System load vs Burner output

Maine Vent

I'm still trying to get less steam some radiators and more to others.



I have switched out 9 Heat timers varivalves to Hoffman 1a's.



Still some of the short main rads are still getting too hot, the long main rads are not getting hot enough.



I have finally got good clean water and pipes are all insulated. I am wondering about going to an even slower venting vent for the hot short main rads.



My topic title concern is load vs burner.



I used jpf spreadsheet and it calculated my overall btu load at 96000 btu's.



My Riello gas burner has an #3 orifice in the burner tube which puts out 114538 btu's.



My load vs output seems pretty close. Do I need more burner output to make more steam?



I have the hoffmans on the short hot main set to 1 and these rads are still getting hot all the way across and they still get steam the quickest.



The long main rad vents are set on 6 and they will not warm up all the way.



Thermostat has been moved from a hot room to more central location.



I used to have slow venting verivents on all my rads with my old burnham they seemed to work ok. Now with this new system I was advised to get heattimers these vents would not balance at all. So I switched them out to the 1a's.



Any thoughts, Thanks again

Dave in QCA

Main Vents?

Of great importance in the balance of the system are your main vents.  What are you using?

BobC

Open the vent up and look.

If you unscrew the top of a Hoffman #1 you will see that there is a lot of slop in the way that cap sits over the hole so you might want to take a couple apart and sight the air vent hole to make sure it really is open just a sliver at a setting of one.



This is especially important if one of the really hot radiators is close to your thermostat.



Also the importance of main vents can not be over emphasized.



Bob

Jamie Hall

In response to the heading question...

Your match is pretty close.  In fact, allowing for boiler efficiency, almost exact.  I would be inclined to check the main venting first, and see what happens. 



Also, I am assuming that all your steam mains are well insulated.



Then, if you are still having difficulty with the long radiators not heating up enough, turn the thermostat up 'way high, so the boiler has to run a long time.  If you do that, and it runs for an hour or more without heating the radiators up enough -- or shutting off at the pressuretrol -- you might want to consider increasing the firing rate, if you can.

Maine Vent

Maine Vent reply

Thanks guys,

Brand new Groton #2 on the end.



All pipes insulated, header, mains, risers,



I noticed the hoffman 1a design, sloppy with a lot of room for error in adjustment. I have taken a sink faucet washer and these fit exactly over the top of the 1a vent hole. I use this in my spare room to stop this rad from venting, the washer works perfect for this. The rest of them I try to manually set the opening then screw the top piece back on.



To Jamie, we have some cold weather coming next week, I will give her a good steaming and see what she will do about heating the long rad.

Main vent seems to vent quick, I haven't time it out from start of firing to hot groton????



By the way, the vaporstat was just not giving us the needed confidence in keeping the boiler running. I broke down to my wife who said put the pressuretrol back on. Having done that the boiler has not failed to fire on therm. call. Pressure is only building to 8-9 0z. I'm alright with this change. I just have more confidence in the system to stay running.



Thanks again

nicholas bonham-carter

venting calculations

i hope you have a good low-pressure gauge, graduated in ounces, because i believe you still need more main venting, and slower radiator vents. while the boiler is firing from cold, your gauge should show approximately 1 ounce of back-pressure. if not, then add gorton #2's until you get to that figure.

next, put hoffman 40's on all the rads with similar riser length [on one floor]. if you have 3rd floor rads which are suffering from "late steam arrival", they can have some of the left over higher capacity vents.

i'm not certain why you were having problems with the vaporstat, and had to reinstall the dreaded/useless pressuretrol, whose best use is to keep papers flying off a desk in a moderate wind.--nbc

Abracadabra

time it from start of steam

time it from start of steam in the header not from start of cycle.

Mark N

Output

In your signature you state you have 404sqft EDR, that comes out to 96960 BTUS. The traditional pickup factor for a steam system is 33%, That comes out to 129,000 BTUs gross output. You state that your output is 114,538 BTUs. That gives you a 19% pickup factor. You might be slightly underfired.

ChrisJ

Hoffman 1A

I agree with Bobc in regards to taking the vents apart.

I run all 1A's on my 10 radiators and found the way the caps are made even varys vent to vent.  Forget about the fact you cant adjust them simply by the number due to slop in the cap.  You can tweak a Hoffman 1A to pretty much stop venting completely but it takes time and fiddiling around.



I have a 1A whos opening is wider on #1 than #2.  In order to get it to vent slow I have to have it set to #2 and the cap slid slightly away from the radiator.  The more I slide the cap from the radiator the slower it vents.

Maine Vent

Reply

Thanks all,

I have a 2 gauge system, 30lb, 10oz from the gauge store.



so by adding another main vent to my long line that should reduce my pressure to around 1-2 oz pressure.



I was leaning with Mark N,on this I think it's slightly underfired also.



If the need for for more fire is right, what is the best way to achieve a higher firing rate?



1. Increase gas pressure????

2. Go to a larger gas orifice in the burner tube??????



My main vent issue is I am limited in how many vents I can add to this configuration. I'll post a pics. The Hoffman75 set was my old configuration, Groton is the new.



As far a the vaporstat/pressuretrol goes I new that there was something wrong with it control when you had to push the silver plate down inside the vaporstat to restart the boiler. Maybe next year I'll try it again??????



Thanks for all your advise, Main venting addition first, then see, then up firing rate next.

Mark N

Burner output

With the # 3 orifice in your burner is the input to your boiler is 114,538 btu's? If that is that is the case you are probably very underfired. I don't know how efficient that boiler is but figuring about 82% and rounding off to 115,000 btu input I come up with a gross output of 94,300btus and a net of 71,000 btus. That comes out to about 296 sqft EDR.

Mike Kusiak_2

Boiler sizing

I would agree with Mark that you are somewhat underfired, but this may not be necessarily a bad thing. If you can arrange your venting to achieve even heating, you may be gaining some efficiency. Here is Boilerpro's article stating a different viewpoint:



http://www.heatinghelp.com/article/323/Boilers/1551/Taking-Another-Look-at-Steam-Boiler-Sizing-Methods-by-Dave-Boilerpro-Bunnell



The fact that you generate 10 oz of pressure on constant firing shows that your steam generating rate is just about equal to your condensing rate. Therefore, you are producing as as much steam as the radiators can condense but no more. If you did, the pressure would rise and the pressuretrol would cycle on pressure, which is not really desireable.



If you did increase the firing rate significantly, the mains would heat faster but you would have to possibly accept some pressure cycling.



My feeling would be to do the best you can with changes with main and radiator venting, and only then consider raising the firing rate in small increments so you don't wind up with a situation where you excessively cycle on pressure.

Maine Vent

Question for Mark N

Thanks for great load breakdown. I have a question for you, if I need roughly 410 EDU for my rads, and my net now is 71000 btus. To get my 410 sq feet to heat would I need about 100,000 net btu's???? I just divided 100,000 by 240, to get 416. Am I on the right track? If I am how do I calculate the gross amount of btu's needed and then how do I calculate the next size orifice for my burner?



We had good cold stretch of weather and I seemed to heat a few more sections of my rads, but that was from the burner having to run longer to satisfy the thermostat. I appreciate your help.



Thank You

Mark N

Reread your old posts

I just read through some of your old posts and came across a thread you started back in March of 2011 titled "Help With Heat loss BTU/hr vs EDR". In that thread you come up with a heat loss of 70,000btu/hr. Is it just coincidence that the net output of your boiler is now 71,000btu/hr. I don't know anything about power gas burners please find a pro who does. The net output of the boiler has to match how much radiation you have connected to it.

Mike Kusiak_2

Firing rate

You mentioned that your current #3 nozzle is rated at 114K BTU but is is only valid at a certain gas pressure. Have you actually clocked the gas meter to see what your actual firing rate is? My feeling is that you are actually firing at above 114K BTU.



If you build any pressure at all on a long run, that implies that the boiler is producing more steam than the radiators can condense. You say that the radiation is capable of accepting 96K BTU. If you can build almost 10 oz of pressure and your venting is adequate then the boiler is generating at least 96K BTU of output.



The net steam rating includes a 33% excess in steam generation to compensate for heat losses in the mains and allow for quick pickup of the load. If the mains are well insulated, the losses will be less and you may not need the full 33% excess capacity.



 As Jamie says above, the real test is to turn up the thermostat and let the boiler run until all radiators are fully hot and pressure builds to a constant level. If you can achieve this level of steam output then the steam generation rate is optimized and the firing rate is correct as is.



Mark mentions that your heat loss is significantly less than the EDR of your radiators. This would imply that under normal conditions the radiators should never heat all the way across, as the thermostat is satisfied before that happens. If the did completely heat the rads you would be putting more BTUs into the house than necessary to meet the heat load and you would overshoot in temperature, overheating the house.



What is it that you are really trying to accomplish? The fact that you are running long constant cycles in cold weather without heating the rads all across seems to indicate you are running your system as efficiently as you possibly can.

Maine Vent

Follow up to Mike & Mark

I was trying to understand what Mark N wrote in Jan 8th post about my about my burner input vs my gross output and my net output.



I kind of understand what he is saying in that post, that if my net output is only 71000 btu's will only heat 296 sq feet of rads. I don't know how to figure what my system is actually putting out for true btu's



All I know for sure is this SGO 4 section will supply 450 sq ft of EDR, my net I B R is 108000.



My thought here is, is this #3 orifice in the Riello gas burner which is rated to put out 115000 btu's, enough to give me enough steam to properly heat my 404 sq ft of rads?



I don't understand gross vs net vs whats left to make 404x240 btu's to heat all my rads.



I going over Dan's books again for some winter reading trying to help sort out all your info.



Good wint'a reading here in Maine.



Thanks for all the great help, I appreciate you time and your insight.

Dave in QCA

figuring backwards

I'll give it a try....



404 sq ft x 240 btu/sq ft = 96960 BTU   (this is the net)  it is the size of your radiation.



96960 BTU Net x 1.34 BTU Gross Output/ 1 BTU Net = 129926 BTU Gross Boiler Output.   (This is the piping loss and pickup factor adjustment.)



129926 Gross Output x 1 Btu Input / 0.84 Btu Output = 154673 BTU Input or firing rate needed.  (this is the boiler efficiency adjustment)



So if your Riello gas burner has an orifice in it that is supposed to fire at 115,000 BTU, you are about 40,000 BTU short of the 154,673 firing rate needed.  Or... is that the firing rate?  You said that the burner as set up is rated to put out 115,000 BTU.  Or... are you firing at a rate at which the boiler will put out 115,000?   Have you clocked the meter to see how much gas you're burning?  This is probably the place to start.

Mike Kusiak_2

Input, output and EDR

Ok, it is a a bit confusing. First of all EDR is a measurement of a radiators ability to condense steam and emit its latent heat to the surroundings. If you have 404 sq ft of EDR then it can condense steam with a latent heat of 240 BTU/sq ft x 404 sq ft = 96960 BTU. So your boiler must have a gross output of at least that amount to completely fill the radiators with steam at 1 PSI pressure. In addition, extra steam is needed to heat up the piping and drive out the air at the beginning of a cycle. So customarily, an an extra 33% of steam generating capacity ( the pickup and piping factor ) is figured into the net rating for this purpose. Depending on the system, you may not need all this extra output. A lot depends on how well the mains are insulated.



Now lets consider how much steam your boiler can produce. If the fuel heat input is 114000 BTU and the boiler efficiency is 82%, the gross output of the boiler is 114000 x .82 = 93480 BTU which is less than the capacity of the radiation  to condense, 96960 BTU. So from this info you appear to be underfired. If you figure in the extra 33% for pickup and piping, the net output would be 93480 / 1.33 = 70285 BTU and that would correspond to the amount needed for 292 sq ft of EDR.



That's why I believe you are firing at above 114000 BTU/hr. If you were really firing at that rate, your radiators would never be filled to capacity and the pressure would never rise at all. You mentioned that when the boiler runs for a long time you generate almost 10 oz of pressure, which is not consistent with the nozzle rating. Perhaps the gas pressure is higher than the rated value which is increasing the gas input to more than 114000 BTU/hr.



The way to check this is to measure how long it takes to consume a given amount of gas by clocking the gas meter. This involves timing how many seconds it takes to complete a revolution of the 1 or 2 cu ft dial. With a little math you can then calculate how many cu ft per hour are consumed. 100 cu ft of gas generates about 102000 BTU so by this method you can figure out exactly what your actual gas BTU input is. You can find more info by searching for "clocking gas meter"

Maine Vent

Thanks Mike great reply

I am getting a much better understanding of this from you and Dave. 96960 btus, The DOE heating capacity figure in the Weil McClain spec sheet is 144,000. My 96960x1.33=129,000btu's. Mains, risers take off all have 1" - 2" of good pipe insulation with plastic white wrap on all runs and joints. So if I'm understanding I need 129000, my boiler has a capacity of 144000 right. Now back to your calculations on the burner, I'm in agreement with you, I think I need a little more output from the burner. Either you or Dave suggested increasing the output in small increments. I will have my heating Pro check this out.



I appreciated yours and Dave's great break down explanations of this.



Over the past few days here in southern maine it has been very cold. The boiler has been running very smoothly, the rads are getting hotter almost all the sections are getting hot. So I am pleased with that.



The boiler never goes off on pressure, it runs straight ahead until the thermostat is satisfied.

I have question about timing my gas meter. Do I time one revolution of the 1,000 meter? Or do I time the next meter to the left which I think is the 10,000 meter?



So once I have a time figure for 1 revolution, what do I do with that figure???



Thanks again to you and Dave and all the others who have broke this down for me.



I appreciate your knowledge and your time..



P.S. It's nice to be warm again in our house.

Dave in QCA

Use the 2 cf dial

You want to use the 2 cubic foot dial.  You want to measure how much it burns in one minute.  Remember, half a revolution is 1 cf, a quater revolution is 0.5 cf.  Do the best that you can in being accurate.  You may need to reference the half cf dial as well.

If you have exactly one and a quarter revolution of the 2 cf dial, that would be

2.5 cf/ minute x 1020 BTU/cf x 60 minutes/ Hr = 153,000 BTU/Hr.   

Easy math!  btu content of gas usually runs between 1000 and 1020 BTU per cf.   I usually just use 1000, but wanted to be more accurate for the purposes of posting on the board.

Mike Kusiak_2

Clocking the meter

Before you consider making any changes to the burner, lets see how much gas you are actually burning now. This link gives you a chart showing gas usage as a function of how many seconds it takes for one revolution of the dial without mathematical calculation. Just make sure no other gas appliances are operating when you do the test. 



http://www.hvacprotech.org/toc/clocking_gas_meter.htm

Maine Vent

Clocked Meter

1. The 2 cu/ft meter 1 complete revolution = 1:31:.8 minutes = 91.8 seconds rounded up 92 seconds.



2. The one half meter 1 complete revolution = 22.2 seconds rounded down 22 seconds.



The chart on 2 cu/ft st 92 seconds = 78 or 78,000 btu's hour



The chart on the one half meter 22 seconds = 82, or 82,000 btu's hour



After 3 tries my knees were freezing up, I feel as though I got 2 accurate readings. The sun was shining right on the dials, I could see the dial hands very good.



Now how do I make sense of these input/per hour btu's numbers.



Thanks again for your guidance on this stump er.

Mark N

Input

If your boiler was the only running when you clocked the meter, then the numbers you came up with are the input to the boiler. You need to get someone in there that can set up that burner at the proper input. How long does this boiler run on a call for heat. If your that underfired I'm surprised that it even turns off. Clock the meter a couple more times to verify your readings.

Mike Kusiak_2

Something doesn't make sense

As Mark says, if your input was that low it would be hard to believe that you would be able to heat the radiators all across in very cold weather and be comfortably warm. So a few questions:



What is the highest steam pressure reading you have seen on your 10 oz gauge?



In very cold weather, how often and how long does the burner run?



Did the installer of the burner do a combustion test and if so do you have a printout of the results?



It seems like you will need your heating guy to come and measure the gas pressure with a manometer. I seem to remember that you had to have the gas regulator moved recently. Did he measure the gas pressure after the regulator was moved? He will also need to check the pressure after the automatic gas valve on the burner to see what the pressure is going to the nozzle. The pressure at the nozzle, along with the nozzle size determines the firing rate.



An 80K BTU input rate just does not seem consistent with how well your system seems to operating.

Maine Vent

Mike and Mark

I have no other gas appliances, just the burner.



I'll get some more readings this week.



I had a new gas valve installed recently, pressure was checked at 3.5 I believe. I know my service tech took out a little 1/4 in allen screw on the outlet side of the valve. He put a gauge into this hole and took a reading. I am sure he said 3.5 and that was in spec I didn't see the actual meter reading.



Didn't move the regulator just vented it to the exterior of the house.



I did see the combustion test readings, carbon monoxide 38, CO2 7.8, efficiency 86, I have no printout but I did see the figures and wrote them down.



The highest steam pressure reading 8 - 9 oz, in goes down to around 4oz.



It will run for 20 30 minutes and it is NOT heating all the rads. I have felt all along that I am underfired. I have just done another boiler flush, the water was a little dirty, had a slight film of oil in some of it. New water plus some 8 way cleaner which doesn't last too long.



So I feel like my water now is of good quality, so steam will be cleaner/dryer.



The burner orifice is a #3 which is rated at 114538 btus, at a pressure of 3.5, I don't know what this figures out to be as far as output.



I'll get a few more meter readings this week, I have 2 psi coming into the house.



Thanks again for this help, I had a very disappointing installer who took the money and ran, he left me and my wife very unsafe and the boiler running very bad. Second technician got my burner in spec by running the combustion test and resetting the air gate on the burner. The third tech. made my system safe, installed a new gas valve and also ran the pressure check and combustion test. So now I feel safe and have a clean system, I just need some more btu's I feel to really start heating all my rads all the way across on a very cold day.



You guys have been great, I offer a big hardy thank you to all on this problem.

polyj79

Uitlity Worker

Dial size x 3600/seconds= cfh(cubic feet per hour)

He should have a combustion analyzer to check for CO if input is change after the initial start up . ALL POWER BURNERS NEED TO BE CHECKED FOR CO PRODUCTION and good draft !

 Note: all CO detectors have sensors that last only 5 or 7 years.

Mike Kusiak_2

Stack temperature?

Mark, when you had the combustion tested, did you get a number for the flue gas temperature? If its below 325 F then you are definitely underfired for the size of your boiler.



What model number Riello burner do you have?

Maine Vent

Stack Temp

Hi Mike, I didn't see a stack temp on the digital readout on his analyzer. The tech never made mention to the stack temp at all.



My burner is a Series 40, g200,



Thanks again Mike

Mike Kusiak_2

Efficiency and stack temp

Found the manual for your burner, but there is no reference to a #3 nozzle or a 114000 BTU rating. Recommended firing rates of 70K to 200K BTU are set by manifold gas pressure of 0.7" to 1.8" wc, so i don't know where the tech's 3.5" setting came from unless you have some custom setup?



http://www.genesyscombustion.com/gs200.pdf



I looked at some of my recent combustion measurements, and with natural gas, efficiency of 86% and 8% CO2, you would be operating at a stack temp of about 275F, which is too low.



If it were my system, I would raise the firing rate to the level where I had a stack temp of around 350 F. At that point you would be generating more steam, yet not sending excessive amounts of heat up the chimney, with a combustion efficiency of about 84%.

Maine Vent

Hi Mike

I am going to try to attach a pdf of my g200 manual, it a from 3/2011.



I'll see it works, 0n pages 10, 11, 12, it gives the diaphragm sizes and specs.



I'll see what you think after I load this, I'm leaning with you on page 10 6c speakes of flue temps.



Thanks again



Mark

Mike Kusiak_2

Firing rate adjustment

Hi Mark,



Yes, your manual certainly is different from what I have.



It seems that the burner output is adjusted  in ranges by changing the orifices, and then fine adjustment is achieved by varying the gas pressure. According to your manual on page 10, the manifold gas pressure can be adjusted over the range from 3" to 5" wc to achieve the desired output. In your case, you mentioned that the tech set it at 3.5" so there is still plenty of adjustment range to increase the output with the existing orifice.



How I would go about setting the output is while monitoring the stack ( flue )  gas with a combustion analyzer, slightly increase the manifold pressure until a temp of 350F is reached, while also monitoring the CO and CO2 levels. Then adjust the air gate for minimum CO and maximum CO2 as described in the manual.



By following the procedure in the manual,  you want your tech to meet all requirements of manifold pressure, stack temp, CO and CO2 simultaneously.



Do not increase the output excessively. With your burner you do not want to produce too much steam and cycle on pressure, because at the start of each burner cycle there is a 30 second pre-purge which blows cold air through the combustion chamber. Each time this happens you are literally blowing boiler heat up the chimney, so you want to cycle as little as possible. In this case, rapid cycling by the pressuretrol will really hurt efficiency.

Steamhead

The oil firing rate of an SGO-4

is 1.2 GPH, which translates to 168,000 BTU per hour. If you're currently firing 114,000 BTU/hour, that's definitely low. But if the system is working properly and the combustion numbers are OK, there's no need to increase the firing rate to the rated maximum, so I'd go in steps and see what works best.



Do you have a printout of the combustion test results? if so, we'd be interested to see them.

Maine Vent

Reviving This Thread

Hi all,

I'm just relighting this thread, I have had 1 winter with this system.



In May had a new Pro come by, we increased the orifice size from #3 to #4.



Also I have increased my venting on my main.



Boiler was flushed out and was very clean after 1 winter.



Lit it off yesterday, had company at the house, and felt like we needed to warm the place up for our guest.



I didn't pay much attention to the system as company was more important.



So I'll be reporting back with my thoughts on the advice from all the Pro's in the earlier threads.



Your help and advice is really taken to heart. So I want to let you all know how the advice was put to good use.



I have a question, I don't see some of the names like Jamie, crash, Jp, just wondering if your still reading here?