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Brian HVAC Guy
Brian HVAC Guy, HVAC Technician
Category: HVAC
Satisfied Customers: 803
Experience:  I have been an HVAC/R mechanic/technician for 30+ years.
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I am sorry must have t the worng button. However, I am

Customer Question

HI, I am sorry must have hit the worng button. However, I am working on the S86H conversion to S8610U3009. I am having some problems with the wire "translation". I am going to have one more test and I will ping you back if not successful. Thank you! - George
Submitted: 11 months ago.
Category: HVAC
Customer: replied 11 months ago.
More information:
OLD unit: S86H1147
I have identified the following wires:
Old - MV => New - MV
Old - MV/PV => New - MV/PV
Old PV => New PV
Old 24V (1) (from transformer leg C) => New - 24V GND
Old 24V (2) (from transformer leg R) => New - TH-W
Old TH-W - not connected to new right now; I am thinking it should go into New - 24V
(Old TH-W connected transformer leg W to roll-out switch to limit switch then to vent spill switch to Old TH-W port; leg W had also thermostat connected to it)
(transformer R had another thermostat connection; transformer C had also blower motor relay connection, as did transformer G; no connections at transformer Y)
(damper port had a jumper plug on it; I did not transfer it to the new module)
At this point, I tested with connections as described above. I have a spark now (old module did not spark and i did replace the igniter) but the pilot did not come on and the main burner did not. I did only once cycle so far. Maybe there is still air in the pilot line....
Expert:  Brian HVAC Guy replied 11 months ago.

Hi I'm Brian and I'm here to help!

Did you get your furnace going? It sounds like you might have, in which case just ignore this post. If your module is sending spark, it should also be sending voltage out on PV to open the pilot valve. If you also changed the gas valve then yes, it may take a few tries before you get gas to the pilot burner. You may also need to remove and clean the pilot burner orifice, it could be plugged.

Post back using reply if you'd like more help. Otherwise, if I have helped, please remember to rate 3 stars or higher before you leave!

Thank you,

Brian

Customer: replied 11 months ago.
Hi Brian,
The furnace is still down. I tried as I explained above but I have later noticed one thing. the spark is there even without the thermostat being on - while the old 24V (2) was connected to new TH-W port. Since this is coming from R (hot), I figure that it is powered regardless of the thermostat setting and the spark kicks in. I did not turn on the gas valve as I wanted to resolve the thermostat on/off and spark problem first (the valve was not replaced). I tried several cable combinations but either I get the constant power from R to new TH-W port or I get no power to TH-W when, for example, my old TH-W cable is connected to the new TH-W port. I am confused at this point because instructions are unclear and nothing I try works. Is there a tried and true cable mapping for this kind of conversion? I should not have to rework all my furnace cabling - I wouldn't think... I can describe the furnace cabling as what connects to what. Please let me know what I can provide for you to help me.
Thank you,
-George
Expert:  Brian HVAC Guy replied 11 months ago.

Sorry you're still having trouble George, if you can give me the make and model number of the furnace, that may help me to get on the same page. This does sound like a wiring issue and we should be able to correct it.

Thanks,

Brian

Expert:  Brian HVAC Guy replied 11 months ago.

I will say that with the S8610U3009 if you have no vent damper, you need not connect anything the the 24 v terminal on the control. Further, if the vent damper plug that was shipped with the control was loose in the box, you should plug it into the control. Lastly, the wire from R should be capped and taped and not used. The wire that was on THW should go on THW on the new control. Regardless of furnace make and model, this strategy should work.

Also of note is if you have a separate flame rod (the ignitor doesn't serve as the flame rod and ignitor rod) you should cut the link for the flame rod on the new board and attach the wire from your stand alone flame rod to the Sense terminal.

Let me know how that goes,

Thanks,

Brian

Expert:  Brian HVAC Guy replied 11 months ago.

Sorry, I misspoke above. There is no 'dummy' vent damper plug anymore. You should not connect anything the the vent damper plug at all. 24 volt power from the W terminal is all that's required at the control, you don't need a 24 volt source at 24v unless a vent damper is being used. There should be a ground at 24v ground and the ground should also route to the pilot burner assembly and ground there. That should get you up and running but again if you give me the make and model of your furnace, I can double check my advice.

Thanks,

Brian

Customer: replied 11 months ago.
HI Brian,I have disconnected the R wire from the new TH-W which now has the old TH-W connect.
The plug does not work out as you know. When I energized the TH-W with R connection, the module complained about the lack of the damper - I removed the plug and the R connection after that.
Still, when I energize 110V, the transformer has 27V on R and 0V on W, C, G so I know it works.
However, there is nothing on TH-W port before I turn the thermostat on (which I expect) but also nothing after I do turn it on - I thought this should provide 24V to the TH-W port.
I ma not seeing why this is. Is there a fuse I don't know about - could not find one. I am at the point where I would be taking the electrical boxes apart to check if the connections are tight...
Sorry to be wordy but I am trying to give you the info you might need - I know it is hard to troubleshoot without being here.
The furnace information:
Luxaire
made by Central Environmental Systems, York, PA - now defunct I think
I believe the furnace was made in 1989
Model number: PDCU-LD16N120AThank you,
-George
Expert:  Brian HVAC Guy replied 11 months ago.

No worries George. Do you have the ability to take some digital pictures and upload them here? You can use the 'Attach Files' button near the dialog box where you type responses to me. That may help. Since your old control had a dummy plug and the new one didn't but you did plug it in anyway, that may have told the control internally that you do indeed have a vent damper and you may need to leave that plug installed. It sounds to me like there is something in the way on the W circuit. When your thermostat calls for heat you should have 24vac (nominal) from ground or transformer common to the W wire or terminal on the furnace that should land on THW. That is what will give the control 24 volts to start the ignition process. I'll see what I can find with that model number. Luxaire (bought by York many years ago now) is still in business but not under the CES name for sure. I may still be able to find some data on it though.

Customer: replied 11 months ago.
I can take pictures - no problem. Please tell me what you would like to see. For one, I can take pics of the electrical diagram that is on the door; perhaps this will help.
W - my thoughts exactly but I don't see what is "stuck". I can tell you that between W and the TH-W, I have the limit switch and two switches (roll-out and vent spill).
I made an experiment where I moved the connection from W to R to see if the current would flow thru the whole path to TH-W.
It did just like when I connected R to TH-W - I moved the connection back to W after that. I am assuming this has proven that all those switches are OK but maybe this is a wrong assumption.
The damper plug - I tried not to exceed the 10 cycle limit when the module configures permanently one way or the other. I have never had the plug more than 4-5 times on or off, I think. I can put it back if necessary, of course.
I have forgotten to mention that the very first thing I had done was to replace the igniter (single rod - Q345A), just in case.
The gas valve on the furnace is VR8204C.
Expert:  Brian HVAC Guy replied 11 months ago.

Thanks for all the additional info. If there's a wiring diagram, a picture of that would be worth a thousand words! If not that, then pics of any of the control wiring throughout the furnace would probably do. I have found some info on your furnace but only replacement parts. Not much help...

Customer: replied 11 months ago.
OK - I will my best on the pics. Is it OK, if I get it done tomorrow and we continue tomorrow once you have looked at the new information?
Expert:  Brian HVAC Guy replied 11 months ago.

That's just fine with me! I planned on working tomorrow. Since you have a meter and I will have your diagram, I'm sure we can figure this out. I'll keep an eye out for your posts.

Thanks,

Brian

Customer: replied 11 months ago.
Thank you, ***** ***** will just reply to this thread once I have something for you. Thank you for your patience.
Good night!
Expert:  Brian HVAC Guy replied 11 months ago.

You're welcome George, good night :)

Customer: replied 11 months ago.
Please confirm you got the zip file (~62MB) in good order. Otherwise, I will resend less pics at one time.
-George
Expert:  Brian HVAC Guy replied 11 months ago.

Good afternoon George!

62MB is too large a file to send through the service. You can either send the files one at a time or if you'd like I can propose an Additional Services Offer where we can share our email privately instead of on this the public forum then we can share files back and forth through regular email. It would be an additional $5. It's your choice.

Thanks,

Brian

Customer: replied 11 months ago.
I will try to resend. Did you at least get the message that I sent with the files describing the stat and connections to the module?
If not, I will retype it.
I am sending the diagram only for now. Let's see if this is enough.
-George
Expert:  Brian HVAC Guy replied 11 months ago.

George,

Sorry for the delay, I had to step away for a bit. The only message I've gotten today was the one asking me to confirm I got the zip file and your last two with the diagram and asking if I got a message about describing stat connections (which I didn't get). I will have a look at the diagram in the mean time and it would be helpful to know how the stat connections are at the furnace.

Thanks,

Brian

Expert:  Brian HVAC Guy replied 11 months ago.

Ok, having reviewed the diagram (thanks for that excellent picture!), as long as your thermostat connects at R and W for heat (and Y, G, then a jumper between the two R terminals at the stat if that's how your stat is, for ac), this is how the new control should be wired: (note wire numbers in reference to the diagram)

*105 Old 24v gnd > New 24v gnd (this is also a C terminal connection for thermostat if used)

*112 Old MV > New MV

*111 Old PV > New PV

*115 Old MV/PV > New MV/PV

*Old Spark > New Spark (single point spark and flame sense so leave New Sense link intact)

*114 Old TH-W > New TH-W

*123 Old 24v (or 25v) unused, cap or insulate and abandon in place

*Old GND (burner ground) New GND (Burner) This is a separate ground wire that should go from the control to the pilot burner and to case ground.

*Leave Vent Damper plug open and unused

Let me know how it goes and we'll go from there.

Thanks,

Brian

Customer: replied 11 months ago.
No problem - I am not exactly sitting at the computer all time too :-)
I working on the answer right now.
-George
Customer: replied 11 months ago.
OK, this will cover my missing email information too.
1. Stat is Honeywell RTH2310B and is wired as follows:
Rh and Rc are jumpered together and the red wire is connected to Rh; this wire goes to the transformer W
W is connected to a yellow wire and connected to the transformer R
I have no AC and other stat connections (Y or G) are not connected to anything.
This is the state how the old module worked. The voltage between Rh and W is ~17V.The current new module connections in the order you wrote them:
wire #105 - as stated (no connection from the stat to transfomer C)
*105 Old 24v gnd > New 24v gnd (this is also a C terminal connection for thermostat if used) - CORRECT (no C connection used) (old module marked as 24V(1))*112 Old MV > New MV - CORRECT*111 Old PV > New PV - CORRECT*115 Old MV/PV > New MV/PV - CORRECT*Old Spark > New Spark (single point spark and flame sense so leave New Sense link intact) - CORRECT (black jumper left in place)*114 Old TH-W > New TH-W - CORRECT*123 Old 24v (or 25v) unused, cap or insulate and abandon in place - CORRECT (wire removed) (old module marked as 24V(2))*Old GND (burner ground) New GND (Burner) This is a separate ground wire that should go from the control to the pilot burner and to case ground - CORRECT (wire #121); this wire is plugged into the new module on GND and is connected to the furnace chassis - this is how it was done in the old setup and it worked; I am assuming I don't need to run a special wire to the igniter and pilot bracket as I did not have to in the past.*Leave Vent Damper plug open and unused - - CORRECTI am glad the diagram helps. Please let me know if it'd be better to move off to the direct emails. If you think it is better then just let me know and we will start it that way.
-George
Expert:  Brian HVAC Guy replied 11 months ago.

Ok, the only thing I see that is not quite right (but it shouldn't make any difference) is that the red thermostat wire connected at Rc and Rh (jumper is not necessary since you have no ac) goes to W at the furnace, it would normally go to R. Then the yellow wire connected to W on the thermostat should go to W at the furnace. Since you have no ac, thereby your thermostat control is just simply a two wire system, polarity of these two wires should not matter. Especially since the Honeywell thermostat you have is powered from batteries only.

No, you shouldn't have to run a special wire to the pilot burner since your old system didn't have one. A simple and solid chassis connection should be fine for spark sense (flame current).

The problem I do see is that you say you have ~17 volts ac from "Rh and W". Where and when are you measuring that? When the thermostat is calling for heat you should have 0 vac from Rh to W whether you are measuring it at the thermostat or at the R and W terminals at the furnace. When the thermostat is not calling for heat you should have ~24 vac nominal between them at either spot too (it is usually closer to 26-27 vac). I believe everything is wired right, we just have to figure out what the voltage issue is. There should not be 17vac anywhere in the system at any time!

Expert:  Brian HVAC Guy replied 11 months ago.

And, I don't really think it's necessary to use email. I got the wiring diagram pic fine and if I need another or two it's not a big deal. I think we're gonna have to troubleshoot your system with the volt meter with the system on and calling for heat and see where you drop voltage. Let me know when you're ready for that.

Thanks,

Brian

Customer: replied 11 months ago.
Got it.
I have actually changed the wires at the transformer to flip the polarity but it made no difference. I put it back the old way so not to introduce multiple changes.
I did find the 17V odd as I expected 24V. Let me check one more time with and without the call for heat.
Expert:  Brian HVAC Guy replied 11 months ago.

Here's also a couple voltage probe tests you can do, all taken at the furnace with both the unit on and the thermostat calling for heat.

1) Measure the voltage from R to C at the transformer. Of course you should have ~24vac.

2) Measure the voltage from C to W at the control center (transformer) you should read ~24vac with the heat being called to run by the stat.

3) If test 1 and 2 passed, measure from C to TH-W. You should read ~24vac there too (I'm guessing you're not though)

4) If test 3 failed, measure between points W and TH-W (this measures for any voltage across all the safeties in the circuit) there should be 0vac.

Let me know what you have on those 4 tests and I should be able to tell you where the problem lies.

Customer: replied 11 months ago.
Got it.
I have actually changed the wires at the transformer to flip the polarity but it made no difference. I put it back the old way so not to introduce multiple changes.
I did find the 17V odd as I expected 24V. The way i did it was with the stat off the wall at the cable ends.
However....
Now, I have redone all measurements.
I did not get 17V but 27V at the cable ends (between red R and yellow W).
Other checks:
R => C is 27V - call for heat off
C => W with call for heat is 25V
C => TH-W 0V - call for heat off
C => TH-W 25V - call for heat on
W => TH-W 0V - call for heat off or on
At this point, the spark started to work even though I have not changed anything.
However, I did some light tugging on the stat wire so I am wondering if that one is not suspect and damaged somewhere in the wall. For the moment, the spark works but the pilot will not light.
What is happening is that the spark goes through its cycle, I can hear the gas going and once the 90s are out the spark stops and I can hear the light click of the valve closing.
I have done several cycles and the pilot will not come on.
-George
Expert:  Brian HVAC Guy replied 11 months ago.

Good morning George,

Sorry I missed you last night. Ok your voltage tests all pass and the controller is doing exactly as it should. It would appear the problem is now that the pilot simply isn't lighting. This usually boils down to one of a few issues. Since you hear the gas valve pilot solenoid, that means the control is sending voltage to the valve and should be flowing gas to the pilot burner so these are the things that are typically the issue:

1) Air in the gas system.

2) The spark itself isn't sparking strong enough or in the right spot to ignite the gas and the pilot burner ground or the spark rod must be cleaned and/or adjusted so the spark is strong and in the right position for the gas flow out of the pilot burner orifice.

3) The pilot burner orifice is clogged and is not providing enough gas flow to light and sustain a flame and the orifice needs cleaned. (it's also possible if the pilot burner and orifice where changed that it has the wrong orifice in it)

4) The incoming regulated gas pressure is too low or the gas valve pilot pressure is too low and needs to be adjusted. The incoming gas pressure to the valve should be checked first then the pilot pressure when the pilot valve opens. This has to be done with a manometer or a Magnahelic gauge. It is best left to a gas tech.

5) There is a problem in the gas valve internally.

I should caution you that a gas issue is best left to a gas tech for obvious reasons!

Let me know what you find or decide to do! Let me know if you have further questions on this subject. Otherwise, please remember to rate before leaving (3 stars or higher please!). Bonuses are always appreciated! Thanks for allowing me to help and thanks for using Just Answer!

Thank you,
Brian

Customer: replied 11 months ago.
HI Brian,Thank you for the excellent write up.
I have removed the pilot tube and the igniter assembly. I thought there might have been something obstructing that gas flow that I missed. I have found nothing but I have replaced the orifice with the old one as it was in good shape. I suspected that the new one might have been bad for some reason. Once I put it all back together I got the pilot to light and furnace is running now!
Before I let you go, I have one question. You mentioned that you have found some parts listings for this furnace. COuld you share with me how to get at this information so I can have it if I need to buy any parts in the future? Where could I find this information?
Thank you,
-George
Expert:  Brian HVAC Guy replied 11 months ago.

Good morning George,

That's GREAT news! I'm really glad we were able to get your furnace up and running! Now you can go apply for a tech position at your local dealer :-P

Here are a couple links to things I found during the course of our conversation that should be helpful in the future:

Click Here for a link to a manual for your furnace

Click Here for a link to a great site with parts available for your furnace

Let me know if you have further questions on this subject. Otherwise, please remember to rate before leaving (3 stars or higher please!). Bonuses are always appreciated! Thanks for allowing me to help and thanks for using Just Answer!

Thank you,
Brian

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