Attic Systern

skibum · September 2010

<span style="font-size:12pt">I just looked at a job that had no sight glass on the boiler. It had a sight glass on a cistern in the attic. The owner takes water up there 2 times per heating season and fills it up to the crack in the sight glass because the sight glass is longer than any available at the supply house. This is one of those converted from hand fired coal or wood but not quite old enough to be covered in asbestos boilers. He wants a new boiler because the old one is basically cemented together and is running at about 73%. Something else I have never seen in steam, there are manual vents on the radiators. He says he only has to bleed them once per season. There is no pressure-trol on this thing either. This appears to be a 2 pipe system and he might consider switching over to forced hot water. He is concerned that the extra weight in existing pipes could cause a problem. I have re-scanned through Dan's books that I own and I don’t see anything covering this cistern in the attic. I may have overlooked it. Any insight anybody has on this would be greatly appreciated. Aparently there are several houses in this area built around the same time with the same kind of set up.</span>

gerry gill · September 2010

its a hot water system.

not a steam system.

skibum · September 2010

Thanks

That was my thought too gravity hot water. The owner kept insisting it was steam so it through me off a little. There was also a pressure/temp guage on the boiler another indication of a hot water system. The temp guage didn't work but the pressure was running a little (lot) high for steam too. but it isn't like 8 lbs has never been done before...not that it should but it has. The customer also said that when he bled the radiators it wouldn't shoot water out, it would just sputter a bit...but an open system would possibly act that way. This is likely what he was told by some real estate agent years ago and he never heard any different. Is 8 PSI in the basement about right for a 3 story building with an open system. I guess that means the cistern was actually the expansion tank. This still could be an interesting boiler swap though. All that 100 year old steel pipe.

gerry gill · September 2010

3 stories high

we usually set at 18 pounds.

skibum · September 2010

open system

That cistern or expansion tank in the attic dosn't have a cap on it. weather or not it is supposed to be, it appears to be an open system and has been for years.

gerry gill · September 2010

you really only have to fill

that system to a head pressure that exists when the water is at the third floor radiator vents..expansion will add some extra height (pressure)..most open tanks had a pipe that overflowed either to the roof outdoors, or the pipe dropped back to the floor drain in the basement, or it was punched into the soil stack vent..

Dave in QCA · September 2010

Gravity is Free

Gravity hot water is a great system as long as the piping was done correctly. It is quiet, even, and there is no pump. So, you don't have to pay the electricity to run the pump, nor the replacement cost when it wears out. The hot water just flows through the system by itself. It can do that because the pipes were installed at much larger sizes than would be necessary with a pumped system.   Since you have those huge pipes, you might as well put them to good use. I had a house back in the early 80s that had a great gravity system. The boiler had been replaced with a modern gas fired cast iron sectional boiler. They had used the round opening intended for a hot water coil as the outlet. A 3 1/2" flange fit it fine. This was piped into the mains in the house.   The return piping was reduced from 3 1/2" down to 2" as the piping dropped and conncected to the boiler.   There was a manual fill valve in the basement, and as long as you were reading the "feet" scale - and you knew what reading was necessary to put the water level (cold) to where about 2" was visible on the site glass in the attic, it was fine!   You cannot use an auto fill because they tend to drift a bit, and a tiny drift can overflow the expansion tank.

Usually when the expansion tank was installed in the attic, it was piped so that water circulated through it, the same as a the radiators. If the attic is ventilated and prone to freezing, the tanks were usually enclosed in some kind of a box structure that was filled with insulation. Of course, if it was installed in a small partioned room in the attic, that was partially heated, or at least did not freeze, then there is no worry. Since this expansion tank has been there for 100 years, it was obviously done correctly, you just need to be aware of if changes are made to the attic space where the tank is located.

In a sealed system with a compression tank, usually located in the basement, as the water gets hotter and expands, it moves into the compression tank and compresses the air cushion in that tank. So, the boiler pressure gauge will read slightly higher as the temperature rises.   In an open expansion tank system, the tank is vented to the atmosphere. As the water gets hotter, it expands and flows into the tank. You will be able to see it rise on the sight glass. However, the boiler pressure gauge will not show an increase. There is no pressure from compressed air, the water mass is the same, it has only expanded, and at the same time, the weight/gallon of the water has decreased. Therefore, the space that the water takes up has increased, but it is still the same amount of water. The pressure gauge at the boiler can't tell the difference.   That is one more nice thing about gravity water, no water logged compression tank that causes the pop off to open when the boiler gets hot.

I am not sure if there are any boilers out there today that could be adapted to gravity flow, but it would be worth looking.

http://www.statesupply.com/displayCategory.do?Id=2119    Here is a link to a supplier that sells sight gauge glass up to 4 feet long.

skibum · September 2010

Forced hot water

I talked to this customer again today and he is still stuck on the idea that he has steam. and wants to convert to forced hot water. all of the supply and return pipes from the radiators are 1" I'm thinking that the easiest way to do this would be make 3 loops I'm not sure if the 3'rd floor had any radiators in use but that floor is being renovated and baseboard might be easier for that one but I will have to see what he wants to do with that zone.I didn't bother to measure the existing radiation until I found more about what kind of system this was. I believe he has gotten 2 other prices but they priced it as a steam system. Imagine their suprise when they took the sawzall to the pipes above the boiler!

I actually have done one new house with cast iron radiators. this customer has a wood fired boiler hooked up in tandem with a oil fired boiler. I used normally opened zone valves so when the power goes out he still gets heat. It works pretty well and he heated it with no power for most of the winter while construction was still going on. This is all just using a 1-1/4 " header and 3/4" copper then some 3/4" Fosta pex

skibum · September 2010

Oh yea

On the picture above, the overflow is actually tied in to the sewer vent pipe. You can see the vent pipe on the left side of the picture.

Dave in QCA · September 2010

Customer demands what he already has?

This sounds like the easiest job one could hope to find. All you have to do is deliver to the customer, what he already has!

You could put in a new properly sized boiler with a circulator and connect it to the existing system that serves the 1st and 2nd floor, without any modifications.

You could add a second circulator to run to the 3rd floor, since it is being renovated and heat added. You will need to separately control this space because there is little chance that the design will match what is propably excess radiation on the first 2 floors.

If the expansion tank on the 3rd floor is in the way of space that is going to be used, you could replace it with a properly sized compression tank in the basement, and an auto fill. Remember when sizing the compression tank that you have a lot of water! These types of conversions usually have a tank in the area of 7 - 10 gallons.

Somewhere along the line, the customer needs to beleive that you have changed his system, since he apparently won't listen to an expert. Perhaps installing new key type vents on the existing radiators will do the trick. Or better yet, level with him. With the use of pictures and diagrams you can show him systems just like what he has, and that they are called gravity hot water. (you have to remember that many poeple see cast iron radiators and think that means its a steam system) There are plenty of diagrams and illustrations available on this website by going to the Resources heading, the choose library.

I did see that pipe heading toward the sewer vent stack, but wasn't sure it was going where it appeared to.

Dave in QCA · September 2010

Here is a particularly good publication on Gravity Hot Water

http://www.heatinghelp.com/files/articles/1208/143.pdf

Attic Systern

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