Electric hot water recirc decom and confusion

[MicEd69]

MicEd - I don't even understand that setup. The pump pushes hot water into the hot piping and then what? How does it get back?

The Arctic Bill configuration at least has a return line/loop. It looks as though it would send warm water to the cold taps when they are correct? That may not be desired.

I don't think the small-diameter recirc loop I have is galvanized - it's copper. The original/main water piping is galvanized.

From my post in question. You need to read TomFOhio's post as well. {The concern in this particular installation is the layout of the recirculating system and the amount of smaller copper tubing that is part of the recirculation piping. That smaller tubing will increase frictional pressure drop on the suction side of a pump which can cause operational problems. Installing this pump on the hot water outlet and using the crossover valve that TomFOhio indicated thereby decommissioning the recirculating piping, which appear to be in part galvanized, would provide a better and proven system.}

TomFOhio uses the classic installation for these recirculation pumps and mentions the "plastic device under your farthest sink upstairs", aka "crossover valve". The pump takes suction off the hot water outlet and pumps it through the hot water lines to the farthest faucet set where the "crossover" valve is located. That "crossover" valve connects the hot water line to the cold-water line at the faucet set returning the water pumped through the hot water line back to the cold-water inlet to the water heater. The crossover valve is thermally set to maintain the temperature of the water through it at approximately 100 degrees F. So yes, without the additional piping of a recirculating line, your cold water will be lukewarm until cold water from the main inlet to you house flushes out the warmer water.

Sloanbj was concerned about additional piping for a dedicated recirculation system. So, the tradeoff is additional piping for a recirculation system and hotter instant water and instant cold water, or reduced piping with the crossover valve and warmer "instant" hot water and warmer cold water until the recirculated hot water is flushed out by the cold water coming into the house. See the Grundfos diagram below for the "crossover valve" setup.

 

[MicEd69]

You can buy whatever flange or union kit to suit your particular installation location. There are many choices for the Up/ups circulators.

Here’s the install manual.

https://www.ecomfort.com/manuals/UPInstall.pdf

Yep, you sure can. But the "theory" used for the "classic" installation of the Grundfos U15 pump is on the hot water outlet of the water heater.

 

[GReynolds929]

Yep, you sure can. But the "theory" used for the "classic" installation of the Grundfos U15 pump is on the hot water outlet of the water heater.

View attachment 32631

The Grundfos U15 pump has many different configurations. The version in the picture you posted is for systems that don't have a dedicated return line, and it is intended to be mounted on the water heater hot outlet. In systems with a dedicated return the pump is installed on the return line at the water heater location and piped to return via the cold inlet, or the bottom of the tank via the drain outlet. OP's system has two dedicated returns. The setup you posted is not applicable in his situation. In regards to OP having temperature issues there needs to be a check valve on the cold inlet line before the return ties in, and a check valve on the return line just before the pump. Without these present cold water can enter the return line and hot water from the return can enter the cold line causing temperature fluctuations. I have seen this happen and fixed it with properly installed check valves.

 

[Sloanbj]

The valve shown on the cold water supply where it comes out of the wall is a stop and waste gate valve. Does this prevent/check circulation upstream into the cold water supply? If not, why was a valve with a waste gate installed here? The cold water supply line here is fairly warm when the pump is running.

 

[Sloanbj]

FYI, the pump shown is a Grundfos UPS15-55SUC. Let's call this Water Heater 1.

 

[Twowaxhack]

The valve shown on the cold water supply where it comes out of the wall is a stop and waste gate valve. Does this prevent/check circulation upstream into the cold water supply? If not, why was a valve with a waste gate installed here? The cold water supply line here is fairly warm when the pump is running.

A stop n waste is not a check valve. I wouldn’t have used a stop n waste valve there, some people would.

 

[Sloanbj]

To make things a little more interesting, since you all have been so helpful, I will confess I have a second water heater with a very similar setup. We'll call this Water Heater 2. It provides water to kitchen, laundry, a couple utility sinks and a powder room sink. 50 gal electric with dual return lines. The geometries look very similar on the two setups. Both appear to have check valves downstream of the coupled return lines.

Don't know where the return lines go but would hope one goes to kitchen sink and another to the laundry room or perhaps a sink farther away in the mud room.

The pump here is a Grundfos UP15-29SU/LC with three speeds. It is set to the lowest speed. I put an aquastat on this one this week and it works great! The pump runs for about three minutes every 20 min or so. It is quieter than the pump on water heater 1. The return lines are significantly hotter to the touch on this unit than on Unit 1. This unit sits central to the area it serves, so kitchen sink is about 20 feet away and mudroom about 40. (Contrast with unit 1 located away from all the taps and the farthest bathroom is about 65 feet away).

I'm not sure why Water Heater 1 has such lower temps on the recirc lines except that they are much greater distance. I'm guessing my only option is to increase the temp on water heater 1. The cold line on WH1 is warm/hot. If the inlet valve which appears to have a waste gate it not serving as a check valve, it seems like one should be added to the cold water inlet. That would be easy on the flex copper just downstream of the cold inlet gate valve.

Thanks!

 

[Sloanbj]

A stop n waste is not a check valve. I wouldn’t have used a stop n waste valve there, some people would.

Obviously some would as one actually did. The question is why use a waste valve here?

 

[Twowaxhack]

Obviously some would as one actually did. The question is why use a waste valve here?

To drain a little water out of it when they turn the valve off I suppose, that’s what they’re for.

I vote for stupid or that’s the only valve they had.

 

[Twowaxhack]

To make things a little more interesting, since you all have been so helpful, I will confess I have a second water heater with a very similar setup. We'll call this Water Heater 2. It provides water to kitchen, laundry, a couple utility sinks and a powder room sink. 50 gal electric with dual return lines. The geometries look very similar on the two setups. Both appear to have check valves downstream of the coupled return lines.

Don't know where the return lines go but would hope one goes to kitchen sink and another to the laundry room or perhaps a sink farther away in the mud room.

The pump here is a Grundfos UP15-29SU/LC with three speeds. It is set to the lowest speed. I put an aquastat on this one this week and it works great! The pump runs for about three minutes every 20 min or so. It is quieter than the pump on water heater 1. The return lines are significantly hotter to the touch on this unit than on Unit 1. This unit sits central to the area it serves, so kitchen sink is about 20 feet away and mudroom about 40. (Contrast with unit 1 located away from all the taps and the farthest bathroom is about 65 feet away).

I'm not sure why Water Heater 1 has such lower temps on the recirc lines except that they are much greater distance. I'm guessing my only option is to increase the temp on water heater 1. The cold line on WH1 is warm/hot. If the inlet valve which appears to have a waste gate it not serving as a check valve, it seems like one should be added to the cold water inlet. That would be easy on the flex copper just downstream of the cold inlet gate valve.

Thanks!

View attachment 32646

it’s not piped correctly either. With multiple returns I assure you it’s not circulating properly. It may be working satisfactory but it’s not proper. It’s also missing a check valve on the cold.

That flex line on the relief valve is not a great idea.

It’s ran uphill, that’s not good, it’s a safety violation.

 

[MicEd69]

Great point Twowaxhack, if the pump is taking suction from two lines, one line will not have the same flow as the other. Perhaps running the pump continuously and taking a temperature reading off both recirculating lines, one could possibly "tune" the system by throttling the valve on the hottest line until both lines are close to the same temperature.

Just a thought.