switch relays, it looks like there is a brown wire leaving the Taco SR-501 and goes to the X-X terminal on a different zone's end switch relay (Zone 7). Zone 7 is also connected to another end switch relay. So it seems that many of them are grouped together and likely head to one of the boilers to turn on when there's a call for heat.
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There are 7 circulators. That indicates 7 zones, or 6 zones and one water heater, or 5 zones and 2 water heaters.
- Are all the heating zones connected to air handlers?
- Are all the AC systems offline?
- How many heating thermostats are in your home?
- How many are having problems?
- Can you take a photo of what you are calling a "Triple Aquastat" because there is a specific part known as a triple aquastat that is used mostly on oil heat when the boiler makes both heat and hot water. Somehow I don't think you have that particular control on those boilers. They have a different control diagram that does not include a triple aquastat.
- How many Taco SR502 controls are there in your system
I find that many problems like yours are resolved after homeowners give all the info after adding small bits here and there before the entire big picture is known. That 7 circulator photo makes a big difference in how to troubleshoot your system and I have a feeling there is more information needed.
It appears that your add on transformer has a pop out circuit breaker. I have a feeling there was a lot of trial and error to get your system to operate and perhaps the air conditioner and heater operated at the same time so the previous owner just disconnected the wire every winter. The original wiring may still work because there is a fuse on the original transformer so that relay and transformer may still be functional. You just may need a 3 amp fuse.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Lots more good info with the additional pics.
Let me study and I will make up something that will work for you that will be an automatic change over.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Not a problem Ed, apologies for not providing a lot of info off the start. Didn't want to inundate with too much info as it pertained to the heating, but starting to realize now it likely affects how we connect the AC system.
There are 7 heating zones, each connected to a separate air handler. All of the AC systems are online and now working, except for this current zone (Zone 6). (A few had other issues which I have already addressed - faulty thermostat, faulty zone board, faulty capacitor, etc. Has been a busy past few months troubleshooting these various issues).
Each zone has its own thermostat, except for Zone 4 and Zone 6 which each are zoned systems and have 2 thermostats each (they both have a Honeywell HZ322 with motorized dampers - I just installed 1 last month as its prior zoning board had failed).
All of the zone's heat have been working, though I have noticed that certain zones turn on 1 boiler while other zones turn on the other boiler.
Each zone has its own end switch relay, most are Honeywells, however 1 is the Taco SR501
The 2 boilers only provide hydronic heat to the 7 air handlers.
Hot potable water is on its own gas hot water heater.
Will upload some pictures shortly, thank you again
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So I don't waste time on trying to fix something that ain't broke, Do all the heat zones operate properly?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Zone 7 air handler on the left (with the Honeywell HZ322 that I recently installed)
Zone 6 air handler on the right (that we are currently working on connecting the AC wiring)
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Yes all of the zones were heating properly this winter. Turned off power to the boilers last month as we haven't needed heat for a few months now.
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WOW
You have a technician's nightmare on your hands. You definitely need a control specialist (I was that guy in south jersey when I was working) to understand your system.
This is what I came up with so far on your problem system
Some of the wires look different in two different photos. I am guessing you have made some changes and photographed the changes so you can go back to the way you found it if your actions do not work. Good Plan!
If I was called to this problem, I would say that you need to start from scratch on that one.
- Put it back to factory specifications using the wiring harness and thermostat connections that have been abandoned.
- Once the Air Conditioning is operating properly continue to step 3
- Add the needed heat relay in the air handler to operate the zone pump relay (Taco SR501) by way of the thermostat W connection. (that is where you can use a RIB. Once that is in place go to step 4
- Check for both summer and winter operation with only a thermostat switch over.
If you are up for that task, I can walk you through the steps
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Off Topic a little, but looking at your system there is at least two zones that have a real convoluted sequence of operation.
- Call for heat
- Zone control operates dampers as needed to feed that zone
- Zone end switch proves zone open damper
- Signal goes to the air handler to start the heat cycle by powering the heat relay
- Heat relay allows power to the fan motor circuit
- Heat relay signals circulator zone to power the pump and operate the boiler
- Boiler gets signal from circulator relay and causes power exhaust vent system to start
- Power exhaust system operates and proves switch allows burner to light thru electronic ignition
- Main Flame lights and flame sensor sends flame on signal to the control to continue the operate the main gas valve
- Water temperature continues to increase in the air handler piping over time and the temperature sensor in the heat coil allows the air handler blower to get power (with both the water temperature and the heat relay Allowing the fan to operate) so the fan blows warm air to the room(s) thru the ductwork.
- if the water temperature is off the fan will not operate to minimize cold air blowing thru the ducts on a call for heat.
- if the heat relay is off the fan will not operate to minimize cold air blowing thru the ducts on a call for heat.
- Call for heat ends and the old man walk back thru that maze and turns off all the lights and locks all the doors until the next call for heat.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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I thought this was a relatively easy question until I saw the picture of the boilers.
the system was built by either a homeowner that knows a lot but not enough or a pro that knows too little.
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Oof I guess that's reassuring that I've been wracking my brain for hours on this. I'm in Morris county if you're free and willing haha! 🤣
Based on other work throughout the house that I had to address, I'm leaning more towards a previous pro that knew too little. The homeowners had no idea what was going on and were getting taken for a ride.
Yes some of the pictures were taken earlier when I was working on connecting a Aprilaire whole home bypass humidifier to this. I temporarily disconnected it to have less clutter while I've been working on the AC.
There also was a strap-on Aquastat whose wires were tied together and therefore the aquastat was not doing anything. So I removed that as well. Heat worked well throughout the winter.
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In regards to your "Off topic" comment, are you referring to the Carrier air handler (Zone 7) that has the Honeywell zone panel?
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YES To the off topic
OK here is a diagram that will work for you
You need to add a relay for the fan ot operate during cooling or if you select FAN ON at the thermostat. That will be called the fan relay. You can use the existing RIB as the heat relay. You just need to do a little rewiring. So the orange and the yellow from the RIB operate the Taco SR501 on a call for heat.
Either RIB will turn on the fan on the same speed. (If you want to use two different speeds, then that will be a little different wiring so you don't power both speeds at the same time.)
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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It looks like it was overengineered but correct originally, then whoever added that second boiler or replaced the boiler and replaced one of the honeywell relays with a taco relay didn't know what they were doing. Unless it is a mansion or apartment building or it is in the arctic I can't imagine it has that much heat loss.
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Ok wow that's a nice install, thank you!! I actually have a spare RIB1UC in the garage that I was saving for another project, but I'll go ahead and wire up the AC with it!
So with the RIBU1C, since I'm connecting G and C to the coil, I would use the 10-30 Vac/dc (Wht/Blu) connection rather than the 120 Vac (Wht/Blk) connection correct?
I'm a little confused on the NO connections though. I understand that I'm connecting the NO (Org) to the fan (just like how my current RIB relay is for heat).
I'm wondering why the other side of the normally open switch, C (Yel), doesn't go to the common of the fan motor instead of the common of the condenser? Doesn't the 24V from the thermostat go to the condenser's contractor and then complete the 240V circuit at the condenser?
And why does the RIB heat relay Common (purple) also go to the common of the condenser?Edit: Oh wait after closer inspection, I think I see what's going on. I didn't realize that you had also made some changes at the 24V transformer. I can use the existing transformer and don't have to run a new one correct? If so, I need to connect the 240V that is going to the condenser to the 24V transformer?0 -
Its always difficult to figure out a system that is wired all hoge poge and its a big…huge time waster. Best thing is to get it all down on paper and make a new print that will work. Then go back in and rewire it
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Ok so I pretty much have it all wired except for the 240V to the condenser. Going to have dinner and will try to finish it up tonight, if not tomorrow.
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Looks like you have a well designed system with some premium accessories. Have you looked at the information on how to wash your electronic air cleaner dirt collection cells using your dishwasher?
I send my dishwasher to the local car wash to clean my EAC innerds. She does it between laundry loads and vacuum cleaning.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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do you remember Jill ?
known to beat dead horses0 -
@loamyroots11 said: I'm a little confused on the NO connections though. I understand that I'm connecting the NO (Org) to the fan (just like how my current RIB relay is for heat).
I'm wondering why the other side of the normally open switch, C (Yel), doesn't go to the common of the fan motor instead of the common of the condenser? Doesn't the 24V from the thermostat go to the condenser's contractor and then complete the 240V circuit at the condenser?
This question is somewhat confusing. I have made the diagram just a little more clear. Note that the Red and Black horizontal wires along the bottom are 240 VAC marked L1 and L2. Also you are not using the Org on the heat relay for the motor you are using the Brn for the motor with the Prp.
The Red and Blue thinner horizontal wires just above are 24 VAC wires from the transformer. Red from the Yel/Wht lead on the transformer the R on the thermostat using the red wire on the diagram, and C from the Yel transformer is the blue wire that is the common for all the relay coils and also goes to the thermostat. (The blue common to the thermostat is optional and your thermostat may not need a common wire.) So all those Common relay wires can be under one big wire nut or otherwise connected together to the 24 VAC transformer common. Those relays include the compressor contactor, fan relay, heat relay, thermostat (optional), and the transformer. They can all be under one wire nut or several wire nuts that are all interconnected. I also changed the RIBU1C wire color to Yel and Org to match the NO and Com contact wires. I did not change the 24 VAC Coil wire colors because I think you know what they are.
To be more clear about the Fan relay. RIBU1C is the fan relay and the NO contacts will be operating the 240 VAC fan motor by breaking the L2 wire between the power source and the fan motor.
The existing RIB24P is the Heat relay. It is doing the same using the Purple and Brown wires to NO and Com to break the power to the fan motor.
It is important to use the same motor speed on this wiring diagram. If you use two different motor speeds, this diagram WILL burn out the fan motor if both the heat relay and the fan relay are powered at the same time. The Orange and the Yellow on the heat relay are connected to a 24 VAC circuit that operates the boiler side of the system thru the Taco SR501. Not the high voltage side of the system
AGAIN: It is important to use the same motor speed on this wiring diagram. If you use two different motor speeds, this diagram WILL burn out the fan motor if both the heat relay and the fan relay are powered at the same time. The old original equipment wiring system that is no longer connected has a way to use 2 different speeds that will not burn up the motor if both the heat and the fan relays are energized at the same time, but that will be more expensive and time consuming to get you there if you need that. I don't believe you need that so I will not cover that now. Just use one speed for both heat and cool like I have illustrated.
Remember to cap off unused motor leads and unused RIB wires separately because they may contain stray voltage that will harm the electrical system if the bare wire contacts a metal part of the air handler or another bare wire.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Some added thoughts. I am trying to follow what is already there and the way it is wired from looking at the photos provided. It is not the best design but it is what you have and you will need to do the least amount of rewiring.
- You may need to rewire the heat relay RIB24P so you can use the Org and Yel for the Taco low voltage connection the R and W on the SR501
- By using the Heat Relay RIB24P as the switch to bring on the boiler system, I have to assume that the Taco SR501 is already wired to bring on the boiler correctly since your heat zone worked fine.
- I can show you where to add the strap on aquastat wires if you need it in the future. That will prevent the zone 6 fan from blowing cold air as soon as the thermostat calls for heat. That may blow cold air for some uncomfortable amount of time before the heat from the boiler reaches the hot water coil on AHU6. If the AHU6 is close to the boiler(s) then it may be unnecessary. Just know it is an available option.
- One low voltage wire may not be needed here
Just put the Red wire it is connected to where the White wire is connected in this picture.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Ed that's super helpful, thank you! Unfortunately, I was told that the EAC were not functioning for a very long time and instead they had been using regular 4" filters instead - so that's what I purchased when it was time to change the filters.
Yes I believe I was able to make all the appropriate low voltage connects, your diagram was very easy to follow, thank you again!
Yeah it might be a good idea to add the strap-on aquastat back into the system. As mentioned earlier, the 2 wires were just connected together and not actually terminating on the R/B/W terminals, so I removed it. However, the other air handlers have strap-on aquastats so it would be nice to include to prevent blowing air until the water is at the appropriate temperature.
And single speed for the blower is more than fine for now!0 -
I added an EDIT above so please look at the photo you may need to remove a wire. Otherwise, next winter you may end up with a holding circuit you don't want. After the first call for heat next year, the holding circuit may not let the the system stop when the call for heat is finished. Just seeing some problems you want to avoid in the future. Electrical circuits and sequence of operation can be mind boggling at times. After you get everything figured out, something unexpected spoils your design and you need to find a work around. That one will be hard to find next September if you don't remember to do it today.
Regarding the Taco SR501, the 5 and 6NO do not need to operate anything in the air hander. 5 and 6NO only need to operate the boiler(s). Having 2 sets of wires there are what often causes burnt transformers and/or holding circuits.
I think this will wrap it up for me. Good night.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Ok thank you for seeing that, yes I completely agree. If I don't correct it now, it will be a headache next winter.
That being said I apologize for having an older pic there. That brown wire actually the wire running to the strap-on aquastat previously. It wasn't terminating at the strap-on, the 2 wires were just connected together. So the strap-on and that wire were removed. The white wire behind it is actually the wire that runs to the T-T of the Taco.
I have that T-T wire connected like your diagram above, will that be fine?
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