Which ignition type is better and why? HSI, DSI or Intermittent?

HP80

Knowing that each manufacturer gives the HSI manufacturer their spec for percentage of iron content which can directly effect the life of the ignitor. Also understanding that Intermittent Spark attracts carbon (which is produced by the use of dryer sheets and coats the flame sensors) and alot of us try to resurface with our carbon based sand cloth instead of steel wool.
Please tell me your experiences.

Unknown

Each one has its particular problems....

I have been looking at ignition systems on gas equipment for over 40 years now and have come to the conclusion we should have stayed with thermocouples. I am sure that will rattle a few cages. My philosophy is keep it simple. Having said that let me try to answer this complex question.

Initially when the energy crunch began to mandate shutting of pilots intermittent spark ignition and direct spark ignition came to the forefront.Hot surface ignition was available (gas ranges and dryers) but was not immediately used on heating.

Intermittent spark ignition gives the OEM the good choice of first lighting a pilot before bringing the main burner on, this is a much safer approach. The flame response time could be reduced also for a safer if not sometimes troublesome approach to ignition. With it came the need to superimpose voltage for rectification, grounding, erratic operation due to electrical interference, failure of the spark to light the gas due to poor gas air mix or spark rod out of posistion. The modules added cost to the mix and then there were so many of them. The trades people initially did not like them (if you do not understand something it must be bad). There was very little training to help trades people to understand microamps and how to measure. The training goes on today and many still do not understand how to properly diagnose. The "Kanthal" steel used in many flame rods, or in the case of Honeywell combination spark/flame rod is very durable and inexpensive. With pilots it was a problem because it had to be ceramically bonded to the metal pilot requiring a complete change of the pilot if the flame rod or spark rod was damaged or needed replaced. I prefer the used of a soft clean emory cloth to using steel wool, I have had jobs where I found a piece of steel wool stuck to the rod causing it to short out. I actually use a jewlers burnishing tool myself. I have found that intermittent spark has had less problems than direct spark and definitely HSI.

Direct Spark was from the beginning a problem due to trying to light the full main burner flow of gas with a small spark. Many nuisance lockouts occured, especially on those systems with one try for ignition. It was a little more successful on gas power conversion burners but even they had their problems. I prefer a seperate spark rod and remote flame sense rod used at the last burner to light for better and safer reliability. With the development of "soft lockout" many of those one try problems have been solved but direct spark would be my least likely choice for igition. It does work pretty well on "Infrared Heaters" however.

Hot Surface Ignition using "Silicon Carbide" has had its problems. It is fragile and often breaks when being removed or installed. It does not like voltages above 125 volts AC. It is subject to contamination from fiberglass, drywall dust, moisture and every other thing that is typically in every home. Due to the frequency of cycles on heating its life is shortened. Dryers and ovens last longer due to less cycling. I find in open atmospheric type burner applications it does not a good rectification sensor make. It works better in sealed combustion chamber applications that use outside air for combustion. I have often added a seperate remote flame sensor to overcome nuisance lockout or erratic operation. The new "Silicon Nitride" so far seems to be a more durable and reliable alternative, time will tell as it has not been around that long.

I could go on here forever with all of the particular problems and alternatives that have arisen to solve what initially was an energy concern. I wonder how much is really being saved (in actual dollars) when the utilities have raised gas prices out of site and yet can still give away boilers and sponsor large trade shows,pay big bonuses to executives etc. somebody is paying.

Robert O'Connor_4

Timmie

Have a great vacation!!

I will you miss your most informed posting here on The Wall while you are gone.

All the best,

Robert

Mike T., Swampeast MO

The \"easy\" out

will always be the first route when requirements are vague.

It doesn't matter if the easy way doesn't address the true problem and itself results in problems worse than the "cure" as the numbers can be contrived to show a reduction that doesn't really exist except in the ASHRAE labs.

But let manufacturers of two-stage air furnaces complain that ASHRAE AFUE numbers don't reflect their product in the best possible light and you get something calling a STAGED furnace "modulating" that seems to only further penalize properly sized and TRULY modulating boilers. Oh, by the way, throw in an EXTRA "post purge" penalty for those nasty boilers while you're at it...

Arthur

Ignition systems

Tim,
I have to agree with you that there is no perfect sytem. Just like there is no perfect man, But with these fancy electronic system like on lennox furnaces which cost an arm and 2legs for a new board or fan (well they do over here)when they go down. I wonder if the so called saving in pilot gas is really that much of a saving.
As they say KISS (keep it simple stupid)But then they wouldn't be able to get the hi efficencies if they didn't use these systems. But then there is the higher maintenace requirements. Like combustion fans which go U/S.I find 95% of the callouts to Lennoxs are either Fans or Electronic boards.And what makes it worse is everyone is different part no to the last one.
The old thermocouple/thermopile/24v system were simple easy to fix on the spot without waiting for parts to arrive. but then lower efficencies.
Seems you can't win any way. LOL.

HP80

Please I have many customers that believe that HSI is a very weak link so if you can help please do!