Z-wave and Instant Hot water

KevB

Member
Hi Guys,

Has anyone out there done this?

Background:

Conservation of water and energy is a big deal right? Soooo Grundfos has an instant hot water system that is only $250 that is easy to install and requires no under the sink wiring or hot water return line. It comes with water temperature sensing value that installs under the sink so that when the pump kicks(timer based on hot water tank) the valve lets all the cold water in the hot water line flow back through the cold water line. When the valve senses that the water is hot, it closes back off again, and you have cold and hot water.

What I don't like is the fact that the pump is based on a timer (set to morning or evenings when you use the bathrooms the most). And it pumps hot water to all of the house(even to the sinks that are not in use). Again a waste of energy.

I propose using more than one pump (3 pumps in my case) and install them on the 'home run' hot water lines that corresponds to the bathrooms.

Plug those pumps into an zwave appliance module (or lamp module) as these pumps use only 33 watts of power, and link it to my Z-wave switch in the bathroom.


So, when the switch turns on, the pump is activated....and I will have instant hot water.

Any thoughts /suggestions on this?
Thanks
kev
 
Search CocoonTech for Tankless water heaters. I know there have been several discussion there about them. You idea sounds a little different but maybe those conversations will spark some ideas about this one.
 
I don't see how I would save much water if it pumps the not-hot-enough water back down the cold-water pipe. The automatic valve under the sink opens at 98 degrees F and allows water cooler than that to return down the cold-water pipe until it feels 98 degree water and closes the valve. Isn't the water in the cold-water pipe kinda warm, like up to 98 degrees? Now I want to brush my teeth or just get a drink, and I have to run the cold water until all the warm water is flushed out of the system. Maybe it would work better if it had a dedicated return line to a point near the water heater, and it left the cold water alone. Assuming you have access to your pipes, it might be less expensive to install the third water line than the cost of the special 98-degree automatic valve.

I agree the switch-on-demand method should be more efficient than a timer. Flip the switch only when you want hot water. You would still have to wait for the pump to purge the pipe of cold-warm water, though.

Last time I gave this serious consideration, I priced out pumps and plumbing needed for the three different directions my hot water travels about the house, and I concluded I would be better off applying the cash to a tankless water heater.

If you go through with your idea, please post your results. Best wishes!
 
I don't see how I would save much water if it pumps the not-hot-enough water back down the cold-water pipe. The automatic valve under the sink opens at 98 degrees F and allows water cooler than that to return down the cold-water pipe until it feels 98 degree water and closes the valve. Isn't the water in the cold-water pipe kinda warm, like up to 98 degrees? Now I want to brush my teeth or just get a drink, and I have to run the cold water until all the warm water is flushed out of the system. Maybe it would work better if it had a dedicated return line to a point near the water heater, and it left the cold water alone. Assuming you have access to your pipes, it might be less expensive to install the third water line than the cost of the special 98-degree automatic valve.

I agree the switch-on-demand method should be more efficient than a timer. Flip the switch only when you want hot water. You would still have to wait for the pump to purge the pipe of cold-warm water, though.

Last time I gave this serious consideration, I priced out pumps and plumbing needed for the three different directions my hot water travels about the house, and I concluded I would be better off applying the cash to a tankless water heater.

If you go through with your idea, please post your results. Best wishes!

Thanks for the reply

I have priced out tankless, but when I did the energy calculations....You actually require more energy to run a tankless then a high effecient tank. Yes yes...sounds like crazy talk but true.

Tankless delivers hot water, but does not solve the problem of cold water in long pipes. You are still wasting the same amount of water, and using more energy.

Also, take into consideration that when you circulate existing room temperature water back into your tank, it requires less energy to heat then very cold water from outside source.

kev
 
I have looked at this as well since I need to remodel my master bath and need a solution for it. Here are my thoughts after alot of research:

1. Alot depends on if it is retrofit or new construction. I think for new, a good recirculation system is a better and more 'green' choice.
2. Tankless systems really are only a good fit in a home with natural gas. In a typical 200A electric home, a tankless system would require way too much work for additional power. But if it is just for 1 location like for me, I just want hot water in master bath (shower) without waiting 40 seconds, you can use a small tankless or even a small 6 gallon or so tank, or a recirc system like you mentioned. And tankless systems work best in warmer climates where there is a smaller rise you need.
3. My latest thought is to use a recirc system and have an 'activate' button somewhere inconspicuous (but handy) in the bathroom. When we go to take a shower, just hit the button first and by the time you grab a towel and get in the shower, it would be warm.
 
They have smaller Point of Use tankless water heaters that are electric. I'm not sure what the energy cost is but it is probably about the same as running your water heater all the time. My opinion on the subject is that water is a renewable resource and although we get close to draining our supply it has never actually happend. Her in Maryland we have feeds to other water supplies and if we get critically low they open up a tube for a day and borrow some from surrounding areas. Since water is so cheap compared to electricity I much rather conserve on the electricity than the water. That said I would be looking for the most economical water heater and not the one that conserves the most water. You are correct that the tankless heaters use more energy but in some peoples situation such as a single man who lives alone and works full time, he would only use his water heater a few times a day. Whereas a family of 5 like me with a stay at home wife uses water non-stop and a tankless would probably cost a small fortune.

I think you need to decide what you want. Do you want low electricity bills? Do you want to save the world by using less water? Do you want instant hot water? You can pretty much only have one at a time. Sometimes you may get two of the three. But, I doubt there is a solution that will get you all three.
 
I have to agree with Squintz. I looked at the cost for the tankless heater when I built my house thinking I would save money on utilities. However what I found was that with the way my family uses water it would have cost more in utilities as well as a higher initial cost. Another problem I found is that tankless water heaters don't like it when the water flow is not very high. So if you want some luke warm water for something the tankless heater will probably shut off due to not enough water flow through the heater.

We were lucky enough to be able to build in a recirculation line and we love it.
 
My opinion on the subject is that water is a renewable resource and although we get close to draining our supply it has never actually happend.

My opinion is that we have roughly the same amount of water as we have had for millions of years. I don't see it going anywhere anytime soon. ;)

now the air we breath and atmosphere we depend on... Totally different story. ;)
 
My opinion on the subject is that water is a renewable resource and although we get close to draining our supply it has never actually happend.
My opinion is that we have roughly the same amount of water as we have had for millions of years. I don't see it going anywhere anytime soon. :lol:

now the air we breath and atmosphere we depend on... Totally different story. :lol:
Take this with a grain (or several bazillion ;) ) of salt but ... Global warm will reduce the amount of available fresh water as the seas rise. Southern Jersey, which has a huge fresh water aquifer (17 Trillion gallons) could be lost in the next century. Of course I'll probably have beach front property by then. :lol:
 
i bought a pump from metlund and it's a bit pricier than yours. However it's quiet (just loud enough i can here it cycle off if no water is running anywhere yet)and well backed by the mfg. There's another brand called cricket which gets a lot of dings for being so loud even though it's much less expensive. Metlund was highly recommended by the gas company that installed my Rinnai tankless and i love both!

To the original question on zwave and the pump, frankly i think zwave is overkill... Metlund offers several features with their pumps, including push button, remote, and motion sensor control as shipped options. But bottom line is that you can trigger via hard wire with a relay / etc from home automation events/etc. I currently have a button mounted in the cabinet when you enter the bath ( i don't need it to cycle when i'm just entering the closet , brushing my teeth or using the john - s oi didnt want motion driven). I will be adding buttons to kitchen and upstairs bath which are in-line with the pipes to my master bed. Water would still have to travel 20 feet or so in the pipe to the upstairs, but i don't think it's worth a second pump. If money were no option, it'd be good. Assuming you already know for sure that there are siginifcant distances between the three bath branches in your house (if they're in-line with only a few feet that wouldn't get circulated, i say its a waste)

Anyway back to zwave. I personally would not recommend paying $60 for switches that you can do via low voltage momentary push buttons from radio sheck (or doorbell pushbuttons at lowes) for far less. If the timer on the unit you're considering is hooked to low voltage you can rewire... Even if not, you could put a relay inplace in the high voltage line. But doing such rigging in a wet bathroom env under a sync would not be my choice - i like 12V for that :lol: But in that regard, i think the flexibility in the metlund is worth the price and would be almost offset by your savings on zwave devices. The ability to hook up to wireless devices/ motion sensors / an elk / whatever would give you a lot of flexibility

BTW : old posting is: http://www.cocoontech.com/index.php?showtopic=7778

metlund's website: http://www.gothotwater.com
good luck
-brad
 
Plug those pumps into an zwave appliance module (or lamp module) as these pumps use only 33 watts of power, and link it to my Z-wave switch in the bathroom.


So, when the switch turns on, the pump is activated....and I will have instant hot water.

Any thoughts /suggestions on this?
Thanks
kev

Well, maybe I am not seeing the whole picture here. You go into the bathroom, turn on the switch, and the pump kicks in to get the hot water up to temperature for when you turn on the faucet.

Wouldn't just turning on the faucet in the sink when you go in the bathroom do the same thing in less time, without using the extra electricity for the pump? I am sure turning on the tap will allow for a lot more flow faster than a 33 watt pump would get the hot water there.
 
Well it used to take around 2 min+ to get hot water to my shower... it now takes between 1-2 starting fresh. If you're interested, i'll disconnect one night and try it two days in a row and offer numbers for comparison...

But part of the point it not wasting the water you're letting come out of the faucet. I think metlunds rough estimate of 20 gallons a day in my house isn't that far off...
 
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