Short vs tall radiators

FranklinD · September 2016

Quick (possibly dumb) question:

What effect (if any) does a radiator's height have on its output? Is it strictly due to better convection due to the taller height, i.e. the air gets heated more on each pass around the room because of the longer travel time from floor to top?

The situation is this: I had a short 3 column in my bathroom, 7 sections wide, but short and squat (22"). 21 EDR. It never seemed to heat the bathroom adequately.

I have now replaced it with a tall (38") 4 section 3 column (20 EDR), and it gets MUCH warmer in there. Even my eternally cold wife mentioned how much warmer it felt in there. This proves to me that I'm not imagining it

Gordy · September 2016

A short long rad will have the same output as a narrow tall rad so long as the SF is identical. It's all in the SF of area. However at the first on set of a heat call the narrow tall rad will reach its full output faster......I believe......is what you are experiencing.

Danny Scully · September 2016

@FranklinD, ran out of regular 90s?

FranklinD · September 2016

I knew someone would notice.... I couldn't find a place that would cut and thread the length I needed that day, and had to get it together before I left town for training. So a coupling and a street 90 filled the space perfectly. I'll get back to it eventually, probably next year when I start the full bathroom remodel.

As long as it heats as well as it does, I don't mind it

Gordy: that's interesting...and could very well be what we're experiencing. And I'm fine with that since it's all about the *perception* of heat, at least as far as my wife is concerned. As long as she feels warm, she feels happy.

Thanks!

Andy

Canucker · September 2016

What is that a function of, @Gordy ? Is there less water in the taller rad? Thinner walls, maybe? The radiating surfaces closer to the person with a taller rad? Is there a larger chimney effect with the taller rad? I'm curious about there being a difference or as @FranklinD said, maybe his wife just perceives it to be warmer. Might be fun to pursue even just as a thought experiment.

Gordy · September 2016

@Canucker In my mind the longer shorter rad that is would take more time to warm the sections along its total length verses a tall rad with a shorter length. I see it as the distance the water travels through the rad warming things up.

That would be an interesting one to view with an infrared video. I'm theorizing and these times in my mind are not huge amounts.

Canucker · September 2016

That's what has me curious. There shouldn't be a noticeable difference, but according to @FranklinD 's wife, there is. I'm wondering if it's a placebo effect or if there is actually something measurable happening. I have different sizes of rads in my house but there are too many differences in variables to make a meaningful measurement here.

Gordy · September 2016

If anyone can sense a difference it would be a woman......built in infrared sensing ability.

Gordy · September 2016

A happy wife is a happy life.

Gordy · September 2016

another thing is if the casting thickness is the same in the two rads.

Abracadabra · September 2016

I sometimes like to think about the extremes when comparing two scenarios and then apply each extreme to the situation. I'd think the taller one would heat better.

Reasoning:

Take the extreme of each radiator.

A single section super tall radiator with EDR of 20
A really long super short radiator with EDR of 20

The really long and short one would tend to have quite a bit of hot water short circuiting the radiator thru the first section before the rest of the radiator eventually catches up and gets hot.

The single section really tall one would guarantee that all the water that comes in goes thru the entire radiator quickly and heat that section quick.

Another variable that could be involved is the mass of each radiator.

Canucker · September 2016

I think I see where you're going @Abracadabra . If I'm understanding correctly, you're saying the actual flow rates through the rad itself have changed? So possibly the short rad would have heated the room better with the return on the opposite side because there is less opportunity to short circuit?

FranklinD · September 2016

Yes! @Abracadabra pretty much mirrored my thoughts on the matter, though I couldn't seem to put it into words.

I'm almost positive that the situation would be exactly opposite if the piping was done bottom to bottom...then the tall & narrow radiator would short circuit across the bottom, and the short & wide radiator would slow the flow enough to cause gravity circulation in more sections.

But because it's piped top to bottom on the same side, the short & wide rad must've had a tendency to short circuit a bit thru that first section and take longer to heat up.

I did try varying the supply valve over the course of last winter to see if that made any difference, but if it did, I couldn't tell.

I've been itching to get an IR camera attachment for my phone (or standalone unit) but I can't justify it as of yet.

As for the casting thicknesses...good question. The tall rad is a "Peerless" non-ornamental 3 column, and the short rad is a "Rococo" ornamental 3 column. Both are made by American Radiator Co, and relatively close in age. The other difference was that the short rad had 1" tappings that I reduced to 3/4 to match the pipes, and the tall rad already had 3/4 tappings.

Canucker · September 2016

I'm going to put the IR camera on my rads this winter. I have a converted gravity system that has the connections on the rads at the bottom on the same side. @Steamhead wanted me to post when I do but he hasn't mentioned whether video or still photos would be better.

FranklinD · September 2016

Fantastic! I look forward to seeing the results. Likewise, if I find an IR camera to borrow for a few days, I'll take some video of the tall rad heating and cooling. Should be interesting.

Also interesting to note: out of 5 radiators on the second floor, the NW bedroom has the only radiator connected bottom to bottom. The other 4 are all connected top to bottom on the same side. The first floor rads are ALL connected across the bottom. Not sure why. I kind of wondered if the dead men were using that one oddball upstairs as the expansion tank, since there was never one found in the attic. Not even a connection in the piping upstairs for one.

I suppose that they could've used a steel compression tank in the basement by 1914, but I'm not sure. One of the many things about this house that I'm very curious about.

Thanks!

Andy

Gordy · September 2016

@Canucker video in my opinion if possible.

Steamhead · September 2016

Either would work. Video can take a while and might result in a (puts on orange wig) yuuuuuge (removes wig) file size that would take forever and a day to load. With that in mind, maybe a series of time-stamped stills would be best.

How many square feet of radiation do you have, and what model is your circulator?

Canucker · September 2016

I have 3 zones, not counting the indirect. A zone for each level of the house. You want the measurements for all or one zone? Each zone has its own pump.

Steamhead · September 2016

Each zone, EDR and circ. I'm assuming the old gravity piping was replaced?

Canucker · September 2016

You would be correct. I'll see if I can get that done tomorrow

Solid_Fuel_Man · September 2016

I know when you put taller enclosures on fin tube the output will increase some. I have no quantification for that, but that was the reasoning behind convectors over baseboard.

Increase the convection due to more stack effect and more air will be drawn over the surface and therefore more btu's pulled from the water. This does not, however, take into account the amount of direct radiation that you (she) feels from the iron itself.

If you now have 2 SF less edr and feel warmer convection must have a greater bearing on the bathroom.

BTW, I will take that short radiator off your hands so you don't need to be bothered with its storage

SFM

FranklinD · September 2016

My system is a converted gravity as well, running a Burnham ESC4 and a Bumblebee set on speed 2 for 10 gpm or so. Speed 1 worked but some rads heated late compared to others.

I have 432 EDR, all one zone, 2 floors, 9 rads, all 9 are ARCo Peerless units.

I did look at your article regarding circ sizing for old gravity systems, that's how I came up with using speed 2 @ 10gpm - and it heats WAY more evenly than at the suggested 6.5gpm (for a heatloss calc of 65k).

FranklinD · September 2016

Heh heh...I have a bunch of radiators in storage now in addition to the shorty...and I have access to 25 more. I just can't store them and therefore have to pass.

It breaks my heart as the building is being torn down Oct 1st, but all 25 rads left there are 42" tall Rococo style, 24 sections minimum, with many of them on the second floor. The roof has been leaking for 20 years and the floors are, well, VERY bouncy and spongy. It's really unfortunate as they're all in beautiful shape, most having only a single coat of paint on them.

I got three out, the tall narrow bathroom rad being one of them, but couldn't justify trying to get more as I'd have to rent a tall cherry picker and a truck. The remaining rads wouldn't fit in my van.

Abracadabra · September 2016

Any IR video should be posted to youtube and then a link to said youtube video posted in thread. Don't try posting the IR video directly to the forum.

Canucker · September 2016

Having a little trouble finding the right size for 1 rad. It's a Corto but it is only 4 tube, about 6.5 inches deep, 38 inches high. Not 8 inch deep, 5 tube like the others, so I'm assuming it isn't 4.5 sq ft per section but I don't know what size to use.

Fred · September 2016

Should be about 20% less than the 5 tube or about 3.6 Sq. Ft. per section.

Canucker · September 2016

Thanks @Fred , I think that will get me close enough

Canucker · September 2016

One more question. The Columbia paper that I used to size my rads says my 38 inch high, 5 tube rad is 6 sq ft per section. When I looked at the pages for Corto rads it says its 4.5 sq ft per section. I assume I should use the one from Corto, as that is the make of the rad and ignore the other one. The Columbia paper sizes it at 72 sq ft, which is a big difference

Fred · September 2016

The Columbia paper is an average of several radiator brands of each specific type (like the tube type). I would definately use the the spec sheet from Corto. I believe, if you look at the Columbia sheet, it shows the depth of the 38" tube type to be about 3/4" to 1" wider than the Corto actually is, as well.

FranklinD · September 2016

@Canucker, @Fred, I was wondering the same thing. I got all my edr ratings from that same Columbia cut sheet, and wondered how accurate it was. I'm still perusing the old catalogs on the website here looking for my Peerless rads. I don't own Dan's EDR book (yet). I have some that are 38", 26", and 22"...all 3 column.

Fred · September 2016

@FranklinD According to Dan's EDR book, the Peerless 38", 3 column is 5 Sq. Ft. per section, the 26" is 3-3/4 sq. ft per section and the 22" is 3 sq. ft. per section

Canucker · September 2016

Thanks @Fred , I ended up using the sheet that Utica boiler supplies. It seemed more consistent.

Canucker · September 2016

Ok @Steamhead , the survey is done and here are the results

Basement
EDR=259 sq ft, Grundfos 15-58FC on speed 1
Main floor
EDR=316.25 sq ft, Wilo Star S16F on speed 1
Second floor
EDR=137.5 sq ft, Wilo Star S16F on speed 1
The system is piped P/S on an old Raypak E105 copper tube boiler. Input of 107000 btuh.

If you need anything else, please let me know

FranklinD · September 2016

@Fred, thanks! That actually matches up to the Columbia sheet I found online...but nice to know that my edr calculations are correct.

It's been windy, rainy, and about 50 here the last 2 days so I turned the thermostat to 68 and left it. There is no doubt in my mind that the tall rad in the bathroom gets warmer faster than the short rad ever did. So my wife isn't crazy (not that I ever thought that at all

)

Steamhead · September 2016

Canucker said:
Ok @Steamhead , the survey is done and here are the results

Basement
EDR=259 sq ft, Grundfos 15-58FC on speed 1
Main floor
EDR=316.25 sq ft, Wilo Star S16F on speed 1
Second floor
EDR=137.5 sq ft, Wilo Star S16F on speed 1
The system is piped P/S on an old Raypak E105 copper tube boiler. Input of 107000 btuh.

If you need anything else, please let me know

This is probably a great opportunity to go to a zone valve setup with just one circ. I think all those zones are over-pumped. But I'll wait for the infrared data to be sure.

Short vs tall radiators

Comments

Categories