Hot Water Recirculation Questions

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SAS

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Our previous house had a hot water recirculation system with a dedicated return line. This worked great (except that when I moved in I had to change the pump to a stainless steel one because the prior owner used a cast iron pump). Our new house does not have a return line, so I am looking at the option of using a crossover under the sink farthest from the hot water heater. With the recirculation line, I controlled the pump with a thermostatic control that attached to the copper pipe and cut power to the pump when the temperature was about 90-100 degrees. In the current scenario, what confuses me is how the thermostatic crossover works. I've read it shuts down at about 90-100 degrees, but it does not shut down the pump. Can the pump continue to operate if all of the hot water outlets are closed? Does the valve never completely shut?

Also, is any brand better than another? In my old house I installed a Grundfos pump. In 7 years it never gave me any trouble. I noticed that Watts pumps are relatively inexpensive, easily available and made by Grundfos. What about Taco?
 

jadnashua

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Some leave the pump running, but the cross-over valve shuts, stopping the flow. The one I have has the pump and cross-over (and a timer) built-in. This means you need to run power, likely inside of a vanity cabinet, which I did. Assuming you can plug it in, it's likely a 15-minute install with moving around a couple of supply hoses, and screwing the mount for the assembly to the wall, setting the timer, and turning it on. Having the pump and cross-over in one unit makes water temperature sensing easier. Sensing near the cross-over means less warm water gets into the cold line. Doing it remotely gets a bit more complex if you want to shut the pump off.

There are some designed to go on top of the WH, where you're more likely to have access to a receptacle to plug it in.
 

SAS

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After comparing several different options, I decided upon the Taco HPLe-1 kit. It comes with the Taco 006e3 pump, a crossover valve for under the sink farthest from the hot water heater, a SmartPlug timer control and two 3/4 inch union fittings to connect the pump. I used Sharkbite fittings on the 3/4 inch copper pipe directly above the water heater. While in theory I could have connected the pump directly to the nipple on top of the hot water heater, my hot water heater has a 1 inch nipple. If I were more confident in my skill at sweating copper fittings, I could have avoided the Sharkbites, but they are not all that expensive and make the job much easier for a DIYer like me.
The system is working great, although I have had to order a second crossover valve because of the way the hot water water system is configured. In my last house we had a dedicated return line and I installed a Grundfos pump. Maybe that's not a fair comparison, but this Taco pump is so quiet that I need to look at the indicator light to tell when it's running. The Grundfos pump, while reliable and effective, was not so quiet.
 

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SAS

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How much did the Taco pump cost you?? Does it have a timer on it??
I purchased the Taco HLPe-1 kit as described above. It was $343 here:

The kit includes the SmartPlug, which is a timer of sorts. I use it in "pulse" mode which runs it for 5 minutes on and 10 minutes off. If you put in it "smart" mode it will spend a week learning your use of hot water (via a sensor valve attached to the hot water pipe near the pump) and then use that data to determine when to run. If you have a very regular schedule, it's probably great, but that mode didn't work well for me.
 

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By the way, I still haven't figured out what happens with the pump when the bypass valve is closed and the pump is still running. Does it pump against the closed valve? If so, it would seem that it would continue to build pressure in the line until it damaged the pump. Or does the pump slow down or stop when it encounters too much resistance? That would seem to require some kind of clutch mechanism in the pump.

It's not something I need to know, since the system works and the pump was designed to work in this way, but if anyone knows the answer, I'd really like to know how it works.
 

John Gayewski

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By the way, I still haven't figured out what happens with the pump when the bypass valve is closed and the pump is still running. Does it pump against the closed valve? If so, it would seem that it would continue to build pressure in the line until it damaged the pump. Or does the pump slow down or stop when it encounters too much resistance? That would seem to require some kind of clutch mechanism in the pump.

It's not something I need to know, since the system works and the pump was designed to work in this way, but if anyone knows the answer, I'd really like to know how it works.
I don't think it runs when the valve is shut. Where (provide a link?) to the info you read that says it runs with the valve closed. This would be very odd.

Circulators don't build pressure they just destroy themselves by building heat though cavitation.
 

SAS

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I don't think it runs when the valve is shut. Where (provide a link?) to the info you read that says it runs with the valve closed. This would be very odd.

Circulators don't build pressure they just destroy themselves by building heat though cavitation.
 

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It definitely runs when the valve is shut, as there is no way for the pump to know the status of the valve. The only way the pump could shut itself off when the valve closed would be if it sensed the resistance in the water line. I have it set to run for 5 minutes and turn off for 10. It always stays on for the full 5 minutes regardless of the crossover valve's status.
 

John Gayewski

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It definitely runs when the valve is shut, as there is no way for the pump to know the status of the valve. The only way the pump could shut itself off when the valve closed would be if it sensed the resistance in the water line. I have it set to run for 5 minutes and turn off for 10. It always stays on for the full 5 minutes regardless of the crossover valve's status.
So the point is I'd like to see the info you have that enables you to make the claim that it's designed to run with the valve closed. Circulators can and do run fine with the flow choked down from the discharge side. But with no flow the laws of friction kick in. There is a calculation that one can do to calculate how fast a circulator will burn up and how fast it'll heat up and what temp in a certain time. It could be the pump is programmed to shut itself within certain parameters, but I've not heard of such a thing.

I'd like to see the design claim that it runs with no water passing through it.
 

SAS

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So the point is I'd like to see the info you have that enables you to make the claim that it's designed to run with the valve closed. Circulators can and do run fine with the flow choked down from the discharge side. But with no flow the laws of friction kick in. There is a calculation that one can do to calculate how fast a circulator will burn up and how fast it'll heat up and what temp in a certain time. It could be the pump is programmed to shut itself within certain parameters, but I've not heard of such a thing.

I'd like to see the design claim that it runs with no water passing through it.
To be honest, what I'm trying to understand is how it's designed so that it runs when the crossover valve is closed. Before I bought it I called Taco and spoke to one of their technical support guys. He confirmed that it just keeps running. His analogy was that it works the same way as a car's water pump and thermostat. I thought that cars had a bypass, but I've looked it up and apparently some do not, so it seems as if his analogy may be apt. But what he said is consistent with how the pump is working in my hot water system. Electrically, the pump is on regardless of the crossover valve. Is it actually pumping if there is back pressure? I couldn't say for sure, but if it isn't pumping it would need some internal clutch to sense the pressure and allow the motor to run without propelling any water. I'm still waiting for someone who has taken apart one of these pumps (Watts and Grundfos have similar systems to the Taco that use crossover valves and no return lines) to tell me what they actually do when the crossover is closed and the pump is turned on.
 

John Gayewski

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I posed the question again to Taco tech support and here is their response:

View attachment 81169
I think the part your getting stuck on is that the pumps are not actually pumps they are just informally called pumps. They are circulators. They work by flinging water outward from the center and increasing its velocity. In through the center out through the side. A real pump like a hand pumped well for example would not be able to pump if you closed the outlet because the piston is inside of a chamber where water cannot pass around the piston. So if you push a handle harder you'd get more pressure. A circulator is more like a ceiling fan.

If the circulator is sensing increased head and slows down then the friction is being decreased. The materials they use nowadays are so resilient it must be that it slows enough and at the same time isn't on long enough to cause the friction to build enough to damage the "pump".
 
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