Steam and pressure(1 pipe system)

CC.Rob_11

it is a digital therm so no heat anticipator.
Anyone else wants to chime in on this?
What is causing the pressure?
inadequate venting?
or bad radiators vents causing the lag in steam to fill it therefore building pressure in the unit?

Iwanttobelieve

Steam and pressure(1 pipe system)

hi everyone. Wonderful site.
I have a question regarding pressure in my Burnham IN5 gas fired boiler.
I just had the unit skimmed and it seems to be producing heat a lot faster than usual now.
But the unit is building a lot of pressure while it is cycling and the installer set the Honeywell pressuretrol Main to 3 and Differential to 2. That means the unit will cut off when the pressure reaches 5. Why is my boiler building that much pressure? I thought it takes about 1 psi to heat a home?
if i lower the pressuretrol setting, then i would be short cycling while the thermostat is calling for heat?

Any advice on how to make it work properly?
Thanks in advance for your inputs.

Brad White_203

The boiler seems to be

doing exactly what it is told... if the controls are being set to make 5 PSI as you say, that is what it is doing. Way too high.

Are you sure that is an additive differential though? Just have to ask.

Short of using a vaporstat (0-16 ounces) you will have to set your pressuretrol about as low as it can go to get yourself to one pound. If your pressuretrol is indeed additive, set the cut-in to 0.5 PSI and the differential to 0.5 PSI if you can.

If the burner cuts out on pressure before the radiators are hot, try venting the system starting with the mains then the radiators, so they all come to temperature at about the same time.

Restrictive vents or lack of them makes for limit pressures very quickly. That air wants out.

Iwanttobelieve

Thanks.
Any harm in letting the system run to 5?
Previously the unit will cycle on and off a few times before the temp is reached. I get nervous that it cuts in and off like 50x in an hour!!
Right now with the pressure set to 5, the unit only cycles off 1x per hour...
damn, what to do?

Im pretty sure its addictive. I will double check.

Brad White_203

Higher Pressure

Among many reasons steam runs best on low pressure is that so many critical dimensions are based on those low pressures. The ability of water to stack in the return line and return to the boiler, the speed at which steam moves in the piping, all are related to pressure.

Rob Stannier

Brad, well said.
But if i lower the pressure, the i will have the boiler short cycle a few times before reaching the desired temperature. What gives?

should i start by changing the radiator valves? i jsut put in a new gorton main.

Bill_110

Heat anticipator

One thing you might try if you have a thermostat with a heat anticipator (like the Honeywell T87) is to adjust the heat anticipator up a notch and see what effect that has in a few hours. This is a tip given on the Honeywell frequently asked questions site, related to preventing short cycling of a system. If you pull off the cover of the thermostat there is a litle dial in there which you can stick a pencil point in and adjust. Apparently a lot of the new digital thermostats don't have this feature.

I tried this with the hugely oversized boiler I used to have and it did make the cycles a lot longer and less frequent, but I thought that overall it didn't heat as comfortably that way. If you have an installation manual it may mention what number to set the anticipator to. The opinion seems to be that steam systems should have the highest settings. Maybe some steam guru will weigh in with a more in-depth opinion on this.

nicholas bonham-carter

short cycling

chime-chime!
i think you should turn the pressure down to below 16 ounces.
many vents will not function correctly at pressures above 3 psi, and may become paperweights [don't ask me how i know this!]. the steam becomes viscous, and slower in the system.the remaining pockets of air are difficult for the vents to handle.returning water may be interrupted in its flow.in addition the comfort level around the radiators is reduced, because the surface temperature is higher.
a vaporstat and a 0-15 oz. gauge [gaugestore.com], both on the same pigtail, would be the gift that keeps on giving for you this xmas! that also means NOT giving to the fuel co!
we are surrounded by things which cycle on and off: the gas valve in the oven,cruise control,thermostat itself,etc.
a little cycling on low pressure is normal and not to be avoided, as long as you have good vents on the mains.--nbc

Steve_168

NBC, thanks!
So ill go out and buy this vapor stat, and replace the pressuretrol? ill just connect it to the pigtail the pressuretrol is currently?

nicholas bonham-carter

vaporstat

yes, and take the opportunity to clean out the pigtail thoroughly [if a new one doesn't come with the vaporstat] get the 0-16 oz.[try pex supply or state supply on line]
a good 15 oz. gauge is about $40 and well worth it. you will need a "tee" on top of the pigtail, with 2 x 6 in. nipples, as well as an "ell" at each end.
you will be on the road to such improved comfort and economy that you will never give a 2nd thought about the new fishing rod you didn't buy, because you got these instead!--nbc

Steve_168

So let me understand, i will tee the pig tail and connect a vapor stat AND a gauge? what will happen to my existing pressure gauge?

Do you have a pic of the set up?

i dont want to screw this up.
Thanks NBC!!

nicholas bonham-carter

vaporstat installation

the 30 psi gauge must remain by code but since its range is so wide it's useless for "tuning" purposes.it can stay at its present location. i presume the existing pressuretrol is mounted separately from the 30 psi gauge. if that is so then remove the old p-trol from the pigtail. clean it thoroughly, and remount with a "tee" at the top. the 6" nipples are screwed into the "tee" horizontally. the "ells" are at each end pointing up.finally the new gauge and vaporstat are mounted on those "ells". mount the vaporstat 1st so thae if you need to be one side or the other to make the wire fit you have that choice. the new gauge goes in the final hole.that way if the pigtail gets clogged up in the future you can see it on the gauge. good luck--nbc

Steve_168

Thanks NBC!

George_36

Pigtail

How do you clean the pigtail? Simple soap and water?

Unknown

Sometimes the pigtails get pretty crudded up. I find it easier to just buy a new one. I've got them from McMaster Carr

http://www.mcmaster.com/

In the upper left hand corner,type in the "Find Product" box
either "pigtails" or the catalog page # "578"
.
I usually get the red brass ones as they seem to stay cleaner.
McMaster Carr` takes phone orders, takes "plastic" and will ship to you the same day.

David Nadle

And, there's a fair chance you'll ruin the old one taking it off! Better to have a new one in hand before you start.