Furnace Ignitor Not Working on Generator

[Denwood]

I have attempted to tune our generator frequency and voltage to get our high efficiency Lennox to fire. No go. I used a Fluke analyzer to get the generator very, very close to 60Hz, and 120V via adjustments to the governor and voltage regulator.

It runs 100% fine now using an inexpensive inverter/generator. With modern electronics/controls everywhere, it's the only way to go these days IMHO.

 

[wyliesdiesels]

Are you sure there is something wrong with the generator? If his generator is NOT bonded, then neutral is floating.

So when the measures from Hot to Ground he gets 60V.
Neutral to Ground also 60V.

If he bonds Neutral to ground - 120V from hot to neutral. And I suspect zero from neutral to ground.

maybe thats a design thing with those generators but ive never seen a generator to be wired like that plus it would make it interesting when used to power a house where the neutral needs to be floating at the generator.

 

[dave*99]

maybe thats a design thing with those generators but ive never seen a generator to be wired like that plus it would make it interesting when used to power a house where the neutral needs to be floating at the generator.

That generator’s output is floating. Think of it as the 120V secondary of an isolation transformer. If nothing was connected to the secondary, due to capacitive coupling to the frame of the transformer, you would measure 60V from each leg to frame.

Same with his generator and it’s frame. In the generator, the 2 output legs are connected to a receptacle whose terminals we name phase and neutral
And ground. Only after we bond the neutral to ground will we see zero between neutral and ground.

 

[wyliesdiesels]

That generator’s output is floating. Think of it as the 120V secondary of an isolation transformer. If nothing was connected to the secondary, due to capacitive coupling to the frame of the transformer, you would measure 60V from each leg to frame.

Same with his generator and it’s frame. In the generator, the 2 output legs are connected to a receptacle whose terminals we name phase and neutral
And ground. Only after we bond the neutral to ground will we see zero between neutral and ground.

maybe i misread his post

i thought he said he was getting 60v between hot and neutral and 60v hot to grnd and neutral to grnd

 

[amh]

A possible experiment: If you have an old 1000W or more UPS (Uninterruptible Power Supply used for PC backup etc). You may try that instead of the generator to drive the furnace, if it cycles your furnace igniter ok then consider putting it between generator supplied power and furnace.

A good UPS regenerates the load side AC and uses the line side AC and/or internal DC Battery to do so (the DC battery charger tends to be quite robust to AC line variation).

Just note that usually UPS boxes have several AC outlets in the back, some are backed up and some are just passthrough (just a power strip), make sure you use the backup outlets.

 

[rlitman]

A possible experiment: If you have an old 1000W or more UPS (Uninterruptible Power Supply used for PC backup etc). You may try that instead of the generator to drive the furnace, if it cycles your furnace igniter ok then consider putting it between generator supplied power and furnace.

A good UPS regenerates the load side AC and uses the line side AC and/or internal DC Battery to do so (the DC battery charger tends to be quite robust to AC line variation).

Just note that usually UPS boxes have several AC outlets in the back, some are backed up and some are just passthrough (just a power strip), make sure you use the backup outlets.

There are VERY few double conversion UPS models out there that are in the 1000W range. I have a couple from Eaton, but they're rare as hen's teeth. APC has never made one, and neither has TrippLite FYI, so don't expect to see this mythical beast on store shelves anywhere.

 

[Denwood]

Speaking from experience, a UPS on generator will turn itself on/off constantly until exhausted. Just use an inverter/generator and the furnace issue is fixed.

 

[rlitman]

Speaking from experience, a UPS on generator will turn itself on/off constantly until exhausted. Just use an inverter/generator and the furnace issue is fixed.

There is that issue. If your generator output is creating enough harmonic distortion to stop your igniter from working, the hypothetical double conversion UPS will also likely switch to battery, even if it is "line interactive". The simple fact is that desktop UPS units, even double conversion ones, are not designed to fix utility power quality issues, just ride them out on battery.

 

[wyliesdiesels]

There are VERY few double conversion UPS models out there that are in the 1000W range. I have a couple from Eaton, but they're rare as hen's teeth. APC has never made one, and neither has TrippLite FYI, so don't expect to see this mythical beast on store shelves anywhere.

Eaton UPSs are awesome. I have a 5px w/ an EBM.

Their battery charging tech is a lot better than APCs and any of the other brands, actually.

they have a fan that runs constantly (slow speed when battery fully charged; high speed when running on battery and when charge is below 90%) that helps to keep the battery at a constant temp. The charger does a float charge when the battery gets over 90%, so that the battery doesnt get cooked.

The fan in APC units only runs when its on battery. So if its running on utility power and the battery is charging its gets hot since there is no forced airflow running over it.

 

[rlitman]

Eaton UPSs are awesome. I have a 5px w/ an EBM.

Their battery charging tech is a lot better than APCs and any of the other brands, actually.

they have a fan that runs constantly (slow speed when battery fully charged; high speed when running on battery and when charge is below 90%) that helps to keep the battery at a constant temp. The charger does a float charge when the battery gets over 90%, so that the battery doesnt get cooked.

The fan in APC units only runs when its on battery. So if its running on utility power and the battery is charging its gets hot since there is no forced airflow running over it.

Interesting. I'm intimately familiar with Eaton's bigger stuff (room sized), but have only limited experience with their tabletop sized equipment, but the 5PX looks really nice, and everything I've seen from them has been tip top.

Heat is the #1 killer of batteries, and active airflow can help a lot. Still, I've also seen APC Symmetra (their mini-fridge sized double conversion) units experience thermal runaway, even though they have fan cooled battery spaces.