Burnham V84 Too large?

joea99

Some years ago replaced a smallish weil mclain that seemed to fire forever when heating. Seemed undersized to me, so when a local shop recommended Burnham V84 based on heat loss calculations. I wanted a 3 section, at most, but they sold me on the 4 with "you don't want to get cold in mid winter do you?". Perhaps they had too many in inventory?

Anyway, it has always "short cycled", that is it only fires for maybe 5 or 10 minutes until heat is satisfied. There are 4 zones for hot water baseboard, which may contribute to a "micro load" issue. Rarely do they all call at the same time, if ever, so the "virtual load" is probably more like 80,000 BTU instead of the 110,000 I had calculated.

I've tried downsizing the nozzle to .85 from the rated 1.10 and that seems to have helped but it still heats too quickly. I looked into under firing it a bit more, maybe with a low firing rate baffle, but, don't really find much supporting information. I guess I could try dropping the pressure from the rated 140, down to 100 or 110 and see if it causes startup issues? I do have soot and CO2 instruments.

Is the only solution to replace the boiler, or, tie multiple zones to run at the same time, via some wiring magic?

Jamie Hall

A common enough scenario, sadly...

Downfiring is not just so simple as changing a nozzle, never mind changing the pressure. I can't seem to locate the minimum firing rate for that model, but there is one -- and it would be unwise, at best, to go below it. It may be quoted in your manual.

Use of a buffer tank may allow it to run longer cycles.

STEVEusaPA

Well you made a whole bunch of bad decisions, so you’re stuck with it, although 5-10 minutes isn’t the worse short cycling.
You’re wasting your time trying to downfire it and it will be even more inefficient. If it’s an AFG, you’ll also probably need to change the end cone. Lowering the pump pressure doesn’t help.
Either a buffer tank, or a proper heat loss and a properly sized/piped/controlled/installed boiler will help. Or have the person who sold it to you buy it back and sell you the correct one.
Maybe you can ask the dummy who talked you into going bigger if they will reimburse you of all the money you’re wasting.
If you or anyone ever looked at any thread on this site about sizing, all the professionals will say somewhere in our posts about a proper heat loss.

.

Steamhead

If the aquastat relay is not a HydroStat or AquaSmart, upgrading to one of these will help by managing the cycling better and not letting the boiler ramp all the way up to maximum temperature unless needed.

joea99

STEVEusaPA said:

Well you made a whole bunch of bad decisions, so you’re stuck with it, although 5-10 minutes isn’t the worse short cycling.
You’re wasting your time trying to downfire it and it will be even more inefficient. If it’s an AFG, you’ll also probably need to change the end cone. Lowering the pump pressure doesn’t help.
Either a buffer tank, or a proper heat loss and a properly sized/piped/controlled/installed boiler will help. Or have the person who sold it to you buy it back and sell you the correct one.
Maybe you can ask the dummy who talked you into going bigger if they will reimburse you of all the money you’re wasting.
If you or anyone ever looked at any thread on this site about sizing, all the professionals will say somewhere in our posts about a proper heat loss.

.

It was a "older pro", probably long gone now and the company was bought out. Not much chance of any progress there. Thought about a buffer tank and other controls, but cost to do vs fuel costs saved do not seem to work out.

If I pull this one out I would just go for propane this time I think.

joea99

Steamhead said:

If the aquastat relay is not a HydroStat or AquaSmart, upgrading to one of these will help by managing the cycling better and not letting the boiler ramp all the way up to maximum temperature unless needed.

I'll look into that, but my half asleep brain does not see how that affects the short cycle issue, but could have fuel over all, I guess.

joea99

Jamie Hall said:

A common enough scenario, sadly...

Downfiring is not just so simple as changing a nozzle, never mind changing the pressure. I can't seem to locate the minimum firing rate for that model, but there is one -- and it would be unwise, at best, to go below it. It may be quoted in your manual.

Use of a buffer tank may allow it to run longer cycles.

I think .85 is shown in the Burnham manual, but beckett suggests .75 with a LFR baffle, but the Head is listed as "special" on the burner which the Becket blurb doe not mention. Probably a no go.

Ctoilman

What you have is definitely not bad, and the short cycling is not using a lot more fuel than what you think.  
You didn't say where the domestic hot water is sourced from, if it's a tankless setup then some fuel savings could be had switching to an indirect tank and a setback style aquastat control (3250 Hydrostat comes to mind, it's what I retrofitted on my oversized boiler that came with the house).
The reality is the short cycling is more an annoyance rather than a gross waste of fuel, meaning if short cycling could be greatly reduced (never can be eliminated regardless of heating configuration) what sort of money saving could be had?...20% maybe?....which is about 100 gallons of fuel....which is about $250 per year.  

HVACNUT

joea99 said:

A common enough scenario, sadly... Downfiring is not just so simple as changing a nozzle, never mind changing the pressure. I can't seem to locate the minimum firing rate for that model, but there is one -- and it would be unwise, at best, to go below it. It may be quoted in your manual. Use of a buffer tank may allow it to run longer cycles.

I think .85 is shown in the Burnham manual, but beckett suggests .75 with a LFR baffle, but the Head is listed as "special" on the burner which the Becket blurb doe not mention. Probably a no go.

I don't see where you got a .75 GPH firing rate on a V84. The smallest nozzle spec'd is .85 @ 140 psi, equals 1.01 GPH.

joea99

HVACNUT said:

I think .85 is shown in the Burnham manual, but beckett suggests .75 with a LFR baffle, but the Head is listed as "special" on the burner which the Becket blurb doe not mention. Probably a no go.

I don't see where you got a .75 GPH firing rate on a V84. The smallest nozzle spec'd is .85 @ 140 psi, equals 1.01 GPH.

The .75 is from a Beckett article that speaks to the burner itself. The Burnham documents I have list .85 as minimum for the V84.

Ctoilman

I always wondered if really downfiring a boiler is harmful or counter-productive ASSUMING stack temp was greater than 275 and C02 level was greater than 11 with zero smoke....anyone?

STEVEusaPA

Ctoilman said:

I always wondered if really downfiring a boiler is harmful or counter-productive ASSUMING stack temp was greater than 275 and C02 level was greater than 11 with zero smoke....anyone?

You would need a net stack temperature above 275° to not do damage either to the chimney or create a gooey condensing mess in the boiler itself.
Or think of it another way. Boiler manufacturer's test all their equipment. Wouldn't make sense if they could practically down fire it that low they would offer it up?
My experience is the equipment is most efficient firing it as the manufacturer tested it as best. In a conventional cast iron boiler, down fired, 0 draft OF, and super low stack temperature, people look at the final (fake) efficiency number and think they are doing better without considering damage to the boiler/flue/chimney, and probably longer run times.
Downfiring usually requires not only the low fire baffle on Beckett, but most likely a head change as Beckett recommends firing their burner in the middle of an end cones' range and not at the edges.

The only cure for oversized oil burning equipment is properly sized equipment. After that a buffer tank, and boiler protection. Some controls will help, but not cure the problem

joea99

I see several listings for nozzles for the V84(x). This one is PV84WC-TBWN. No clue how that affects nozzle size, but presume selecting in the specified range and adjusted properly, any are fine.

At some point, someone recommended an 80 degree instead of the spec'd 60 degree. Would that be significant?

CO2, without smoke is always under 10. I have a V74 elsewhere that also is under 10 for CO2.

Robert O'Brien

joea99 said:

I see several listings for nozzles for the V84(x). This one is PV84WC-TBWN. No clue how that affects nozzle size, but presume selecting in the specified range and adjusted properly, any are fine.

At some point, someone recommended an 80 degree instead of the spec'd 60 degree. Would that be significant?

CO2, without smoke is always under 10. I have a V74 elsewhere that also is under 10 for CO2.

Way too much excess air, CO2 should be 11% minimum. True zero smoke, not a trace and single digit CO.

joea99

Robert O'Brien said:

joea99 said:

I see several listings for nozzles for the V84(x). This one is PV84WC-TBWN. No clue how that affects nozzle size, but presume selecting in the specified range and adjusted properly, any are fine.

At some point, someone recommended an 80 degree instead of the spec'd 60 degree. Would that be significant?

CO2, without smoke is always under 10. I have a V74 elsewhere that also is under 10 for CO2.

Way too much excess air, CO2 should be 11% minimum. True zero smoke, not a trace and single digit CO.

Well, maybe I need new fluid? I can get to a trace of smoke and then add just enough air to get zero smoke and that always seems under 10.

Robert O'Brien

https://www.beckettcorp.com/support/tech-bulletins/proper-burner-adjustment/

joea99

Robert O'Brien said:

https://www.beckettcorp.com/support/tech-bulletins/proper-burner-adjustment/

Pretty much what I do.

I will say that the flame does not look "solid" to me but "stringy" that is pretty much solid core (hard to look at) but with "flickering or dancing" fingers at the edges of the flame mass. Especially toward the front of the flame. This is with any nozzle I've used.

That does not seem consistent with my concept of "solid", but is exactly how "pro's" around here say is correct.

EBEBRATT-Ed

@joea99
If you had put propane in what would that have done? You would still be oversized.


This is where you went wrong:

"if ever, so the "virtual load" is probably more like 80,000 BTU instead of the 110,000 I had calculated."

If you start wrong it won't get better.

Put a buffer tank in down fire it slightly. Check with instruments.

Jamie Hall

joea99 said:

Robert O'Brien said:

https://www.beckettcorp.com/support/tech-bulletins/proper-burner-adjustment/

Pretty much what I do.

I will say that the flame does not look "solid" to me but "stringy" that is pretty much solid core (hard to look at) but with "flickering or dancing" fingers at the edges of the flame mass. Especially toward the front of the flame. This is with any nozzle I've used.

That does not seem consistent with my concept of "solid", but is exactly how "pro's" around here say is correct.

As has been said before... there is no way to check correct combustion by eye on these things -- particularly once you start to play with other nozzles or pressures.

You have to do a complete combustion analysis by the numbers, with the instruments.

SuperTech

joea99 said:

https://www.beckettcorp.com/support/tech-bulletins/proper-burner-adjustment/

Pretty much what I do. I will say that the flame does not look "solid" to me but "stringy" that is pretty much solid core (hard to look at) but with "flickering or dancing" fingers at the edges of the flame mass. Especially toward the front of the flame. This is with any nozzle I've used. That does not seem consistent with my concept of "solid", but is exactly how "pro's" around here say is correct.

Real "pro's" don't rely on looking at the flame, we use digital combustion analyzers. No fluids required.  The best oil fired boilers don't have a spot to eyeball the flame. Too much excess air will cause problems during ignition. Best to keep C02 between 11-13% depending on equipment.  Buderus might want 13% CO2, EK wants no more than 10.5% C02 on their boilers.  

joea99

EBEBRATT-Ed said:

@joea99
If you had put propane in what would that have done? You would still be oversized.


This is where you went wrong:

"if ever, so the "virtual load" is probably more like 80,000 BTU instead of the 110,000 I had calculated."

If you start wrong it won't get better.

Put a buffer tank in down fire it slightly. Check with instruments.

If I went with propane, it would be a new unit, properly sized, not influenced by "old school pros".

What buffer tanks are considered "best" of class?

joea99

SuperTech said:

joea99 said:

Robert O'Brien said:

https://www.beckettcorp.com/support/tech-bulletins/proper-burner-adjustment/

Pretty much what I do.

I will say that the flame does not look "solid" to me but "stringy" that is pretty much solid core (hard to look at) but with "flickering or dancing" fingers at the edges of the flame mass. Especially toward the front of the flame. This is with any nozzle I've used.

That does not seem consistent with my concept of "solid", but is exactly how "pro's" around here say is correct.

Real "pro's" don't rely on looking at the flame, we use digital combustion analyzers. No fluids required.  The best oil fired boilers don't have a spot to eyeball the flame. Too much excess air will cause problems during ignition. Best to keep C02 between 11-13% depending on equipment.  Buderus might want 13% CO2, EK wants no more than 10.5% C02 on their boilers.  

I have the old Bacarrach stuff. With the fluid absorption tester and hand pump for smoke and anlog draft meter.

Most of the Beckett writings speak of looking at the flame for shape, for gross problems, as seen through the inspection port. They are clear about needing test gear for proper settings.

I put "pro's"n quotes for a reason. No one I have every called in, around here used anything beyond a pump pressure gauge. Draft the set by adjusting the damper to "see it opens and bounces around, it's good".

So, like most other stuff, I started doing it myself. My mistakes are mostly my own and at least I learn from them. Sometimes.

STEVEusaPA

That magic juice (highly toxic) doesn't last forever. Old fluid won't be accurate. Please dispose of it properly.
I used it starting out, just long enough until I could buy an electronic analyzer. Draft gauge, thermometer are worth keeping.

joea99

EBEBRATT-Ed said:

@joea99
. . .
Put a buffer tank in down fire it slightly. Check with instruments.

From what I have seen, a tank of 100-120 gallons might be needed. The prices of those things, plust ther rework needed, makes a new boiler seem like a simpler and only slightly more costly solution.

EBEBRATT-Ed

@joea99

You calculate the buffer tank based on the size of the smallest zone. You wan't to get a 15-20 min run time on the burner.

Get the water volume of the boiler + the water volume of the smallest zone.

Get the but output of the boiler (about 80% of the input and the btu output of the smallest zone. Some buffer tank MFGs have an on line calculator. 100 gallons seems like to much

EBEBRATT-Ed

@joea99

first step is an accurate heat loss not a guess