Power Conditioners

Mangas

New to this interesting site. 

Have a large remote off grid photovoltaic system (four 5500W True Sine Wave Inverters, large field array, 68 batteries etc.). 

But, had to install two EMI Power Conditioners to enable cycling of our two 2.5 ton furnaces hot surface ignitors.  Everything on the ranch and in the ranch house is powered by the solar system but the furnaces gave us trouble.  Is this unusual?

mike95490

Re: Power Conditioners

Do you know what is so unique about the ignitors that requires the conditioner ? Perhaps, just a simple isolation transformer could have cleaned up the noise and have done the trick. Anybody look at your 120V waveform with a o'scope, and see if it's really clean, or maybe as the inverters are stacked, there is glitching going on that drives the ignitors nuts.
AFIK, the Hot Surface ingitor, has a couple of simple circuits, one is a heater, to heat the element, and then after sequencing a heat up time, it fires the pilot burner. Then it monitors the heater, to check it's resistance against cold, and if the pilot burner (way bigger than a pilot light in a thermopile furnace) keeps the heater element above the threshold resistance, it then sequences the main burners. While the circuts are simple (in every gas clothes dryer since the 70's) they are measuring in the miliohm to just a couple of ohms. Line noise or distortion will likely mess them up. Supposedly, the modern inverters are very clean, so maybe noise is coming from something else. "The Grid" has lots of transformers in the distribution system, and maybe the ingnitors need some interaction with an iron core ??

Mangas

Re: Power Conditioners

Thanks Mike. Yes, the HVAC Mfg Tech claimed it was line noise confusing the hot surface ignitor circuit and board. Techs said the furnace electronics were very sensitive in this brand.

But, the two Power Conditioners appear to have cleaned up the ignitior circuitry as the furnaces are cycling, so far. They just plugged the conditoners into the 110V outlet and the furnace random lockouts stopped. Curious though tat the other Hot Surface Ignitors (Stove, Gas Fireplace, Dryer, etc) worked from the get go.

Didn't do the scope yet since everything in the house seems to run fine except the furnaces. Grid Power may be messy compared to inverter output. Does the inverter vs grid wave steps have something to with this too? I'm certainly no engineer.

BB.

Re: Power Conditioners

It is also possible that there are grounding issues too... I have a stove with spark ignite (sparks until flame is detected, sparks again if flame is blown out) for the burners that would work very erratically if the hot and neutral wires where switched in the wall plug.

I also had a brand new drier that the hot surface igniter would only light the gas flame 1/2 of the time (I am on utility power--even before I installed my Grid Tied solar system). Repair guy replaced everything but the sheet metal for the burner assembly--and it still failed. New drier replacement works just fine.

It is hard to tell from here--all depends on how the electronics for the furnace were designed. It is possible that you have more noise on the inverters (whether because it is not a perfect sine wave or just because as other loads are switched on and off that current/voltage fluctuation caused problems) and utility power would have been more stable.

In the end, it is probably that the circuit was designed "just good enough" and your installation (using inverters) just pushes to its limits.

-Bill

Mangas

Re: Power Conditioners

House Voltage and Grounding checked several times. They're fine.

It's the stacked true sine wave inverters line noise and furnace electronics sensitivity which apparantly was are very unforgiving.

Mangas

Re: Power Conditioners

With the Power Conditioners installed still had problems.

After months of trying to figure out why the furnaces failed to start and or cycle properly, inverter manufacturer suggested electricians install a Motor Run Capacitor on each furnace motor.  They immediately began to run, cycling normally.  We'll see how they do long term but this looks like the fix after all. 

Now, I am wondering if I should disconnect the Power Conditioners since it looks as if the Motor Run Capacitors were the fix all along?

Brock

Re: Power Conditioners

That makes more sense to me. The motor starting probably dipped the voltage enough to have the control circuit drop out thinking it was a brown out or some other bad grid situation. I would take the conditioners out of there.

On the other hand you could leave them in line for now and remove them once you’re sure the problem is fixed.

How are the 4 inverters wired? 2 pair stacked and parallel or all 4 in parallel with a balancing transformer? I am assuming SW5548's? I am asking because if your using a transformer anyway it should even out the output already, unless it all on the same side?

Mangas

Re: Power Conditioners

After months, yea it looks like the capacitors fixed the two vaiable speed furnaces.  You're rught about the motor too.  Interesting how much havoc a little minor induction can cause the ignitor circuitry and mother board cycle controllers.  Xantrex figured it out and recommended the GE part which is easy to get and costs only $30 each!

I agree with you, we're going to leave the conditioners hooked up this week but the consensus is we didn't need them in the first place. 

After installing the capacitors, I checked the battery voltages early this morning at sun up after both zones had cycled normally all night.  Both battery banks were still coming in at over 51 volts.  That explains why I was getting only 46 to 47 volts before i.e the furnaces were locking out and trying the restart cycle all through the night continuously running the air handler blower.  Also. during the day I am now finishing up at between 54V and 56V systemwide which is terrific and within the planning specs for our two stage central A/C zoned units.  Again what havoc that furnace problem caused the system.

The four Sine Wave Plus 5500W inverters are stacked in pairs and parallel with the AC going through two 100 Amp service panels (each zone wired to a different AC service panel for redundancy purposes.  With the fix, I am amazed at how much the system is now generating with the 40 185 W panels.