Zero steam pressure, can’t find any leaks

NealJ

I now have a 0-3 psig pressure gauge on the boiler, but the system doesn’t seem to build up any pressure. I had the boiler shut down for most of the day today while I clean & replaced some condensate drain piping. This is a two pipe, vented system. Most of the radiator vents have been replaced, the rest have at least been inspected. The boiler ran for almost an hour after starting back up today, but still, no pressure buildup. I’ve inspected all of the accessible piping & looked for signs of moisture where I know there is piping in the walls, but can’t find any leaks. Thoughts?

neilc

is your pigtail and port into the boiler clear and free breathing?
have you tried a cool flooded boiler check?

Long Beach Ed

Are the radiators heating? If so, you have no problem. If not, you have no fire or no water.

pecmsg

Do the pipes get hot?

KC_Jones

We need a sticky post here to explain to people that pressure is essentially evil in a steam system.

If it’s heating everything is fine, if it’s not, pressure still isn’t the issue.

NealJ

Yes, the radiators are all (mostly) heating fine. I was just expecting a half pound or something, not the needle staying on the pin.

NealJ

And yes, the pigtail is brand new and clear.

Jamie Hall

To dive into the theory, the reason you don't see any pressure is that the system is condensing steam in the radiators as fast as the boiler can make it. Which is exactly what you want to have happen. The slight pressure you will see is the friction loss in the piping, which is very small.

The only time pressure will build up is when all the vents are closed and there is nowhere for the steam to go -- which is wasteful.

EdTheHeaterMan

Then there is just enough pressure to get the steam to the radiators. If you want to see the needle move, you need a gauge that measures ounces. Do you know how many people in New Your Housing Authority buildings wish they had your problem? ... heat without pressure, noise, or cycling burners. This just goes to prove: "you can't please all of the people all of the time". PT Barnum

Big Ed_4

No pressure and heating fine , sounds perfect to me ..

reggi

Probably a optical illusion... but your 3lb and trols look like they're piped off the top of the boiler w/o any pigtail OR is there a 1/4" brass pigtail coming off the side of the boiler into a fitting with the 30 lb gage and then nippled up and supporting those 'trols and 3lb er's weight Plus the fitting and pipe?
Can't see that well on my phone screen..

mattmia2

your boiler is properly sized?

reggi

mattmia2 said:

your boiler is properly sized?

Ahh These are the Bundy 2 pipe with rad vents..be interesting to see the boiler and plumbing setup. . . Interesting time in the industry with radiator patents being... developed 

NealJ

Thank you all for your comments. I’ve really been enjoying learning a totally new technical system. It sounds like the boiler and the system are at equilibrium. Steam output of boiler = Steam needs of system = zero pressure buildup. Along that vein, I have several radiators (especially the larger ones) where the exit end never gets hot. Somewhere around 75% of each radiator gets too hot to touch, where the last “loops” (as Bundy calls their vertical sections) stay at or near room temperature. Drains have been verified clear, and I have large vents so that they heat up quickly. That makes me think that maybe the boiler is slightly undersized. Also, there are two radiators that are valved off (the rooms are not heated) and there are 4 large convectors in the basement ceiling that are either capped off (due to leaks) or not heating (next on my list to cut out the condensate return piping to check for plugged piping). If I get these convectors working or if they decide to heat those two rooms, how will that affect the system? I have most of the radiators sized so that I can calculate the EDR, but have no idea how to size/calculate the convectors in the basement ceiling. I suspect they will be huge numbers. Am I right to verify the boiler sizing? Thoughts on adding radiator load to a system with zero psi after nearly an hour of run time? Caveat: the near boiler piping is copper and not insulated. It is not ideally configured, something I plan to address this summer.

Jamie Hall

Not to worry. The worst that will happen is that the boiler will have to run a little longer to persuade the thermostat to shut down, and some of the radiators may not fill quite as much.

Those big basement radiators may not be as big as you think -- they just look huge, lurking over your head.

mattmia2

Before you re-do the near boiler piping, flood it, fill it until the water starts to fill the riser above the boiler to make sure the boiler isn't leaking above the water line.

Adding more load to the system could be tricky if it is a little undersized already. If you are only adding a little as a percentage of the whole system it should be fine. If you are adding a significant amount more then it may become very difficult or impossible to get the system to all heat at the same time. You may end up with entire radiators that don't heat and you may or may not be able to fix that with changing the venting speed of various radiators. It is possible that something is causing the boiler to be underfired as well.

EdTheHeaterMan

After you calculate the EDR of the connected radiation, then calculate the EDR of the proposed radiation then compare it to the I=B=R Net Sq. Ft. rating of the boiler, you will know if you are undersized or oversized or like the Baby Bear's porridge "JUST RIGHT". Don't do the new near boiler piping on something that will not work for you in the future. Test as @mattmia2 suggested and check the size. if you get positive results, then repipe. If you don't get the boiler top be just right. then replace the boiler at the same time as the repipe. That is where most of the cost is, in a new installation. The labor and piping to connect it, is usually near 2/3rds the price of the job.