AA260M Boiler Room and Run Video.

Your red expansion tanks look like domestic water tanks. If so, are they rated for the temps they might see on a boiler? Or maybe they're a style I haven't seen. Just curious.

Nice video! Thanks for taking the time & sharing.

mikeandgerry wrote:Thanks John.

I understand the height issue. I have a split entry home with living space at boiler level. The extrol tank is mounted high (over the boiler). There is 22 inches from tank top to ceiling. The upper floor is approx 1 ft above that (2x10 joists, + flooring + wall board=1 ft), the radiators on that floor are 25 inches tall. That all adds up to about 5ft.

Actually in your last run with the calculator the total system should have been 93 gallons, not 53 gallons. I am going to re-calculate my system volume again. Having older radiators and a system that is not easily drainable (boiler at same level as a lot of the radiation), I couldn't determine system volume by measurement, nor by calculation, without estimates.

I find all of these calculators and rules of thumb quite interesting because of their different approaches. The Engineering Tool box has a formula that considers system volume, intial and operating specific volumes, intial and operating pressures and a safety factor. Your calculator considers those variable but adds the system design pressure at its highest point. The Amtrol calculator considers volume, maximum system output, type of radiation distribution, and system temperature but not a word about pressure. The rules of thumb usually consider only BTU output and assume the rest.

In this case it would be acceptable to err to the larger tank sizes but space and cost are always issues. The right size is always best. It seems elusive in my case since I cannot accurately estimate my old radiator capacities.

Thanks again, John

I'm going to post how I got to my size but am waiting for the time to type it out,,,, but what type of rads to you have.

There are two steps in determining the sizing of a diaphragm expansion tank. The first step is calculating the proper air side pressure. This is the pressure set on the tank before it is installed. The formula is:

Pa = H x (D/144) + 5

Where Pa is the pressure (air) in psi, H is the distance in feet from the inlet of the expansion tank to the top of the highest heat emitter or pipe. D is the density of the fluid of the initial fill fluid (cold) in lbs/cubic ft. The 5 psi is a safety margin. It's purpose is to assure that the tank is sized so the max pressure is never more than 5 psi below the boilers safety relief pressure.

Next you need to determine the minimum volume of the tank. The formula is:

Vm = Vs x (Dc/Dh -1) x ((Prv + 9.7)/(Prv - Pa -5))

Where:
Vm is the minimum sized diaphragm tank (gallons).
Vs is the system fluid volume (gallons).
Dc is the density cold (lbs/cubic ft)
Dh is the density hot (lbs/cubic ft)
Pa is the pressure determined in the previous formula (psi)
Prv is the pressure rating of the pressure relief valve (psi)

Notice the formula make no assumptions, you can have pressure relief valves with pressures greater than 30 psi, as you would need in a multi-story tall building.

It also permits any fluid, you just have to calculate the fluid density at each of the temperatures. The formula to calculate water density is:

D = 62.56 + 3.413 x 10^(-4)(T) - 6.255 x 10^(-5)((T)^2)

Were D = density lb/ft
T = temperature deg F.

If you have anti-freeze fluid added it's still more complicated, but just another formula.

For most installers they just use the short cut methods ... table lookups, gut feel, what worked on the last job or guess.

Freddy wrote:Your red expansion tanks look like domestic water tanks. If so, are they rated for the temps they might see on a boiler? Or maybe they're a style I haven't seen. Just curious.

Nice video! Thanks for taking the time & sharing.

They are a B&G HFT-30V expansion tank which is a 14gallon hydronic heating expansion tank tank that is floor model, I went this way for two reason #1 cleaner install and two by have the tanks further from the boiler it takes removes most of the heat out of the water except in the coldest days when the water is really heated and by keeping the heat away from the tank you don't heat the air. remember when you heat the air in the tank it expands and when you do that you loose take up potential meaning this, say your tank is preset @ 12psi now you just installed it in a heated system the air pressure that was once 12psi is now say 14psi your tank won't take on water till the system pressure goes over 14psi now instead of 12psi. large systems use remote tanks for two reason heavy and can be put out of the way and keep them from the heat so you don't have this problem. in my case the point of referance is at the same place as my pressure reducing valve.

U235a4 wrote:I'm going to post how I got to my size but am waiting for the time to type it out,,,, but what type of rads to you have.

Zach, I know you are busy young guy and I appreciate the thought. I don't want to waste too much of your time. I think John (Yanche) has fixed me up with the formulas....he's retired and got a little more time on his hands. I appreciate the thought and if you find the time I am willing to read what you have to say.

As for the rads:

I spent the autumn of 2006 buying up certain sized used cast iron radiators off ebay and locally. I had them bead blasted and painted with auto body paint. They all look and act brand new.

Five are Burnham Slenderized for which I do know the exact volume, four are AERO by National Radiator Co. (about 80 years old, very heavy duty tube radiators, unknown volume) and two are Utica (boiler co?, unknown volume), one is marked SD and is a Burnham Slenderized clone, one is marked ARCO (also similar to Burnham Slenderized), and I have 5' of Weil-Mclain Snug No.9 cast iron baseboard (a known volume). All are tube (not column) style. I used various charts online to calculate their btu/h outputs at a 170degF awt.

I have estimated the AERO's as having 1/2 inch i.d. vertical tubes using my little finger . The sections are connected with 2" push nipples. I've made reasoned estimates of the unknowns. I'm close. My AA 130 has a capacity of about 20 gallons by my measurement but Pete didn't seem to know off the top of his head what the volume was. I've got 490' of 3/4" M piping, 30' of 1-1/4" piping.

After next week, I will revisit this problem. I got a few things going on myself.

Thanks for your time and input!

Yanche wrote:There are two steps in determining the sizing of a diaphragm expansion tank. The first step is calculating the proper air side pressure. This is the pressure set on the tank before it is installed. The formula is:........

...........For most installers they just use the short cut methods ... table lookups, gut feel, what worked on the last job or guess.

That formula differs from the Engineering Toolbox formula but it's similar. I will have to attack this problem next week. I have too many things to do this week and weekend.

Unfortunately, though I made an effort to get the size right, I resorted to the short cut method because I didn't want to do the math.

I see math and a larger tank in my near future.

Thanks, John. I'll get back to you when I've finished the homework!

I'm sorry about the delay but after seeing john pickup the ball and run I sorta stepped back because hes taking you on the right path, I used a old gravity system method of sizing for a compression tank and then converting that to a diaghram tank size. at the given moment I have more expansion then I need but I planned ahead because I'm still adding to the system and those are know loads that I could go by. If you go back and look at the tanks in the vid you will see that one valve going to the tanks is shut the other is open. I have 948.5 sq ft of cast iron radiation so I used this formula

948.5x.03 = ~28 (compression tank size)
28x.55 = ~15 ( this is the diaghram tank size for the install load at this point I also added the future load and decided is was close enough to just use two 14 gal tanks.)
.44 1 story house
.55 2 story house

As for being busy I'm a senior networking field engineer for fortune 500 company and the network administrator for a local 911 center plus family life so I need a vacation in a small island at the moment.

I have 500 sq ft of radiation, about 10% more than I needed.

I see from your system and the equation that you have a need for that much expansion tank. While I haven't completed my calculations I see that I have a need for an 8 gallon tank and though my load isn't that great, the amtrol online calculator suggests a 14 gal tank given the potential output of the boiler.

I have a clearer understanding of your need (and mine!)

I can tell you are busy: Your website hasn't been updated in a while. You know the old adage: the cobbler's children usually go barefooted.

BTW. I love your system and I am curious about the 260-m. I put in the 130m but I have never seen a 260 up close or in action. I appreciated the video greatly. I had a great time designing my system and getting the radiators. I wish I had the engineering backround to have tweaked it better but I am learning as I go on certain things. I seemed to have avoided catastrophe up to this point with the help of good people on this forum, John Sigenthaler and many websites.

Thanks again.

mikeandgerry wrote:
BTW. I love your system and I am curious about the 260-m. I put in the 130m but I have never seen a 260 up close or in action. I appreciated the video greatly. I had a great time designing my system and getting the radiators. I wish I had the engineering backround to have tweaked it better but I am learning as I go on certain things. I seemed to have avoided catastrophe up to this point with the help of good people on this forum, John Sigenthaler and many websites.

Thanks again.

You were also wondering about water volume of a 130m.

130m = 22 gallons
260m = 34.5 gallons