Dayton LP unit heater burner problem?

knickNovember 18, 2008

Hi Everyone

I just installed a new (bought from a liquidator not sure how long its been sitting around) Dayton 200,000 BTU LP unit heater w/standing pilot. The unit does not seem to light well each time and I dont see much of any pattern.

It has a 8" B-vent that comes out of the heater about 12" into a Tee and straight up through the roof. It sticks up through the roof about 24" on the high side (of the roof). Total length of vent is about 5'.

Gas pressure was set by propane company @ 11 psi where it enters the building, when the unit is running it shows about 10.5 @ the inlet of the gas valve. burner side of gas valve shows about 9.5-9.75 with unit running. It calls for 10. Propane guy tried to adjust pressure up @ gas valve but it would not change no matter how much you moved adj screw.

This problem has been there since the first lighting.

Come in first thing about 55 degrees inside and turn up stat.

Now when it lights some times the flame will pop back, some times worse then others. This has 8 burner tubes and most of the time 4-6 of those tubes will have the flame burning above the tube slightly and noisy ( no nice blue tips like when there burning good).

Some times only 3 tubes may act up, some times 1 tube, but most of the time some of the burners act funny. I Let it run a couple of mins, then turn down stat and let it shut off it may start fine with no problem. Yesterday unit was off and cold, turned up heat and flame popped back pretty good, and maybe 6 - 7 burners were noisy and flame was lifting per say. I shut it down after maybe 2 mins and restarted and no pop back and all burners were fine. Now Im thinking the flame pop back may be causing the burner problem.

One odd thing I did noticed was that when unit is running pilot gets big,yellow and lazy (floaty), once it shuts off it goes back to normal size with nice blue flame.

kind of made me think some problem with gas valve since we cant seem to adjust it.

Owners manual lists

to much primary air, I checked that(I re-adjusted and I ended up right back where it started as per book)

or orifice to small (did not check that) Any ideas where to start with this? there was nothing else during install that looked out of the ordinary.

Thanks for your time

hope this all makes sense

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zl700

First, it doesn't matter where in the US you are; someone started teaching the LP techs to set the maximum inlet pressure to a building at 11" WC. Just look at most gas valves and may have stamped right on it that the pressure drop through valve is 1-1.5" WC. Coupled with piping loss, 9X out of ten, you won't see or get 10" WC on the manifold side. So if they agree that that the manufacturers want 10" at burners, what code do they follow that they wonÂt give you enough inlet pressure to accomplish this? Add some additional appliances with marginal piping that is common, especially by the LP supplier if they installed, and you will have this problem which results in low manifold pressure causing, lazy flame, delayed ignition, sooting, burner resonance, pop back at orifices and so on.

One additional problem is the size and amount of gas line before the appliance. The gas needs a chance to atomize and expand for best performance. Many times installing oversized pipe or a larger pipe chamber before or even after the appliance helps. This offers a storage that allows the regulator to catch up. Depending on whether you have a single regulator or a dual, (one on tank second on house) that plays apart and capacities are affected. If you have a single regulator on a smaller tank feeding this fairly large heater, that could be the problem. Add that when it gets colder the bonnet of the tank through the single regulator canÂt process the liquid into a vapor fast enough.

The regulator size, tank size, distance & capacity, piping and pressure settings need to be confirmed as proper. There is nothing wrong with supplying the appliance with 13" WC, gas valves are not harmed until over 25" regardless of what someone may tell you.

    Bookmark   November 18, 2008 at 9:17AM
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knick

Hi ZL
The day the lp was installed it was 60 degrees out.
I think the tank is 475 gallons about 50 feet from the building. I think he said there was a regulator on the tank and at the building. The gas pipe to the unit is 3/4" about 50'-60' long.

He was connected to unit while it was running and watching as I increased the reg on the back of the building and we could not get over 9.5 psi. This is the only appliance that we have on LP (its a pole barn)
I guess I will have to verify the pressures myself.
is .5 off enough to make it act up? Also I forgot to mention a few times I have heard a fairly high resonance
at the same time this is happening. I thought that may be from to high of pressure but maybe not. Im going down there today I will see how it acts.

Thanks for you time
Knick

    Bookmark   November 18, 2008 at 12:07PM
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zl700

High pressure to the house with a secondary regulator is the way to go.

I guessed on the resonance which happens. Some people when the appiance is in the basement describe it as the 5 am train.
Resonance and burning at orifices is usually a sign of under pressure. Once pressure is adjusted correctly the fine tuning is done with air shutters sometimes but as a last resort as it affects clean burn.

Thats a full port gas cock everywhere on the piping, piping was reamed if iron, right?

    Bookmark   November 18, 2008 at 2:05PM
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knick

Hi ZL

I did use a gas cock and I take it its a full port, all pipe was reamed when threaded. Whats your take on not being able to adjust the gas pressure at the gas valve above 9.5"
I tried the unit yesterday and it fired up fine no pop back and all burners were smooth and quiet and it was about 30 degrees. I am going to keep a eye on it and see what it does and if I have problems I am going to start with getting pressure at 10" with unit running. I will keep you posted as to what I find. Thanks again for your time.

Knick

    Bookmark   November 19, 2008 at 9:06AM
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zl700

With 60' of black iron pipe and a normal amount of fittings, the pressure drop is almost 3/4", fired at 200MBTUH, add multiple valves, extra 90's and it gets worse. Perhaps 1" pipe should have been used so that the drop would barely be measurable

That being said, losing 1/2-3/4" for piping, 1-1.5 on gas valve, you have no chance of getting 10" on the manifold side with an 11" supply.

Ask for more, perhaps a different regulator?

    Bookmark   November 19, 2008 at 9:35AM
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knick

Hi ZL

I have been keeping a eye on it. This unit is at a storage building and has not been cold enough inside to turn on by it self as we keep the stat @ 40. So I have been turning it up when I go there. It some times lights fine no pop back and flame nice and smooth. other timers pops back and all but maybe 1 burner acting up. Let it run for 30-60 secs and shut it off and restart and it may be fine or it may be better as in a 1-3 burners acting up. I have not been able to come up with a Manometer to do my checking. As soon as I find something out on pressures I will post my findings. thanks again for your time!

    Bookmark   November 23, 2008 at 7:55AM
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kalining

Are you sure your regulator vents aren't plugged ?. Was your heater pulled apart and all burners, ribbon lighter, and flue chamber cleaned before your install ? You never know what could be inside plugging small holes. Spiders love to hide in small places. If this thing has been sitting more that a few months it could be plugged with god
knows what.

    Bookmark   November 24, 2008 at 11:13AM
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ekgordon_charter_net

I don't check mt mail daily. I often deal with problems like this. call Eddie 707-224-8686 & I may can give you some info. I need the BTU inlet, size fuel line & exact distance.

    Bookmark   February 3, 2011 at 7:28AM
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