Boiler hot water coil question.

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  #1  
Old 09-23-20, 07:17 AM
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Boiler hot water coil question.

Hello I have a Burnham oil-fired boiler forced hot water heat with the coil for domestic hot water. My coil has become clogged and I have decided that I am going to have a 50 gallon electric hot water heater installed and not use the coil anymore. What should I do about the coil should I cap off the pipes should I leave the water connected to it? Is there any harm if there's no water in the coil in the boiler fires up? do I have to do something to the boiler so it's not looking to make hot water anymore?
Thank thank you
 
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  #2  
Old 09-24-20, 11:17 AM
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f,
You can leave water hooked up but if the coil springs a leak it wil have to be removed. You don't want to cap the pipes of the coil because it will create dangerous pressure when ther water boils from the heat. You can shut the cold water off to the coil and hot or mix line valve also to isolate the coil from the system and then cut the pipes on the coil to allow the water to boil out as the boiler is running. Eventually it will stop and that will be all you need to do.

After no longer using your coil for hot water you can make your aquastat cold start instead of maintaining temp all the time. Pics would be helpful in order to know what you have.

Hope this heps a little.
 
  #3  
Old 09-24-20, 07:02 PM
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Frankjc boiler is for hydronic heating so temp would not exceed 180F. It is not a stream boiler so suggestion
"allow the water to boil out as the boiler is running" is typically not likely to happen.

The clogged coil does not have to be removed. Because it might develop leaks, the cold water feed should be removed and both in and out fittings sealed.

Cold start is totally different issue that may result in delayed heating response for many homes. Cold start is complex decision with many trade offs.
 
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Old 09-25-20, 04:50 AM
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I may be overthinking this, but I have a few thoughts and questions.
Is it worse to have no water in the coil? Would air getting in there make it deteriorate faster?
I was also thinking of just leaving the piping intact, let it feed the coil water, set the aquastat to cold, close the ball valve on the hot out side. One reason for this would be so it can go back to using the coil for hot water if or when the hot water heater fails.
One reason for deciding to go with an electric hot water heater is that this house has never had sufficient hot water, I have been there 12 years, and have never gotten a good shower.
When I first moved in I talked to the company that was servicing it and he told me there wasn't much he could do with it, and gave me a quote on an indirect system for about $1800.
 
  #5  
Old 09-25-20, 12:02 PM
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f,
Lets take this a step at a time.

1) NEVER CAP AN UNUSED COIL. Running the boiler with the coil empty will not harm it. If you google "disconnecting a tankless coil" there is plenty of info you can research. It is much easier than trying to explain why and be corrected by D with his irresponsible and in this case dangerous responses. It gets old real quick.

You can leave your coil connected without doing any harm but as I previously stated and was again misquoted by D, if you leave your coil in and it developes pinhole leaks, which some do over time. It is just a fact of nature. After all they don't sell separate coils because they last a lifetime. The fact is that coils DO clog up and they DO leak and if yours does spring a leak you must either replace it or remove it and put a blank plate in its place.

If you decide to cut the pipes from the coil, leave the ends of the coil UNCAPPED. You can research why if interested. If you cut the pipes from the coil then you must shut the cold water off to the coil and shut the valve on the mix or hot line going to the system if you have one so the potable water cannot feed back down the pipe.

As far as your control goes you can either turn your low limit all the way down or depending what control you have you can disconnect the LL. and make it a cold start boiler only operating on a demand for heat and NOT maintaining for hot water.
 

Last edited by PJmax; 10-12-20 at 06:09 PM. Reason: removed remark toward member (usenote1)
  #6  
Old 09-27-20, 08:40 AM
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The danger of leaving a clogged tankless coil connected to water supply is it may develop leak and pressurize system to 60 PSI or more, creating other issues.

A disconnected, capped off tankless coil that leaks will just equalize with hydroponic water and be another piece of debris in system.

Google searches return data, they do not validate it. DIY.com is the same. Readers are the judge.

Doughess post #3 quote was “cut and paste” from another's post. It was not a “misquote”
"allow the water to boil out as the boiler is running" is typically not likely to happen.

Those words no longer are in original post.
 
  #7  
Old 09-27-20, 09:28 AM
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I AM NOT a boiler pro but I can read. These replies were obtained from other sites. I did not read in any place to cap the coil off. Therefore the coil should remain open and unconnected.

I was just reading an old Crown boiler manual. The manual states that if you abandon the tankless coil, the coil should be drained and left open to atmosphere.

the easiest way i know is to leave it in the boiler and cut the cold water feed and the hot out pipes and leave them open to the atmosphere

Leave the lines into the coil UNCAPPED. The coil can be empty and dry, no harm will come.

Basically..... end of discussion.
 
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Old 09-27-20, 11:48 AM
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Here's another option: Pipe the new water heater so the existing coil outlet connects to the new heater's CW inlet. Set the boiler for cold start. That way you'll preheat the CW anytime the the boiler is used for space heating. Just a thought. You could even valve it so you could bypass the coil for coil maintenance/repair and still maintain DHW service using the new heater.

You'll see significant utility savings with your new water heater, because using a heating boiler to generate DHW when space heating is not required is quite inefficient.
 
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Old 09-27-20, 01:23 PM
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If you leave the boiler hot water coil connected but the coil was clogged then you will have sluggish water flow through your new water heater and on to the faucets.
 
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Old 09-27-20, 02:58 PM
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In winter to increase DHW capacity from tankless coil I use small Taco 007 circulator activated by temperature control aquastat for heating 50 gallon water heater. In summer, with boiler off, direct fire water heater.

Valves allow either boiler or water heater to be used separately for DHW.

Last month ran boiler for DHW while replacing leaking, 18 year old, water heater.
 

Last edited by doughess; 09-27-20 at 05:46 PM.
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Old 09-28-20, 06:29 AM
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<< either boiler or water heater to be used separately >>

Note that the "last" device in the domestic hot water path has to be live all the time to maintain DHW temperature as opposed to sap the heat out of the DHW.

Passively routing cold water through the boiler coil and then into a stand alone water heater that is powered off (say, in winter) will not work.
 
  #12  
Old 09-29-20, 07:29 AM
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A check valve prevents reverse flow. If taps or faucets are not open there is no “sap”

The taco cirulator is not “passive” but activated by falling temperature of hot water in heater.

Boiler aquastat controls its hot water temperature independently and separately from Taco controller on water tank.

Have used this ”hybrid” system for many years to increase tankless coil hot water capacity. Provides plenty of hot water at low energy cost. Recently replaced 18 year old 50 gallon water heater that had 7 year warranty.

Recommend installing whole house water filter on feed to system and separate wire screen filter on inlet to Taco. Rust particles from "city water" chew up Taco plastic impeller and build up around inlet port.
 

Last edited by doughess; 09-29-20 at 09:11 AM.
  #13  
Old 09-29-20, 10:22 AM
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"...Passively routing cold water through the boiler coil and then into a stand alone water heater that is powered off (say, in winter) will not work..."

Gee, I never realized it wouldn't work all those years I used the setup in my Wilmington home.
 
  #14  
Old 09-29-20, 02:52 PM
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<<< never realized >>>

If no one had been using hot water for many hours, say, overnight, did the first person, say, up the next morning find the water (that sat in the switched off tank) less than satisfyingly hot?
 
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Old 09-29-20, 08:32 PM
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In winter when boiler on, water heater temp control/aquastat activates Taco to keep water in well insulated tank at 120 F. In summer tank is gas fired.

This is very simple, low cost way to expand DHW capacity. New 50 gallon gas water heater $500, Taco 007 $100, PID temperature control $20 = $620

If frankjc's tankless coil ever unclogges it can still be used in winter.
 

Last edited by doughess; 09-29-20 at 08:51 PM.
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Old 10-04-20, 11:40 AM
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I had a gas hot water heater, left it "Switched On" 24/7 365. Aside from the usual delay for hot water to arrive at the point of use, there was never a problem.
 
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Old 10-12-20, 05:53 PM
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Not sure what your original issue is with the coil, other than the obvious symptom of not having sufficient hot water. However i will say one thing different between tank hot water systems and tankless often times is how they are measured in ability to deliver hot water. Tankless systems (including coil) are often rated in how many gpm they can deliver. For my coil in my oil burner / boiler system its rated at 2.5 gpm, not exactly a lot in fact that would be 1 shower with no airater thing on it or any measure at water conservation and that is the performance from the factory so add a little time into the mix and i am sure it deteriorates. The issue could also be a poorly performing mixing valve, assuming you havent already checked and or replaced this.
 
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