Hot Water Re-circulation System?
- Thread starter Quattro Pete
- Start date
I believe the Grundfos pump is 1/8 horsepower, so we're not talking about a lot of electricity usage anyway. Last I checked it seems the Grundfos prices have increased 30-40% over the past five years.
AZjeff
$50 Site Donor 2023
Since the electric bill is sitting here I calc'd how much it costs to run the circ pump. It draws .5 amp and runs 18 hours a day and our electricty costs $.21/kWh all in so it costs $6.80/month to run the pump. YMMV. You can only guestimate cost/savings on your variables but the pump isn't a big monthly expense. If you're thinking about it strictly for cost savings you probably can't prove it out one way or the other. Whatever the cost delta is and I don't think it's much is worth instant hot water to us. One less Starbucks a week would cover it.
Thanks for this data point. That's actually less than what I thought.
AZjeff
$50 Site Donor 2023
The Taco pump I have is 1/40 hp and .5 amp, that 1/8 seems pretty high. May be a hot water heating system pump.
Correction: my newest Grundfos is 1/25 HP and uses about 25 watts when running.
AZjeff
$50 Site Donor 2023
That would cost me $2.85/month. You say newest, did you replace a pump or put in a new system?
My last one was a new installation three years ago and the Grundfos pump kit with timer was $219. It was a good deal at the time.
Do it. As others have said, Grundfos seems to be the way to go.
Energy Dept. regs made them set defaults for one button cycles, like heater usage and cold-water rinses. Many machines have options to override the defaults, but option usage is something only a select few use. Sanitize cycle is marketing, hot wash with heater temp. boost. I can't remember what the target temp. is but it's not really high due to energy usage targets imposed on Mfgrs.
Washer heater is sanitizing cycle only.
Machine water heating really only came into play when domestic water heaters were mandated to be factory set to 120f. That really affected dishwashers taking a normal cycle from 1 hr. to 2 hrs. or more.
Most euro machines and the NHS & NIH recommend a target temp of 60C for (I forget 15 or 20) minutes.
what a mess
lil messy for sure but it works great.
sometimes that is all that matters.
Recirculation hot water is great if you are not paying the bills. Even with insulated pipework the losses are significant. When I tried it in our 68ft long house it would lose a couple of kw of heat every 24 hours.
This issue is common place with large commercial premises where the distances involved mean there is no choice but to circulate the hot water. But actually there is a choice, when you add the heat losses to the concern and expense of legionella testing, a financial case can be made for local point of use under sink electric heaters that store a couple of litres of at at the desired temperature ready for instant use.
If you must do recirculation It can be done without a pump. In the old days it was normal to take the supply off the top of a hot water storage tank and bringing the return back in at the bottom of the tank. The thermal gradient in the tank drives the circulation quite effectively, I even found an old plumbing book that had a formula to work out what the flow rate would be.
This issue is common place with large commercial premises where the distances involved mean there is no choice but to circulate the hot water. But actually there is a choice, when you add the heat losses to the concern and expense of legionella testing, a financial case can be made for local point of use under sink electric heaters that store a couple of litres of at at the desired temperature ready for instant use.
If you must do recirculation It can be done without a pump. In the old days it was normal to take the supply off the top of a hot water storage tank and bringing the return back in at the bottom of the tank. The thermal gradient in the tank drives the circulation quite effectively, I even found an old plumbing book that had a formula to work out what the flow rate would be.
The energy savings are quite small and hugely exaggerated and are offset by more water usage since it takes longer to get hot water to run and periodic descaling.
Their main advantages are small footprint and no running out of hot water.
Unless used with a recirc pump, then the immediate hot water negates the "extra" usage with tankless. The maintenance cost, yes, is definitely higher. Like all things certain applications make a case for a certain installation. My parents have a single Navian tankless heater that not only heats the consumable water for the house but also heats the entire slab of concrete under the house and garage (about 2500 sq. ft. in total).
Run the return lines from the far end(s) back to the WH. Put valves on them and plug them. You can use them in the future if you want.
We have a recirc pump. I can set it to run on a timer (to prep for morning showers or evening dish washing) or "on demand" based on wireless switches in the bathroom, laundry, etc. If you want to be super cute you can put a temp sensor on the line and the pump only runs until hot water warms the fitting at the turnaround. (No preheating of the return line). Mitigate water wasting, mitigate waiting, and mitigate thermal energy loss. Heat the lines only when you have/anticipate the need.
We have a recirc pump. I can set it to run on a timer (to prep for morning showers or evening dish washing) or "on demand" based on wireless switches in the bathroom, laundry, etc. If you want to be super cute you can put a temp sensor on the line and the pump only runs until hot water warms the fitting at the turnaround. (No preheating of the return line). Mitigate water wasting, mitigate waiting, and mitigate thermal energy loss. Heat the lines only when you have/anticipate the need.
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