How should radiators warm?

LukasBux

Hi,

I just had a new steam boiler installed in the middle of winter last year and I have to say the guys that did it were about the most professional people I've ever dealt with. Now, my question...



I am not sure HOW this system is supposed to work. There is a new boiler with a Honeywell thermostat in the dining room. If the heat is NOT on and the temp reads, say 63, and I turn the thermostat up to 68 to start the heat, the rads downstairs get hot about halfway across, and the rads upstairs get hot about a 1/3 way across. If I keep putting the temp up higher (70-72-74), the rads eventually get hot all the way across.



Is this the way it is supposed to work, or is there a venting issue that I need to deal with? I am not sure if ALL the rads are supposed to be a little warm all the way across at 68, and then warmer all the way across at 72...or if they are supposed to slowly warm from one side to the other.



I run into this situation where the dining room rad warms up and shuts of the thermostat when the rads upstairs are barley warm. If I want to warm all the rads in the house, I have to jack the thermo to about 76. Sound normal?



thanks,

Lukas

SBoston

Warm radiators



Just a home owner,  but I have been dealing with my steam system for a few years now so I have a little insight.

I am not sure if you own any of Dan's books, but they are a great read (even funny at some points) and well worth picking up. Helped me greatly when trying to learn about steam (and there is a lot to know).

Pressure is your enemy, make sure that you have your pressuretrol set correctly… depending on the type you have (again Dan's book is a great aid on this). Also make sure that your main vents are working properly. Venting your whole system through the little radiator vents can cause the system to heat slowly, unevenly and build pressure.

How far across the steam get on a radiator depends on several factors like the size of the radiator (compared to other radiators in the house) and venting. The fact that your radiators are not heating all the way across during the shoulder months doesn't seem unusual; however, the fact that rooms are still cold when the thermostat is satisfied sounds like it could be venting/ balance issue. Adjustable vents could help you balance your system.

Posting pictures of your boiler and near boiler piping might help some of the professions identify some other problems as well.

Big-Al_2

Could Be Normal or Not

When steam enters a radiator it does two things.  It pushes air out the other end, and starts condensing and heating up the sections one at a time . . . starting at the inlet end and progressing towards the end with the steam trap or the vent.  the longer the steam is on, the further across the radiator it gets hot.  On a small radiator, this happens quickly.  On a longer radiator, it might take several minutes or longer to get all the way across.  If the thermostat is satisfied before the radiators get fully hot, the boiler shuts down, and the radiators never really get hot all the way across.



Potential problems:



1) Steam Pressure.  If you have one-pipe steam, the vents (opposite the end of the radiator inlet) will need to open and close a few times to let the air out.  If the steam pressure gets too high, it holds them shut and traps air in the radiator.  It can also get high enough to permanently damage the vents.  The steam pressure should never get higher than 2 PSI. A more typical system runs at 1.5 PSI.  Lower is better, because the steam actually travels faster.  1/2 PSI is enough pressure to heat a large apartment building.  3 PSI will damage vents. 



2) Venting.  If parts of your system aren't letting out the air fast enough, then parts of it won't get steam. Single pipe systems have vents on each radiators.  Two-pipe systems typically have condensate traps opposite the supplies that also act as vents.  If you have a really restrictive vent on a huge radiator, it might take a long time to get hot all the way across. 



3) Thermostatic valves.  If your radiators have thermostatic vents or supply valves, then they will stop the steam or stop venting when their own temperature is satisfied . . . maybe long before the thermostat shuts down the boiler.  Thermostatic vents and valves typically have big whitish knobs on them with numbers.  You can move the knob to different settings to choke off the radiator when a certain temp is reached.





There is more.  I'm sure others will chime in.



Yes, buy Dan's books.  If you don't want to spend a lot of money, at least buy "We got Steam Heat." It's a good read.

nicholas bonham-carter

venting problems?

as a wise man once said here, "air is the enemy, to be chased away like the raccoon from the garbage cans!"

check your main vents [usually on the returns]. the aim is to let the air escape rather than to have to burn extra fuel pushing it out. i don't think you can ever have too much main venting capacity, so gorton #2"s are my favorite. remember that low pressure steam [8 oz.] will move more quickly through the pipes, that's why i like a vaporstat.

also when checking the steam distribution patterns, after you have improved the main vents, don't pay attention to the room temperature at first, just check the radiator temperature. they should all get steam at the same time. a radiator at the top of a very tall riser may need a larger capacity vent.

if after all this there is still a cooler room, you might want to put the thermostat there rather than downstairs. that way it will more quickly sense the falling temperatures outside.--nbc