recirculating hot water system (recommendations)
tonystargell
| Posted in General Discussion on
I read the article a couple months ago about these, but really don’t know what to look for. There are two at our local hardware store one that just pumps then one that has some kind of temp. gauage at the end of the run.
Which would be best. our hot water tank is in the basement about 25 feet from the kitchen and 15 feet from the shower.
Replies
recirculating hot water
I don't know of the products you are referring. I don't know if this is plumbing in an existing house or proposed plumbing in a new house. I don't know how familiar you are with plumbing in general.
1) Other than supply lines to each fixture you will need return lines from or near each fixture, or at least as near the area as possible, back to the water heater. The return is normally connected to the drain cock at the bottom of the heater.
2)You will need a good quality circulation pump.
3)You will need a aqualstat that will activate the pump when the temp. of the water in the lines reaches reaches the specified temp.
4)You may want a timer on the pump so it will not run at the times that there will be no demand, i.e. while you are sleeping or at work, to save operating cost.
5)If the water heater is electric, you may want a timer on the water heater that can also shut down the water heater when not needed to further save operating cost.
6)You wiil want to insulated the hot water supply and return lines to minimizes heat loss to save operating cost.
I hope I havn't insulted your intelligence, but I don't know what you know. You profile didn't say.
This is what I do. Others may have different ideas or additional comments.
thanks. sorry, it's an exsisting house. i think the guy in the next post is what i'm looking for.
There are basically three different schemes. The most expensive to install and operate is the old "traditional" recirculating system that has a separate hot water return line (a third pipe) that feeds from the most distant sink back to a pump near the water heater. An improvement over the scheme of 30 years ago is that they now have a thermostatic control so the pump doesn't run continuously.
About 20 years ago several companies started producing small pumps that you place under the sink in the farthest bathroom. When you need hot water you press a button and wait 15 seconds or so. The pump comes on and pumps water from the hot water line to the cold water line, stopping when it senses hot water. This scheme has the advantage of not requiring a separate return line, making it ideal for retrofitting in an existing house, plus it's quite inexpensive to install and operate.
The 3rd scheme is basically a hybrid of the second, with various timers and sensors so that the manual button press is unneeded.
The one you mention with the pump under the sink farest away is what I'm looking for. Do you or anyone have any suggestions on reliable ones.
Honestly, some much stuff I've gotten is just rotten.
I have no first-hand knowledge, but I believe that Taco is one of the leaders in the field, and reasonably well respected.
http://www.taco-hvac.com/products.html?current_category=59
Thanks.
Another option.
http://www.google.com/products/catalog?q=grundfos+recirculating+system&rls=com.microsoft:en-US&oe=utf8&safe=strict&um=1&ie=UTF-8&cid=5810036383185484987&sa=X&ei=pLV3TffAM4a2sAO8v_XGBA&ved=0CDgQ8wIwAw#
The pump in this system installs at the water heater, and the mixer installs under a sink. The pump starts when the thermostat at the mixer senses that the temperature in the hot line has fallen below the setting. The pump is also programmable to run only at the times you select so that the thermostat doesn't start the pump at times when no one is home.
thanks.
Simplest
version of this type of "system" is what I installed in my home. Gravity powers the recirculation (technically convection). Simply have a recirculation line connected from the furthest supply branch from the water heater to a Tee at the WH drain. I put a ball valve in the "downcomer" to limit the flow. No pumps, no thermostats, no switches. Gravity does the work. Never have to wait more than a few seconds for HOT water at a sink or shower/tub. 1/2" copper line, uninsulated will do the trick.
I like simple. I also wonder if the constant loss by what amounts to a radiator offsets the energy that would be used by a circulating pump that works on a timer and aquastat. Just an idle question, because it would be very hard to quantify this, due to the varying habits of different households.
Factors
There are a lot of factors to consider. Of primary importance in my installation for my use, is convenience. When I turn on the hot water at a sink, I don't want to wait very long. Another factor is waste. How much clean potable water is dumped down the drain waitng for the hot water to get to the fixture. In my case, all the water in my household i taken directly from the ground and ultimately returned to the ground via my septic field. I only pay for the power to run the well pump. The amount of heat lost to the envelop is insignificant, though I have not quantified it. It is to the conditioned envelop. All of these factors could be calculated should someone be curious enough to do so. Over the years, I have gone through the excercise in similar instances, only to find that my "intuitive ananlysis" was right.
My water heater is in the crawlspace and I installed the loop last year with no automation, just the gravity / convection loop. Insulate all but the last 15 feet of line and feed the return into the bottom of the water heater. Mine worked immediately, however I do think the radiator effect you refer to does exist. I could not prove it, but I would say the bathroom sink near the end of the loop does not deliver as warm water as the one nearer the beginning. I also noticed my gas bill go up, but I cannot say it was entirely due to this. What I do know is that my most remote fixture used to take almost 2 minutes to get hot water and now has it in 5 seconds.
Also, when computing costs, you have to look at your water bill. In Atlanta, we have some of the highest water rates in the country, so the 2 minutes I was running the shower waiting for it to get warm was running up my water usage. Now I suspect I am paying a little more on gas and less on water, but like you said, how do you quantify that?
Since your heater is in the basement, you definitely don't need a pump. You might look at a timer valve on the return feed to reduce usage in off peak hours.
I would start with no automation, it's easy enough to add a pump or timed valved after the fact.
Jon
Initial design and intelligent use makes the most sense.
Back when the well could go dry in the summer, simply kept the tea kettle handy in the kitchen (30 ft from HWH) to save the water before it was hot. Filling the tea kettle was every bit as easy as 'pushing a button and waiting 15 seconds'.
Design of house is such that it is only 4-5 ft to the other fixtures.
Even now when the well is good year around, DW still catches and saves the water before it is hot.
Economics. Say you make $100/hr, say $60 after taxes. That is $1 minute. 15 seconds is 25 cents. You wait for hot water say 30 seconds a day every day. That is $183 per year. Calculated once that circulating HW with uninsulated lines is about $5 month cost at 10 cents kW-hr.
So, if you only make $33/hr, you are wasting money with HW circulation without saving any time.
Just to keep the discussion going, IMO only the hoity-toity have circulating HW, like all the new houses built around me. Grandma now, she thought it was 'hoity-toighty' to even have indoor plumbing other than the small pump right on the kitchen sink. Hmm, grandpa kept the outhouse and barn in order, grandma got to clean everything inside the house, wonder if that was a factor?