potable water pre heat

Bob Gagnon plumbing and heating

think of all that hot water going down the drain. We should be able to get some of that back. Check out the thread on my planned grey water heat recovery system. Bob Gagnon

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=331&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

Couderay

pre heat for potable water

Have a mod-con boiler with a 60 gallon super store was looking for any ideas how to preheat water before going into superstore. Up stairs in the house has baseboard heat was wondering if i took the return to the secondary loop and diverted it for preheating.

Mike T., Swampeast MO

That doesn't sound like what I'd call "pre-heat". Pre-heat can be as simple as a non-heated "tempering" tank that brings ground water up to near ambient air temp. It could also involve recovery of heat from otherwise wasted sources like hot water down the drain or condensing units for cooling.

Are you having problems with insufficient domestic hot water? If so, please describe.

Couderay

No,no problems at all,water coming into house is very cold. I was looking for methods to somewhat temper the incoming water before it enters the superstore. Hoping to try and use return from baseboard loops from upstairs,that may help with the condensing on the boiler.

Howie_3

I considered this...

And made sure the main drain had space to cut it in if I decided to do it, but I wasn't sure about recovering the expense.

http://gfxtechnology.com/

ALH_4

But

Your baseboard heat is likely coming from the same source as your superstor. I'm not sure about the wastewater heat recovery. Most homes discharge on average around 100-300 gallons of wastewater per day. 300 is a home with very wasteful fixtures. Generally the toilet is #1 or #2 (no pun intended) in the water usage list. So how much gray water is there from which to recover heat? How much of the heat can you recover? How much maintenance is the system? If you install water saving fixtures and appliances it affects your pre-heat. It sounds to me like more trouble than it's worth. It's probably a much better (and lower maintenance) investment to install a small solar pre-heat system.

-Andrew

Bob Gagnon plumbing and heating

check out

my planned grey water heat recovery system detailed on a thread below. Bob Gagnon

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Bob Gagnon plumbing and heating

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Larry Weingarten

Howie:

The GFX is a lot simpler to install if it simply is put in the main shower drain and then preheated water plumbed to the cold side of the shower. It can be an easy installation with very little length of pipe to waste heat from. Compare it to active solar and I'll bet you get more BTUs per dollar ;~)

Yours, Larry

mark schofield

If your incomming cold water is really cold and your basement is warm, possibly an electric water heater (40 gal?) not electrified could serve as a storage before the water gets heated. The water would probably raise to room temp overnight and give you a 20 to 30 deg headstart.

hr

I'd challange you on that claim, Larry

My sdhw supplies 70% of my dhw needs at my shop and home. How could a reclaim on a shower only, seeing maybe 105F discharge for a 10- 15 minuite period harvest near that many BTUs?

My shop has solar only DHW. We shower easily 100- 150 times a year with that water. Without a back up source of hot water I couldn't shower at all with heat eclaim unit.

I expect a 15- 20 lifecycle from the solar.

Granted climate condition play into the selection of solar, but it gets sold and installed in Seattle

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

And...

if you live in the muggy part of the US, expect condensation.

Even here in Dry Colorado, the preheat tank I had for the waste heat recovery system I had sweated like a pig when operated without a heat source.

Proceed with caution and knowledge...

ME

ALH_4

Calculations

Are there any calculations to back this up? How many btu's can you recover from 10-20 gallons of shower drain water?

-Andrew

[Deleted User]

Roughly 50%...

according to GFX manufacturers, and they have data to back it up.

ME

Larry Weingarten

Here are some....

... really rough calculations. Remember the statement is BTUs per dollar. Assume showering uses 50% of the hot water. My GFX claims 60% efficiency. If so, than GFX saves 30%. My cost was $300, add $100 for simple install. That works out to $13.33 per DHW percentage point. Solar saves 75%. Let's say it costs $3000 to put in. That works out to $40 per DHW percentage point. You may wish to use other numbers, but they would have to be a LOT different to make solar look better than GFX. If I'm confused, please let me know. ;~)

Yours, Larry

ps. Let me add, I'm not dissing solar at all. I've been doing it since 1978. Rather I'm advocating doing the most cost effective measures first. After creating an efficient DHW distribution and heat recovery system, a smaller solar might do the job nicely.

clammy

wondering myself

Would a instantious hot water heater like a bosch or whatever brand work as say a pre heat or as the secondary heater when lower supply temp from the indirect is sensed .I have been toying with this idea in my head for alot of jobs i see kinda knowing and waiting for when peoples domestic hot water needs are not being meet ,the other reason i ask is for alot of work i have been doing i have been seen alot of large water use fixtures like large custom showers soaker tub with no pervision for there large volume use except for the fact of a indirect held at higher temps with a good mixing valve .Would installing one as a pre or post for systems who indirect only see 50 to 80 ,000 but's input improve the domestic production when incoming water temps are 40 .What do you think peace and good luck clammy

hr

I'm all for energy recovery

and conservation. Especially the latest and greatest inventions. Just trying to wrap around the numbers. H=8.33 V (delta T).

So 20 gallons that would raise the temperature from 55F incoming to 105F would = 8330BTU. At 50% recovery 4165 BTU recovered from the shower drain?

Seems the addition of the dishwasher drain would be a big plus with a higher discharge temperature.

For your cost of product and installation that makes sense.

In Bob's case with a 500 gallon insulated tank, hx, insulation, etc, probably not a very sell-able concept.

Still I'm not one to put a damper on creativity. I just wanted to share my experience with tanks of stagnet water inside a structure

I'd love to visit your home some day, Larry. The gravity powered radiant alone would be worth the trip. I'm thinking about the solar expo out that way this fall. In your neck of the woods by chance?

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

Was the tank

insulated ? I guess an insulated tank used just as a preheater would slow down warmup time considerably .

Larry Weingarten

Solar Expo?

Is that in San Francisco? Anyway, I'm about 120 miles South of SF, by Monterey. You're invited! ;~)

Yours, Larry

Larry Weingarten

A huge shower...

... would be the ideal application for one or more GFX heat exchangers. When you can get true "counterflow", that is warm drain water going one way and cold input water going the other way at the same time, GFX is working at its best. Once that's done and capturing 50 to 60 percent of the heat, your BTU requirements will be easier to manage.

Yours, Larry

[Deleted User]

The problem with GFX...

is that it is not conducive to multiple points of use, unless each point is served by its own individual heat source.

It works best if all showering occurs at one point in the home, and there is one heat source to sever that point of use.

If there are multiple points of use (typical American way) and only one source, the HXer's would need to be piped in series on the potable side, which wuld KILL any residual pressure at the points of use.

If piped in parallel, the dillution factor would probably negate any noticeable rise in temperature.

But in MOST cases, its still a great idea.

Larry Weingarten

GFXs...

...can be installed basically in two ways. One is as a system pre-heater, with warmed water going into your water heater. The other way is to plumb it in so warmed water goes directly into the shower being used, on the cold side. The latter way is how I prefer even though it may not be quite as efficient. It is a simple application with little added piping. Also, if the house has ten showers, you can put in ten GFXs with no problems about interconnectedness. (don't know if that word is in the dictionary) Trying to recover heat from applications like tub and clothes washer, that have intermittent flow is where things get complex and probably smelly!

Yours, Larry

Solarstar

My new GFX tested out 0ver 80 % 6 years ago for a unit that was supposed to be around the 60% mark. I'm sure it has scummed a bit and eff. has dropped. I have nothing but good to say about this other than I would like to add another unit ...Paul

ALH_4

??

80% of what? Sorry, maybe I'm not seeing something on the web site. What is "peak effectiveness"? How many btu's do you estimate you save per shower? How much money is that per day?

-Andrew

Bob Gagnon plumbing and heating

I like the GFX but,

It won't work that good in my house because my hot water main already snakes through two heat exchangers in two solar tanks, so if I run the hot water main up to the GFX, and back down to the begining of the hot water main, it will take way too long for hot water to get to the faucets. If I pre heat the cold water going to the shower, I'm not going to get much recovery because I'm on the solar and in the winter, when I need it most, the hot water temp is often close to 110 degrees, so I don't mix too much cold water in with the hot at my shower valve. But the trump card here is the free water for flushing. My tank system isn't for everybody. High water bills and cold incoming water are the requirement for the tank system to be efficient. People with well water will probably never use the tank recovery system. Thanks, Bob Gagnon

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Cliff Brady

GFX installed both ways at the same time

is the recommended way for the best heat recovery. Both as a system pre-heater, with warmed water going into your water heater and to plumb in a tee so warmed water goes directly into the shower being used, on the cold side. Works great in my house. Plumbing the cold side of the shower in addtion to feeding the the water heater with the GFX is supposed increase the heat recovery by about 5 percentage points.

clammy

what about a tub

GFX may work great on shower but what about tubs no wasted heat dumping until the tub is drained? would a direct vent instant hot water heater do the trick on a pre heat or as a final to raise indirect water temp before fixture.Run into this alot big tubs large flow rates out of those waterfall tub fills .I have used resticters but to me it's a cheat and a domestic water mixing valve and hold the tank at higher temps 150/160 i know higher stand by loses with higher temps but more useable tempered water any ideas ?peace and good luck clammy

ALH_4

Forgive my ignorance

But 5% of what? I guess I need to see some calculations showing just how much heat gets recovered. "Percent effectiveness" is a confusing term for me.

-Andrew

Cliff Brady

50% to 55%

I tried to come up with wording that reflected what I rembered from the GFX website that I believe stated a general 5% of additional recovery. ie. 50% to 55% when cold water shower supply was tapped off the GFX in addition to the usual "50%". More flow = more heat recovery.

Uni R_2

Pull the Plug

Just remember to start filling the clothes washing machine full of whites with hot water right after you pull the plug! ;-)

Cliff Brady

I've done that

but baths are a rarity around here with youngest turn 11 soon.