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Posted By sparke,
Mar 1, 2008 at 9:53 PM
Jebatty, Do you use dip tubes? Turbulence in the tank?
Have not because don't currently heat DHW with the boiler, but will consider in the future. I'm finishing my first season with the Tarm. I'm waiting for the LP tank to be delivered, and I'm not sure of the maximum opening into the tank that could be used to insert a coil. What do you suggest?
I do not on the open system tank currently used because the tank had an inlet fitting on the top and a drain fitting on the bottom. Also, I do nothing to create turbulence. Hot water in on the top and cold out the bottom results in very heavy stratification, which seems to be most desirable. A really good part of the heavy stratification is that the return to the hx is coolest possible, which also results in the highest rate of heat transfer through the hx. I get as much as an 80F heat rise through the hx.
On the soon to be pressurized system, as I don't have the tank yet, I may have to use a dip tube on the return side to draw cool water from the bottom of the tank but I don't think I will need one on the top side for supply hot water. What do you have in mind?
I am trying to educate myself on that method. If I had known you could use a plate hex with an open tank I am sure I would have gone that route... That's why I am here, to learn! If the ole pex trick don't work, we will be talking soon : )
The main benefit of the closed coil is reducing the number of pumps. Every pump costs money to run.
Finally got this thing up and running. The tank made it from 50* (guess) to 120* overnight. The tank was only heating when the boiler overheated. I temporarily hooked tank pump to overheat aquastat. Right now I am running a dedicated load through the tank. As the Delta narrows I am not sure how well it will go from 150* to 180*.. So far so good on the experimental hex... Here's a few pics before I sealed it with the cover.
For all you code freaks, I am going to remove the light fixture... someday... : )
Well Sparke...how did Day 2 go? Were you able to hit the temperatures in the storage tank that you desired as well as keep the house warm? Any obvious issues thus far?
Day 2: Lit the fire at about 5:00 P.M. Loaded the boiler about 1/2 to 3/4 full. Got up at 5:00 a.m and switched over to the tank. Warm day - it was about 35 -38* but the tank supplied 3 showers and kept the house at 72* (set point). I relit the fire at 9:00 p.m. I dont have controls hooked up. So the operation is not automatic yet. So far so good...
Congratulations Sparky on great job .
What temps are you hitting in your tank?
Thanks Anthony. I can honestly say I learned the majority of the information for storage tanks from this site. Thanks guys!! Also Chris Holley who is the Garn Dealer in this area sent me a drawing to plumb the tank.
Mike, I do not have an answer for you because I do not have the sensors hooked up yet. I was checking it with a meat thermometer but now the tank is sealed. I plan on installing a pipe through the lid tomorrow. Then I will install 2 maybe 3 sensors in the tank. Top, middle, bottom. I have not purchased them yet...
Great job - looking to do similar setup.
What temperture sensors are you going to use and where (through the ouside or on a vertical pipe or other) are you going to mount them?
Please keep the update coming,
The sensors are going to be submersible (if I can find some) and they will enter the tank through a pipe in the lid. I may go with traditional thermometer with long stems like this one: http://www.marshallinstruments.com/products/GJ.cfm The stems range from 2.5" to 84" but I don't know if the temp. reading is on the tip or the whole stem. If the whole stem is reading temp. then that model will do no good for middle and bottom readings. I am also looking at 10K sensors but the ones I have found have to be sealed. They can not get wet...
I finally found a gauge. I got it at a Johnstone supply. Even though they said they did not have anything for this application over the phone - I found this hanging on a display wall. The bottom pic is the supply gauge from the tank/wood boiler which ever is running. In this case this is the temp from the tank. The other pic is where the sensing bulb goes through a pipe into top of tank. The sensing bulb is attached to a 48" capillary tube.
Great job, Sparke. I didn't think that a pex hx would work this well, but it obviously does. Keep us posted on your progress. One question...What is the average temp difference going into and coming out of the hx?
By the way got an e-mail from Greenfire about the changes they are making. Sounds good.
That all depends on how far I draw the tank down. If I run the tank down to 120* When I start to recharge with 190* water, I will get return temps of 120-130* Of coarse I am circulating cold water in the pipes at this point too. I would say a 20*-30* difference is average until the temp in tank starts to approach 180* Then the supply and return temps get closer to each other...
Drawing from tank:
This depends on ambient room temp.
Right now I am lighting one fire a day. Burning about a load and a half through the boiler. That supplies all domestic use and heat for about 24 hours.( Five people live here all take at least one shower a day). The tank really shines in warmer weather.
very intriguing - I may have to consider using pex for the tank I am planning. Do you have any experience with a copper hex? Do you think your pex works as good as a shorter copper hex?
No experience with a copper Hx. But if the 3x ratio is correct (this is open to debate). Then I have the equivalent of 266' of 1/2" copper. For 700 gallons. ( The tank held about 750 before the lost space of the Hx's. I have no idea how much space in gallons is wasted). What I will say is I can charge the tank from 120* to 180* in about 6-8 hours while still drawing domestic and heat. However it is not cold outside. Probably around 30 to 35* at night.
Sparke, I was wondering how after market automotive temp gauges would work. They have capillary tubes fairly long.
Thanks for the updates.
The ones I have seen would probably work fine except you would need a 12 volt DC power source. Actually they may run on less signal like 5 volts DC but I am not sure...
Nice job! I'll be interested to here how the polypropylene reacts with the hot water. Is EPDM sold in large enough sheets to avoid lap joints and glue. Any thoughts on fiberglass lined DIY storage tanks. Can you reline your tank without a major rebuild sparke? I'm trying to get all the info I can before I buy or build storage for my tarm solo 40 thanks sweetheat
Your tank gives me a lot of ideas about building a tank. I'm not clear on how you reinforced your tank so it can support the pressure of the water. I'm sure I could build a tank and support it with steel like angle iron bolted together.
The box would be made of ¾ inch plywood or even advantec if supported correctly. The corners supported by vertical strips of angle iron. The sides would be supported by horizontal straps of angle iron running around the box say at 2 foot intervals from top to bottom. Then insulate the inside and the outside.
The liner is key, what does Tarm us for a liner on their tank?
No problem yet with the polypropelene. Yes you can buy it in large sheets but anything over 10' will have a glued seam from the factory. I can not replace the liner easily. The tank was built under a stairway in a corner. All components were installed before the last wall was put on. The liner and Hx are performing quite well but the real test will be time.
Rich, The tank has support on 2 foundation walls. Three walls are againts foundation footing.. The front wall is supported by 2- 45* braces cleated to 2-2x4 nailed together and bolted to the floor with concrete anchors.
I thought of doing something similar to the box you are describing. I think it would work if you banded the box using thin metal straps. I am not sure where you can get the banding or the tool to tighten/lock the end. In another thread someone mentioned using aircraft cable... Check out http://users.telenet.be/hagim/zonne_energie/hot%20water%20storage.htm.
Great job and please keep the updates coming...
Do you have any feel for how much wood you are using now compared to before the tank?
It is really hard to say because the weather turned warm just about the time I finished the tank. Right now I am making 1 fire a day, about a full wheelbarrow. But that is green wood. When it was cold, I was burning 24/7...