I need HELP with slow heating/panting radiators

Jeff_130

I have two problematic rads in my house that pant and don't get hot all the way across even when it is COLD in the house.  I have 1890s house with a one pipe steam system fired by an old American Standard boiler (60s or so).  I've read Dan's books and am still puzzled...

One suggests cleaning the runouts to the risers for these radiators... How do you do that???

Another says that it may be a pitch problem... how much pitch should there be?  How many inches per foot of rad?

Thanks.

Jeff

nicholas bonham-carter

american standard panting

you don't need much pitch, as gravity is going to make the water move. you just have to point the way. you must have a level, and get a definite slope going towards the valve.

next, check the insulation on your steam mains. there should be one inch on them to stop early steam condensation, which could cause the panting.

now for pressure and main venting. get a good low pressure gauge [gaugestore.com 0-2 psi] on a tee with your pressure control, and of course keeping the code required, but completely useless 0-33 psi gauge. make sure the pressure is set as low as it can go. watch the gauge during the air escape part of the cycle. the back-pressure you see will indicate the presence or absence of adequate venting. my system can allow the air to escape before the gauge reads 2 ounces. with inadequate venting, the boiler may short-cycle before all the air has been squeeeeezed out of the constipated little vents, causing greater profits for the fuel company.

once the main vents are able to do their job, then look at the other problem rads, whose radiator vents can be taken off for the" blow-through", and "turn upside down while blowing to see if they close" test.

assuming the radiator pitch, venting, and pressure values are correct,then look at the thermostat, to see if the anticipator, or cph factor, is set properly. if the thermostat only allows the boiler to run short periods of time, some radiators at the top of a long riser may not get enough steam before the system cuts off.--nbc

crash2009

I don't know exactly why

 radiators do these strange things such as panting, inhaling and exhaling.  In my case it could be from opening and closing the shut-off valve.  But every once in awhile, one of my rented rooms goes stone cold.  What I usually do to see what is going on is remove the air vent.  Then light a match and hold it up to the air vent hole.  Most of the time the flame of the match will get sucked in.  When I see this, I go get the vacuum and vacuum the air out of the radiator, through the air vent hole, until the radiator gets hot.  This usually takes about 15 minutes.  Once I get the radiator hot again, and tell the tenant not to touch the shutoff valve everything works fine. 

This little vacuuming trick may or may not work for your problem, but it is a way to get heat in the room NOW, at least for today, and for me, usually continues working, until I get a new tenant.

Rod

"Panting"

Hi- My understanding of "panting" is that it is caused by small amounts of steam collapsing (condensing) in the piping. The things that can cause this are: "wet steam", missing insulation and possible places where condensate (water) could pool. These "pooling places" may also have a collection of "crud" so that could cause a problem too. 

As for cleaning the horizontal lateral runouts, I haven't done anything like as they are usually pretty clean if they have some pitch. My experience has only been flushing my wet return. It obviously would be a warm weather job and I guess could be done by removing the radiator and using a hose to put water down the pipe and draining it off by the wet return. I'd be cautious with this as it is a major job and with condensate normally flushing the line may not be really necessary.

Pitch on a one pipe radiator should be enough to "encourage" the condensate (water) to flow back out the inlet pipe. Use a bubble level to determine this. Too much pitch can cause problems so it is a matter of experimenting a bit to find the optimum pitch for the radiator.

Minimum pitch for a radiator lateral is 1/2 inch in ten feet (Page 87 TLAOSH) There may also be a problem if your piping to the radiator is undersized.

- Rod

Brad White

Rod and Nicholas are correct

on panting. The ebb and flow of steam to vacuum to steam is the root. I think we agree that lack of insulation or a pool of condensate en-route would cause a collapse of steam (inhale), followed by a new charge of steam to fill the void (exhale). Absent other information, I would start on that premise.



One system I came across had what seemed like good insulation but one pipe traversed an unheated garage and panted like a dog for the first few cycles, despite the insulation. Only that radiator and only until the system was thoroughly hot. That made a good imprint in my mind.

Jeff_130

Forgive my ignorance

I took another listen and maybe panting is a little extreme... my reference point for panting is after I run and I pant rapidly.  This is more like an audible exhale and then it stops on these two radiators.  Does that constitut "panting" for a one pipe steam system? 

The pipes are insulated except for a few inches here and there at connections, which I will rectify.  My daughter complains about "breathing".

Thanks.

Jeff

Jeff_130

Neat trick... I will try that just to see.

That vacuum trick sounds awesome, at least in the short term.  I'll recheck the pitch on the rads and see.

Thanks.

Jeff

crash2009

After thinking about what NBC and Rod had to say

  I think I may have a low spot in my main just upstream of the rad that went cold.  I remember hearing the popping sound of the collapsing steam bubbles for about a month prior to using the vacuum.  The vacuum may have cleaned out the low spot because now there is no popping sound.  Originally I thought the popping sound was the bass from a surround sound.