I have a recirc system with return line. The gas usage is huge if the timer is one for even 4-6 hours per day.
I want to install a flow switch/delay off timer system similar to Prygaard's diagram below. I have read his posts and he changed the diagram over time.
Should the flow switch used to turn on and off the pump be installed in the cold water supply line or the hot water feed line?
My hot water recirc return comes into the drain line at the bottom of the tank.
I want the pump to come on instantly when any hot water valve is opened. Is there any delay in flow in the cold water supply line?
Intuitively I would think the flowswitch should be in the hot water side for faster switch response. But Prygaard has it both ways. Thanks
Both methods can work.... I think (see my comments below).
I set up my system with the sensor on the cold water side and the delay-off timer. I still have it set up that way and it is working very well. I also have a fast acting Aquastat on the line so that when the loop is 'hot' the pump no longer runs at all. This keeps the pump time down to just a few minutes a day (15-20 min with a family of 4)
After I posted my solution, other people pointed out that with an aquastat, you could put the flow sensor on the hot water side of the heater and let the aquastat turn it off once the system is 'hot'. The advantage of this is that there is no need for the timer circuit.....just the flow sensor to turn it on and the aqustat to turn it off. Since I already had the timer and the cold-sensing set-up, I have not tried the hot-sensing set-up so I cannot personally speak to the results.... but it seems like it should work. (I was intending to but never got to it…too many other projects to work on .
Warning: Some of the cheaper 'clip-on' aquastats are very slow to react. This would cause the pump to run longer than needed before the aquastat kicks it off.
In both set-ups, the Aquastat should be on the return line as close to the furthest faucet as possible. However, even if the aquastat is on the return pipe near the heater.... it should still work OK.
BTW: It goes without saying.... but the full loop really should be insulated even with one of these set ups.
If you have any questions.... feel free to post them.
Paul, thanks for the quick reply. I was hoping you were still out there. I have followed your project for some time now.
My plan for now is to install just the flow switch and delay timer. I haven't yet found a reasonably priced aquastat (immersion type).
Do you feel that there is flow in both the hot and cold sides at the same time when a faucet is opened. I was concerned that there would be a delay on the cold side.
I supposed you could add a short section of clear PVC in each side as a test.
Since water is not compressable, there should be no delay between flow on the Hot side of the heater and flow on the cold side.
The only way there would be a delay is if there were some kind of expandable bladder someplace in the system.... the most likely case of this would be if there is an expansion tank someplace in the system. These tanks are seperate from the HW heater and are designed to 'absorb' extra preasure due to expansion. I don't think expansion tanks are very common in residential situations, but they are code in some places if you put a check valve on the cold water in. It is concievable that water could flow from the expansion tank for a moment before it flows from the HW heater. I have never worked with an expansion tank but my guess is the delay would be very small.
Note that if the flow sensor is on the HW but before the expansion tank you would still see any such delay.
BTW: You can see diagrams and pictures of my install at:
Diagrams are there for both the 'cold-flow-sense' and the 'hot-flow-sense' but the pictures are only for the 'cold-flow-sense'
Paul, I don't have an expansion bladder. I see your point - there should be no delay (unless the laws of nature have changed).
I will install the switch on the cold side simply due to much easier access. Your source for the delay off circuit is a good one. I had looked everywhere and couldn't find one. Thanks again.
One more thing: You mentioned that you are having a hard time finding a good Aquastat.
I ordered a White-Rogers 1127-2 strap-on aquastat (cheep on E-bay). I hooked it up next to the pump at the Water Heater (The pump is on the return line at the heater)….and it makes a big difference. It reacts very fast to the changing temp and shuts the pump down quickly. I have a run-timer on the pump and before the new Aquastat the pump was running just under 2 hrs/day. With the new aquastat it seems to be about 20min/day.
I suspect an immersion aquastat would be even better..... but I am happy with the strap on.
If I get a chance, I'll try to get some pictures of it onto the PhotoBucket link in my post above.
If your pipes don't run through the slab in contact with the ground, and they're insulated, I find it hard to believe your gas usage went way up. An occupancy sensor might also work for you to run the pump. That way, it would likely be hot when you wanted to say wash your hands after using the toilet rather than turning the faucet on, then off, and waiting. As soon as you left the room, it would stop. This would require potentially multiple switches, but eminantly possible.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014
Paul, I received my delay off circuit board today. I'm not sure how to wire this up with just the flow switch and delay.
On the delay circuit board:
Line power to AC In.
AC out to the recirc pump.
SW to the flowswitch.
That's what the diagram shows for the delay circuit. If that is correct, does the delay circuit provide power to activate the flowswitch through the SW terminals?
The flow switch diagram shows a hot line leg going to the common terminal on the switch. That makes sense.
I've seen the photo of your control box but I can't really follow the wiring plan. Thanks again.
I just wanted to check in with you and see how your system is working. Any reliability issues? Any changes you would make?
I'll be installing a very similar system in the next couple of weeks and would appreciate any advice from a veteran.
I found the solution that is best for my setup. Redwater Diverter www.redwater.net.au No pumps, no energy use no buttons or timers and purely mechanical. Australian invention.
Last edited by Terry; 08-18-2010 at 02:40 PM.
You are all talking about a hydraulic loop. It should work fine without a circ pump. You only need a 3/8" copper insulated line tied into the drain port of the water heater with a check valve. Heat will naturally rise forcing the loop to flow on it's own. I would not think it would cost a fortune to operate. Once everything is up to temp it should be fairly economical, but I'm no engineer. I have known home builders offer this as about a $500.00 option to the price of a house.