Shower pre-heat idea - Page 2

Ryland · 03-14-14, 09:54 AM

It's counter intuitive to many people that a drain heat exchanger should be vertical, but in a vertical pipe the drain water tends to cling to the surface of the inside and cover the whole inside instead of flowing down a narrow stripe of a horizontal pipe.

Something I just found in searching for shower drain heat exchangers is this: Drain Heat Exchanger | Vandenergi.com

If you took hour long showers where the floor of the shower was absorbing a lot of heat, then I think it could be worth embedding tubing in the shower floor, but I don't think you are going to end up doing much more then pulling the heat that is already in the floor out, you should also make sure that the cement doesn't have any issues with reacting with the copper or whatever type of tubing you use.

ecomodded · 03-15-14, 03:22 AM

I followed the link and I`m impressed that this technique or technology is commercially available. This type of tech in a Apartment building or highrise would save a incredible amount of energy. A family would save large over the years too.

ecomodded · 03-17-14, 02:52 AM

This thread has got me thinking of using cold water for air conditioning in 1 room, Imagine all your houses water needs being piped threw a heat exchanger for cooling, so your tap water gets warm and your room gets cooled.

workaholic · 03-17-14, 10:47 AM

Assuming you already have low flow shower heads there won't be very many gallons of water per shower, therefore not many btus of heat transferred. On my showers I adjusted the anti scald metering until the output was all hot water and no cold mixed in, that made the water temp too hot at the shower for comfort. Then I went to the water heater and adjusted the thermostat down until it was comfortable in the shower(I think I ended up at around 105F) I am of the opinion that water only has to be warm enough for showers. There are three people in our house, including our 19 yr old daughter and we never run out of hot water for showers. Modern laundry detergents will clean well in cold water, same with dish detergents for hand washing. I believe automatic dishwashers even have their own heating element to boost water temp. Why should we heat 40 gallons of water to 130F just to cool it back down when it gets to the shower.
The rate of heat loss ( $ loss ) increases with temperature differential.

AC_Hacker · 03-17-14, 12:42 PM

Quote:

Originally Posted by workaholic

...Then I went to the water heater and adjusted the thermostat down until it was comfortable in the shower(I think I ended up at around 105F) I am of the opinion that water only has to be warm enough for showers...

I did exactly the same thing with my tankless, demand-style water heater about 10 years ago and it is working great, reducing the amount of energy being consumed all the while.

The one potential downside to this practice is that it may be have a health hazard if you have a tank-style heater.

legionella pneumophila bacteria

It turns out that Legionella pneumophila can thrive in standing water, with temperatures between 25°C and 45°C (77°F and 113°F).

If you have a tankless, demand heater, no problem, or if you have a tank system with sufficient water volume going through it, no problem.

But an infrequently-accessed, cooler-running tank system (below 113°F) could see a legionella pneumophila bacteria buildup.

Best,

-AC

NiHaoMike · 03-17-14, 04:01 PM

City water will have chlorine in it to prevent that exact problem. Just beware if you are on well water or have whole house filtering that removes the chlorine. Also note that dishes won't be very clean at 105F.

workaholic · 03-17-14, 04:17 PM

AC Hacker said: It turns out that Legionella pneumophila can thrive in standing water, with temperatures between 25°C and 45°C (77°F and 113°F).

That's good to know. I do have chlorinated water but I think I will check the temp with a thermometer and maybe bump it up a little if it really is only 105. Not young anymore, but still too young to die.

pinballlooking · 03-17-14, 05:12 PM

That is one thing I do like about our tankless heater when I shower I bump it to 130 then when I am done I drop it back to 120. I put a remote to the tankless heater right buy the master bath shower\garden tub. With 0.95 energy factor it does well.

AC_Hacker · 03-18-14, 11:41 AM

Quote:

Originally Posted by Ormston

I'm doing something very similar, built and installed a heat recovery pipe on our shower drain to warm the cold supply to the thermostatic shower mixer valve...

I saw a similar idea in a 1970's energy-saving book...

The guy just got a coil of soft copper tubing (it already comes coiled up), and shaped it into a flat spiral which he put on the floor of his shower. Over top of this he put a nicely crafted, flat teak-wood grate, upon which he stood.

Into one end of the spiral he plumbed a tube from the cold supply, and to the other end of the spiral tube, he plumbed a tube to the shower's cold supply side.

It all looked rather temporary, but easy to implement and efficient.

-AC

03-17-14, 10:47 AM	#14
workaholic Lurking Renovator Join Date: Jan 2011 Location: evansville, indiana Posts: 18 Thanks: 1 Thanked 1 Time in 1 Post	Assuming you already have low flow shower heads there won't be very many gallons of water per shower, therefore not many btus of heat transferred. On my showers I adjusted the anti scald metering until the output was all hot water and no cold mixed in, that made the water temp too hot at the shower for comfort. Then I went to the water heater and adjusted the thermostat down until it was comfortable in the shower(I think I ended up at around 105F) I am of the opinion that water only has to be warm enough for showers. There are three people in our house, including our 19 yr old daughter and we never run out of hot water for showers. Modern laundry detergents will clean well in cold water, same with dish detergents for hand washing. I believe automatic dishwashers even have their own heating element to boost water temp. Why should we heat 40 gallons of water to 130F just to cool it back down when it gets to the shower. The rate of heat loss ( $ loss ) increases with temperature differential. __________________ If there are two ways to do a job always choose the hardest; it'll take twice as long but you will learn twice as much.

03-17-14, 04:01 PM	#16
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	City water will have chlorine in it to prevent that exact problem. Just beware if you are on well water or have whole house filtering that removes the chlorine. Also note that dishes won't be very clean at 105F. __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

03-17-14, 04:17 PM	#17
workaholic Lurking Renovator Join Date: Jan 2011 Location: evansville, indiana Posts: 18 Thanks: 1 Thanked 1 Time in 1 Post	AC Hacker said: It turns out that Legionella pneumophila can thrive in standing water, with temperatures between 25°C and 45°C (77°F and 113°F). That's good to know. I do have chlorinated water but I think I will check the temp with a thermometer and maybe bump it up a little if it really is only 105. Not young anymore, but still too young to die. __________________ If there are two ways to do a job always choose the hardest; it'll take twice as long but you will learn twice as much.

03-17-14, 05:12 PM	#18
pinballlooking Super Moderator Join Date: Jun 2013 Location: SC Posts: 2,923 Thanks: 172 Thanked 564 Times in 463 Posts	That is one thing I do like about our tankless heater when I shower I bump it to 130 then when I am done I drop it back to 120. I put a remote to the tankless heater right buy the master bath shower\garden tub. With 0.95 energy factor it does well. Last edited by pinballlooking; 03-18-14 at 12:26 PM..

03-14-14, 09:54 AM	#11
Ryland Master EcoRenovator Join Date: Mar 2009 Location: Western Wisconsin. Posts: 913 Thanks: 127 Thanked 82 Times in 71 Posts	It's counter intuitive to many people that a drain heat exchanger should be vertical, but in a vertical pipe the drain water tends to cling to the surface of the inside and cover the whole inside instead of flowing down a narrow stripe of a horizontal pipe. Something I just found in searching for shower drain heat exchangers is this: Drain Heat Exchanger \| Vandenergi.com If you took hour long showers where the floor of the shower was absorbing a lot of heat, then I think it could be worth embedding tubing in the shower floor, but I don't think you are going to end up doing much more then pulling the heat that is already in the floor out, you should also make sure that the cement doesn't have any issues with reacting with the copper or whatever type of tubing you use.

03-15-14, 03:22 AM	#12
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	I followed the link and I`m impressed that this technique or technology is commercially available. This type of tech in a Apartment building or highrise would save a incredible amount of energy. A family would save large over the years too.

03-17-14, 02:52 AM	#13
ecomodded Supreme EcoRenovator Join Date: Sep 2012 Location: Vancouver Island,Canada. Posts: 1,037 Thanks: 116 Thanked 100 Times in 87 Posts	This thread has got me thinking of using cold water for air conditioning in 1 room, Imagine all your houses water needs being piped threw a heat exchanger for cooling, so your tap water gets warm and your room gets cooled.