Need guidance in re-filling tank and radiators in unusual situation

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Old 01-16-18, 01:50 PM
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Need guidance in re-filling tank and radiators in unusual situation

Hi! I have a very unusual situation, for several reasons. First, I'm the rare person forced to convert from natural gas to oil, second, I have an open (not closed) hot water/radiator system as my deliberate choice, i.e. it's a so-called 'gravity' system that does not have a circulating pump but works by convection (and very nicely, too) and third, there are some idiosyncrasies that I have to bear in mind when filling it with water.

So, I have the oil storage tank installed, filled with oil, and with the connections to the outside and inside in place. All that remains is the oil boiler itself, which will be installed tomorrow. But it's the refilling that has me concerned, because of what happened years ago when I had my current gas boiler installed-- I let the installers take care of the refilling of the system with water and it went awry. Basically, they filled it all the way up, which was NOT what I wanted, since I didn't want to heat the attic. But what was worse, when I tried to bleed the radiators of air, the tremendous pressure of all the water above it, violently propelled the thing you unscrew with the special key out with tremendous speed, and it landed God knows where (I never found it). I had to have a repairman come in and fix it, and didn't have heat in the meantime.

So this time, I'm going to take charge of the refilling, and tomorrow I plan to only fill it up to about 13 feet, just enough to heat the first floor of the house. I'm going to carefully bleed the radiators on that floor of air once they have a chance to heat up, and then when I'm sure everything is working okay and the first floor is heated, I'm going to raise the water level to about 23 or 25 feet, enough to heat the second floor, but not the attic, and with not much water above it, I won't be creating a tremendous amount of weight and pressure in the radiators on the second floor so I don't have a repeat of what happened when filling the system last time.

First of all, is there anything wrong with my current plan?

Second, I have rooms that I don't use and don't want to heat, but I don't know if I should leave the valves to the radiators in those rooms open or closed when I fill the system. Does it matter?

Third, is there anything else I should know?-- I'm just an ignorant layman who might very well benefit from being told things that seem 'obvious', so please don't be reluctant to point out anything at all that occurs to you, whether important or trivial, obvious or a subtle point that's easily-overlooked by someone in my position.

Truthfully, I'm really extremely nervous that when I'm so close to getting my heat back after weeks without it, something will go wrong.
 
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Old 01-16-18, 01:59 PM
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I'm the rare person forced to convert from natural gas to oil
I feel compelled to disagree - you made this choice despite many of us advising not to do so.

https://www.doityourself.com/forum/b...ly-stupid.html
 
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Old 01-16-18, 06:02 PM
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stickshift, the fact that many of you (virtually all of you, in truth) disagreed does not mean I wasn't forced. Actually, the essentially unanimous disagreement in DIY with my notion of converting to oil had a strong impact on me-- for almost two weeks, I delayed pulling the trigger on the conversion to oil precisely because I felt I was obliged to more thoroughly explore the possibility of getting a reasonably timely restoration of my heat yet staying with gas.

So I called in several more plumbers, and they told me honestly-- and I can say 'honestly' because if they'd recommended staying with gas they could have had a big, expensive job in my house-- that given the situation in my basement, with so many small and large gas leaks in the pipes requiring essentially a complete replacement of all the gas lines and fittings, and especially given a leak in the line between the gas intake line at the outer wall and the gas meter, which was the utility's responsibility but which would make them require a new service line to the house, a procedure for which they are badly backlogged, and given the rigorous inspection by NYC of all the work done on the gas lines, and given the considerable time lag between the request for an inspection and the execution of the inspection by NYC, and given the separate inspection required by the utility, given all that (which must be done in its entirety before gas can be restored), the best estimate by all three of the plumbers was a minimum of three months and more likely four or five months before restoration of gas service. It doesn't require sophisticated math to recognize that I'd have had to spend the entire winter without heat. That, stickshift, is why I said I was forced to convert.

Does anyone have any advice on how to best refill my open (i.e. no circulating pump) hot water system while avoiding disaster? I'm eagerly seeking any pointers!
 
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Old 01-16-18, 06:17 PM
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The thingy you unscrew with the key is supposed to start letting air (or water) out before it is loose enough to be violently propelled out across the room.

If/when it lets water out then close it. There is no (more) air pocket at that location at that moment to necessitate waiting at that radiator. Go on to a different radiator.

I think free standing radiators in rooms that will not be used can be left unbled and that baseboard radiators must all be bled. In addition, baseboard radiators are more likely to need repeated bleeding because air pockets can migrate more easily from one radiator to another.
 
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Old 01-16-18, 06:35 PM
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L,
First of all you have a CLOSED system. All hot water systems are closed. Once filled, bled and completely closed to outside eliments and fresh water that brings air with it.

Why do you think it's open and what do you mean by open system.

Next, your filling system in stages is going to be I believe, bleeding repetitiously the same radiators just because they have been bled once, when fresh water is introduced there is no telling where the air will go.

If you have to bleed your system by each individual rad and not by one common drawoff in basement you either have a monoflow or 2 pipe system which means you can shut off any rad without affecting the rest of the system as in a loop system, which is a good thing.

As far as not filling the system all the way because of the pressure when bleeding at the vents is silly. You should know better than to NOT remove the bleed screw all the way when bleeding. When bleeding in stages you will most likely have to rebleed the same rads over and over as fresh water is applied to system unless you isolate those rads before you refill and get lucky.

With your type of system you can as I said, shut off any rad you don't want to heat and not affect any others so I would fill and bleed entire system so you will only go through this once and then the whole system will be ready for use as you need it.

Once filled and bled and tested on line you can isolate rads as you wish and reinstate as needed just by turning them back on.

As bleeding with any hot water system you want high pressure, at least 25psi to force all the air out and then bring pressure back to about 20psi when done as your running pressure.

No sense mentioning you bleed with pump off since you chose not to have one.

I think I've answered all of your questions as best I could for now.

Hope this helps a little.
 
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Old 01-16-18, 08:10 PM
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First of all, although I don't want to become maudlin-- you know, it's supposed to be very undignified for a man to become too sentimental!-- I have to say how very grateful I am to you, Allanj, and you, spott, for your responses. My friends and family have been wonderfully supportive emotionally, and I'm certainly appreciative of their buoying me up when I've been depressed by this unrelenting nightmare, but they all know even less about these subjects than I, and getting some sound, important advice about what to do bolsters me in an even more substantial way than their emotional sustenance! It really means the world to me, you guys!

I want to assure you both that when this incident with the 'thingy' occurred after the filling (and overfilling) of the gas boiler radiator system way back when, I knew not to unscrew the 'thingy' more than a little bit-- I suspect you won't believe me when I tell you that I only unscrewed it the tiny amount that I normally do (perhaps an eighth of a turn), when it violently-- and I mean VIOLENTLY-- exploded out, losing both the 'thingy' and the key and damaging the valve seat itself so badly that the repairman had to cement on a new seat!

spott, regarding your insisting that , "First of all you have a CLOSED system. All hot water systems are closed. Once filled, bled and completely closed to outside eliments and fresh water that brings air with it."

And then your asking me, " Why do you think it's open and what do you mean by open system."

Spott, here's why I think it's open (apart from the master plumber from the company doing the installing tomorrow CALLING it that, as opposed to what he called a circulating pump closed system ): Spott, there's a tank in a storage area of the attic that is intended to provide water to replace that which evaporates during the normal operation of the system. But leading from that tank is a pipe that penetrates the OUTER wall in the attic and leads to the outside. If, when filling the system, you don't pay attention to the water-level gauge, you may very well continue to put water into the system when all the radiators are filled and so is that tank in the storage area. What happens then is that the water simply flows through the pipe and out of the house, making a big splash thirty feet below when it lands in the yard. That's what is meant by an open system, and back when the installers of the gas boiler (that I'm now having replaced) told me they wanted the new gas boiler to have a circulating pump in order to more efficiently move the hot water from the basement boiler to the radiators around the house, they said they would have to close off that tank in the attic, in order for the circulating pump to work-- otherwise it would pump the hot water right out of my house and into the yard!

Regarding how I want to fill up the system: No, I wouldn't repeat the bleeding of any radiator, I'd just do each one once. The idea is to carefully avoid creating any sort of very high pressure situation at any radiator. So, by filling it only to around the 13 foot level, I'd only be filling it a little higher than the first floor. Thus, when I bleed those first-floor radiators (after they've heated up and the water inside has expanded), at that point-- with so little water above to press downward-- there's no chance of any exploding 'thingies'! And I'd repeat the process with the second floor, again only filling it to a level a little higher than the second floor. And ultimately I would only fill it to perhaps 25 feet, so I'd have enough extra water to compensate for evaporation without having to heat the attic rooms, which I don't use, or heat the storage tank in the attic. It not only saves money, but allows the lived-in portion of the house to heat up much more quickly, since the hottest of the hot water only rises to the second floor, where it's usefully employed, and not to the attic, where it wouldn't be.

I gather that nothing untoward will occur no matter whether I have the valves on the radiators in the unused rooms closed or open during the filling process, is that correct? I guess if there's extra air in those radiators, it doesn't matter anyway since my intention is to keep them cool, and there's no risk of air pressure inside compromising the integrity of the radiator, right?

Allanj, I have no baseboard radiators, they're all free-standing. I'm not sure if the valves are open or closed in the closed off rooms-- I'm using them for storage and it's difficult to access the radiators. But I gather nothing terrible will happen during the filling whether they're open or closed, is that right?

Thanks again to you guys, I count on DIY forums as my surest means of staving off disaster, which-- since Dec. 5, 2017 anyway-- has been nipping at my heels with alarming constancy, and taking huge bites out of my rear end with dismaying regularity!
 
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Old 01-16-18, 08:46 PM
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Is it possible to get pics of this system and tank. Curious to see the setup.

Does this system have an auto feed valve and where is the expansion tank.

Very curious about setup. Why didn't you want a pump installed rather than gravity,

Generally hot water systems don't run high enough temps to have any appreciable evaporation. That's why you can run them with the feed valve open or closed vs steam, because of the temp maintained, and continuously needs water.

Is that tank you have in the attic the expansion tank by any chance.
 
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Old 01-16-18, 09:54 PM
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spott, using the definition of expansion tank given by wikipedia, "An expansion tank or expansion vessel is a small tank used to protect closed (not open to atmospheric pressure) water heating systems and domestic hot water systems from excessive pressure" it can't be an expansion tank for two reasons: 1) my system IS open to atmospheric pressure, as indicated by what happens to the system when it's overfilled-- water shoots out of a hole in the wall (through a pipe) into my yard! 2) the tank's purpose is not to protect the system from excessive pressure, but to store water to automatically refill the radiators when they have the air bled out of them-- yes, believe it or not, spott, when you add up all the radiators in the house, there's considerable evaporation over time, and it's useful to have a water supply available that's not being used for heating to replenish what's lost.

No, it doesn't have an auto-feed valve, but it 'automatically' feeds new water into the radiators when the radiator is bled-- the water comes ultimately, in my house's case, from the hot water pipe leading up to the attic. Remember, I fill the system up to about 25 feet, about five feet above the second floor, which provides more than enough water to replace what's lost due to evaporation for the entire heating season.

Unfortunately, I can't supply pics, but I don't imagine it looks any different than any other system USED TO LOOK before they were all converted to closed systems, with a circulating pump, whenever that was.

The reason I rejected the closed system with the circulating pump was, simply put, AGE. Not mine, but the radiators'! As near as I can tell, they are well over a hundred years old, and, worse than mere age, is the fact that they were never designed to withstand the rigors of water almost continuously circulating through them. And even worse than that, is that no adaptation would be made to the radiators to make them more able to withstand that uncontemplated abuse! So I was sure that leaks would develop over time, and be calamitous, both in terms of my temporarily losing the ability to heat my home, perhaps at the very bitterest time in the winter, and in terms of requiring a very costly expenditure to repair. And considering the positive side.... well, from my point of view, there really ISN'T a positive side, because any savings due to a more efficient distribution of heat around the house by the pump, would be more than offset by my being forced to heat the whole house, a large portion of which I don't have to-- and in fact do not-- heat with my open, non-pump, gravity system, because I can either close off the radiator in the room (as is the case on the lower floors) or not raise the water level high enough to even reach the radiators (the case in the attic). Spott, I only heat about half of a very large house!
 
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Old 01-16-18, 10:14 PM
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These gravity systems are as much art as science, and so I would recommend operating as originally designed, with the attic radiation filled. Otherwise, you may have trouble getting the right flow/heat to the other radiators and some rooms may be too hot or cold. This will be more of an issue if the home has a large footprint with a lot of radiators. If you have a small footprint and only a few radiators per floor, probably will be more forgiving.

Keep in mind that partially filled and without an expansion tank, the piping will act as an expansion tank, and the water level will expand up and down depending on how hot the water is. If you fill the system hot to the 2nd floor ceiling, when cold the level may fall below the 2nd floor radiation, which will cause air problems.

While you might leave the 3rd floor unfilled, don't leave a radiator unfilled on the same level as a filled radiator, unless you can isolate the radiator with valves. Otherwise, you will be asking for a a nightmare of air problems.

Consider adding a pump and modern diaphragm expansion tank. Not that expensive, and will make the boiler much more hands off, and will greatly simplify heat balance and air elimination and provide other benefits. Because of the large diameter gravity piping, you can use a low head, low power, low cost pump.

​​​
 
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Old 01-16-18, 10:54 PM
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It's too bad about the pics. I would love to see this system.
 
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Old 01-17-18, 06:20 AM
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Everything is going to be at roughly the same pressure whether or not you have a circulator pump and regardless of which radiators are bled of air or not. (The pressure measured in the basement will be higher than the pressure measured on the top floor.) So bleeding a radiator of air or not bleeding it will not cause unusual high pressure to occur there or anywhere else.

As the boiler cycles on (and heats up) and cycles off (then cools down) the water in the system will always expand (in your case up into the attic reservoir) and contract respectively, although I guess no more than one gallon for a fairly large heating system. So there must be some air filled expansion space somewhere, probably in the reservoir on which the overflow pipe is probably mounted. Evaporation that ultimately requires adding water will only occur in the vicinity of the overflow pipe. Any air trapped in radiators will quickly reach 100% humidity and no more evaporation will occur there.

Settling of the house may have changed the angles and slopes of pipes going to and from the radiators and this in turn may cause erratic heating of radiators given the gravity flow. To achieve a given amount of room heating, a radiator needs just as much water throughput in a gravity system as it would in a forced hot water system with the same boiler temperature characteristics. So I would not expect converting to forced hot water would put stress on the radiators and piping.
 

Last edited by AllanJ; 01-17-18 at 06:45 AM.
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Old 01-17-18, 06:43 AM
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For those interested the first two diagrams.Fundamentals of Heating Systems
 
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Old 01-17-18, 09:45 AM
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Allanj, you say, "Evaporation that ultimately requires adding water will only occur in the vicinity of the overflow pipe. Any air trapped in radiators will quickly reach 100% humidity and no more evaporation will occur there."

If that's true (and your analysis seems very plausible, in fact, far more than plausible-- irresistibly logical!), then when you bleed all the air out by turning the key, hearing the whoosh, and finally getting water, there should never be any need for repetition-- UNLESS, of course, you haven't in fact bled all the air out, and air elsewhere in the radiator over the course of time worked its way back to a position at the top of the radiator, which is entirely possible since a given volume of air is lighter than water and would therefore -- quite possibly aided by a convective flow-- eventually rise to the top of the radiator. And then you'd have to repeat the bleed, and each time you did so in that or any other radiator, the water level in either the storage tank in the attic (if I were to allow the water level in the system to go high enough to fill it) or, in my case, in the heating system pipe leading up to the attic, would drop, as water moved, through gravity, into the radiator after the bleed, thus depleting the amount of water in the heating system pipe leading up to the attic. So although evaporation will lower the water level in the heating system pipe leading to my attic, evaporation occurs only in the vicinity of that pipe. All other lowering of that level-- due to bleeds of radiators-- is caused by already-existing air pockets in the system being bled out, not evaporation.

Excellent analysis exploding my myth of evaporation, Allanj!

So what is your final verdict on whether or not it matters if I have the valve to a radiator open or closed during the filling? One concern I have during every winter is that the radiator water in unheated rooms (those with the valve closed) not freeze during an extended stretch of bitterly cold weather-- and I guess freezing is possible even though all the radiators, including those with the valve closed, are still connected to the overall system through the back way (obviously every radiator is connected to the system in two ways, and closing the valve only keeps a radiator from connecting with the hottest water through the 'front way'). The radiator on my front porch is a good example. I keep a thermometer on top of that radiator, but keep the valve closed normally. But as the front porch temp drops to the low 20s during very cold periods, the thermometer on top of the radiator drops, sometimes, into the mid 30s, at which point I briefly open the radiator valve and let the very hot water on the other side of the valve mingle with the radiator water, causing-- after mere seconds-- the thermometer on top of the radiator to shoot into the 50s. But what if I didn't do that? And, on the other hand, what if that radiator had a big air pocket? Allanj, would a big air pocket prevent damage to the radiator from freezing if the water in the radiator froze because the water, though expanding upon freezing, would have a place to expand into? But if the air pocket (and place to expand) is too small it wouldn't prevent damage? If that's true, since I can't know how big a given air pocket in a radiator is, then filling all radiators as much as possible would be the most sensible thing to do by leaving the valve open during filling, and ONLY THEN closing the valves on the radiators in rooms I don't want to heat-- and then briefly re-opening the valve if the room temp in the closed off room fell too much during extreme cold. Allanj, does that course of action withstand your logical scrutiny?

Or maybe the best course is regardless of whether I kept the valve open or closed during filling, and regardless of how big or small the air pocket in a radiator may be, I should just keep a check on the temperature in the radiator in every unheated room during cold stretches by positioning a thermometer on top of the radiator in each of those rooms. And a few ounces of water in a glass, to provide an objective check on the room temp, to see when it's approaching freezing.

Allanj, am I overthinking this, or simply doing sensible precautionary analysis?
 
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Old 01-17-18, 01:28 PM
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Let me add my 2 cents. I live in a town north of Pittsburgh and in 1968 I started working for a heating and A/C company. We serviced heating systems in homes in the area many of which were systems similar to yours, gravity flow with a vented, open, expansion tank . The expansion tank had an overflow pipe that ran down to the basement so that any water in excess of that which the system was designed to hold would run down the pipe to a basement drain instead of outside so that the overflow water would not freeze in the winter. The open tank (vented ) system was manually filled with water until water would flow down the overflow pipe , then the manual valve was closed.was fThe tank was usually mounted in the top of a cupboard on the top floor or in the ceiling of that floor. The tank had to be mounted above the top of the highest radiator to insure that the system remained full at all times. The only problem with this system design was that temperature changes either up or down were slow due to the slow flow of water throughout the system. The heated water would expand and become lighter and flow upwards in the system . Upon cooling the water would become heavier and drop down the return piping causing the water to flow through the system, hence the term "gravity flow system". You could increase the systems efficiency and response to temperature changes by adding a small B&G circulating pump into the piping to speed up the flow of water in the system. The gravity systems worked great except for the before mentioned lag time in response to temperature changes. Now for an explanation of the systems pressures. The pressures in either system should be almost the same. The closed loop system pressure should normally be no higher than that of the open tank system since the water in either system has to be held up to the top of the highest radiator. So, 1 pound of water pressure will hold a column of water up 2.31 feet. So if the distance from the boilers pressure gauge to the top of the highest radiator was 40 feet, then 40 divided by 2.31 feet/lb = 17.31 lbs. pressure at the gauge. (This is the same for both systems, either the open or the closed) There is no difference in the pressure in either system. Now, if the water blew out of a vent when the vent valve was turned only slightly then the vent valve was bad or worn out and should be replaced. I would replace them all due to their age.As far as your choice of fuels that is your choice. My choice would be the natural gas since it is more dependable and cheaper to service and requires less maintenance. An oil unit will require more cleaning, and annual oil filter and fuel nozzle replacement. Again, the choice is yours. I would recommend that you fill the whole system , vent out all the air, heat the water and drive out all the entrained air and vent again. If you want a reduced temperature in those rooms partially close the radiator valve feeding that radiator. Remember that gravity flow is dependent on volume flow. Closing some radiators may unbalance the system and could reduce the water flow. MY 2 cents.
 

Last edited by Steamboy; 01-17-18 at 01:31 PM. Reason: more information
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Old 01-17-18, 06:19 PM
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Air in radiators that have not yet been bled could migrate over to the radiator you just bled, thus you may need to come back and bleed more air from radiators that have already been bled.

Given the open overflow tube with no pressure sensitive valve in it, the system pressure will never get very high. For the reservoir in the attic about 30 feet above the basement floor, a radiator sitting on the basement floor will have a pressure of about 13 PSI or the system pressure at the bottom will be about 0.43 PSI more for each foot below the reservoir the system extends. Still, this should be enough to bleed the radiators with.

If you do not bleed a radiator at all, for example it is in a room that you do not want to waste heat on, water will still enter through that radiator. The unbled air will compress a little to let water in and some water will pool up in the bottom of the radiator. How much water pools up there depends on the system pressure.
 
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