Steam boiler gas shutoff valve adjustment

kevinA60

I am beginning to think my boiler installed last year is oversized. When the heat cycles for a long time (when thermostat changes from 65 to 69) it short cycles. Pressuretrol set just under 2 and .5 differential. I'm thinking the boiler could be overfired. Is it safe to adjust the gas inlet valve by closing it a little so that the flames under boiler are not on as high. Like a stove top. I don't believe there is any safety hazard doing this. Just worried it isn't good for the boiler. Thanks for any input

pecmsg

No
no
and
NO

ratio

It is not at all safe.

JUGHNE

You could get delayed ignition.....or none.....just gas coming out without being burned....but it would eventually ignite.
You (and the entire room) would know it and maybe feel it.

kevinA60

Copy that. Thank you 

mattmia2

But we can tell you how to do the calculations to see if the right size boiler was installed and help you with likely system problems that are causing pressure to build quickly.

ratio

Unfortunately, the only real fix for oversized equipment is correctly sized equipment; however, cycling on pressure after a setback isn't necessarily a sign of the terrible oversizing more commonly seen here.

Steam systems aren't very well suited for rapid setbacks.

EBEBRATT-Ed

@kevinA60

The right place to start is to measure every radiator and calculate the total edr value of all your radiation. This is simple to do and we can help you do that.

Then compare thattotal # to the "sq feet of steam" on the boiler nameplate.

Ho much does the boiler cycle on a normal call for heat when not coming out of set back?

ethicalpaul

What is the timing of your cycles? 

BobC

Once you have measured the edr of all your radiators/covectors you should check how much gas you are burning to see if it matches the nameplate on the boiler.

Correct clocking of a 2PSIG Meter
When ever you have a high pressure meter set, you must compensate for the increased volume of gas at low pressure.  So multiply your calculated consumption by 1.13
So say you take 34 secconds on a 1 cu foot dial:

3600 [secs /hr] X 1 [cu ft dial size] X 1020 [local btu value of gas]
________________________________________________
                               34 [seconds]

=108 000 X 1.13 [2 PSIG conv]= 122 040 BTUs / hr actual consumption rate.

Note due to the limit of how accurate you are eyeballing the time, your calculation will only have accuracy of about +/- 3%

The gas utility calculates the difference between differing service pressures in the billing process.

kevinA60

I have to measure the edr and find out. Heating cycles for about a half hr. Granted, I do not have main vents. Need to add them in summer. Guess old coal boiler years ago didn't need main vents. I have multiple issues. Near boiler piping causing wet steam and water to be pulled into mains (I hear the swooshing), no main vents, boiler too big. I say boiler too big because pseg installed in5 in neighbors a few weeks ago. Same size house and I have in6

kevinA60

EBEBRATT-Ed said:

@kevinA60 The right place to start is to measure every radiator and calculate the total edr value of all your radiation. This is simple to do and we can help you do that. Then compare thattotal # to the "sq feet of steam" on the boiler nameplate. Ho much does the boiler cycle on a normal call for heat when not coming out of set back?

What is the calculation again? I know height depth and number of sections are in it

jhewings

Generally one uses a chart to find the EDR of a radiator. I used the charts in Dan Holohan's book "The Lost Art of Steam Heating".

PMJ

@kevinA60,

Here is a link to a thread about what I found was available on my 1950's boiler. Adjusting the flame by modulating the supply gas on an atmospheric boiler is quite possible and obviously was done and not considered a risky proposition. My manual talks about simply changing springs to change the operating range.

https://forum.heatinghelp.com/discussion/160380/cool-1950s-control

Having said that I agree with those who advise against making fire changes without combustion analysis by a pro. I say that mostly because I think oversize capacity issues are so much more easily handled digitally with a very simple control change. I just don't see the point for any extra expense or worry about potential combustion problems.

Jamie Hall

You don't? I'll grant you that it's quite possible to get a flame which ignites and provides heat without paying much attention to the fuel to air mixture, particularly with either LP or natural gas. They are very forgiving fuels in terms of the fuel to air ratio which will work. Otherwise, you gas grille or stove wouldn't work well at all.

That, however, doesn't mean that they will provide the best efficiency or economy at a fuel to air ratio which isn't very close to correct. It is quite possible to drop the efficiency of a very good burner system from the mid 80s to mid 90s to the mid 20s to mid 30s with a simple tweak of the fuel to air ratio but have it still light and often look pretty decent. You also start producing large amounts of unhappy compounds in the exhaust if the mixture is off.

Not that, within the design of the firebox, you can't underfire a boiler and make it perform well. Particularly for atmospheric boilers, you can. But you can't make it perform efficiently and cleanly without changing both the air and the fuel at the same time.

If I may, I would point you to gasoline engines in cars and trucks. They do change power output over a remarkably wide range. In the old days, this was done with a carburetor -- a device which was both amazingly simple and at the same time astonishingly sophisticated -- which adjusted the fuel delivery rate to match the air flow within a very narrow range. Nowadays, the same thing is accomplished with computers which also vary the fuel delivery to match the air flow, but do it digitally. Most of them use a rather long string of sensors to improve that ratio. (among others, coolant temp, air temp, barometric altitued, mass air flow, manifold pressure, and oxygen concentration in the exhaust, at a minimum).

PMJ

Jamie Hall said:

You don't? I'll grant you that it's quite possible to get a flame which ignites and provides heat without paying much attention to the fuel to air mixture, particularly with either LP or natural gas. They are very forgiving fuels in terms of the fuel to air ratio which will work. Otherwise, you gas grille or stove wouldn't work well at all.

That, however, doesn't mean that they will provide the best efficiency or economy at a fuel to air ratio which isn't very close to correct. It is quite possible to drop the efficiency of a very good burner system from the mid 80s to mid 90s to the mid 20s to mid 30s with a simple tweak of the fuel to air ratio but have it still light and often look pretty decent. You also start producing large amounts of unhappy compounds in the exhaust if the mixture is off.

Not that, within the design of the firebox, you can't underfire a boiler and make it perform well. Particularly for atmospheric boilers, you can. But you can't make it perform efficiently and cleanly without changing both the air and the fuel at the same time.

If I may, I would point you to gasoline engines in cars and trucks. They do change power output over a remarkably wide range. In the old days, this was done with a carburetor -- a device which was both amazingly simple and at the same time astonishingly sophisticated -- which adjusted the fuel delivery rate to match the air flow within a very narrow range. Nowadays, the same thing is accomplished with computers which also vary the fuel delivery to match the air flow, but do it digitally. Most of them use a rather long string of sensors to improve that ratio. (among others, coolant temp, air temp, barometric altitued, mass air flow, manifold pressure, and oxygen concentration in the exhaust, at a minimum).

I think you misinterpreted what I said. Sorry if I wasn't clear about it.

I did say combustion should be checked by a pro. What I meant here was that I don't think one should go to any trouble or expense trying to change the firing rate from what the manufacturer intended attempting to fix capacity issues and risk creating problems. I think that excess boiler capacity is much more safely and much more easily addressed with control changes leaving the firing at a single properly adjusted rate.

Jamie Hall

Oh quite. Completely agree!

SteamingatMohawk

Do you know if the gas pressure to the burners (at the regulator outlet) is correct for your boiler? If it is high, that could supply excess gas to the burners. It's not necessarily a DIY thing, because you need the right tool to measure the gas outlet pressure.