hot water recirc

Mark Eatherton

is that NO circ return pump should be allowed to run WILD, like 99% of the circ return pumps I see out there. I've seen the Metlund system, and it's a good idea. Overpriced, but functional.

I THINK we are pushing the same point, just looking at it from different perspectives.

One of the biggest problems with continuous circ return pump operation is the hydraulic erosion corrosion that eventually causes the pipes to pin hole, causing a lot more dollar loss than the energy could have ever caused...

One problem I see with the Metlund is if you are using the motion sensor, you COULD be flushing hot water down the drain in a lot of cases....but that is true of any system that uses the cold water line as the return back to the source. Ever tried to get a drink of cold water with those systems? I prefer a properly sized, properly insulated, properly isolated (don't run hot and return in the same joist bays as cold water lines) system.

If you don't want the pump running when you are at work, you set it to be OFF during that time frame.

There are a million ways to do it. It just needs to get done, no?

ME

Heatman_2

dhw recirc

why the check valve on dhw return with circulator systems?

gerry gill

in case the circs

not running..if its constant circ its really doing nothing.

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Mark Eatherton

It keeps cold water from charging backwards through the return..

Otherwise, the hot water temperature at the far end of the system fluctuates like a banshee roller coaster ride. UP, down, UP, down, UP, down....

Let me also state publicly, that there should ALWAYS be a timer, and an aquastat, in addition to the check valve on EVERYY domestic hot water heating system.

ME

Jack

Respectfully, must disagree MArk

Time and/or temperature controlled recircs are serious energy wasters. Why would I want my aquastat running my recirc pump while I am at work or in bed? The best of the recirc systems is the demand system, imho. Go to www.gothotwater.com and look over the Metlund system for comparison purposes.

Joe Mattiello

Agreed Mark; the timer, and clamp on aquastat are a great combination. The aquastat allows the pump to cycle on and off within the parameters set on the clock timer. This is a great opportunity for people that have a regimented weekly schedule. The same philosophy applies to setback thermostats. Why operate your boiler when no one is home to enjoy the benefits. The D’mand pump is great for retrofit applications and for tankless heaters too The erosion issue can be minimized with low head circulators. I get calls all the time from customers complaining about noise emanating from the recirculation piping. After one or two questions, you quickly uncover a high head pump installed. Sometimes, it’s because of ignorance to pump sizing. Taco, offers an intuitive guide for selecting circulators available at www.taco-hvac.com. It’s one of approximately 35 documents encompassing most of the Taco product lines found in the Radiant made easy application guide Great resource tool!!

Jack

Running wild

recirc is not really a solution to anyones issues and we are certainly in agreement with that.

The Metlund's electronics are designed to only recognise the call for operation every 8 minutes, so it will prevent the short-cycling to which you refer. As well, because it has the thermistor on the hot side of the pump, when it sees an 8F delta t it will shut off because it knows that 2' behind that there is hot water. I think it is a pretty slick system

One of the biggest issues for us here in MA is that with the Boston Harbor and Charles River clean-ups, worthwhile projects, but we are paying for them, we have the highest water rates in the US. I was reading a report (I think from Lawrence Livermore labs that said that every 3 gallons of water down the drain is equivalent to approx 1kw of energy/cost for delivery and treatment. I think we will be seeing more attention placed upon recirc. I'm looking forward to it and the further discussion.

In my own home, I re-modelled two fo the three bathrooms last year and didn't install the recirc. I'm now doing the master bath and will install it there. Without it, in the morning, I have a 45second wait for hot water with the shower going. I'll report back what the time difference is when I get the Mstr Bath done...ahem, whenever that is;/

Tim_41

ck valve

Service call last week about a recirc pump running and yet the shower (grohe temp valve) would cool down while the recirc was running. No check valve installed on return. Good example of how water will take the least path of resistance even with a low head pump running. I have a retro fit pump with a timer It works great and eliminates those 45 second waits. Don't forget to insulate your pipes.

Michael Rogers

I am an electrician and we just finished a low energy house where there are micro motion detectors in the baseboards entering the bathrooms. These motions run the recirc pump for a set amount of time only once someone has entered the bathroom, works really well.

Erik J. Hoffman

Metlund also has one that can be

installed with a loop back to the water heater. And uses low volt door bell buttons at the fixtures.

We have been installing a few, I don't like the lack of pump options. They only have a taco oo8, seems a bit over sized.

I don't like timers they are parasitic and don't get set by owners. They usually override them and have them run all the time.

Chris S

recirc

How about the Laing autocirc. Built in timer and aquastat, I use these on retrofits at the fixture. I have also used them for freeze up protection for where a bath is over the garage and not insulated properly. Low wattage etc.

Jack

The reason

they use the higher head pumps is to pump the water at high velocity. Metlund has a drawing of the actual flow characteristics in the piping of the hot/cold relationship. It's pretty neat. It shows that at 1gpm you end up with a skim coat of hot water going over the cold remaining in the pipe. At 1-3gpm yo end up with what looks like a long spear point of h/c and in the 5gpm range you basicall have "plug" flow where the hot totally displaces the cold. That takes a higher head pump. Given they have the temp sensor for shut-off purposes, the high head pump is best.

If you are recircing to an on-demand make sure you run your return line in 3/4" so you can get the higher flows.

Harold

retrofit

I made two mistakes in the plumbing for the house. I wanted hot water pipes insulated. Plumber quoted an astronomical price so I didn't. Bad move. He also used 1/2 pex for all internal water and external hose bibs. The hoses are almost non-functional and the shower heads provided work on only one of the spray patterns. And I did not include a return pipe for circulation.

I have two distribution manifolds for the house and they have 3/4" pipes. It takes a real long time to get hot water and it cools quickly. I am planning to use cold pipe for return and a user operated switch of some sort at the major use points, with temperature detection at the recirculation point.

I do have a 1/2" pex line to all the sinks. It was to be used for RO water. The problem is that this is the supply for the ice cube maker and I can't get in to change it.

Any thoughts on if it would be a problem to use this line as the circulator return? It is small, but I am concerned about the odds of hot water being injected into the ice maker.