How do I figure out the correct GPH firing rate?

Brad White_154

Apparently you did try the Find a Professional tab on the site, but there should be more than one. Do understand that this is a busy season. Where in RI are you? (That was you in the other EDR post was it not?)

For 72 degrees the output drops just a wee bit, call it 237 BTUH :)

Angela_2

How do I figure out the correct GPH firing rate?

Hi,

Everywhere I read that I need to be sure that my oil burner is firing to the connected load, but I can't figure out exactly what this calculation is.

I have figured out that I have a connected load of 739 sq ft EDR (with pickup factor). How do I then figure out what the firing rate should be in GPH for my burner and boiler?

I may replace the current burner, and if I do so, I want to be sure that I get the right size burner and adjust it properly. I've read that sometimes a new burner burns hotter than the old ones (mine is very old), and the firing rate may have to be reduced to compensate for this.

Mike T., Swampeast MO

Steam or hot water?

It makes a BIG difference.

Brad White_154

Hotter Burners

are just that, hotter. The BTU rating is the same.

Your 739 EDR would be, if steam, 177,360 BTU's per hour in a 70 degree space. (240 BTUH per EDR)

If you have conventional hot water, this drops to 110,850 (150 BTUH per EDR) if supplying 180 degree water and returning at 160F. As Mike pointed out, huge difference.

If indeed you have steam, sizing to radiation is the way, but it would also be nice to know the heat loss. We know you are in a hurry with no heat so repent at liesure later...

To support 739 EDR of steam radiation at 84% efficiency (fair average) you will need about 1.7 GPH. Sizing nozzles to actual radiation (how close to cut it) is an art though.

The formula assumptions are:

BTUH Output/ Efficiency = Fuel Input

Divide this number by your fuel value, generally 140,000 BTU's per gallon for #2 fuel oil, to get GPH.

Angela_2

Thanks, Brad. I do have steam, and the combustion efficiency on my old black and white Richardson steam boiler has been 76% for the past few years running. Of course a lot of heat goes up the chimney and into my ordinarily very toasty basement.

And what if I want the space to be 72 degrees? (I have a higher standard

The old oil burner isn't working. Have had two knuckleheads here today and I think they just managed to break it further, though by the condition of the wiring I can see that my yearly maintenance guys were ignoring a bad situation. There was a lot of missing/broken wire insulation and tape, and I've been thinking about replacing this burner for months, was even searching for someone to do it but the only contractor listed on this web site never got back to me after many calls.

Angela_2

A couple more questions.

Hi Brad,

There is only one Rhode Island contractor listed. He did return my phone call once, but I missed it. Then I left him messages that were more specific about the work I wanted done: possible burner replacement, reinstall main vents, clean wet return, cleannout of my gas boiler next door (I own a duplex and so have another steam boiler next door). I told him he could pick any time for the appointment and I'd make sure I was there, but he never called back after at least four calls from me, so I guess he wasn't interested in that work. I think that all anyone wants is the big boiler job. But I'm not giving that job to anyone who's too good for these other jobs (or wants to argue with me about the things I've learned from reading Dan's books).

So anyway, I keep having to get smarter and smarter.

Question: you came up with a firing rate of 1.7 gph, but when I follow your calculations, I get 1.51 gph. What am I missing? Did you add a fudge factor?

I am also wondering if the boiler itself affects the needed gph at all, or if it is ony connected load I have to worry about. For example, if this huge black and white is oversized for the load it's carrying (and I can't find the info on this Richardson model in the Richardson charts), does that mean I might need to fire more just to heat up all that water?

Sorry if that seems like a dumb question, but I'm still trying to get my mind around steam heat.

Thanks so much for your help. (And yes, that was me in the other post.)

Mark Hunt

Angela


You need to be careful here.

If the current boiler is grossly oversized and you throw in a burner with a firing capacity that matches the load, you could have bigger problems.

Imagine removing the current burner and sticking a candle back in it's place.

Also, there are spray patterns to consider as well.

Until you find the info on the boiler vessel, I would make no attempt to play with a new burner.

Hope this helps.

Mark H

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_9

My Fat Fingers...

Thanks, Angela- Careless mistake on my part, I used 74% efficiency, not 84%. My bad, you are correct! Double-checking is a good thing.

No fudge factor (except as the holidays approach).

You may want to cast a wider net for a contractor, especially if you are in northern RI. Such a huge state, right?

The GPH firing rate is directly related to steam production, not your radiation load necessarily but the ability of your boiler to produce steam.

Where the radiation comes in is how fast it condenses hence how long or short between cycles.

The relationship of the boiler size to connected radiation is fairly clear- you need enough boiler to support the radiation.

Some have experimented and reported on this site about under-sizing their boilers relative to the radiation and making up for that by using thermostatic radiator valves, scrupulous pipe insulation and maybe some plain dumb luck.

While this is encouraging toward getting smaller boilers, keep in mind that this was done at some leisure, experimenting or deriving during warm weather times. You would be on thin ice without full knowlege of how your building responds, given your current no-heat situation. Stick with sizing to the radiation.

The relationship of radiation to heat loss is the one that frequently gets ignored. Often there is a surplus, sometimes 50% or more than the heat loss requires for the simple reason that you have insulated the house.

The only way to narrow this (toward getting a smaller hence more efficeient boiler) is to know with excellent documentation what your building heat loss is. Then and only then would you remove or down-size radiators on a PER ROOM basis. Radiation in the end has to be proportional to the heat loss.

Are you up for that, cutting back your radiation? I did not think so!

Having a surplus of steam radiation especially in a tightly insulated structure, is not such a bad thing. A good vaportsat can help tighten the band of pressures between starting and stopping (Cut-in and cut-out). Venting the mains, insulating the piping and all of that.

EDIT: Oh, to be clear and to expand on what Mark Hunt said (listen to Mark always): I am thinking along the lines of replacing your boiler, not just the burner. Sorry if I did not grasp that until now.

Angela_2

Thanks again Brad. One last question (maybe... for now when you say 'efficiency,' do you mean combustion efficiency, or another measure? Combustion effiiciency has been at 76%, but I understand that this isn't so great when you figure what goes out the chimney and basement windows. Do I have to take that sort of heat loss into account?

My house has been somewhat insulated, but not at all thoroughly, and what was blown in has probably settled down a great deal so that all three floors are not covered, and of course I have old windows, etc.

You are right that I'm not trying to cut down on radiation. I am happy with my gorgeous old radiators and have no interest in trying to replace them with smaller ones (what a hunt that would be). Plus I like it WARM.

Brad White_9

Bless You, Keeper of Old Radiators!

We love you for that!

By efficiency I am referring to combustion efficiency, fuel output divided by fuel input. System efficiency and AFUE are different. Those numbers are less. Over-sized systems might get to the mid-high 80's efficiency but because they cycle on-off repeatedly or suffer a lot of cold starts, annual efficiency can be in the 50's or 60's if you are lucky.

You may want to have your house thermally scanned. Talk to the folks at RISE or your local utility if applicable; they may have references, sub-contractors, subsidized vendors for those purposes. It will be good to check the integrity of the insulation and top it off if necessary. Tighten up as much as you can, even some storm windows are as good as the prime windows these days.

Cheers!

Brad

Angela_2

I did think of another question!

Brad,

You have been so helpful, you may never get rid of me...is this your job? I have noticed that there is always a response when you post to the wall, and have wondered if there are a few of you employed for this purpose.

so the next question is: when is an antique radiator no good? I have a gorgeous, sandblasted and repainted radiator that isn't connected. The previous owner told me that this is because it is no good. He said the valve is broken and can't be replaced, so the radiator is beyond repair and they didn't throw it away just because it's so pretty. But since then, I've learned that valves can be replaced-- at least the ones that the radiators hook up to. Are there other valves inside that he could have been referring to? this thing is taking up space in the house, but I don't want to toss it if I could use it later.

Brad White_9

Job??

Heck no, Angela- I am quite gainfully employed and multi-task between the myriad projects I work on (engineering). Always waiting for information or returned drafted drawings so there are breaks. Keeps my mind going...



The spuds and bushings can be removed and the radiator pressure tested for integrity. It may have a hairline crack and that is a shame... hard to repair but I am told it is possible with JB Weld. No guarantees though! If it passes the pressure test (air pressure or water to about 40-50 lbs.) you should be good to go. Stand back when this is done though.

In operation it should work at less than one pound of pressure ideally. Ounces if you are really good.