Pump head increase pumping through a vertical storage tank vs. same height pipe

[rwh442]

I would like to add just enough storage to help eliminate my idle times and help increase my boiler temperatures when I come home from the 12 hour work day away from the boiler. I'm thinking a vertical air compressor tank of 60 -80 gallons would be perfect for that time period.

My question is this. I run series piping from the boiler though a DHW sidearm to the furnace water to air HX and then back to the boiler. So I have a 6' or so vertical run from the exit of the DHW sidearm to the water to air HX. If I would replace that vertical run with the 60 or 80 gallon tank how much would the pump head increase? Instead of pumping through a 1" pipe I would be pumping through the vertical storage tank so to speak. My flow rate is around 5.5 - 5.75 GPM and I don't want to lose too much more GPM. Would the flow stay the same?

Also, is a bottom to top feed through the vertical storage tank recommended?

Thanks for any input.

 

[101x81]

roughtly your head will increase of 1 psi/foot if your new system is higher of your high point of your existing system. 2 feet higher= +2psi. but by remplacing your 1inch pipe by the tank, you help yourself by losing a tiny bit of head.
good idea that compressor tank, i never hear about it yet! this boiler room forum is helpfull

 

[Dune]

If the vertical run does not increase, the head does not increase.

 

[leaddog]

I don't think that 80gals will do much for you. Any storage will help but if you are going to go to the work of adding I wouldn't go with less than 250gal and better yet 500. As far as adding head Dune is right.

 

[emesine]

For friction through your pipes, I have found the "engineering toolbox" very helpful. You can get specific pressure loss based on pipe size, material, etc.

So now you have a length of straight 1" pipe, right? Draw up your replacement and record the following:

Total length of pipe used
Number of 90 degree bends and other fittings

You can find specifics on the engineering toolbox, but add roughly 2 feet of pipe for each fitting. For instance, if your have 20 feet of 1" pipe plus one 90 degree bend, then your total "effective" pipe length is 22 feet. If you have 20 feet of straight pipe with 5 90 degree bends, then your total effective pipe length is 30 feet. When you are finished, just compare what you have now to what you will have. You don't need to add anything for the storage tank itself, it will add practically zero pressure drop. You do need to adjust for any fittings into the tank (especially if they are smaller than 1"!!) The height of the tank is not an issue.

Nice to see a fellow Hoosier. I am in Oldenburg.

Andrew

 

[emesine]

Here is the chart for plastic pipe.

http://www.engineeringtoolbox.com/pressure-loss-plastic-pipes-d_404.html

For 1" plastic pipe at 5 gpm you are looking at 1.6 ft of water per 100 feet of pipe, which is a very small pressure loss. How long is your run now? What kind of pump are you using?

As to how to plumb the tank, have you looked at the sticky above- "Simpliest pressure storage design?" At 5 gpm you will be replacing a 60 gallon tank every 12 minutes, so it won't make much difference how you plumb it. A bigger tank would help you a lot more. 60 gallons isn't going to help you much.

Boiler temp- 180F
water to air HX needs 140F to run properly
Delta T is 40F (180-140)

60 gallons X 8 lbs/gallon X 40F = 19,200 BTU of storage. That's not going to get you very far.

Andrew

 

[rwh442]

Andrew,

I live close to you at the Dearborn/Franklin countly line. Good luck with your housebuilding in this weather. Hope it's at least under roof by now. Nice boiler room in the basement. If I was building again that would be the way to do it, plus a walkout basement and shelter/awning for the wood.

My boiler is of the conventional style (indoor) and holds 130 gallons. That 130 gallons lasts me 10 hours. That's about the time I am away from work - maybe 12 hours sometimes. Hence my thinking is that I don't need much more to get me to 12 hours. So if 130 gallons lasts for 10 hours would 190 gallons last for 10 + X hours? Again, thats my thinking. I just want to make it reach the 185 degree mark and minimize or eliminate idleing and give me that extra buffer time.

I was most concerned about any flow restrictions (lower GPM) that a tank would add. Sounds minimal the way everyone is talking.

 

[emesine]

Looks like a nice unit. OK, so a little calculation..... Your 2000 unit is rated to 125K btu and it will last you 10 hours. You are hoping to have just enough storage to get you to 12 hours. Lets assume that you are running around 75 KBTU per hour for heating: That means you need the ability to store 150,000 BTU to cover those 2 hours. Your boiler is at 185F. Your HX is water to air, so it needs water at around 140 to function effectively. Once you have your storage up to 185, it will work efficiently until it cools to 140F. Below 140 you will get less heat transfer to the air in your house.

Water holds 8 BTU per gallon per degree F. Your storage tank will start at 185 and drop to 140. 185-140= 45F. 45F X 8 BTU/F= 360 BTU per gallon of water in your storage tank.

150000/360= 416 gallons.

In order to store 2 hours worth of heat for your house, you need around 400 gallons of storage.

I am certainly not an expert, but those are my thoughts.

Andrew

P.S. Amazingly, I have a crew out doing brick today. I suppose it is better to work now than to wait for the ground to thaw and turn the site into a mud pit.