HO question about Steam Heat Up Time!

Jamie_6

I recieved this e-mail this morning.

Jamie

First of all, the boiler is running great since the new returns went in - no hammering and no short cycling! Couldn't be more pleased. Thanks again Steamhead.
Last evening I finally had the chance to monitor the performance of the system. There is a thread on "the wall" called Programable Thermostats in which someone quoted Dan as saying that a steam system should be able to take a house from cold to cozy in 20 minutes...


Well last eve. it took a full hour from ignition at 64 degrees to get up to 67 degrees. That seems like a lot of work by the boiler (which fired continuously) to move the needle three degrees. What seems wierd to me is that it took only 10 min to start making steam (seems reasonable) - then only 5 min later the main vents are hot and expelling air (seems really fast) Then once the steam gets to the rads, it seems to really slow down (strange?) Here is the whole sequence from 6:05pm when the boiler fired up.


What do you all think?


6:05 boiler on - Thermostat reads 64 degrees

6:15 steam starts building up

6:20 main vents hot and close

6:35 rads (on all three floors) hot one-third to one-half across

6:45 rads (on all three floors) hot one-third to one-half across Thermo to 65dg.

6:55 all rads hot all the way Thermo to 66 - boiler off on pressure

6:55 - 7:05 boiler short cycles, shutting down on pressure each time.

7:05 Temp reaches 67 dg. Thermo shuts system off.


Why wouldn't the steam, which moves like a rocket to the main vent - then take a full 35 min. to heat the rads? Is this normal or is Dan's notion of moving a house from cold to cozy in 20 min just wrong?


There are all new gorton vents on the rads - could they be venting too slow? Incidently, the boiler is running at a steady half-pound pressure and the gague glass is surging a bit from +1 to -2 inches around the normal mark. Wondering if this slow rad heating could be contributing to my larger than expected gas bills.


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Jamie_6

First thing I can think of about the previous high bills is because that return was not on the floor which made the system short cycle and hammer like crazy.

Now, we sized each radiator vent according to EDR and location in the house. Trying to get the house to heat evenly; maybe this is why the radiators are heating a little bit slower then Dan's predicted time?

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Thad English

covers

Jamie,
I talked with Wes, the owner of the system in question, last night. In the email, he left out a little piece of the puzzle: there are radiator covers on all the rads. Removing them should heat up the house a little faster, which in turn should stop the boiler from running as long since the stat would be satisfied before it shut down on pressure.
I know that they do a setback during the day, and they have a well insulated envelope. On the day when the test was done, it was almost 50 outside in Philly. mild temps + setback + a well insulated structure could cause the boiler to barely run during the day. Turning the stat up 3 degrees after it hadn't been running during the day would definitely explain the long time to fill the mains with steam.
If Wes removes the rad covers and doesn't set back as far, I think he may see an improvement in performance.
-Thad

Ted_4

Recovery

20 minutes seems like an awfully short time for a house to recover to "cozy" from setback. Would somebody (maybe even Dan)please post the quote from Dan on this subject. It would seem more reasonable to expect fully hot radiation at pressure in this length of time from a cold start.

Jbaha14

Quote from Pg 21 of \"We Got Steam Heat\"

"And if all is well within your system, you should expect your rooms to be cozy within 20-minutes from the time your boiler first starts. That's what I would consider normal in a typical house."

I was the one that posted that quote and it was in regards to programmable thermostats.

Hope this helps.

Mad Dog

Let me step in here

Every house and system are VERY different. 20 minutes is a nice benchmark, but there are many variables at play. Are we talking an ice cold, cold-start boiler? No-way. A properly sized boiler AND properly vented system, WITHOUT a programmable t-stat, and still sort a warm from an earlier cycle? YES - do-able! If folks are ready to spend the money to get a system responding that quickly, Jamie and I will be there with wrenches in hand - ready to go. However, we are often expected to replace the boiler and cure ALL!!!!! the systems woes. I think alot of the folks that call us in are very knowledgeable and have figured out sorta what is wrong. Correcting it to their expectations is a very subjective "reality" and needs to be discussed in depth and detail before ANY work is done on the system. Just my experience. Mad Dog

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Paul Mitchell_2

35 minutes is a piece of cake. I think it is working great. Other factors such as home insulation, insulation on pipes, etc. Could effect the gas bill. 3 degrees in 35 minutes. I do think that is good

t. tekushan

start-up time

Sounds like a very well balanced system to me, since all the radiators are equally 1/3 then 2/3 and then fully hot. Not that easy to pull off.

Beyond that, my question is, how long was the house at the colder temp (think of the mass that has to be heated-heating air is easy--everything else...)?

What is the EDR of the radiators and what is the I=B=R sq. ft. rating of the boiler? (I know it shuts off on pressure, but that means all the air vents are closing at about the same time--another good thing, I say) If the boiler is under-fired or undersized you can decrease the time for radiator saturation. Your cozy can come a little more quickly, but i'm not sure if its going to ultimately save you gas$. I've seen enormous savings on upsizing the boiler, but in those situations the boiler was so small that it NEVER shut off in cold weather, let alone shut off on pressure.

Steamhead

I got that e-mail too, here's my reply:

"Well, 50 minutes from cold start to all-rads-completely-hot and 20 minutes to heat them up partially isn't bad. I would have waited to see how fast the temp rose once everything was hot. If this is too slow for you, try opening your rad vents a bit if they're adjustable, or go to the next larger sizes if you're using Gortons.

You might want to add another Gorton #2 to the steam main if it's taking 5 minutes to fill with steam, measured from the point at which the boiler starts sending steam to the main."

I'd forgotten about the radiator covers- they really should go. They really restrict the heat output. Besides, why would anyone want to hide those glorious American Rococo radiators?

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Christian Egli

But how do you measure coziness?

That's the beauty of radiant systems, you heat objects, not air, and so you needn't waste your money on warming all of the air in your home. It's a total rip off when you then realize how easily hot air blows out of your home. Meanwhile, the objects, unless you throw them out the window, they stay inside where it's warm.

The thermometer measures the air temperature, it may not be telling the whole truth.

Here's what I'd look into.

The thermostat crept from 64 to 67, but how quickly did the occupants stop shivering? 20 minutes? Less?

Frankly, your numbers are not bad.

Does the thermostat location make sense? What do other thermometers say? Does the rest of the house overheat? Is the vent in the room with the thermostat way too slow?

Covers can work both ways. Either restricting heat flow or boosting air movement. Are they clean and unobstructed?

Wes_2

Some clarifications

Wow, thanks everyone for all the thoughtful responses. Let me provide some clarifications in response to some of the issues you raised. First of all Jamie has been unbelieveable in his dogged determination to get this system running right. This issue is really trivial compared to the challenges that have been overcome. But rest assured that there is no chance the boiler is undersized, the piping is bad or the system isn't balanced. Jamie made sure of that. The mains are insulated as are all the risers. The house is VERY well insulated.

It is true that the day the test was conducted was a warm day. I do not set back usually. To conduct the test I upped the thermo to get the boiler going. Yes it was a cold start. Cold boiler is why it took 10 min to make steam - makes sense. Cold mains is why it took 5 min to exhaust the air - makes sense. My real interest is what happens once the steam gets to the radiators.

Now lets forget about the covers for the moment. The covers have no bearing on how fast the radiators heat up.

So, 15 minutes after the main vents close the rads are beginning to heat. When I felt them at this point, 3 or 4 columns would be scorching while the next column over (and the rest) were not hot at all... THEN a full 10 minutes later -boiler firing continuously- There is no progress at all in warming additional columns. Isn't that odd? During this 10min and then for an additional 10min I can hear a slow, intermitent stream of air from the rads. All the rads are heating at the same rate (3 story house) but I guess the real question for me is - Are all the rads heating too slowly, and if so WHY??

The gorton people chose the vents for each radiator based on each rad's EDR and position in the house and the result is a system that is balanced nicely. I've just read that steam wants to move FAST (especially at the nice low pressure I have). Would it be wrong to assume that if the steam could move faster to the end of the rad, it would heat faster and the boiler could shut off sooner?

Thanks again and Have a great weekend everyone!

Mike T., Swampeast MO

"Now lets forget about the covers for the moment. The covers have no bearing on how fast the radiators heat up."

Not a valid assumption.

Some radiator covers are able to enhance the output of radiators--particularly steam radiators. If convection is enhanced, the rad will be slower to heat because more is being given off by the heated sections with less excess available to heat the remaining.

Wes_2

say what?

Mike,

Maybe I'm dense, I am afterall a mere homeowner,but I have no idea what you are talking about. If you can spare the time, I would enjoy a more detailed explaination. Steamhead hates my covers!
Thanks, Wes

Mike T., Swampeast MO

Yes, covers do generally reduce output and they all essentially destroy the radiant energy associated with "coziness".

But, the dead men found that covers could be made that increased output. Rather unusual as they were very tall relative to the radiator with a very large output screen above the rad itself and an inlet screen that went around the sides of the rad as well as the front.

Wish I had more familiarity with the action of steam radiators--not just hot water rads used in gravity conversion systems.

Your heat-up times don't sound unusual to me though. A stone cold radiator has a lot of mass, but the steam has very little. When it first enters a cold rad, it's going to be condensing very rapidly--and likely very close to the steam inlet. Since it rises displacing the air, the sections heat from the top down. With the top getting hot first, I believe this will really crank the convective BTUs. Once the bottom of the sections heats, the convection will decrease somewhat and leave more steam able to heat sections further away from the inlet. In the few steam heated buildings/houses that I'm in frequently enough to actually feel the radiators (and they're not covered) it doesn't seem unusual for longer radiators to only get really hot part of the way across in mild weather.

If you repeat the test during colder weather when the rads haven't had a chance to cool fully, I bet you'll find that they heat much more rapidly.

ThermalJake_2

Wes, if you go over to the T-stat and turn it up to 85, how well does the rad heat from when the first section gets hot until the last section gets hot? The elapsed time from the first cycle, through steam in the main, main vents closing, steam in the risers, and steam in the first section should be the same. From there, if the steam wont travel into the rad at the same rate as the steam traveled to the rad, you probably can't evacuate the air. Try a cycle without the vent (if there is one) or with the return line union broken. Be prepared to put it back on if you get steam out of it. Do you get good steam now?
Jake

michael_15

Radiator heating speed

This is a lot slower than the radiators in my home. None of my vents are bigger than the Gorton #6, though I have predominantly thin-tube radiators which means there isn't nearly as much air in them (per sqft EDR) as the column radiators. The sections probably heat up at a rate of around 1 section per 30-40 seconds (that is, if I lay my hand across the top of the sections, they successively get too hot to touch at that rate).

I'd guess that the covers marginally impact the rate at which the radiators heat up. Since most (not all) of them lower the overall heat output of the radiator, they would help the radiator heat up faster (like insulation, I suppose). Some covers are designed to increase heat output, which would slow down the rate at which your radiator heats up, but I can't imagine this is a major factor.

-Michael

Wes_2

teens tonight

The cold is back now so I'll try the whole test over again - this time it will not be from a cold start. I'll put it at 85 and take all the same measurements again. It will be interesting to see the difference.

I am interested in the varied opinions about the covers too. I can post some pics of my covers. We like the way they look so I was thinking maybe I could modify them to allow better air flow. Currently they have solid tops with a slab of heat absorbing material on the underside of the top (asbestos maybe?). (Found the reciept in the attic when we bought the house ~1954) The tops do get hot and the cats like to lie on them...But I thought it would be good to cut away most of the top and put the same metal grate that is on the front -on the top too- so heat can get out more easily. There is plenty of open space at the bottom.

Steamhead

They'd work better that way

since you would be able to get a small "chimney effect" from the hot air rising out the top.

But the covers do diminish the radiant portion of the rad's output. That's the most comfortable part of the way rads emit heat, since the heat shines on you like sunlight.

And once your rads are cleaned up and painted, they'll look better than any cover ever could.

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michael_15

radiator covers

http://www.heatinghelp.com/newsletter.cfm?Id=77

http://www.heatinghelp.com/newsletter.cfm?Id=115

Good stuff.

-Michael

EBEBRATT-Ed

An EDR is based on 215 deg steam with 70 deg. air surrounding the radiator. If the air is colder(64) wouldnt the radiation be condensing more edr than what the vents are sized for?? What effect does the vent size have on a cold start and piping/radiation pickup??

Reinvent

'the cats like to lie on them'
Now we get to the heart of the problem. A furry feline can suck up BTU's better than a heat exchanger at a nuke plant.

t. tekushan

edr vs temp

The load the boiler sees is not the venting. Its the cold radiation and cold room temp. You are right in that a 64 degree radiator condenses A LOT more steam than a hot one, but the air cushion is minor compared to the outrageous btu's converted in such a cold "climate." As a matter of fact, in single pipe steam, fast venting can create a water-logging at the bottom of the radiator, where the tremendous condensate counterflow gets in the way of the steam at the inlet nipple.

I often see a situation upon a very cold start-up a room temperature overshoot after the T-stat has shut down the boiler. All this means is that the radiators have finally hit full stride about the time the t-stat is satisfied.

t. tekushan

solid tops

a HA!

It is my understanding that solid tops can reduce the radiators's total output up to 20%

A cover can inrease a radiator's output if the top is open and the lower opening (at the floor) is 80% of the top opening (provided the top opening is the same as the depth of the radiator). But you lose the radiant component to some extent.

If you have a full open front and open top, the output characteristics are similar to an uncovered radiator.

Factoid in the form of an observation: The closed top covers make little difference if you are maintaining a temperature in mild weather. If the boiler comes on every, say, 3 hours and the rads don't close the vents, the heat eventually gets into the room. However, any time the vents close, you know that closed top cover is getting in the way!

BTW, search the 'net for "perforated metal" and I can guarantee that you will find many suppliers that carry a perf that will match the fronts of your covers.