Tempstar NUG5050BEA1 no ignition


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Old 02-10-14, 10:34 PM
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Tempstar NUG5050BEA1 no ignition

Here goes, I apologize in advance if I don't have all the info up front, so feel free to ask for more...


1. In which area you live and ambient temperatures you usually experience.
NJ - currently below freezing....
2. House style and construction details.
Split with 4 levels, and luckily 2 zoned (up and down) central heat/AC
3. Make, model and age of equipment related to the problem.
Tempstar model # NUG5050BEA1 was relatively new when we bought the house in 1998.
4. Fuel type.
Natural Gas
5. Water temperature and pressures of boiler systems.
none
6. What type of zoning do you have with your boiler system.
n/a?
7. Thermostat type.
it's a Honeywell electronic one. PSE&G installed them last year as part of a energy efficiency promo. not sure if this is the model # but there is a sticker on the bottom T412066555 with a barcode above it.

So here's the problem - the other day, I noticed it was cold upstairs (where this unit covers). Seems as thought the thermostat was calling for heat, but it was blowing cold. As I've done some troubleshooting and repairs on the other unit downstairs, I first checked the thermostat. I noticed that the CR2032 battery was about 1.3v instead of the 3v it should be. bought a new battery and that seemed to fix it.
great!
then a day later, the same problem occurred, except now, no airflow but I hear the blower fan (is that the correct term?) that always kicks on before the heat came on.
So I went up the attic to check out the situation, and here's what I found:
I have honeywell S8600M module and a honeywell VR8204M smart valve. I tried to do some testing to make sense of this and here's what I found -
With the thermostat on heat and auto fan, set above the current room temp, I get the exhaust fan to come on but NO sign of a pilot ignition (or main for that matter). I don't see a glow of the ignition coil. I tried to check the voltage coming out from the S8600M and found this:
VAC across the 24VAC terminal and 24VAC grd, I get around 26-28 VAC when it is trying to light the pilot, zero after about 90 seconds. But when I check VAC across the PV and PV/MV connectors on the valve during the 90 secs, I only get about 9.3VAC. I didn't bother to check the MV and PV/MV terminals since I figure if there is no pilot confirmation, it's not going to call for the main to ignite.

So my questions are:
1) what should I be reading VAC across the PV and PV/MV terminals when calling for heat?
2) is 26-28VAC norm across the 24VAC and 24VAC grd on the S8600M when calling for heat? (zero when it's not)
3) are there any other tests of voltage I can check to verify if the problem is the S8600M vs the VR8204M smart valve?
4) would a faulty ignition coil/burner be the culprit?
5) how can I check the output of the ignition circuit of the S8600M with a multimeter? am I looking for a certain # of volts, amps or resistance of either the S8600M or the pilot itself?

The S8600M replacement is $150 or so and the smart valve is $230, so I'm hoping I can pinpoint what's going on before just guessing and ordering parts.

Or is it time for a new unit?

I think that's enough to start on, thanks in advance for your help.

Bud
 
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Old 02-11-14, 08:36 PM
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That ignition control does not use a glow coil. It is a spark ignition module. The fact you are only getting 9.3VAC on the PV terminal of the valve isn't good. You should get +/- 24VAC. Try disconnecting the PV wire & running thru an igniton sequence while monitoring the voltage between the PV wire & common. IF you get the full 24VAC, the valve coil is drawing the voltage down.
 
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Old 02-11-14, 10:01 PM
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Grady:
Thanks for the reply.
Just so I understand the suggestion, disconnect the wire from the PV terminal and check the voltage between that wire and the common (PV/MV)? there are only 3 wires on the valve, PV, PV/MV, and MV.
Does it make sense to disconnect all 3 wires and check the voltage back where they originate on the S8600M?
If the voltage coming from the S8600M is 24VAC, then are you suggesting it's the valve that is bad? and if it's still NOT 24VAC, then the S8600M is bad?
Just trying to figure where I should spend the money and replace the proper part to get it back online... it's cold around here!
Thanks again for your help.
Bud
 
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Old 02-12-14, 06:14 PM
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It makes perfect sense to disconnect the wires going from the igniton module to the valve & test at the module. You will want to measure between terminals 2 & 3.
If voltage is coming from the 8600, then you would want to check as I previously stated. I'd hate to see you replace a valve or a control for something as simple as a bad wire or terminal end.

In re-reading your first post, I noticed a mention of the exhaust blower. Have you verified the pressure switch is closing?

BTW: The VR8204 is not part of the Smart valve series. It is a simple gas valve.
 
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Old 02-12-14, 07:56 PM
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Grady:
So in disconnecting the 3 wires going to the valve, and calling for heat again, across 2 & 3 I only get a max of 2.67 VAC. nothing across 1 & 2.
How would I verify the pressure switch is closing? I see a round approx 2 inch device that had 2 blue wires going into it. it also has a short hose that attaches to the exhaust blower. Is that the pressure switch?
What should the voltage read if it closes as it should?
Thanks again.
Bud
 
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Old 02-12-14, 08:23 PM
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That is indeed the pressure switch. Easiest way to check is with continuity. Venter off = switch open Venter on (give it 5-10 seconds) = switch closed.

You can also check for 24v to common on each side of the switch & zero across it, all with the venter running.
 
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Old 02-12-14, 08:55 PM
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Checked it - the blue wire coming out goes to the 24VAC terminal on the S8600M. Yes, it appears to be working, when it activates, I get the 26VAC across the pressure switch and common.

Based on this info, would you agree the S8600M is faulty? it takes the 24VAC in and only puts 2.67VAC max back out to the PV.

I've ordered a replacement, hopefully that's the problem. Should know in a few days. Expecting up to a foot of snow tonight...

Thanks.

Bud
 
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Old 02-12-14, 08:58 PM
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You get 26v across the switch when the venter is running? Each side to common, ok, but across the switch should be zero.
 
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Old 02-12-14, 10:07 PM
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I meant from the leg of the switch to common.
 
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Old 02-13-14, 05:56 AM
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I too believe the 8600 is to blame.
 
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Old 02-20-14, 10:36 PM
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So finally the new ignition module arrived. They sent me a Honeywell S8610U to replace the S8600M.

For anyone else who comes across this problem, I want to mention that it took some troubleshooting to get it up and running again.

I reconnected all the leads/wires to the ignition module, matching the same ones that came off the S8600M. The DIP switches were both set to OFF from the factory, and that matches what the manual reads for replacing a S8600M.

At first I got the same result, exhaust blower would come on, 24+/-VAC would come in from the vaccum switch (and the common wire), but now no voltage out of PV and PV/MV. Not even the LED that should have come on when heat called for, indicating power to the unit, would light up.

Then I re-read the instructions and realized that the blue wire coming from the vaccum switch that was originally on "24V" connector needed to be on the "TH-W" connector. This is interesting because on the S8600M the "TH-W" connector was unused.

Now it worked! exhaust blower came on, ignition lit the pilot, then the main valve opened and we got flame!

The only problem I have now is that the blower motor doesn't come on. I waited almost 2 minutes one time and the high temp sensors left the exhaust blower running and shut the system down.

I've verified my thermostat settings haven't changed and I even swapped them (I have the same thermostats on both units), thinking the original no flame was a thermostat problem after the new ignition circuit was installed.

The odd thing is that if I manually change the "fan" mode from "auto" (where is always is) to "ON", the blower comes on (and off if I change it back). But why doesn't it come on as part of the call for heat cycle?

The blower was never an issue before this. Any suggestions?

Thanks again for your help.

Bud
 
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Old 02-21-14, 08:41 PM
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You either have a fan motor problem or one with the fan control.
It is possible for the fan to run when the fan switch on the stat is set to "on" but not work when in "auto" & still have a bad motor. With the stat switch set to fan "on" the fan usually runs in the cooling speed instead of the heating speed. The heating speed (usually low or med. low) could be bad yet the cooling speed be ok.

To check, switch the heating speed & cooling speed fan wires on the circuit board & try again. If the fan now works in auto, you have a bad motor. If not, it's likely the board.
 
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Old 03-02-14, 05:03 PM
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So I took a chance and ordered the fan control module, which was a FTC5-EH01. Sure enough, when we swapped it out, things are operating as before. So with your help, and $155 for the ignition module, $115 for the fan control module, we were able to save a ton of dough doing it ourselves.
Thanks again for your help!
Bud
 
 

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