Dual hot water heater, timed pump purpose?

[TT_Vert]

I just purchased a house which has new dual water heaters. It also has a new additional bathroom. What baffles me (Ill get pics later today) is the spigot drain on one of them has a T before the spigot valve that goes up to a pump which is on a timer (Currently timer is set to off) and that pump sends water somewhere over to the new bathroom addition. After some research it seems to circulate how water using a timer. My question is, if this is a deadhead system it cannot circulate I don't think and also, why would there be a timer on something like this? Wouldn't you want the benefit of this 24/7? Perhaps I am not understanding the purpose of this pump.


The pump in question is a Grundfos UP10-16BN5/TLC,.
Thanks much

Dave

 

[ard]

Almost surely a hot water recirculation pump.

The hot water is 'pulled' from the end of the hot water line in new bathroom (usually this is hidden in the wall or commonly in a crawl space), and is recirculated back into the bottom of the HW heater

 

[TT_Vert]

ard, pulled from where?exactly? What is the purpose of this?

Dave

 

[yeldogt]

Sounds like a system to insure hot water is available at the distant bathroom w/o waiting. The pump is circulating water from the faucet location back to the bottom of the tank using the drain location of the tank. Some tank have a dedicated recirculation port. The timer is so the pump does not run all the time -- there is often a thermostat in the pump as well so the pump cycles while in timed "on" mode.

 

[TT_Vert]

Sounds like a system to insure hot water is available at the distant bathroom w/o waiting. The pump is circulating water from the faucet location back to the bottom of the tank using the drain location of the tank. Some tank have a dedicated recirculation port. The timer is so the pump does not run all the time -- there is often a thermostat in the pump as well so the pump cycles while in timed "on" mode.

Yeah looking at the docs for this pump that makes sense. What is confusing is that is actually uses both a temp sensor and a timer. However if the temp sensor is at the spigot which is the feed for the pump I think wouldn't that be useless as the water isn't circulating ? Or perhaps this is a circulating system? I will research that bottom port to see if it is a recirculation port. So you think the pump is more of a puller than a pusher? I'm trying to understand the direction of flow here.

Almost surely a hot water recirculation pump.

The hot water is 'pulled' from the end of the hot water line in new bathroom (usually this is hidden in the wall or commonly in a crawl space), and is recirculated back into the bottom of the HW heater

So in essence water is always circulating? I do have exposed pipes so I'll see if there are three pipes.

Dave

 

[nh_yota]

There are two types of hot water recirculation systems - one has dedicated supply and return lines that make a loop just for hot water (more common in commercial buildings) and the other uses the cold water line from the farthest fixture as the return line (more common in homes). In the latter case a special crossover fitting is used to allow the recirculation to function without causing hot or cold water to come out of both taps.

 

[johnnyradiant]

At the far end, the bathroom, close to the faucet, tub or sink there will be a tee in the hot water line that is coming from the top of the tank. The branch of that tee will go back to the pump and into the bottom of the tank. The pump, when on, is circulating the hot water line so that you don't have to wait, and likely dump cold 'hot water' down the drain for the actual hot water to flow. The timer is because you don't, ususally in a single family residence, need hot water right there 24/7. Circulating the water 24/7 costs money to heat, especially if the hot and recirc line are not insulated, and if it is copper pipe, it will wear the pipe out far faster than if it is not circulating. The temp sensor, if set-up the way I've seen them, will turn the pump off when the recirc line is up to set temp, but only when the timer has energized the system, or if the timer was not used and just on all the time. A compromise, energy/$ saving method to have hot water at the tap 24/7.

It could be that the recirc line is not just serving that one bathroom. It would only take a couple tees and some more pipe to bring other parts of the house online with the recirc system.

Unless the pump is backwards it is pumping from the pump to the tank. Often times you will find the recirc line will tie in to the cold feed to the tank.

https://sportbig.com/wp-content/uploads/2018/01/hot-water-pumps-circulating-recirculating-and-recirc-systems-for-hot-water-recirculation-pump-piping-diagram.gif

 

[engineer2]

When I did mine it was to get hot water from the basement to the second floor bathrooms faster. It only runs a couple of hours a day to coincide with normal shower times. A heat switch shuts the pump off when hot water completes the loop.

Mine is a lttle unconventional, but works great. I ran a second 1/2" water return line to the farthest convenient hot water fixture on the second floor. Hot water is pumped from the WH hot water outlet into the house hot water lines. The return line goes into the HW heater cold water inlet. There is a check valve to keep things going in the right direction.

 

[pima67]

We have a timer operated recirc pump next to the heater. The hot line is a big "circle" that runs from the heater to each hot water outlet then back to the pump next to the heater and then into the heater at a T on the drain (installed during construction). Since we don't have a fixed bath/washer, etc schedule I plugged the pump into a X-10 appliance module. Using a remote controller (one in kitchen and 1 in bedroom) I can turn the pump on and off as needed. The down side is that I had to time how long the hot water got to the various outlets and so have to "plan ahead".

 

[yeldogt]

The thermostat controls the flow once the timer activates the system. There is no point in circulating the hot water once the water temp in the pipe has been raised to that of the tank. The pump will go back on when the temp in the pipe drops.

The water is circulating ... pumps create negative pressure

 

[Showkey]

Mine works without a pump by using a gravity recirc system. No power, no maintenance, no wait for hot water.

 

[TT_Vert]

Thanks guys I'll look a bit more into it when I go back. The bathroom is very large and complicated so i'll have to get under there and see what is going on In the bathroom there is a dual shower w/ 2 separate heads on ceiling, two on opposing walls that I suppose shoot water at you, a toilet, a bidet and a very large hot tub not to mention the sinks. I have a feeling when they built this new bathroom they added this recirc pump and did not tie it into the rest of the house but I'll follow the copper and see. I have to say, all these mysteries are sort of fun to figure out. I had a stray 22 gauge wire switched that I had no idea where it was going. The previous owner was a bit difficult at closing and wouldn't tell us where the switch went. I finally figured it out, she had a garage door opener OUTSIDE behind a gutter which would open the door any time the switch was on. So basically the first week I owned the house someone could have pressed that button and gained entry into the property.

Dave

Dave

 

[58Yeoman]

The one I have in my house is timed to supply hot water to the kitchen at morning, noon and evening times when we would be washing dishes. The kitchen is farthest from the heater. It pushes hot water through a connection below the kitchen sink to the cold water line. During those times that it's supplying hot water, you have to run the cold water a bit to get rid of the warm water that's there. The hot/cold connection senses the hotter temp and closes the valve.

 

[TT_Vert]

got it, ill take a look when I have a chance i'd love to blueprint the system for troubleshooting assistance later.

Dave

 

[ard]

The timer and thermosensor is very common.

The system recirculates water until hot water travels from the HW heater, out to the end by the bathroom, AND comes back to the pump itself. Once it 'sees' this hot water arrive, it turns off. It will come on when the temp there drops, say 10 degrees, 20 degrees- whatever. If the temp there drops 10F, assumptively the temp on the whole circuit will have dropped. The system will cycle like this as long as power is on.

When you are sleeping, or perhaps at work, the timer cuts power- no need to pump water or waste hot water when nobody is home. (This is where modern occupancy sensors can be used to enable a HW circ system.)

Have two circ pumps- one upstairs one down.

I took 500 or so pictures when building...better than blueprints!

 

[kbs2244]

I think no yota (post 6) has the idea

 

[redmondjp]

. . . It pushes hot water through a connection below the kitchen sink to the cold water line. During those times that it's supplying hot water, you have to run the cold water a bit to get rid of the warm water that's there. The hot/cold connection senses the hotter temp and closes the valve.

We had this at our previous work location and it was annoying, because you would turn on the cold water in the bathroom sink and you'd have to wait 20-30 seconds for all of that warm water to get flushed out of the line. But contractors do it because it requires less piping than having a dedicated hot water return line.

 

[ard]

But contractors do it because it requires less piping than having a dedicated hot water return line.

Eh, Im of the opinion that these systems are only used for a retrofit- when you CANNOT install a return recirc line. Or forgot to.

 

[Git]

A recirc pump got me involved in Z Wave type devices back in 2003 when we moved into a brand new house.

As mentioned, the system had a timer and a sensor but I just set the timer to run all the time, but I controlled the power to it with a Z Wave outlet. Each of the bathrooms had a small remote to turn on the pump when needed. It usually only takes a couple of minutes to get the cold water out of the line

Nowadays, it is very easy to do with voiced controlled devices (Amazon Echo) or other sensors, like a motion detector. Lot's of options. With the HomeSeer software, I have it turn on the recirc pump at a certain time each morning and it can also detect how long the electrical outlet that powers the pump has been on and it will turn it off if it has run more than 5 minutes