Home gas boilers

magicmike · Post by **magicmike** » Wed Jan 11, 2006 3:29 am

Anyone know anything about gas boilers/forced water heaters. I drained my upstairs zone in the summer when I did some work on adding some baseboard sections in the bathroom renovation. So I refilled the system and everything seemed to be fine. Now just recently, the pressure relief valve has been discharging water while its heating (full flame). The PR valve is a 30psi and I looked and the boiler was reading 35psi. I saw online that domestic boilers should only reach 15-20 psi when operating normally so I'm not sure whats up. I need to know:

1. how to know if all the air is purged from the system? And how to purge it if its not.
2. What psi should the expansion tank be set at?
3. What should the max temp be set at the boiler thermostat (I think its at 190° now.

I spent about an hour at the book store tonight looking at HVAC books and there is nothing out there on this particular problem. I also spent all last night looking online for something and didn't really find too much.

Any help would be great guys, thanks

dzx · Post by **dzx** » Wed Jan 11, 2006 4:16 am

If I had internet at home, I would ask my uncle since he works on them all the time. I guess i could write it down and post tomorrow though.

magicmike · Post by **magicmike** » Wed Jan 11, 2006 4:29 am

I'm looking into on a site I found "do it yourself.com" they have a forum section but no search function so I'm on like the 300th post and havent found what I'm looking for, plus the topic names are vague. I would apreciate the help if you could ask youe uncle. I wont be returning to the condo until tomorrow night.

dzx · Post by **dzx** » Wed Jan 11, 2006 4:40 am

Pressure regulator is shot, should be at 12psi when its cold and should be 20psi at most when its real hot.

expansion tank should be at 12 psi when cold

3) should be between 180-200 F. The hotter you set it, the more efficient the baseboard heating is. He said 190 is good.

expansion tank, could also be shot. Take the cap off the shrader valve a little and if water comes out, the expansion tank is shot. If air comes out, then its good. There should be no water. That would also set off the pop valve

That's all i could understand since he's at the house in the mountains and we don't get great cell reception there. I kinda don't like asking him questions because when i ask, he makes me an expert on the subject...I know way more about things that i never wanted to know about than i should.

He said it's most likely the pressure relief valve is shot. He's had a lot of problems with those going bad in some of the buildings his employer owns.

dzx · Post by **dzx** » Wed Jan 11, 2006 4:55 am

mostly they purge themselves automatically

when everything is cold, you should be sitting at 12psi.

expansion tank should come with 12psi in it.

pressure regulator could be shot, not the pressure relief valve sorry.

let it cool down then open the drain valve and let it drop down to 9 or 10psi or so if it's above 12 or 13psi when it cools down. Then let the regulator fill it back up and if it doesnt stop at 12 or 13, then the pressure regulator is fucked.

When it's hot open the shrader valve and let a little squirt of air out and if water comes out the diaphram on expansion tank is bad.

Thanks, now he's gonna draw me a picture of how everything works when i get home from work.

I guess it never hurts to know how stuff works.

magicmike · Post by **magicmike** » Wed Jan 11, 2006 5:11 am

sorry for opening a can of worms on your end but the information is very helpfull. but I'm a little confused on what the pressure regulator is and where it is.

dzx · Post by **dzx** » Wed Jan 11, 2006 5:14 am

Ok, the pressure regulator is where you hook up the supply for water. I think city water pressure is around 30-40psi. The pressure regulator kicks that pressure down to about 12psi because the copper piping used for baseboard heating is thin wall.

I'm sure i'll have a much better understanding of this when i show up at work tomorrow. He'll draw me a picture when i get home, then take me in the back room where we have a boiler and point everything out for me since we use baseboard heating to keep the house somewhat livable in the winter when we dont have the woodburning stove going.

magicmike · Post by **magicmike** » Wed Jan 11, 2006 5:16 am

oh ok, well when the boiler is off it is stable at 12-15 psi so I dont think the pressure regulator is bad or it would be high when it was off.

dzx · Post by **dzx** » Wed Jan 11, 2006 5:18 am

apparently it shouldn't be above 13psi at the most when cold.

You can do the shrader valve check then and see if its the diaphram on the expansion tank

He said if there is air in the system, you won't get heat from it.

magicmike · Post by **magicmike** » Wed Jan 11, 2006 5:21 am

if I'm not mistaken I had it set at 30 psi when I refilled the system because my dad who doesn't know anything about this shit let all the air out thinking it was the way to purge the air out of the system. I put my compressor on it and set it to 30 which is the rating of the PR valve but I wasn't sure. sounds like I need it at 12. When I checked it today it seemed like a little mist blew out when I tried to force the air gage onto the nipple and it red like 10 psi. maybe that tank is going bad but there is a 2003 date on it so I wonder...

dzx · Post by **dzx** » Wed Jan 11, 2006 5:27 am

I guess the expansion tank is supposed to have 12psi in it when you get it.

However Matt said they always screw it up so he usually has to add a little pressure to get it to 12psi.

magicmike · Post by **magicmike** » Wed Jan 11, 2006 5:56 am

ok I have some things to check tomorrow, thank you so much, I'll let you know what I come up with tomorrow night, I'm off to bed.

stipro · Post by **stipro** » Wed Jan 11, 2006 6:04 am

when you filled the system, did you hear the air escaping? is there a spirotop or manual air vent? The SRV is set @ 30*, so if the system pressure is greater the SRV will leak.

professor · Post by **professor** » Wed Jan 11, 2006 10:52 pm

It is likely that your expansion tank air bladder is flat as a pancake and waterlogged. It has an air bladder in it, so as to accomodate expansion of the water when it gets hot.

If the air is not at the correct pressure, or similarly if your cold water starts at too high a pressure (thus compressing the air bladder before you even start), then the expansion with heat will cause the expansion tank to be almost entirely filled with water, the pressure to skyrocket, and you get water all over the place

it is also possible that the bladder has failed. Home Depot and the like have replacement tanks, not too expensive.

The "proper" temperature for your system depends upon how much heat you need. Hotter is not necessarily better, if 170F water does the job, then heating it to 190F is not necessary and is wasteful.

go to www.heatinghelp.com to find the real pros who will answer your questions promtly, in the section "The Wall"

professor · Post by **professor** » Wed Jan 11, 2006 10:54 pm

I should have mentioned, that if you have an "instant" hot water system rather than a conventional tank heater, it is possible for the heat exchanger to be cracked, which causes supply line cold water to enter the heating system, since house supply is 50-100 psi normally.

It is also possible that your boiler make-up water valve is leaky, which results in the same thing.

dzx · Post by **dzx** » Wed Jan 11, 2006 11:13 pm

If you put 30psi into the expansion tank, there's your problem. Inside the expansion tank is the "bladder" or diaphram. So when the pressure of the water would have to be over 30psi to push the diaphram up.

So with 30psi in the expansion tank, the water has no place to go and its popping the pressure release valve.

Let the boiler cool down and cut off the water supply. Then lower drain the boiler down to about 10psi, then lower the pressure in the expansion tank to about 12psi and turn everything back on.

magicmike · Post by **magicmike** » Thu Jan 12, 2006 5:19 am

ok heres an update. First off thanks so much Dan and please pass on a big thank you to your uncle for me. I actually might be out to golden CO at some point again in the future, I was out there for work durring the fall. Not sure how far that is from you but I'll buy you a beer if its close enough

. now for the boiler. my expansion tank was fucked. It was totally full. I bought the exact same tank at lowes for 32 dollars. Thankfully there was a ball valve on the exisiting expansion tank so I was able to swap it out without draining the whole system. The new one actually had about 20psi in it so I lowered it down to 12 before I ever hooked it up (per the instructions) and after damn near dropping a nut into my sock I was able to lift the old tank out lol. I bled the system (2 zones) using a technique read on "do it yourself.com" and there was alot of air in the system in both zones. so I fired the bitch up and it didn't go over 20psi so I am very excited. the only thing that still troubles me is that everywhere I read says that when it heats up the temp should be around 170-180°s ish. When mine cycles it goes all the way up to 230° before is shuts off. Here is a pic although its a little blurry of the therm control. It looks like there is one set screw that adjusts something and another just behind it thats locked with a tamper proof screw of sorts. The one that is locked looks to be set at 200 something and the other one that you can adjust is around 170 or so. I'm not sure the therm on there is working properly but I'm satisfied for now. I think I saved some serious money by getting this figured out with you guys.

I took a few pics of my marble tile progress while I was there and my new jetted bath not yet installed.

(Insert bitches here) lol

stipro · Post by **stipro** » Thu Jan 12, 2006 6:04 am

the one that is locked is the high limit control,the other is what you set as your opperating temp.

dzx · Post by **dzx** » Thu Jan 12, 2006 6:05 am

Glad I could kinda help lol. I gotta say, I learned a lot about how the system works last night when i got home.

I'll ask him about the temp thing.

Golden is pretty close to Boulder, probably about 20 mins south so if you happen to be in the area, hit me up and we can have some beers

professor · Post by **professor** » Thu Jan 12, 2006 5:28 pm

If you are really getting 230F water, your boiler would have exploded by now.

actually it would have blasted water/steam out the pressure relief regardless of the condition of the expansion tank

you need to check into that. As I said above, heating water above the temperature necessary to comfortably heat your house is wasteful. Start at 170 as a good guess if the original installer chose the rating well. Adjust from there.

Over 190 and you're playing too close to boiling, you can get localized boiling that will mess up your system pressure

Don't know if the "deadband" can be set on that controller, but its the difference between the temp at which the boiler shuts off, and the temp at which it starts up.

ask the dudes at www.heatinghelp.com about that controller. Even with that fuzzy pic you'll get a quick and courteous answer. Those dudes helped me totally fix my one-pipe steam system, about which I knew nothing when I bought my house.

magicmike · Post by **magicmike** » Thu Jan 12, 2006 10:31 pm

Hey professor, Thanks for the info, I posted on there asking how to debug the thermostat. How does that site work? Do the peolple email you or do you need to go back there find your post and read it?

magicmike · Post by **magicmike** » Fri Jan 13, 2006 5:51 am

OK update here. I borrowed a digital thermometer from work and checked the actual temp of the unit right at the pipe that feeds the BOV (pressure relief valve

) and found that the analog gage on the front of the boiler is off by at leaste 20 degrees in the possotive direction. It was only going up to about 200-210 degrees when cycling. I also saw that it looks like there is a knob missing on the thermostat controler where you can adjust "limit control" thats the white blob on the left side of the black box in the blurry pic. Anyway I played with the only thing that I was able to adjust on there and noticed that the disk thing that was pointing at the 180 degrees controled when the unit fires. It seemed to be the starting point for the burn. I set it to 150 degrees at which point when it cooled down it fired right around my measured value of 150 and shut off right at 175 so I gather that the knob that was taken off adjusts the "burn time" which must be set at 25degrees instead of there being two disks to set a high and low you set the low and tell it how much to rise. I normally set the house themr to 60 degrees because i'm not living there and jack it up when I show up to work on the place. With the temp set like I have it now it was cycling on and off and the temp was not really going up, maybe like 1 degree in a half hour or so. I may have to jack it up a little or something to get it to heat faster. What do you think?

professor · Post by **professor** » Fri Jan 13, 2006 3:39 pm

you mean the temp in the house wasn't really going up ? how far below the thermostat set-point was it ? Was it turning off on thermostat reaching setpoint ?

the 150-175 you set is reasonable but if the boiler is a bit on the smallish side you may have to jack that up a bit, but stay under 190. A 20 degree deadband is typical and 25 is fine (delta between on and off for the boiler gas, you called it burn time but its temp not time), so that should be OK.

If you fired from a dead cold stop it can take 20 minutes for the boiler, metal, water, and cold pipes to get heated up, and start distributing heat. If the boiler is in a cold basement without insulated pipes that hurts a lot.

Unless you can't maintain the thermostat setpoint, or the last room in the loop is cold, I wouldn't worry too much. Also depending on how "smart" your thermostat is, there may be a setting for reaction time. Boilers are slow so that should be set to the slowest setting. Dumb thermostats (mechanical) have no such setting but do work well with boilers.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Home gas boilers

Home gas boilers