Author Topic: Can't get a clean burn  (Read 858 times)

Offline mike117

  • ***
  • Posts: 2
Can't get a clean burn
« on: February 14, 2018, 04:43:44 PM »
Hi everyone I'm new to the forum and been in the trade for roughly 4 years now. I primarily work with natural gas and propane but do on occasion work on oil. I went to a no heat call where the company I work for had installed a roth tank. We do not know when the furnace had been running previously, but the guys who installed the tank said they fired the furnace and it ran for 30 mins before they left. Okay so I go in a couple days later to see whats going on (house is vacant).


furnace is a newmac LFR-2000 running a 0.50 45B nozzle

I had to push the nozzle assemble forward the z setting to get the furnace to fire, as soon as it lit looked through inspection smoke and sparks...coming out the draft regulator. I pulled the vent connector off and took a look to find a 3/4 plugged base of chimney...cleaned that out and used mirror up chimney to see an obstruction, climbed up and took the cap off and top 3 foot section ( manufactured chimney) the inside pipe was some how collapsed. I removed that section and put the cap back on to try and fire the unit again. Put a new nozzle in and fired the unit...smoke test...black adjust air ....smoke test black ....more air or less air still getting a dirty burn . I know its bad idea to use analyzer in a dirty burn but I wanted to get an ex air reading , couldn't even let the reading equal due to rising co levels. I've played with all the settings and the air restrictor plate is installed as per rating plate and nozzle size also have correct pump pressure of 180psig. The unit does remain running but I cannot get a safe and clean burn on the unit.

Any input is much appreciated! Thanks

Offline slo-115

  • 313D Supporter
  • ****
  • Posts: 62
Re: Can't get a clean burn
« Reply #1 on: February 14, 2018, 06:51:57 PM »
Does the system have a tiger loop installed? Sounds like it could be a fuel supply issues. Top draw tanks can have problems with fittings sucking air, but not leaking.
Chamblerless furnaces tend to be more fussy with air settings, some times too much air will cause big problems. Cut the air back. I would suggest setting up the burner to 12co2 4oz 25% excess air.
Are you sure your Z setting is bang on? The AFG can be a real bugger if its off even a little.

Offline slo-115

  • 313D Supporter
  • ****
  • Posts: 62
Re: Can't get a clean burn
« Reply #2 on: February 14, 2018, 06:58:42 PM »
Should also be noted, that .50 nozzles are notorious for partially plugging. The system should have a A130 and spin on. I ve also had many bad .50 nozzles right outta the box.

Offline mike117

  • ***
  • Posts: 2
Re: Can't get a clean burn
« Reply #3 on: February 15, 2018, 06:56:26 PM »
Yes the system does have a tiger loop.

When I get back there Im going to pull the burner and set the z dimension with the beckett gauge.

https://imgur.com/a/Ojtja