What should I do with DHW?


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Old 10-15-06, 05:52 PM
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What should I do with DHW?

Installing 32 gal. Indirect to my boiler with mixing valve. Currently have electric 40 gal. DHW tank. What should I do with it? Should I use it as backup/storage tank? If so how should I pipe it? I'm really want to keep it just in case my indirect won't satisfy HW demand and for boiler shut down time.
 
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Old 10-15-06, 07:02 PM
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DHW and Electric

I have an Amtrol indirect 40 gallon tank running off the boiler, and it is followed by a fairly new AO Smith electric 60 gallon water heater. I've used ball valves tot permit bypassing either HW heater, or running them in series. I needed the electric for hot water while I was installing the new boiler and indirect. I also have a multifuel boiler in parallel with the new high efficiency boiler. When burning wood there's no gurantee the boiler will be running hot all day to supply the DHW demands, and then the electric will be doing most of the work. The other boiler is set to provide about 140 degree water to the electric, which is set for 130 degrees. Most of the time it is just a storage tank, and there is a tempering valve that feeds the domestic hot water to the house. I plan to drain the electric tank when the wood burning season is over, and bypass it. It's kind of a complicated mess, but it is what I wanted.

Pete
 
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Old 10-15-06, 08:30 PM
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How did you run cold water supply to your indirect and to electric heaters? Do they share the same pressure reducing valve,backflow preventer etc?
 
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Old 10-16-06, 04:08 PM
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zaq123

The indirect will supply WAY more hot water than that electric ever dreamed of. Throw the electric away & run your boiler all year for domestic. Unless you have dirt cheap electric rates, you can run the boiler cheaper than using the electric. Also the boiler will thank you for it by staying cleaner & lasting longer.
 
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Old 10-16-06, 04:46 PM
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heaters

Originally Posted by zaq123
How did you run cold water supply to your indirect and to electric heaters? Do they share the same pressure reducing valve,backflow preventer etc?
They are in series. Indirect first. Only time the electric is really needed is when I am burning wood in the multifuel boiler...
 
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Old 10-16-06, 06:02 PM
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guys, how do you think I should feed indirect with water?
Should I share autofeed pressure reducing valve, backflow preventer or should I run two separate lines? Obviously I need them for boiler.
Tank critical specs are: 145psi for domestic water. Way higher than water line pressure but should I still install PRV, just in case (pressure spikes etc)?
 
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Old 10-16-06, 06:20 PM
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Indirect

No need for a reducing valve. The tank, like any water heater, must have a temperature & pressure relief valve. No need for a backflow preventer either. This is domestic water. Just feed it with line pressure. There should be a diagram in the installation manual.
 
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Old 10-16-06, 06:41 PM
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Valves

Originally Posted by zaq123
guys, how do you think I should feed indirect with water?
Should I share autofeed pressure reducing valve, backflow preventer or should I run two separate lines? Obviously I need them for boiler.
Tank critical specs are: 145psi for domestic water. Way higher than water line pressure but should I still install PRV, just in case (pressure spikes etc)?

Any PRVs, backflow preventers between the tank and water line might require an expansion tank on the heater. Just as info.

Pete
 
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Old 10-16-06, 07:06 PM
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Expansion tank

Pete has a good point about an expansion tank. Some areas now require an expansion tank on a water heater. It is a good idea anywhere.
 
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Old 10-16-06, 07:55 PM
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Originally Posted by Grady
Pete has a good point about an expansion tank. Some areas now require an expansion tank on a water heater. It is a good idea anywhere.
Well, the reason they require expansion tank cuz they require back flow preventer and with it installed there is no place for water to expand.

Buderus indirect manual calls for : purge valve/vacuum breaker, flow check and PRV on their diagram for water supply. Funny thing is with all that stuff they said nothing about exp.tank, go figure.
http://buderus.net/Portals/16/S120-IOM-01.pdf
 
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Old 10-17-06, 03:28 AM
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Smile vacuum relief

I wonder why have of the DHW install sheets call them a "vacuum breaker"? I think the correct term is "vacuum relief valve"? From here, there is a big difference. My local plumbing house thought I was nuts when I asked about a "vacuum breaker" on an Amertrol tank.
 
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Old 10-17-06, 10:10 AM
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What is standard/normal psi setting for PRV to feed indirect?
Would 12 the same as for boiler, be enough?
 
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Old 10-17-06, 03:37 PM
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Prv

I think there is some confussion here on the abreviation "PRV".
This is sometimes used to mean Pressure Relief Valve & other times Pressure Reducing Valve. In the case of this tank, on the domestic side, it means Relief not reducing. If someone had 12 psi coming out the tap, someone would be very unhappy.
 
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Old 10-17-06, 04:30 PM
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Psi

Originally Posted by zaq123
What is standard/normal psi setting for PRV to feed indirect?
Would 12 the same as for boiler, be enough?
If the DHW tank is on the same level (same floor, say both in cellar) then 12 PSI on the closed loop is MORE than you need for that part of the system. 12 psi assures the pump will be able to circulate one floor (story) above the boiler.

Pete
 
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Old 10-17-06, 05:11 PM
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Domestic H/W pressure

The domestic is not circulated. It depends on house pressure to push the hot water out as cold comes in, just like any other water heater.
 
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Old 10-17-06, 06:08 PM
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I meant pressure reducing valve by PRV, sorry Grady. The reason I asked cuz my current electric hot water heater (in the basement) has no PRV.

What is normal pressure of tap water, 60-80 psi?
So folks, should I install PRV for indirect or not? Grady has a point about 12 psi in the tap. LOL. Should I just go with 80 psi one just to be on the safe side or feed it without any ?
 
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Old 10-17-06, 06:23 PM
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Prv

There is no need for a reducing valve on the domestic side. The tank is rated for 145# & the relief valve probably 125#. NOTE:If you use a backflow preventer, the installation of an expansion tank is almost a must.
 
 

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