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Lennox EL18XPV/CBA38MV & Hot Water Baseboard Aux Heat

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Hi all

I recently installed two Lennox variable-capacity heat pumps (EL18XPV / CBA38MV / S40 thermostat).

As I live in Massachusetts, I need to maintain my existing gas boiler & hot water baseboard system. To accomplish this, it looks like my installer made use of Lennox's 90W84 Hot Water Heat Kit (their website also refers to it as a Hydro-Air Kit).

I am curious if this is an appropriate application? I ask because the system keeps the air handler running (at some low CFM) when the gas boiler is being called.

If I had HydroAir, this would make sense but since I have baseboard heat, this seems inefficient since the ducts aren't actually conveying any heat.

I don't know for certain that this is the wiring option that they've done but this guide was in my attic and it's the only one that seems appropriate. I'm not sure, though, because my S40 doesn't have W1/Y1 terminals.



Thoughts?


Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    Nice idea, I suppose, but not correct for your situation. You need to completely switch over to the boilers, and that arrangement is, as you say, correct for air handlers. This may take some creative wiring, depending on what thermostat you have.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JustinS
    JustinS Member Posts: 259
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    Nice idea, I suppose, but not correct for your situation. You need to completely switch over to the boilers, and that arrangement is, as you say, correct for air handlers. This may take some creative wiring, depending on what thermostat you have.

    Hi Jamie

    Thanks for the reply

    Not quite sure how to completely switch over to the boilers. I've read through the installation manuals a fair amount before purchase (to make sure that i understood what I was getting) and since they were put in (to see if I could figure this out).

    The installer has told me that this is how it needs to be (going so far as to agreeing with me that he doesn't think the air handler should keep running but that's how all manufacturers do it). I tried calling Lennox and they basically won't talk to me about this, redirecting me to the dealer.

    In fact, since I posted this, I read and thought more on this - it's unclear me how the above even works with the S40 because its only connections to the air handler are those 'R / i+ / i- / C' terminals on the bottom center. Those terminals that show the relay connected are input terminals and from what I can tell, the air handler board doesn't have output terminals that say "I need auxiliary heat".

    Thanks again
  • pedmec
    pedmec Member Posts: 998
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    The fan running sounds like you have a setting in the thermostat that is constantly calling for the fan to run for filtration. this is actually a nice feature when used as it really does limit dust in the house with a decent filtration system. Nobody ever uses it as a lot of customers thinks it use a lot of electricity but with ecm technology it uses a lot less electricity than they think and runs at a very low speed.

    the r/c connections your talking about are the communication connections that allow the thermostat to talk to the air handler. this is a communication system. its relaying information back and forth between the thermostat and air handler and condenser to air handler.
  • JustinS
    JustinS Member Posts: 259
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    pedmec said:

    The fan running sounds like you have a setting in the thermostat that is constantly calling for the fan to run for filtration. this is actually a nice feature when used as it really does limit dust in the house with a decent filtration system. Nobody ever uses it as a lot of customers thinks it use a lot of electricity but with ecm technology it uses a lot less electricity than they think and runs at a very low speed.

    the r/c connections your talking about are the communication connections that allow the thermostat to talk to the air handler. this is a communication system. its relaying information back and forth between the thermostat and air handler and condenser to air handler.

    Hi

    I thought there might be something in the thermostat like that but the fan mode is set to Auto (vs Circulate)... having said that, it seems directly tied to a heating call... if the heat is not calling for an extended period of time, there is no intermittent fan operation (as best as I can tell).

    Understood about the communicating system, I just mentioned those to point out that it doesn't have the Wx/Yx/etc shown on that wiring diagram. And since the air handler doesn't seem to have output terminals, I don't understand how they're interfacing with the auxiliary heating system.

    Thanks
  • pecmsg
    pecmsg Member Posts: 4,949
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    Are the ducts are in the attic?
  • JustinS
    JustinS Member Posts: 259
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    pecmsg said:

    Are the ducts are in the attic?

    For both systems, they're in unconditioned space (1st = basement, 2nd = attic)
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
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    I believe I can help you with the wiring design logic to get you where you need to be.
    As far as Lennox design is concerned, that is the correct diagram for hydronic heat connected to a heat pump. They are of the belief that hydronic heat should be a hot water coil in the duct work, (Not baseboards like you have). After I Digest the wiring and control logic they are using to get the result THEY (LENNOX) want, I believe there is a small relay that can stop the fan operation. I just need top study it for a little while. Will get you a diagram by tomorrow.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    JustinS
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
    edited November 2023
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    Is your thermostat a communicating thermostat? Usually 3 or 4 wires marked A B C D or 1 2 3 4

    OR

    are you using a thermostat with Legacy wiring... R W1 Y G C O Aux. or something like that

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
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    If you are using a standard thermostat with Legacy wiring (Not communicating) then the time delay relay connected to W1 and W2 and W3 on the air handler is what is bringing on the fan for Hydro Coil Heat. By removing the wire from W1 to the optional relay for Hydro Heat, the bower should not operate. That relay will do the other function of turning off the compressor when the boiler is operational, as it should

    Try it, and see if you get the desired result.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • pedmec
    pedmec Member Posts: 998
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    the auto/fan on setting is not what i'm talking about. look for the clean air setting
  • JustinS
    JustinS Member Posts: 259
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    pedmec said:

    the auto/fan on setting is not what i'm talking about. look for the clean air setting

    Pretty sure that's the 'Allergen Defender' mode which monitors pollen levels - I think that it's supposed to stay "Cleaning Air" as a status on the home screen when active. That mode is 'Off' and that status isn't shown on the home screen.

    Thanks for the suggestion
  • JustinS
    JustinS Member Posts: 259
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    If you are using a standard thermostat with Legacy wiring (Not communicating) then the time delay relay connected to W1 and W2 and W3 on the air handler is what is bringing on the fan for Hydro Coil Heat. By removing the wire from W1 to the optional relay for Hydro Heat, the bower should not operate. That relay will do the other function of turning off the compressor when the boiler is operational, as it should

    Try it, and see if you get the desired result.

    Hi Ed

    Thanks for the suggestion - I was thinking that might be the appropriate course of action but wasn't sure how that kit could be wired into my S40 (which is a communicating t-stat).

    The S40 only has the 'R / i+ / i- / C' terminals and I believe they are connected to the air handler board on the t-stat terminals on the bottom middle of it.

    Since i don't seen any output terminals for auxiliary / electric heat in air handler diagrams, I have to assume that there are additional terminals on the board beyond those in the diagram (oddly). The installer mentioned some relay and I briefly saw it, although not how/where it was wired.
  • HVACNUT
    HVACNUT Member Posts: 5,887
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    Upper left has a heat relay that shows only the coil wired. Can you physically see if the contacts are wired, and where the wires go?

    It looks like the heat kit is used with conventional wiring, not communicating, but it works, other than the fan part. The diagram is obviously not using the S60.
    Can you show how the kit is actually wired?

    Step 6 in the diagram, any way to adjust CFM to zero?

  • JustinS
    JustinS Member Posts: 259
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    OK, I took some pictures of the wiring. Looks like the only reason that they had the hot water kit was for the relay, I think it's the black object connected to P8-1/3 (the red/yellow wires from the top-left 9-port plug). In fact, it must be the 'Heat Relay' that was inquired on.



    I believe that the two thin wires coming out of the black object are the wires that used to be tied to the conventional t-stat, going to the boiler zone controller.





    Here's the details on P8 - it looks like they're "pretending" that my boiler is an electric heater which I guess is why the air handler continues to run.





    I believe the 4-pin HEAT strip in the top middle is the 'ELECTRIC HT BLOWER MODE' and it's in the factory default position of High Speed (pins 4/5 to the right). I will say, though, the air coming from the vents is not at all what I would call "high speed".






  • HVACNUT
    HVACNUT Member Posts: 5,887
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    Did you try removing the jumper completely?
  • JustinS
    JustinS Member Posts: 259
    edited November 2023
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    HVACNUT said:

    Did you try removing the jumper completely?

    I did not - the system was just installed and am having issues with it so I didn't want to mess with it.

    Also, I believe that I've seen some mention of error codes in certain cases if a jumper was not present. I checked for this one but not seeing it or others...
  • HVACNUT
    HVACNUT Member Posts: 5,887
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    JustinS said:
    Did you try removing the jumper completely?
    I did not - the system was just installed and am having issues with it so I didn't want to mess with it. Also, I believe that I've seen some mention of error codes in certain cases if a jumper was not present. I checked for this one but not seeing it or others...
    Trying won't damage anything. If it throws a code, just shut off the power for a minute.
  • JustinS
    JustinS Member Posts: 259
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    Here's another question - I've been told that no manufacturer out there truly supports integrating a hot water baseboard conventional system with a variable capacity heat pump.

    Seemingly, the only way to tie it into Lennox is to use the auxiliary electric heating contacts, as my installer did. Alternatively, a 24V interface panel (Lennox calls it EIM) could be used but doing so isn't compatible with a variable capacity outdoor unit; if it were used, the outdoor unit would be reduced to some form of multi-stage unit.

    Does anyone know if this is truly the case? I have trouble believing that the industry as a whole would be so limited but at the same time, it seems that if one wasn't limited, they'd all support it.

    Thoughts? Does anyone know of a system that does what I think it should be capable of doing?
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,166
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    JustinS said:

    Here's another question - I've been told that no manufacturer out there truly supports integrating a hot water baseboard conventional system with a variable capacity heat pump.


    Seemingly, the only way to tie it into Lennox is to use the auxiliary electric heating contacts, as my installer did. Alternatively, a 24V interface panel (Lennox calls it EIM) could be used but doing so isn't compatible with a variable capacity outdoor unit; if it were used, the outdoor unit would be reduced to some form of multi-stage unit.


    Does anyone know if this is truly the case? I have trouble believing that the industry as a whole would be so limited but at the same time, it seems that if one wasn't limited, they'd all support it.


    Thoughts? Does anyone know of a system that does what I think it should be capable of doing?


    My understanding is that there are hundreds upon hundreds of combinations of heating and cooling system combinations. When you consider Hydronic and Air and electric resistance, then Steam, cast iron radiators then heat pumps, and gas and oil fired furnaces, and the different efficiencies and the different combustion processes along with radiant and convection and conduction processes of getting heat from one place to another, and the variable input v. two stage v. on/off control technology, add to that the over 500 major manufacturers of HVAC Equipment/Designs/Controls and the like, there are just too many possibilities for having a single control platform that can reduce all these technologies from over 150 years into one app on your smartphone.


    Manufacturers of control systems are looking for the biggest bang for their buck. The most common HVAC system in North America is the fossil fuel furnace with a central air conditioner using simple on off control technology. The second most popular system is the heat pump with on off technology. That is where the big money is. If you are going to market a control after research and development costs are considered, production costs and the market demand, You are not going to look for the consumer with a multi zone baseboard hot water system, that would like to integrate it with a variable speed heat pump and have that control make the decision when it is most economical to switch from fossil fuel, to heat pump, and back to fossil fuel. The place where that particular conversion point is will vary from day to day based on the cost of the fossil fuel and the cost of electricity and the outdoor temperature that day. Who is going to input that data on a daily basis for every neighborhood in the world where your type of system is installed? Being that your particular system components make less than one percent of the total number of potential consumers of HVAC systems in the world, I don't think you will find many manufacturers of HVAC controls jumping to fill YOUR individual needs.


    Remember your great grandmother probably was putting a shovel full of coal in the furnace or your grandfather was adding another log to the fire a couple of times a day, to be comfortable over 100 years ago. The fact that you have a thermostat at all is pretty amazing compared to that. I don't think that the CONTROL BOX you are interested in is made by anyone. There is just no demand for that product. That is going to be a custom made collection of parts for you and only you.



    How much would you be willing to pay for that control?
    $1000.00? $5,000.00? $25,000.00.


    Research and development ain't cheap. Then divide that cost over the number of units that would actually get sold. There is no profit! in it.

    Good Luck with your project.


    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • JustinS
    JustinS Member Posts: 259
    edited November 2023
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    Manufacturers of control systems are looking for the biggest bang for their buck. The most common HVAC system in North America is the fossil fuel furnace with a central air conditioner using simple on off control technology. The second most popular system is the heat pump with on off technology. That is where the big money is. If you are going to market a control after research and development costs are considered, production costs and the market demand, You are not going to look for the consumer with a multi zone baseboard hot water system, that would like to integrate it with a variable speed heat pump and have that control make the decision when it is most economical to switch from fossil fuel, to heat pump, and back to fossil fuel. The place where that particular conversion point is will vary from day to day based on the cost of the fossil fuel and the cost of electricity and the outdoor temperature that day. Who is going to input that data on a daily basis for every neighborhood in the world where your type of system is installed? Being that your particular system components make less than one percent of the total number of potential consumers of HVAC systems in the world, I don't think you will find many manufacturers of HVAC controls jumping to fill YOUR individual needs.

    I absolutely understand this.

    I'm not expecting any sort of automated or predictive conversion point - these thermostats all are relatively simple in this particular area with a simple low/high balance point which I am perfectly fine with.

    I'm just saying that I find it surprising that the mere action of adding in this 24V interface module would dumb down the rest of the system. The logic seems relatively simple, if I'm below X temperature, close this contact and shut down the heat pump. If I'm above it, allow the heat pump to operate. After all, that's essentially what it's already doing, albeit with its electric heating relay contacts.

    *EDIT*

    Something else that I forgot to mention... what I was asking about should also apply to conventional gas furnace which, as you said, is quite common. It's just a 24V contact, it shouldn't really matter whether it's forced air or steam or HW or etc...