domestic hot water

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Old 03-26-18, 10:08 AM
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domestic hot water

My daughter is unhappy with the hot water for domestic use from a Peerless WBV-03-110-WPCT,boiler with baseboard heat.The heating is fine but there is insufficient hot water. She wants an electric hot water heater installed. If I simply cap the domestic hot water pipes coming from the boiler will this harm the boiler, in that it is still needed to heat the house. Also would there be any harm or benefit from simply running the domestic hot water from the boiler into the electric water heater to pre-
heat it?
 
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Old 03-26-18, 05:07 PM
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R,
No harm in running the tankless water into the hot water heater. It's done all the time.

As far as capping off the coil pipes, you do not want to cap the hot water pipe coming out of the coil. It will cause internal pressure in the coil.

If you cut the coil pipes leave them open. It will not effect the boiler operation because it is a separate sealed coil separate from the boiler water.

Hope this helps a little.
 
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Old 03-26-18, 08:31 PM
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One problem with leaving the tankless coil inline is if it's partially clogged with minerals..... you could have lower than desired water pressure coming out of the water heater.
 
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Old 03-27-18, 12:28 PM
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Pressure coming out of the tank shouldn't be a problem if set up correctly because the tankless coil is not the only feed to the tank. It also has it's own independent cold water feed from the main cold water line. The tankless line is teed into the cold water line to temper the water going into the tank and you still get street pressure going into the tank.

If you plan on just using the tankless hot water as a feed then as PJ mentioned you could have a problem.

At least that's the short version of how we used to set them up.

Just my thoughts.
 
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Old 03-27-18, 08:40 PM
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Increase DHW System Capacity & Lower Fuel Costs

R6Jim might consider a hybrid approach for more hot water.

Had the same problem years ago solved problem and reduced fuel cost.

Added separate oil fired 50 gallon water heater to existing oil fired W-M boiler & tankless coil system.

Round oil and gas fired water heaters are very inefficient. In winter main boiler is more efficient as source of heat for hot water.

Now in winter use small circulator to circulate water between tankless coil and water heater tank.

Aquastat on water heater tank activates circulator to maintain water temperature. A two position switch selects water heater burner in summer and W-M boiler burner in winter.

Key is using tank aquastat with adjustable delta T. In winter deltaT is 3F and summer 5F.
 

Last edited by doughess; 03-27-18 at 10:22 PM.
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Old 03-28-18, 12:54 AM
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In my opinion.... a little confusing and an expensive proposition.
 
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Old 03-28-18, 07:36 AM
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Oil fired hot water heaters are expensive now and are inefficient as well and what is being suggested does sound complicated just to produce hot water.

If you wanted to use your coil and just need more hot water you can get an aquabooster, which is simply a tank that will store hot water from your tankless coil. It has an aquastat and circulator but no separate burner so there is no other appliance to maintain and using fuel.

Much cheaper than oil fired tank and more efficient since a boiler is more efficient than a stand alone water heater.

Just my thoughts.
 
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Old 03-29-18, 12:57 PM
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This is about increasing DHW capacity. An issue is cost of fuel of gas, oil or electricity. Electric water heaters prices are lowest but most expensive to operate in New York at $.25 KW.

My system is basically an “aquabooster” with oil burner for heat in the summer. Installation cost difference is price of burner which is along side boiler. Common oil line, flue and electric source., but can be operated independently.

In the winter , boiler tanklesss coil heats water. As Spott posts:
…. a boiler is more efficient than a stand alone water heater.

Have years of data showing benefits after installing this system. Over many years savings adds up.
 
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Old 04-11-18, 07:01 AM
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I disagree that capping off or valving off a tankless hot water coil in a boiler will cause pressure problems.

If you have a complete water heater that runs stand alone in summer togeher with a tankless boiler coil loop through the heater for winter then the tankless coil needs to be valved off in summer when the boiler is shut down. This is to prevent eddy currents in the loop from transferring heat from the water heater tank contents to the cold boiler contents.

Tankless domestic hot water is not supposed to commingle boiler water with domestic (and potable) water. This allows the boiler pressure to remain at its usual 20 or so PSI while domestic water is at its usual 40 to 60 PSI.

Some boilers allow a choice of domestic hot water tankless coils for more domestic hot water output.
 

Last edited by AllanJ; 04-11-18 at 07:20 AM.
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Old 04-12-18, 11:04 AM
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No Pressure or Eddy Problems

Good design practice is use check valve in circulator loop.

Both in theory and practice see no reason to block off tankless coil.

All I do at season change is to flip a switch so aquastat/temp control that activates circulator for winter or water heater burner for summer.

For reliability, service or other unforeseen event valves can isolate either boiler or water heater to be operated separately.
 
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