Thermosiphon(All You Ever Wanted to Know)

 
BIG BEAM
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Post by BIG BEAM » Sun. Sep. 14, 2008 4:57 pm

There are so many questions about this.Look at the way it was done years ago.Notice that you don't need check valves.
Just google range boiler,click on STANDARD PRACTICAL PLUMBING about 10 items from the top of the page.
Maybe someone can link to this I don't know how.


 
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Richard S.
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Post by Richard S. » Sun. Sep. 14, 2008 5:04 pm


 
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traderfjp
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Post by traderfjp » Sun. Sep. 14, 2008 6:31 pm

In the end I decided to use a small circulator. I wasn't a fan of that setup either.

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ceccil
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Post by ceccil » Sun. Sep. 14, 2008 9:57 pm

I had to put a swing check on my supply line for a small 110v hot water tank hooked to a shallow well tank. If it sat very long without using hot water, it would build heat all the way to the diaphram tank. Sometimes the cold water would come out quite hot. Not an issue after I added the swing check.

Jeff

 
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Dallas
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Post by Dallas » Sun. Sep. 14, 2008 10:12 pm

There is another way to do that without valves. I can't remember what it's called, but it's simply putting a loop in the water line and running it "down" for a bit, which will break the gravity flow of the hot water.

 
BIG BEAM
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Post by BIG BEAM » Mon. Sep. 15, 2008 8:39 am

That's right dallas,
A thermosiphon will not go down hill MOST of the time.When you tie in the cold water you run a loop about 1' down the side of the heater on the cold side.That stops the gravity feed(thermosiphon).
DON

 
BIG BEAM
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Post by BIG BEAM » Mon. Sep. 15, 2008 8:44 am

If you guys look at the 1910 book that I posted you will see 1 tank 2 stove systems.1st and 2 nd floor systems .STOVE ON THE 2ND FLOOR TANK ON THE 1 ST FLOOR.Like I said all you ever wanted to know about thermosiphon.
DON


 
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Richard S.
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Post by Richard S. » Mon. Sep. 15, 2008 9:01 am

BIG BEAM wrote:If you omit the check valve on the cold water line feeding water to the tank it will expand into the well tank or city water line.
DON
I believe in some places that's code??? They don't want water from your house going back into the city water lines. Contamination would be one reason. The check valve on the return line insures that all the water from the inlet is forced through the coil first. ;)

 
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Post by Adamiscold » Mon. Sep. 15, 2008 9:11 am

BIG BEAM wrote:If you omit the check valve on the cold water line feeding water to the tank it will expand into the well tank or city water line.
DON
I believe in some places that's code??? They don't want water from your house going back into the city water lines. Contamination would be one reason.
I believe you can skip the check valve on the feed line into the house if you are using a pressure reducer since they have a check valve built right into them.

 
BIG BEAM
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Post by BIG BEAM » Mon. Sep. 15, 2008 2:12 pm

I'm BACK
I don't think a whole house presure reducer has a check valve.
A what we call water feeder(boiler reducing valve) does.

I have a 120 gal water heater on a timmer.We have a cheap rate at night.When I get up in the morning and the water heater has been running all night the cold water pipe will be hot for 10 or 15 feet.Thats how much 120 gals. will expand when heating up 100F temp rise.

I know city water don't like backflow (I sat on the village board for 8 yrs) but this they have to except.

Let me tell you a little story...
I have a customer that had a P and T valve leaking every night for 30 years.He would put a bucket under it and empty it every 3 or 4 days.He said no plumber could figure it out.He had a strange system.A range boiler full but not using it.The heating system was ci radiators and oil boiler.A 80 gal electric water heater(that's what leaked EVERY night.He had a new water service copper, put in about 30 yrs ago.LIGHT BULB.I looked at the water meter and sure enough a check valve for the whole house.The guy that installed the water service said it was needed for the boiler.Removed said check valve problem solved.
DON
These people think I'm some sort of god now,crazy.

 
BIG BEAM
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Post by BIG BEAM » Mon. Sep. 15, 2008 2:21 pm

Richard,
The check valve will do nothing but hamper the thermosiphom flow.
It is not needed.The hot water will expand in the coil thus becoming lighter and rise.

You can even gravity off a coil on the 1 st floor and have the tank in the cellar!
I know I'm opening a can of worms here but read the book it works!
DON

 
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Richard S.
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Post by Richard S. » Mon. Sep. 15, 2008 2:40 pm

BIG BEAM wrote:The check valve will do nothing but hamper the thermosiphom flow.
Yes I understand that, I believe Yanche mentioned that and suggested a "swing gate".

In any event if we're trying to extract as much heat from the coil as possible I don't see the point of sending cold water into a hot water tank to be heated by the HW tank when you can force the coil to preheat every drop. As I mentioned before out HW heater isn't anything more than a glorified storage tank. Realistically we could probably get by with a insulated tank but prefer to have the convenience for the few days in the summer the furnace is shut off.

 
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Post by BIG BEAM » Mon. Sep. 15, 2008 3:38 pm

So your system isn't a pure range boiler set up.You are preheating your domestic cold water through the coil first then feeding it to the tank.When there is no load(no hot water being drawn) then the tank heats up the rest of the way with the thermosipon?
DON

 
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Richard S.
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Post by Richard S. » Mon. Sep. 15, 2008 3:58 pm

Well I don't know what the definition is and as I said its no longer set up that way, and not because it didn't work. Now it's fed right into the tank.

 
BIG BEAM
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Post by BIG BEAM » Mon. Sep. 15, 2008 4:34 pm

From what you just said the coil and tank were in series.First the cold water would go through the coil and than from the outlet of the coil to the cold water into the tank.Do I have this right?
DON


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