capacity of 1 1/4 pipe to displace air in a radiator

misterheat

Good morning all, recently i have added a radiator to the end of a run that feeds 3 radiators . The first 2 rads are fed by 1 1/2 pipe and after the second tee it reduces to 1 1/4 (why they did it this way is beyond me .Its very old piping ) The last radiator is big for a big room and it replaced a smaller one which was not quite heating the room properly . Since the change to the new bigger rad ,it is only heating the first 3 sections of the rad during the long calls for heat in the morning after a 3 degree set back . I m still under my sq ft (386) for my IN5 boiler . The new rad is 5 tube 25 high 16 sections its a big rad for a big big drafty room . Have i exceded my capacity to displace the air in this new rad ?? It has a heat timer vari valve open all the way on it . Because this is basically the end of the run (main ) . * This is a branch and not the official main . The main that runs directly off the boiler is 2 inch . I will get some pictures up soon to help .Thanks

Abracadabra

It has nothing to do with "ability to displace air". All that was changed was the radiator? No changes to the runout ? Is that runout pitched correctly? Is the upfeed from the main to the runout branch piped using a 45 or a 90? Does that 1-1/4" to the last radiator feed anything else? That new radiator looks to be about 65sq.ft EDR if it's a column type and not a tube type. Is the 1-1/4" pipe a "main"? Is so, that's a problem. Mains shouldn't be less than 2". Pics will help.

KC_Jones

Another thing to keep in mind with a bigger rad. A bigger rad has the capacity to heat more, but it won't heat more than the amount of steam getting to it. If you had say a 10 section rad there before and the first 3 sections got hot when the thermostat called for heat and you replace that with a 16 section rad it will still only heat the first 3 sections. This is with all things being equal, same vent same pipe etc. Also each pipe size has an EDR capacity it is capable of delivering. I suspect as was already eluded to the piping may not be adequate for what you are trying to do.

Abracadabra

if the 1-1/4" is simply the runout and riser the EDR is limited to 55 sq.ft. EDR, if the riser isn't dripped, that's assuming the Deadmen piped and pitched it correctly and it's still pitched correctly. If it's not, then that capacity drops.

misterheat

SO the pipes in question are the one that goes toward the back wall . the one with the drip pipe it goes around the corner . the first 2 rads are 1 1/2 than i included a picture of the 2nd rad tee and as u see reduces to 1 1/4 and then goes to the last rad. SO starting at the 1 1/4 tee it runs straight 7 feet 90s into 5 feet of 1/14 and then turns 90 up thru floor to valve

misterheat

its a tube style rad .pitches look good.i guess its considered a main but it end in a radiator

ChrisJ

We could use a picture or two of the new radiator showing it's valve and vent.

Also, how was that boiler skimmed? I don't see a skim port?

Danny Scully

The radiator is actually 48 sqft. The runout to it should be 1-1/2, and the "main" itself should be 2", or dripped somehow. Hopefully we can accomplish heating this radiator with a better venting approach (for now).

ChrisJ

I have a 60sqft radiator on a 1 1/4" runout and it works perfectly fine. I also have another 50sqft on a separate 1 1/4" runout that is around 10 feet long and it also works fine.

Why should this specific one be 1 1/2" and not 1 1/4 for a 48sqft rad? Not able to get proper pitch?

Danny Scully

Any runout over 8 feet should be up sized. Im suggesting that on paper, it should be 1-1/2, but as you've exemplified, sometimes things can still work perfectly fine when they're wrong on paper. That's why our 1st approach will be venting.

ChrisJ

Danny Scully said:

Any runout over 8 feet should be up sized. Im suggesting that on paper, it should be 1-1/2, but as you've exemplified, sometimes things can still work perfectly fine when they're wrong on paper. That's why our 1st approach will be venting.

Ah.
I was remembering what Abracadabra had also mentioned, and that was TLAOSH stated 55sqft was the limit. I didn't realize that was only for up to 8 feet.

One of mine is only 2 feet long, but the other is at least 10. It has good pitch and I keep my pressure really low so maybe that's why it works.

Paul48

Try reducing the venting on the first 2 radiators.

EBEBRATT-Ed

Steam will take the path of least resistance, simple as that

Steamhead

In the picture "boiler3", does that horizontal pipe slope back toward the boiler, or the other way?

Fred

Steamhead said:

In the picture "boiler3", does that horizontal pipe slope back toward the boiler, or the other way?

That's the pipe I suggested a couple months ago needed to be pitched. It's a return. He says it is pretty much level. I think he said he would address that when the weather breaks.