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solarusmc

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Reply with quote  #1 
Check this out..

This idea is for someone who is using a hot water boiler in conjunction with baseboard heating to heat their house and using a separate domestic hot water heater for domestic hot water use. electric, gas or propane.

so let's say you are running baseboard heat at your house.
Baseboard heating requires water temps in the 180 degree range.

What if you were to setup a hot water pre-heat storage tank in 'front' of your domestic hot water heater.

so instead of your hot water heater bringing in ground water temp water at 48 to 50 degrees it brings in water from your pre-heated storage tank instead.

((((To benefit by a pre-heat storage tank even more.... install it in a heated conditioned air space such as an upstairs laundry room or upstairs in your house where room ambient temps are stabilized at 68 to 72 degrees. This way when ground water enters that tank it is heated by room air naturally))))

NEXT, SO HOW ARE WE HEATING THE PRE HEAT STORAGE TANK?
This newly installed storage tank would have a heating coil in the bottom of it, which is of course separate from the domestic hot water inside the same tank.

When your thermostat calls for heat...
Why not pipe your boiler water thru the heating coil in the pre-heat tank prior to it running out to your baseboards?

You would be pumping 180 degree water thru the coil, ON ROUTE to your baseboards.

by doing this you would be pre-heating water in the primary storage tank so that when water is drawn from your existing hot water heater that water is being replenished by pre-heated water from your primary storage tank instead of ice cold ground water.

Heat exchanger coils in the bottom of these solar storage pre-heat tanks only contain about 1 gallon of water or less so I highly doubt the heat dump you've created by going thru that coil would really affect the cost of heating your home thru the baseboards. 

Yes, by running your boiler water thru the coil would cause the water temp going out to your baseboards to drop a bit but I don't think it would really drop that much. 

This is just some nutty idea I was thinking about so thought I'd share it with everyone.

Of course it would be useless in the non heating season but during the heating season when your boiler is running day and night as you sleep, you just might be able to save a good chunk of change by pre heating the water entering your existing independent domestic hot water heater.

Would be kinda cool if it worked right?
Everytime you hear your boiler kick ON for heat in the winter you would know that you are also pre-heating the water storage tank that feeds your existing hot water heater.. same time.

What do I do during the summer? [confused]
Well, I suppose you could build your own aero generator or install a couple 200 Watt solar electric panels and run that juice to a 12v electric heating element installed in your pre-heat storage tank. Missouri Wind and Solar now sells a thermostatically controlled 12v or 24v heating element that installs in water heaters. Pretty cool gagit!

anyway.. just some crazy thoughts I had.
Got comments on all this?,... by all means chime in!
 
Good luck to all and Happy Holiday Season!

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Pat B. Warwick, Rhode Island Rest Assured! Comments and/or suggestions I make here at the forums on 'your' projects as well as my own have all been carefully and scientifically calculated by the 'seat of my pants'

stmbtwle

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Reply with quote  #2 
They'll work but you'd have to do the math to determine whether they're worth the investment.

You can get heat exchangers that will replace the lower element in any water heater, one of those could be hooked to your furnace system or a hot water solar collector.

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Willie, Tampa Bay
EcoMotive

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Reply with quote  #3 
It doesn't matter if you preheat the water with the boiler or not, you're still using fuel to get the hot water.

Assuming that both the boiler and the DHW tank are both gas fired, you would probably save a marginal amount of fuel on account of the boiler being more efficient than the DHW tank. If that's the case, why not skip the gas fired DHW tank altogether and just go with a dedicated indirect tank fired from the boiler?

Lance in Newfoundland

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stmbtwle

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Reply with quote  #4 
Exactly. Likely the only way you'll see a significant difference is if the boiler and the DHW heater use different fuels with different prices.
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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
solarusmc

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Posts: 180
Reply with quote  #5 
My boiler uses propane to heat my house..
My hot water heater is electric with solar hot water storage tank installed 'before' the electric hot water heater..

My thoughts were that if I have to heat my house with the boiler in the winter why not run a tiny bit of that water thru the heat exchanger in a preheat tank going to my domestic hot water system.

I know I'll be extracting heat out of the water used to heat my house each time the boiler kicks on but don't really think I would be removing too too much because the heat exchanger coils only hold a tiny bit of water.

I figured it wouldn't hurt anything and may reap a nice benefit out of it?? who knows right? Just a thought.

so if I end up doing this project I'll come back in and post my results.

Thanks for your feedback guys! Appreciate it for sure!

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Pat B. Warwick, Rhode Island Rest Assured! Comments and/or suggestions I make here at the forums on 'your' projects as well as my own have all been carefully and scientifically calculated by the 'seat of my pants'
Garage_Hermit

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Reply with quote  #6 
Solar Marine, not a bad try [rolleyes] dont sweat about those thinking you are looking for free lunches again !

A BTU is a BTU, so if you are sneaking hot water off of your baseboards, to preheat DHW, you need to replace the heat you just snook...

The only free way to do that (unless you live in Iceland or NZ...) is to pick up some solar hot water.

But you already have the free solar hot water !

Another way, for anyone wanting to emulate your Green Initiative [biggrin]would be to use solar warm air...

So said solar air is ingested by a thermodynamic hot water tank (fitted with a heat pump).

Would need some electricity (EEK [redface]) to run the heat pump, and to blow warm air at it.

With a good system, COP 3 (coefficient of performance), this set-up would generate 3 kW of heat, for 1 kW of power consumed, providing HW at around 140°F.

So now the DHW is SSS ("semi-simply solar"), running on 95°F air, it will be at maximum efficiency; run off a timer, it would take advantage of the best part of the day.

On lousy days, warm water can still be produced off the electric supply (preferably on an off-peak tariff) (better still if PV available...).

In this case, warming the baseboards would be achieved by bleeding water off the DHW tank.

Apologies for borrowing your idea somewhat [frown]

Happy New Year to you, the above has just become my new-year resolution  (for which year, I'm still not sure...)

G_H

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SolarInterested

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Reply with quote  #7 
solarusmc getting a gas hot water heater might be a simpler option.
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Garage_Hermit

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Reply with quote  #8 
Yes, but I ain't got gas !

G_H

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(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...
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