Re-circulating Pump

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  #1  
Old 09-25-03, 02:36 PM
smiholer
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Re-circulating Pump

I plan to add a re-circulating pump to my hot water system in the near future. With a new addition, our furthest fixture will be 60-70 ft from the hot water heater, and we like the idea of 'instant' hot water. There are a few things/questions I have come up with. Maybe someone can help...

-What size pump (amp, hp, etc.) should I be looking for? The house will be 2200+ sq/ft when the add-on is complete.

-Should the pump run 24 hrs, or should I use a switch or timer? I ask this thinking of energy use, heat loss in pipes, etc.

-How long can I expect a pump to last (considing the answers to my 2nd question)? The big commercial pumps at the high school I work at have been around for over 30 years, but I imagine some work has been done on them.

Thanks for any help!!!
 
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  #2  
Old 09-25-03, 08:46 PM
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You hit some key points about heat loss and efficiency.

A normal sized pump should suffice in your situation; nothing above normal installation.

A timer can be installed to operate this pump when not in use.
 
  #3  
Old 09-25-03, 09:42 PM
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My situation is very similar to yours -- here's what I did.

Used a TACO recirc pump on the return line. (Cost me about $120). It draws about 1/2 amp WHEN RUNNING. (60 watts -- the same as a common lite bulb.)

I wired the pump to be turned on with an Intermatic 30 minute wind up timer. When I want hot water in the bathroom, I twist the switch and wait about a minute. I have hot water, NOW!!

(Actually, I used 2 of the switches -- one in each bathroom, and wired them in parallel. If the one in the main bath gets turned on, and then the one in the master bath gets twisted -- DOESN'T MATTER!! The pump will run until the last timer shuts off.)

Run it 24 hours?? No -- NOW you're talking heat loss.
 
  #4  
Old 09-26-03, 09:20 PM
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If the main idea is to supply instant hot water to the sink, I think I would just put a small electric water heater under the sink and forget about the recirculating pump. Small water heaters can be had for about a hundred dollars and, if you buy a well insulated model, it will probably cost less to run than a recirculating pump and the associated heat losses through the pipes.

Robert
 
  #5  
Old 09-27-03, 12:08 AM
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Liquid plumber,

It may be that we will just have to agree to disagree.

Your small water heater reheats whatever water is in it EVERY time that the thermostat tells it to. The 'stat pulls what -- 4500 watts? If it runs for 30 minutes every time it comes on to get the water back to temp., at $.10 per KwHour, that's about $.25 cents every time it comes on. If it kicks on 4 times a day, you're looking at $30 a month on the elctric bill.

My 60 watt pump can run for about 3,000 hours before it costs me $30 (at $.10 per KwHour) -- i run it about 30 minutes a day -- it'll take me something like 8 or 9 YEARS to use $30 of power!!!
 
  #6  
Old 09-27-03, 01:10 PM
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I think the keyword here is [SIZE=1]small[/SIZE] water heater. I don't think the water heater you describe would qualify as a small water heater. This 4 gallon unit would be just about right for a bathroom sink.

http://doitbest.com/shop/product.asp...652&sku=449318
 
  #7  
Old 09-27-03, 06:50 PM
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That water heater is 110 volts; that means it's not efficient by no stretch of the imagination.

It has a small reserve capacity, so it will come on even if a small amount is used.

On top of that, it has a T&P valve that has to be piped to a indirect waste. That costs money.
 

Last edited by Plumber2000; 09-28-03 at 08:02 AM.
  #8  
Old 09-27-03, 07:27 PM
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If the recirc pump is on a timer, there is no additional heat loss through the pipes, other than what you are going to loose anyway between the water heater and the bathroom that is 60' or 70' away.

In the system I installed, the return line is directly below the farthest shower vavlve from the WH (a pipe run of about 6o'). i wind up the 30 minute timer, wait about 20 seconds, then turn on the shower valve and hot water within 4 seconds -- whatever time it takes for the hot water to go through the seven feet of pipe from below the floor to the shower head.
 
  #9  
Old 09-27-03, 10:08 PM
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If the question from the POSTER is how to get instant hot water, the answer is that there is more than one way... A recirc line can be very effective with a small pump, and even a pump that runs 24 hours uses so little power that it will be negligible on a monthly power bill... A water heater specifically for the lavatory faucet is another way... It does have some disadvantages, one being that it takes some room from the vanity or whatever storage area it is installed in... MOST electric heaters are in the mid to high 90's as far as efficiency rating so they lose very little energy... And the fact is, that if you have a circulating pump instead of the secondary heater, then the PRIMARY heater would have to heat the same amount of water every time you run the water as the secondary heater would have to, so the energy use is virtually the same.... However, having the unit closer to the lav being the one doing the heating, wastes less water and will save you a very small amount on the water bill... All in all, the energy use is a non-factor in my opinion for those reasons... A significant advantage to a circ line is that it will give you very quick hot to any fixture that is run in that bathroom group or even on that end of the house... Choose the method that seems to fit your needs the best...

As for the timer switches that have to be turned on manually, as Lefty suggests, they do save a little power each month and a little water, however, if even PART of your reason is that you want INSTANT hot, then the timers won't be necessary as you will only trade the 30 seconds of waiting on water for 30 seconds of waiting on the circ pump to fill the line with hot water... But again that depends on your individual needs...
 

Last edited by Ragnar; 09-27-03 at 10:31 PM.
  #10  
Old 09-27-03, 10:57 PM
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Ragnar

Explain how 110 volts is "not efficient".

Explain how a small capacity translates into high energy consumption.

Explain why a T&P valve would have to be expensive to install.

Robert
 

Last edited by Plumber2000; 09-27-03 at 11:51 PM.
  #11  
Old 09-28-03, 12:07 AM
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I'd have to agree that a recirc line and a timer switch would be the best option here.
 

Last edited by Plumber2000; 09-28-03 at 08:03 AM.
  #12  
Old 09-28-03, 05:48 AM
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I think the choice today is up to 'smiholer'. He asked the question and he got several answers. Now he can research the validity of the information he recieved and make the final decision about what HE wants in HIS house. All the ideas I read here will work. Some will be worth the effort and some will not. Some will be energy efficient and some will not. Some are easier to install than others. We don't know which of those things appeals more to 'smiholer' and it doesn't matter because this is a DIY forum. He is probably planning on doing it himself. And he is aware that if he makes the wrong decision, he will have to live with it. That will make him cautious. The more information we give him, the better off he is. Whether we agree or not isn't the issue. Start a new thread and hash it out there.

Ken
 
  #13  
Old 09-28-03, 07:44 AM
brickeyee
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I am just curious if that $120 TACO pump is rated for pottable water. It needs a brass or stainless housing and the ones I have purchased cost a little more than that. Could also be area, but an iron TACO pump is not a pottable water pump and will corrode pretty fast in chlorinated water.
 
  #14  
Old 09-28-03, 08:04 AM
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It has a brass body where the plumbing connects, a stainless steel liner and impeller in the pump itself, and a tin cover over the motor. It's been hanging out here for 10 years so far. (I'm sure the price has gone up some in that time.)

Advantages, at least for me, are "instant" hot water, and it saves more money on the water bill than it adds to the electric bill. And our water rates are going to rise significantly in 2004 -- at this point they are talking a 50% to 75% increase.
 
  #15  
Old 09-28-03, 08:08 AM
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Is this what you used lefty?




I have installed this before and they work great.

Set Up Just like this.



For more info on the autocirc click link.

http://www.lainginc.com/act303.htm
 

Last edited by Plumber2000; 09-28-03 at 08:40 AM.
  #16  
Old 09-29-03, 12:55 PM
smiholer
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Thank you ALL for the info and suggestions. I got a lot more info than I thought I would, and each of you brought up the same ideas I have been toying with.

As one of you noted, I do want 'instant' hot water to the whole house, noting that the furthest fixture is far away.

So, a pump set to run from 'wake-up-time to bed-time' will probably be best for me. I know there will be some energy loss through the pipes as the water flys around, but I've got a family of 6 that use water throughout the day. So basically, I don't mind a little extra heat loss, but the water and time savings should be worth it to me.

Thank you all again!!!

smiholer
 
  #17  
Old 09-29-03, 06:50 PM
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Thanks Plumber 2000 for the link to that site. I am going to purchase one of those pumps to have on my truck for when a customer is presented with this situation. Its seems to be the best route to go with the least amount of work.
 
  #18  
Old 09-29-03, 09:08 PM
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There pretty cool units, they can also have a buttom activated switch.
 
  #19  
Old 09-30-03, 04:44 PM
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Ron, no, that's not my system at all. The Laing pump unit you showed has a thermostat in it, and it uses the existing cold water line as it's return line to the WH. As long as the pump is getting the cold (or cool) water out of the hot line, it runs. As soon as the hot water arrives at the pump, it shuts off. (If it kept running, it would be putting hot water into the cold line.)

My system has a seperate return line (1/2" copper) all the way back to the cold inlet of the WH. There are check valves to -- 1.) Keep the water from the return line from going into the cold water line, and 2.) To keep the cold water from going into the return line.

Like I said, I run my recirc for 30 minutes. The first few minutes it is putting cold water into the WH (whatever was sitting in the return line and whatever was sitting in the hot lines in the house. At some point, the return line will be full of hot water, and that is what is being put in the WH (along with the incoming cold to make up for the water going down the drain in the shower.) Doesn't matter -- the WH is going to heat it to whatever temp the gas valve is set for (120 degrees at my house).
 
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