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Author Topic: running out of hot water  (Read 8922 times)

hondaracer2oo4

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Re: running out of hot water
« Reply #15 on: January 27, 2014, 07:19:41 PM »

Ambonci, If I were you I would dump the idea of the coil in the boiler. I think that they probably work OK but not the greatest. If you have good water(which I am guessing you don't since I think your coil is covered in lime scale) I would go with a plate heat exchanger preheats the water before it dumps it into the water heater. If you have bad water I would use a side arm heat exchanger. If you are hell bent on using the coil in the boiler I would flush it out with CLR. How long have you had the boiler? Is this a new problem or has it been like this ever since you put it in?
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Wood Nutt

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Re: running out of hot water
« Reply #16 on: January 28, 2014, 12:28:15 AM »

Based on the new posts, still sounds like your copper coil inside your OWB that heats your domestic water is either partially plugged and you are not getting good flow and/or too much build up that you are not getting a good heat exchange into your domestic hot water flow.  It might be time to disconnect your domestic water line to see what kind of flow you are getting thru it and if it is partially to mostly plugged, that is probably least difficult.  I am guessing your OWB is not adding enough heat to your electric water heater and the electric water heater cannot keep up with the demand by itself.  If you have good flow thru your domestic line thru your OWB coil, next would be to look at your copper coil inside the OWB and that involves unsealing the plate on the back of your OWB and pulling the coil out.  As mentioned, there is probably some type of build up, probably scale, insulating your copper from allowing a good heat exchange to your domestic hot water flow.  Cleaning the build up off would then be necessary.

If you put a HX inside the house off your heating line from the OWB, I would probably abandon or eliminate the domestic loop to the boiler and not have to maintain that entire 2nd loop and keep the domestic water system inside the house.

A late thought, does your OWB have a 2nd set of boiler water inlets/outlets that are capped?  If you are willing to install new 3/4 lines, maybe you should install a 2nd loop of boiler lines and then put a new HX in the house.  that still keeps all of your domestic hot water lines in the house.  Just a thought?
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racnruss

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Re: running out of hot water
« Reply #17 on: January 28, 2014, 10:12:05 AM »

Pretty sure going to 3/4 in copper coil in the boiler is less efficient than 1/2" because a 1/2" copper pipe has more surface area per gallon of water than 3/4 pipe.

So, if the 1/2 is clean, don't waste time and money changing it.  Make sure coil is clean and pump is working and it should work fine without having to redo all the plumbing or buy any other heat exchangers.

However, many options are available if you want to change things around and some good suggestions already made.
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hondaracer2oo4

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Re: running out of hot water
« Reply #18 on: January 28, 2014, 11:13:40 AM »

Rancruss is right about the 3/4 coil. If the returning water from the boiler is not hot enough you need more surface area contacting the dhw which means that you need a longer 1/2 coil. The 1/2 is good because it doesn't restrict flow which would reduce water pressure but still has a good amount of surface area to make contact with the boiler water. 3/4 pipe would allow less surface area because more water would be insulated in the middle of the 3/4 pipe as it flows. 
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Wood Nutt

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Re: running out of hot water
« Reply #19 on: January 28, 2014, 03:00:20 PM »

Is the pump multi speed and it is flowing too much water thru the coil, not allowing it to get sufficiently warm before leaving the OWB?  :o
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willieG

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Re: running out of hot water
« Reply #20 on: January 28, 2014, 04:09:14 PM »

if you have 1/2  pipe in the boiler it is likely flowing between 2 and 3 gpm from house pressure.

my home built water to water exchanger has a 1/2 coil 50 feet long wrapped up in it and the water at the tap is always hot (as long as there is wood in the stove)

not sure how long your coil is but i know 50 feet is plenty (perhap more than you really need?)
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hondaracer2oo4

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Re: running out of hot water
« Reply #21 on: January 28, 2014, 05:37:46 PM »

I am pretty sure that the way his is set up the domestic cold water flows through the owb before dumping into the water heater. Correct me if I am wrong ambonci. In this case I believe that he isn't getting good heat transfer because of build up in the coil.
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willieG

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Re: running out of hot water
« Reply #22 on: January 28, 2014, 05:46:42 PM »

I am pretty sure that the way his is set up the domestic cold water flows through the owb before dumping into the water heater. Correct me if I am wrong ambonci. In this case I believe that he isn't getting good heat transfer because of build up in the coil.
i would tend to agree, as house pressure in 1/2 pipe is likely  between 2 and 3 gpm and when the factory put in a coil they would take that into consideration (i hope) it must have worked good at one time?
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ambonci

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Re: running out of hot water
« Reply #23 on: January 28, 2014, 07:37:22 PM »

i have been at this house for 3 winters.  it was here when we bought the house.  I have never put in any additives.  no one ever told me but I have since been reading and trying to figure things out.  I have played with boiler in many phases.  I have loading times and all that stuff down now I want to fine tune the system a bit I guess.  the circulator on the OWB is multispeed and is set on med.  since we lived here it seems like hot water has never lasted long.  when we put in new HWH I had to disassemble circulator at HWH because of buildup inside.  hondaracer im not sure on how its hooked up.  I think I have a build up issue more and more bc my house only 1500 sq ft I can have OWB up to temp all day and house set at 76 and it will never get past 72 if real cold out.  that maybe normal and I may be asking to much from OWB but I would think it should heat it.  I guess im gonna have to disassemble boiler in spring.
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hondaracer2oo4

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Re: running out of hot water
« Reply #24 on: January 28, 2014, 07:43:05 PM »

Wow, how is your owb hooked up into the boiler system in the house? What are your temps coming in from the owb and headed back to the owb? Also what are your water temps on the boiler system in the house side?
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doug

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Re: running out of hot water
« Reply #25 on: January 28, 2014, 08:21:58 PM »

I too have had problems with hot water during the winter months here in Oklahoma. I have a shaver 165 and only a 50 gal. hot water tank installed like their directions show you. The warmer months are fine but during the winter months we can only run two showers(back to back) and the third has to be fast    :D before running out of dhw. My stove has aprox 70 ft of pipe to the hot water tank and is well insulated(that high dollar insulated pex in the loom).  Heat works great and I even tried the hot water on demand but the dishwater supply takes too long to heat up and through country boy experimentation I don't think that the 50 ft coil in my shaver is suficiant to heat the water on demand. It just dosen't stay in the coil long enough. I think a 100-150 ft coil in there would have worked better. :thumbup: I've tried pump on every speed , location, etc.  I have an ETC on the stove and the hot water tank and temp gauges inline with the pipe. I've considered buying a larger hot water tank but hey get really expensive over 50-80 gallons. I'm going to try a plate heat exchanger and rig the pump to run 24/7(at least during the winter months) to see how that works. I have three daughters at home now and go through hot water like kids with candy my shower is always last. If anyone has tried a plate type exchanger on demand please chime in. thanks and good luck!
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hondaracer2oo4

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Re: running out of hot water
« Reply #26 on: January 28, 2014, 09:14:11 PM »

Doug, Personally I use a side arm which is just hooked up inline with my heat exchanger for the house. I plumb it through the sidearm first then to the water to air hx. I have a tube in shell side arm and actually found out this year that I had it installed wrong. I would get about 20 gallons out of my 55 gallon hw heater before the temp started to drop. Well I found out that with the short shell in tube design side arm that you actually have to mount it at the bottom of the tank so that it fills the whole tank with hot water, not just the top. Long sidearms don't have this issue since they run the whole height of the tank. I installed a pump on mine that circulates water through the sidearm on the dhw side until it reaches 140 degrees and then shuts off. I never run out of how water. I went with the sidearm hx because I have hard water. If you don't have hard water I would go with a plate heat exchanger and you will have endless hot water.
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doug

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Re: running out of hot water
« Reply #27 on: January 29, 2014, 07:10:59 AM »

Thanks for the help
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yoderheating

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Re: running out of hot water
« Reply #28 on: January 29, 2014, 08:30:04 AM »

I would just throw a flat plate inline if your pump on the furnace runs 24/7. If not then you need to flush that coil out.
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gandgracing

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Re: running out of hot water
« Reply #29 on: February 01, 2014, 10:39:18 AM »

That coil is on the back of the tank and I bet its getting the cold water return in that cavity.  Those return lines are not far enough into the tank itself, so the cold water returns and goes directly all around your copper coil.
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