Advice on Continuous Hot Water Loop
Runner1
| Posted in Energy, Heating & Insulation on
Hello All. I had my plumber install a hot water loop in our house so that we weren’t continually running water to get hot water to a fixture. It works great, but I am concerned about the way it was installed.
The circulator on the loop runs all of the time. I thoroughly insulated all of the pipes before we closed up, but I still think it is a bad idea to be cirulating such hot water all of the time.
Shouldn’t my plumber be able to install a heat sensor on the return pipe, so that the circulator only comes on when the water temperature drops to a certain point? My plumber seems not to know what I am talking about.
Any advice you have will be helpful.
Thanks!
Replies
Some people just put the pump on a timer. Most hot water use is first thing in the morning and then a few hours in the evening. No reason to run the pump the rest of the time, whether the water is hot or not.
A timer is easier. The downside is you must set the time after a power outage. I have two loops here, one for the first the other for the second floors. It does not take a large amount of flow to keep the water loop hot. After your last point of use and prior to returning to the storage tank, you should have a ball valve that you can adjust the flow rate with.
I found the timer to be a PITA and don't use anything anymore. Insulation is a good idea.
Mine is on a timer set for multiple times, it also has battery backup so it won't need to be reset after power failures.
I know they can use a termostat to control the pump. It basically cycles the pump to maintain the line temperature. I know that with my circ pump continuously running and insulated pipes, I was spending aroun $20-30 extra in gas due to losses.
Certified boat fetish.
I set my timer for the times I anticipate the need for hot water usage. That seems to work well. A thermostat seems like it might be on at times when I don't need the circulation.
I just had this installed and where I had to wait 2-3 minutes for hot water it is 2-3 seconds now. My pump Grundflos has a built in timer -- it was so good that my plumber is going to install on on his own house -- he is going to run it 6am to 11pm and not fool around with breaks in the day -- from what I paid him, I can understand why he can let it just run and run.
Take a look at the Grundflos pump installation. The shaft should be in the horizontal position as stated in the instructions. I have seen them go bad when the Plumber did not read instructions.
A long time ago, apartment buildings would use a large pump, (the smallest pump will work on any system), the water would circulate so fast, that it would wear out the copper or galvanize pipes.
Does the loop cover more than one floor? If so, you can probably turn the pump off and let gravity do the work for you. That's how mine works, and with gravity alone I still have to "throttle" it with a mostly closed ball valve.
Else, since you already have the circ installed, the controller you're asking about is an "aquastat" and is relatively easy for someone familiar with residential electrical wiring to install. It has a sensor that will measure the circ line temperaure and will turn on the pump when the temp drops below the setpoint.
Something like http://customer.honeywell.com/honeywell/ProductInfo.aspx/L4008A1015
I like when this thread pops up, I now have to do 'up' my house with dom. hot water circ. Looking for link to plan grav or convective loop as you noted. Have a tall 2 storey in Toronto, Ont. with cool basement and a long run from w/h to first taps and then rise to 2nd floor. I would like to keep some heat in lines (like throttled convective loop) so I can run appliances (clothes and dish washers) at night in preperation for demand metering.
Another possibility could be a flow sensor on w/h supply, kick in high volume pump when demand warrants.
thomas
Don't know of a link, maybe Google can help. The standard (and it works well) for single family residential and small commercial is to use a 3/4" line routed from the farthest fixture back to the water heater inlet or tee'd into the drain connection. Pumped or not, with mutliple floors, a pump is not necessary. If you tie the recirculation loop into the cold water supply into the water heater, you will need to provide a check valve. For this install, I prefer a swing check valve installed in a vertical drop. Gravity holds it open and allows for gravity circulation. Insulate the recirc line, but leave the last 5 to 10 feet bare. If you tie the recirc into the drain, you don't need a check valve but it will "stir up" the tank, amking it seem like it runs out of hot water (normally a DWH relies heavilty on stratification to get as much hot water out before you feel the temp drop before it catches up).
Edited 6/29/2006 1:52 pm by Tim
I was going to say the same - at a forestry camp we had pipes running through a wood stove, connecting to the bottom & top of a 8' tall water tank. No pump, just the 8' difference in tank outflow (bottom) and inflow (top). When the stove (and hence water) got hot, hot water rose, sucking cool water into the pipes in the stove, where it would quickly heat up -- etc. etc. etc.
Sometimes the water would start moving so fast you could hear it . (And it got so hot a couple times that we were almost blowing steam from the shower heads -- well, if they make me get up first to heat the water, they shouldn't complain!)
I have installed them with timers, thermostats, and used the plain old gravity system. If you have it plumbed correctly, the gravity system is by far the best. It doesn't circulate as fast and will cause a lot less problems.
One of the most annoying problems with a pump system, is that you can get sediment of one kind or another, being kicked up and pushed through your system. This can cause problems with plugged screens in dishwashers or other appliances.
I would try disconnecting the pump and see if the system works on its own. If it does, you have lucked out. It should work unless you have created some kind of a thermal "trap" in your line plumbing.
I plumbed the nearest toilet the farthest from the w/h with hot water..each flush ( means house occupied) charges the faucets in the nearest bath/sink, and keeps condensate from the toilet tank in high humid away.
No more sweaty terlet tank in the summer, warm butt in winter after the wife been in the bathroom before me, and my ele. is real cheap.
Spheramid Enterprises Architectural Woodworks
There is no cure for stupid. R. White.
In the wirsbo manual it lists and suggests using a motion detector to run the pump... I've never done it... but plan to soon... seemed to be a good idea... if you want a timer setup i have some i use on a commerical building to trip the magnetic contactors on the air handlers so that they shut off and drain every few hours... mine have a battery (9v) backup and work like a charm...
p
I don't know about you guys, but I get some pretty wicked water hammer from the check valve closing. The mrs likes to take a shower and then pushes the button down on the tub spout causing the water flow to increase. She then shuts the handle off causing the flow to stop. I've asked her not to do this, but there are bigger things in life to fight over. I believe the extra water flow is actually reversing the loop causing the check valve to slam shut. This is the only time I get hammer. It has been suggested that I try installing a soft closing check valve. Been 5 years and it's one of those projects I just havn't gotten to. To prevent a potential problem, you guys might consider installing soft closing check valves.
Certified boat fetish.
We use spring loaded checks on any system that has an expansion tank with a pump.
I thought it was overkill untill I installed a swing check on my house & @ 3am when my sprinklers would kick on---- there was a massive slamming of the pipes that drove the dw nuts.
She complained I told her to call a plumber, & that was proceeded with a good amount of name calling----- oh she was callin a plumber allright---- to the point I can't say what she said or I'd have to take a 2week timeout.
That's right. I forgot about the expansion tank. I needed to add one to my system. What I found was happening was a pressure build up in the hot water loop that was causing the T&P valve to drip. I added the tank and the problem went away.
Certified boat fetish.
Taco has a clip on aquastat for about 20.00 that i have used on my circulating loop, works great. you could install it in conjunction with a timer so that only at certain times of the day and only if the water temp drops below a certain level does the circulator turn on. a great cost savings and easy to install.
I think it is great that you have installed a recirc loop...I wish this house had one like our old house!
A word of warning: Constant recirc of the water can sometimes play havoic on the anode in your water heater and make it ineffective and hence shorten the life of your water heater. We really don't completely understand the behavior but sometimes the anode becomes completely covered with a very fine layer of copper. This copper layer makes the anode ineffective in protecting your water heater tank. We don't know if this comes from desolving minute amounts of Copper from the pipes in the loop or if it is due to fine copper powder left in the loop during construction. In any case, you should do regular preventative maintance and pull you water heater anode out (about one a year) to make sure it is still there and it is not coated with Copper. If it is severely corroded or covered with copper, it should be replaced. A replacement anode will probably cost $10 t0 $15. Please do not listen to your friends who say to just remove the anode...it is a vital part of your water heater. The manufacturers do not install them in the factory at a significant cost without a reason.
Bill
AOSmith Corp.
Have you seen any issue with a constant recirc and a PEX line, as opposed to copper?
Not that I am aware of!
Bill
What would be wrong with having a switch to run the pump before drawing hot water?
We use a centrally located timer called a Digi42 , by grasslin. It has a battery backup and automatically adjusts for daylight saving time. It has 42 setpoints for on and off cycles and these can include using one setpoint for m-f on at 5:30 for instance. We set ours to come on at 5:30 AM and off at 8:00am. It comes on again at 5:00 PM and off at 10:00 PM. In actual practice, I set the manual override to permanent off when I leave for work most mornings and don't turn it back on at night unless we are going to use hot water. It is easy to do and I have the whole family in on it. If it was inconvenient they wouldn't go for it. This gives us the convenience of instant hot water with a small fraction of the cost. Since we use a tankless heater, there are no standby losses for a huge part of the time. We do dishes in the morning while we all take our showers. Most nights we find that we don't even use hot water. These timers are available in line voltage and 24 volt models. We use ours in the 24 volt model with a relay that operates the pump. On weekends the pump may be on for a large part of the day as we do laundry and other household chores.
All recirc lines should have a conveniently located switch for turning them off, even if only for vacations.
I'm "lucky" enough that my tiny house does not need something like that. My parents house really could use one though. It's a long ranch, quite a wait for hot water in the kitchen.
Thanks everyone. We ended up putting in an aquastat, but now I am realizing how helpful a timer is. We have a large, stretched out house, and although all of the pipes are well insulated, I didn't like the idea of having a huge radiator running throughout the house - especially in summer.
We will definitely put in a battery backed up timer. at the very least, we will shut off the circulator at night.
Thanks again. This was very helpful.