View Full Version : .85 or.90 nozzle
Have a 2 year old lowboy Thermopride OL11-belt driven oil heat.. It came with a ,90 nozzle but after having it cleaned last month a .85 80A nozzle was put in since it seems most hvac people do not carry the .90. I wanted the heat to be as warm as possible so want the .90 put in. Question is . Is there much difference between the two? The hvac man said he has it fired up to almost a 90. How much warmer will a 90 be over a .85 and is it worth the aggravation. In Connecticut (East Coast) He also increased fan speed to med hi. Is it bad to have it set so high? Seems to blow better since I have long rooms that are hard to heat?
10-01-2005, 08:56 PM
Should be just a feww degrees differance. I dont think you'll miss it.
10-01-2005, 09:09 PM
The difference between a .85 and a .90 is 7000btu's.
Or, at 1200 cfm, about 4.5°f, temp rise difference.
10-01-2005, 09:59 PM
okay turn up the pump pressure a little bit
10-01-2005, 10:43 PM
The difference of nozzle sizes is meanlingless regarding temperature difference. The fan and limit switch governs when the unit begins to blow warm air and with either nozzle, the furnace will begin to blow when the unit reaches about 150°. Maybe the .85 nozzle will take an extra 1/2 minute to get there as compared to the .90. If it were me, I'd install a .75 gph nozzle and boost pump pressure to about 135 psi for a better, cleaner flame.
10-01-2005, 10:48 PM
I like running fan speed at the lowest setting that will heat the house. Low fan speeds don't create drafts and reduces the fan cycles quite abit too. If you have hot and cold spots in a house for whatever reason, run the fan constant at a very low speed to overcome it. It costs about $1/day to do that, though.
10-01-2005, 11:32 PM
I don't know anything about oil furnaces.
But, I supposes they are the same as other gas furnaces when it comes to needing the proper heat rise. The heat rise is set by the fan speed after the firing rate is set. I would think the firing rate would be set with the nozzle. The heat rise is set by the blower. You can take a temprature reading in the return duct and supply duct. Do not that the temprature reading within a foot of the supply plenum. You could get an appoxament at the return grill and supply register closest to the furnace. You can find you temprature rise on the furnace's data plate. It might be 40 to 70 degrees F. If it is in the range listed on your furnace you are okay.
10-02-2005, 12:31 AM
Originally posted by casturbo
The difference of nozzle sizes is meanlingless regarding temperature difference.
If the nozzle size was meaningless, then we could put .75 nozzles in all furnaces and get the same temp rise at 1200cfm, as a 1.0 gph nozzle.
The fan limit only controls when the fan starts and shuts off, not the temp rise itself.
oil lp man
10-02-2005, 08:41 AM
.85 and .90 is very close. Chances are its overfired for the duct sizes anyways if he had to increase the blower speed. Does the burner cycle on and off before the thermostat is satisfied? If yes, then its cycling off the HIGH limit control anyways. Furnace may be oversized for the house. Most are.
He increased the fan speed so it would just blow better than it was and cool down quicker at the end. I was confused because its not direct drive, but belt driven. I did not realize you could adjust the speed on that to med hi. I have no a/c involved in this unit. Plus i guess if the speeds are there why not utilize them. I have a bedroom at the end of a house with long heat runs on a bottom floor so i guess a faster speed pushed the air better. Got me. seems i can never get good answers from the HVAC men.
10-03-2005, 12:11 PM
Originally posted by bb50
....I was confused because its not direct drive, but belt driven. I did not realize you could adjust the speed on that to med hi.
I think the tech just referred to a higher speed setting as medium high, in actuality there is infinite fan speed adjustment with a belt drive blower. You just adjust the pulley ratio to adjust fan speed. Direct drive units don't have that advantage of course since no belt or pulleys to deal with. With no A/C, a belt drive blower is more desirable actually.
10-03-2005, 10:07 PM
Adjusting the fan speed with a pulley is probally becoming a lost art to the ordinary tech.
I've never done it myself. Although I've seen a couple guys try to adjust the belt tention with the pulley.
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