OIL USE and Burner setting

Keeping your max temp setting at 200 vs. 185 will certainly use more oil. No question there. But lowering from 200 to 185 shouldn't have made your registers warmer, it should have done the opposite. So not sure what happened there.

Not so sure about the oil pressure thing.

The aquastat setting definitely makes a difference unless you are short on baseboard and need the temperature. If you want to gain more efficiency an outdoor reset controller would vary the aquastat depending on outdoor temp for more efficiency.

The low pump pressure would tend to reduce the atomization of the oil reducing the burner efficiency slightly if it was way off, not sure if you see a benefit

I'm confused here. You're considering more oil usage an improvement? In regards to the pressure being turned up, did they swap out the regular burner nozzle for a smaller one?

You're considering more oil usage an improvement?

Don't think that's what he said. I think he said more oil since the oil company started servicing. Now he's seeing less oil since they aren't. I think.

I've spent way more time tinkering and pondering with my old oil burner than with a wood stove, so I'll offer a few thoughts. It doesn't mean I'm right, but then others can prove me wrong.

The 185 or 200 setting, if I'm remembering correctly, that's your start up temp, where the blower will engage. You know how you kick the t-stat, the furnace hums along, warming the firebox/refractory up, and 3? minutes later, the blower kicks on, and warm air comes out. If the fan doesn't kick on, your furnace will shut itself off as a safety if this temp keeps rising.

I believe if you had left the nozzle at the original 100 psi and lowered the setting to 185, you should have noticed it not quite as warm when it kicks.

Now, with turning the pressure up, and using the same nozzle, you're going to use more fuel. How much? I'm not sure. Usually when they turn up the pressure, they drop the nozzle size down to approximate the same fuel use per hour. The fuel under higher pressure mists better and burns better.

So even if all you did was drop the nozzle size, bumped the pressure, and did nothing else, the fuel in theory should burn better and probably slightly more efficient.

I'll add a thought about short cycling times with my furnace. We had a thermostat where you could set the on/off cycle so to speak. Moving the needle one way would make the furnace tend to kick in sooner, with less temp drop in the home, and would cycle for shorter times.

I found it tended to get dirtier (nozzle/burner assembly) than when the temp drop setting was greater, and the furnace ran longer, but fewer times per hour. Sounds crazy, but I think it used more fuel this way. It spent more time running to heat up the firebox without the blower on. One guys opinion anyways.

I'm also wondering if the service guy didn't swap your nozzle size down. If I bumped my pressure 40 psi with the same nozzle, I'm thinking she would be smoking like an old locomotive!

Is this a boiler, or a hot air furnace?

I think you're worrying about this too much. There are a lot of incompetent and unscrupulous oil techs out there, but one thing that most of them do is badmouth whoever worked on the system last time. You know, if they can convince you the previous guy was a doof, then you'll call them back. Maybe the previous guy was ok, and the new guy is ok. How do you know?

In my own case, I noticed this badmouth habit, and started calling them on it. When one guy was badmouthing the 'previous tech' as incompetent, I pointed out that it was his boss. On anther occasion, the 'previous idiot' was the same guy doing the badmouthing!

The oil pump pressure thing sounds pretty fishy to me. It all comes down to the oil flow rate...gallons per hour, gph. The nozzle is a service item, every tech should change it out every time they're there, they cost like $2. Maybe the previous guy put in a low-pressure nozzle (which needs less psi to get the same gph), and correctly adjusted the pump to match. This is not rocket science....you put in a nozzle, set the pump to match, fire it up and adjust the air until in burns right (hopefully with an instrument, not just eyeballing it). That and scrubbing all the soot off the heat exchanger. If the previous guy had grossly messed up the pressure for the nozzle, it is hard to see how it would have burned right (with the right spray/flame shape).

As for the aquastat, I played with mine for years, finally turned out mine was malfunctioning, and I replaced it myself. They are designed to 'fail safe' and can still cycle and deliver heat even if half the circuits are dead. I don't doubt that it is cycling differently now, but it is very hard to speculate. Generally, burning at a lower gph (your theory) gives better efficiency (and a lot more sooting). But running the boiler at 200°F reduces efficiency. So, if your theory is that it never reached 200°F, or even 185 (based on the hotter radiation now), then your oil consumption should go up, not down. Probably just a few %, BTW, not a lot.

Techs like to adjust for higher boiler temps....it makes for happier customers with faster warmup, better DHW service, less sooting, you name it. Sounds like what your guy did...the problem is all that usually reduces efficiency.

Yeah, I get the burner has a sticker on it. But you are not hiring a tech to dial in what it says on all the stickers, you are hiring a tech to get it to burn and cycle right. Maybe with the nozzle the previous guy was using, the way he set it might have been correct for getting proper operation. There is no way to tell with the nozzle in the trash now. Even if the new tech says it was burning wrong when he showed up, the nozzle might have clogged after the previous tech left, absolving him of incompetence. Nozzle corrode and or clog...its why you have annual service.

If the new nozzle works properly with the 'sticker value', great. If you get a good vibe from the new tech, even better. I learned about this back in the day because all the techs I had were creeps.

200 is too hot to keep a boiler - big waste of heat up the chimney. Shouldn't have to go more than 180.

Do you heat your DHW with this boiler too? Year round?

I agree that I walked my boiler temps down below 185 to get higher efficiency, but in the end the unit started sooting up a lot more, and my DHW got crappy.

Its set to 185 now. And it sounds like it wasn't reaching 200 before.

That is likely costing you large $ in the off-heating season.

When I was heating our DHW with our old oil burner, I turned it down to the 150 range for the non-heating seasons.

Indeed BG, my HPWH is set to 120. But many oil boilers set that low will condense and then soot up. No bueno.

All burner nozzles I've seen are stamped for "flow rate" referenced at 100 psi.

Unless the tech puts a gauge on the pump while running, he's just guessing. Most will simply adjust the pump pressure screw a set number of turns from bottom and then play with the air control to get a pretty flame. Installing a small 0-200 psi gauge on a 2 inch riser nipple ends the mystery for good. I always set pressure close to 100 psi, although there are a few burners which call for higher (as yours may). Be careful to make sure your 0.85 nozzle running at 140 psi isn't over-firing your boiler's firebox.

Your 0.85 nozzle running at 140 psi is delivering about 1.05 gal/hour, or about 147,000 btu/hr input.

As for the Aquastat, 175-195 deg cutoff settings are quite normal. I don't like 200+ deg settings, it's too close to boiling, but I've used that when there just isn't enough baseboard for the heat losses.

CaptSpiff said:

All burner nozzles I've seen are stamped for "flow rate" referenced at 100 psi.

Unless the tech puts a gauge on the pump while running, he's just guessing. Most will simply adjust the pump pressure screw a set number of turns from bottom and then play with the air control to get a pretty flame. Installing a small 0-200 psi gauge on a 2 inch riser nipple ends the mystery for good. I always set pressure close to 100 psi, although there are a few burners which call for higher (as yours may). Be careful to make sure your 0.85 nozzle running at 140 psi isn't over-firing your boiler's firebox.

Your 0.85 nozzle running at 140 psi is delivering about 1.05 gal/hour, or about 147,000 btu/hr input.

As for the Aquastat, 175-195 deg cutoff settings are quite normal. I don't like 200+ deg settings, it's too close to boiling, but I've used that when there just isn't enough baseboard for the heat losses.

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I have been tuning my 3 year old Carrier forced air oil furnace myself for the past 3 years. When I bought the house 3 years ago it was brand new and was tuned like crap. Wrong nozzle, pump pressure way off, air setting, etc.. With a lot of stuff these days if you want it done right do it yourself. Not saying all techs are bad but the majority probably just slap a nozzle and filter in and leave.

All I did was read the installation manual and the Beckett Oil burner guide and tuned it myself.

It takes all of about an hour and I am lucky that my cousin is an HVAC tech and lets me use his Testo combustion analyzer.

I just tuned mine last week and at the factory recommended settings I just had to increase the air just a slight bit after checking it with the analyzer and doing a smoke test.

The big player here is having a combustion analyzer. If I didn't have access to one I would probably just buy one. After a few tune ups it would pay for itself for the peace of mind knowing it was done right. I think the going rate around here is $150+

Here is the printout from when I tuned it last week. 89 percent efficiency according to the printout.

Brian26 said:

I have been tuning my 3 year old Carrier forced air oil furnace myself for the past 3 years. When I bought the house 3 years ago it was brand new and was tuned like crap. Wrong nozzle, pump pressure way off, air setting, etc.. With a lot of stuff these days if you want it done right do it yourself. Not saying all techs are bad but the majority probably just slap a nozzle and filter in and leave.

All I did was read the installation manual and the Beckett Oil burner guide and tuned it myself.

It takes all of about an hour and I am lucky that my cousin is an HVAC tech and lets me use his Testo combustion analyzer.

I just tuned mine last week and at the factory recommended settings I just had to increase the air just a slight bit after checking it with the analyzer and doing a smoke test.

The big player here is having a combustion analyzer. If I didn't have access to one I would probably just buy one. After a few tune ups it would pay for itself for the peace of mind knowing it was done right. I think the going rate around here is $150+

Here is the printout from when I tuned it last week. 89 percent efficiency according to the printout.

View attachment 166942

Click to expand...

I just checked some friends/family furnaces this weekend with my cousins combustion analyzer. I am sure there are some good techs out there but it seems most of them just slap a nozzle in and change a filter. My mothers furnace had a way over sized nozzle and was running really inefficient and was burning heating oil like no tomorrow. She had an overpriced service contract for service/oil delivery and no longer does after what I found...

I've been out of the business for a long time, but I agree that Oil Burner Techs swap "same for same" when they have it on hand. If that nozzle size was not in my stock, I was told to put in one size larger. The argument was "better heat recovery", but I always suspected he meant "we sell more oil".

With all the home efficiency over the past 30 years (insulation, low flow products, etc) I cannot think of a reason not to down size the boiler nozzles in those older units by about 10%. A little longer run time, but most people would likely not notice any real heat reduction. Just make sure you do the complete "tune up" which will adjust the air to match the new fuel flow.

I agree that it is plausible that the previous tech set your unit to be less efficient. That is common practice in the name of 'fewer callbacks' from irate users. Whether that inefficiency was caused by a reduced pressure is impossible to say. As in our prior discussion, the techs do a number of different adjustments, to the oil flow rate (which depends on the oil pressure AND the nozzle used), the air flow rate, the aquastat temps, etc, all of which can impact the efficiency.