Trane vapor system tuning

alcraig

I'm looking to add insulation to the rest of the piping on my Trane vapor system, and I was wondering if I needed to also insulate the dry returns (or wet ones for that matter).

As I understand it, there should be no steam in them, so I wasn't sure if insulating them was necessary.



Once I finish insulating, will I need to downfire the burner since it's running fairly well with lots of piping uncovered?

If that's the case, what is the goal for proper firing (in other words, not over or underfiring) for a vapor system? What cycle times should I aim for?

Currently, the burner fires up for 5-8 minutes and stays off for 10-20 min (mid-day reading).

And since the cycling was a result of the thermostat reaching temp rather than pressure cut-out/in...is that okay? or should I have the Pressuretrol changed out for a Vaporstat to get more cut-ins & outs?



Thanks for any help.

Al

jpf321

from an efficiency standpoint..

it makes sense to insulate the returns since the water is headed back to the boiler to be turned back into steam .. the cooler the water gets in the returns, the more the boiler needs to work to get it back to steam. i'm not sure if a 10 Fahr or 30Fahr drop really matters in the grand latent heat scheme of things .. but it would make sense to get the water back to the boiler as hot as possible.

Jamie Hall

Thermostat vs. Vaporstat

If the cycling is on the thermostat, no need to change anything -- although you might want to experiment with 1 cycle per hour if you are set for more than that.  There the question is: does the house maintain a reasonably even temperature?  Not too much overshoot when the system's on, and not too much droop between firings?  If it does, leave it alone...



You may find you need to down fire a bit to compensate for the insulation, although the main effect of the insulation will be to reduce the time for the heat to get to the radiators -- and if the thermostat is working right, that will just shorten the overall on time.



The pressuretrol will only come into play on very long runs, like recovering from a deep setback or something.  Then it will cycle on pressure, but that's normal.



Myself I wouldn't bother with insulating the wet returns at all.  And to be honest, I've never insulated dry returns, either -- but as jpf says, if you like it won't hurt anything.

alcraig

good feedback

Thanks for all the good feedback I gotten.



I'm happy to hear it's normal to cycle via thermostat rather than

pressure. From my Wall reading, I've gotten the impression that it

should be the other way around. My house temp is normal and even, so

I'll see what insulating does to my cycles/hour.



Another question I had was how does one check boiler efficiency. I have

a plate on my HB Smith that shows a GHP of 3.15 and an I=B=R Net rating

of 255,000...so I figure that it's Gross rating should be 339,150 BTUs

(Net*1.33), which means 339,150/441,000=76.9%. Is that the correct way

to calculate the efficiency of a boiler? I'd like to know if a new

boiler would save me a lot or a little.



Just as a comparison, I looked up a Slantfin Intrepid TR-70...it has an

input of 3.10gph (434,000btus) and a gross rating of 354,000BTUs. If

that's the way it's figured, that makes this unit 81.6% efficient, true?



Any comments from readers regarding my boiler would be appreciated (ie,

what you think it's age is, how long it should last, and whether you

would recommend replacing it for efficiency reasons).



Happy New Year!

Jamie Hall

Based on nameplate ratings

You are very much on the right track as to efficiency.  However, keep in mind that those are theoretical figures -- and, as the EPA says, your mileage may vary!  It depends very much on how well the folks who adjusted the particular burner did.  But the comparison you are using is a reasonable comparison, at least.

Steamhead

The Mills boiler

was one of the best in its day. Due to its high mass it can't quite equal a modern boiler, but it's better than a lot of the older ones out there now. Whoever specified a Trane Vapor system with a Mills boiler was really going first-class.



Given the age of the boiler, keep in mind that the firing rates on the plate were likely assuming a typical old-style burner, which was less efficient than your Carlin. It is customary to drop the firing rate 20% or so when retrofitting a flame-retention burner to an older boiler, since the new burner produces more heat from the oil. So the original firing rate of 3.15 GPH would go down to 2.52 GPH and you'd still get the same amount of heat. BTW, which Carlin is that- the 201CRD?

alcraig

since that photo...

I've switched over to gas, and installed a Heatwise SU-4. It's purring like a kitten. I love this burner. The old Carlin was working well, but since I never dealt with oil before buying my house recently, I was bothered by the inconveniences of delivery, price fluctuation and a heck of a lot of soot.

The SU-4 can downfire as low as 199,000Btus. Given my ERD of 766sqft +pickup, I figure I need around 250,000Btus.

Can I set the firing rate for 250,000Btus since that includes my pickup factor, or do I still need to calcuate the boiler's Gross (Net rating X 1.33) and then reduce by 20%?



PS. My house was built in 1936, but I didn't think my Mills boiler was that old. To my eye, it doesn't look a day over 30. Do you really think it's 74 years old?

Mark N

Firing Rate

I think you also have to take into account the boilers loss up the chimney and out the boiler jacket.



Mark

Steamhead

Don't want to go too low

The SU is also a flame-retention burner- a very nice one. But I wouldn't want to set the firing rate too low since that can cause slow steaming and flue gas condensation, the latter occurring at a slightly higher flue gas temp on gas than on oil. No such adjustments should be made AT ALL without a digital combustion analyzer and a pro who knows how to use it.



With that said:



The input with an older gas burner was 448 MBH. 80% of that figure is 358.4. This would allow for flame-retention's better efficiency, OR, would probably be an acceptable down-firing if the original gas input was actually based on a flame-retention unit. Regardless, the stack tamp should not go below 350° F.



See how if does when down-fired to this level.



The Mills boiler dates back to the late 1800s, so it might have been original to the house. Not sure when they quit making them in that size, so it also could have been newer. The Carlin looks like a retrofit, from the type of flange they used to mount it. And BTW, a properly-installed and properly-tuned flame-retention oil burner will not produce soot.

alcraig

I checked the Carlin

The Carlin was a 150FRD-1A.



I'm not sure what you meant by this comment:

"OR, would probably be an acceptable down-firing if the original gas input was actually based on a flame-retention unit. "

Do you mean this boiler could have been designed/built in the 60's when flame-retention burners were introduced? And if so, the implication is that I won't be able to downfire by 20%?



I understand the need to test the various firing rates with a pro w/ a combustion analyzer. I just want to know the info beforehand since not all techs are created equal.



Assuming a stack temp above 350F, will setting my firing rate lower until I get a 1 cycle/hour (as Jamie suggests) the key (with a hot system)?



Thanks.

Steamhead

The Mills 200/2000 series

appears in the Beacon reference in the Library of this site, both before and after 1959. So it might be older or newer, but regardless, it was one of the best in its time. It might be possible to call Smith and see if they have a record of the serial number. Also, if there are unions in the steam pipes leaving the boiler, it was probably a replacement for an older boiler that failed.



Flame-retention burners came out around 1970, and I believe Carlin was one of the first to offer them. The 150FRD was an early high-speed flame-retention model (the FRD means Flame Retention, Double-speed {which means it has a 3450-RPM motor instead of a 1725-RPM one}), which has been superseded by the CRD (Controlled Retention, Double-speed) series. Prior to this, the "Shellhead" was the burner of choice- it was better than the original type of burner but not as efficient as a flame-retention model. Each successive design has reduced the amount of excess air needed for good clean combustion.



It helps to know what type of burner was used originally, that way we have some idea of what we can do with a modern one. But the combustion test is the final determining factor.



Can we get you down to 1 CPH? Not sure at this point. I sure wish you lived around Baltimore- this is a challenge I'd like to take up.

alcraig

I'm in NY

From all my reading of your past posts on the Wall, I know you're a real expert on Mills boilers and Trane vapor systems. Too bad I'm not near you.



After you mentioned the Beacon Boiler Reference books, I looked up and found that the ratings for the HB Smith 200/2000 boilers were quite a bit lower on the pre-1959 units. My boiler matches the 1959-1972 series ratings exactly. Thanks for the clue.

alcraig

more on Mills boiler...

Upon inspecting the firing chamber on my boiler, I noticed it has a back wall lining (target wall) and it's crumbling a bit. I'd like some advice on what's the best course of action for replacement or removal (assuming a pro will be called to do the work, of course).

Is a target wall on the back of this boiler:

1) necessary with the higher temperatures of a flame-retention burner

2) optional,

or

3) not necessary, since the original assembly/installation manual for the HB Smith Mills 200L boiler only called for a floor insulation & refractory pellets.



I spoke with an HB Smith engineer and he said that it was probably added by the contractor, but it wasn't specified to be installed with this model boiler. Since this is a dry based boiler, I thought a target wall must be used. He didn't suggest it (nor did he disapproved of it). Without a clear answer, I'd like some feedback from those with experience. Will it improve efficiency (ie, lower stack temp) or lower efficiency (ie, less heat transfer)?



TIA,

Al

Steamhead

On a dry-base boiler

any metal surface in the firing zone that does not have water on the other side needs refractory on it. Including the target wall. This is so it doesn't burn out from the high flame temperatures.