Bypassing &/or Gerrry-rigging a boiler expansion tank

[copperkid3]

I have a home-made super sized outside wood boiler that is mainly based on the pattern of the commercial unit that it replaced.

The installer who helped me with the original unit, put in a 2.2 gallon diaphram expansion tank that connects directly below the air

scoop.  The first tank lasted about 8 years and then developed a leak; first in the the diaphram and eventually then through the side

wall of the metal portion of the tank.  I located a replacement the same size on eBay and replaced it myself, but for some unknown

reason, it only lasted about 2.5 yrs this time before doing the same thing as the first one did.  Again, I found another on eBay and

purchased it late last week, but it will probably arrive sometime towards the end of the week.  We had some delightfully warm days

over the weekend, but the forecast shows temperatures dropping back into the low 30's and inside the house yesterday started dropping

while waiting for this part, to around 58; a bit too cool for me.  I know that the tank is "supposed" to be an essential part of the boiler

system, but I decided to try and see if I could do without it for a few days and see if it would still work, by placing a 1/2" standard threaded

plug into the bottom of the air scoop, to keep the water flowing in the right direction.  Imagine my surprise, when the temperature started

climbing by nearly 5 degrees in less than 3 hours....something that normally takes about an hour/degree to get moving.  In the next 5 hours,

it went up another 5 degrees and although I do like it around 72 normally, the 68 was much better than what I had been having to put up with.

Since this works so well without the tank, I'm wondering what the ramifications would be to leave it off, or better yet, explain to me, the general

concept of why it is working so well and what might be the downside?  I do plan on replacing the plug with the tank when it arrives, but I'm left

wondering.....  

[Bear Foot Farm]

It's probably running higher pressure without the expansion tank.
Is there a safety "pop-off" valve?

[copperkid3]

Two of them, as a matter of fact and neither has blown off since I've started this experiment.

I'm thinking that because I'm being careful NOT to fire it up so high as I've done in the past,

that this may be the primary reason that it is operating without problems...the new tank should be

here by the end of the week and will be put back in place then.

[beowoulf90]

The expansion tank is a safety thing. Back in the day they didn't have good safety "pop-off" valves and the boilers would explode if pressure wasn't released, so they used expansion tanks to help accommodate the expansion of the water as it heated. Remember these were normally inside your home, in the basement.

The safety valves of today are better then days past, but having the expansion tank is still a good idea.

If you want to see what happens when the pressure builds too high search for the Myth Busters Water Heater explosion episodes. You will see how a simple water heater can become a projectile/bomb. Same thing with boilers..

[Deleted]

Careful Icarus.

The increased efficiency, assuming that is in fact true, can be attributed to the tank being outside the heat exchange. The tank would be losing heat outside the house.

The danger you face is from the fact that fluids are practically incompressible with this technology. The tank adds gas that is compressible with this technology. PV=RT is the simplest way to state the danger. R is the Rankin constant and T is Temperature. As Temperature increases Pressure(P) and/or Volume(V) must increase. You have practically eliminated the possibility of Volume increase.

More to the root of your issue, what media are you using?

[shellymay]

Here it is mandatory if you have a plumber replace a hot water heater, they have to now add the expansion tank as well or they
won't install a new hot water heater, We had our replaced last year and oh the joy of this ugly extra price expansion tank thingy
ours is a 80 gal tank.....


 

[copperkid3]

Feb 24, 2016 22:46:30 GMT @skamp said:

Careful Icarus.

The increased efficiency, assuming that is in fact true, can be attributed to the tank being outside the heat exchange. The tank would be losing heat outside the house.

The danger you face is from the fact that fluids are practically incompressible with this technology. The tank adds gas that is compressible with this technology. PV=RT is the simplest way to state the danger. R is the Rankin constant and T is Temperature. As Temperature increases Pressure(P) and/or Volume(V) must increase. You have practically eliminated the possibility of Volume increase.

More to the root of your issue, what media are you using?

Pure well water with an automatic filler valve.  There is a smaller expansion tank inside the house *(probably a one gallon size) that is used just in front of,

(but below) a similar sized tank like shellymay has.  I've been diverting my hot water into this tank BEFORE it goes thru-out the rest of the house, so this

fact, as well as keeping the fire low in stature inside the boiler (so far I've been able to keep it around 100-120 degrees at the source and been able to

maintain a consistent 67-68 degrees F. inside the house.  It actually got away from me for about a half an hour with a reading for a short time of 69 and now 70.

The worst of the storm has been thru here....have about 8 inches of wet snow, but the outside temperature is a steady 35F, so a difference of about 35

degrees - the outside from the inside.  The tank should be here in the next day or so and will immediately be put back in place.  I've got plenty of spare

Grumman circulatory pumps, T&P valves and magnesium anode rods to keep on hand for "emergency repairs" on the boiler, but apparently figured that I

still had a few more years on the expansion tank.  I figured wrong, but I hesitate to actually buy another and keep it around for who knows how many

years while the diaphram likely deteriorates with age.   Best bet....keep a close eye on it and when it starts looking "funny"....place the order for replacement.


BTW:  THIS is as close as you'll see me getting into feathers & wax.....although as a teen, I was trying to figure out a way of taking enough of my mom's
bedsheets so she wouldn't miss them, while a friend of mine was going to be doing the same with his mom, and then combining our haul into some type of
hot air balloon.....fortunately, we both got caught and that 'idea' never got off the ground.  Too many high power towers & lines in the area we were considering.

[Deleted]

shellymay, city water?

[Deleted]

There is no such thing as "pure well water". Minerals, and particular electrolytes wreak havoc, you don't dope the water?

[shellymay]

Feb 25, 2016 2:33:14 GMT @skamp said:

shellymay , city water?

YES................