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Author Topic: Water heater water to water heat exchanger install  (Read 8070 times)

T28c34

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Water heater water to water heat exchanger install
« on: November 02, 2016, 07:16:44 PM »

We have been using our system for four years with no problems at all. We do have the water to water heat exchanger installed on our water heater as per the Central boiler instructions as well as the installers instructions. The pilot light has been going out on the water heater for some reason. Why is it when the pilot light goes out, we have no hot water during the heating season? we do feel a difference in the water temperature being hotter when the system is up and running.
It is set up with the water heater side of the exchanger connecting to the output on the side of the water heater for the pressure relief valve and a tee extending out to re install the relief valve. The bottom end of the exchanger connects into the bottom of the water heater. On the boiler side, hot comes in to the top of the exchanger, then out the bottom of it and off to the furnace. The outside of the exchanger gets plenty hot.
How is water from the water heater forced though the exchanger, and out as needed? When the pilot is out, we don't get any hot water.
I would have thought you would put in a valve and cold water line to the input side of the exchanger and the output in the bottom of the water heater. With a shut off valve on the cold going into the water heater you can then shut if off and heat solely off the boiler heat exchanger.
Am I right?
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slimjim

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Re: Water heater water to water heat exchanger install
« Reply #1 on: November 03, 2016, 03:50:24 AM »

Are you saying that you are using a plate exchanger but it must thermally siphon from the drain to the pressure relief valve, if so I would say that it would be very prone to plugging at the plate exchanger and problematic with air in the loop, stopping flow on the domestic side.
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willieG

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Re: Water heater water to water heat exchanger install
« Reply #2 on: November 03, 2016, 06:09:38 PM »

I have my homes cold water supply in one side of my exchanger and then out to the cold water supply of my hot water heater, I leave my home hot water heater turned on but it rarely ever fires in the winter
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T28c34

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Re: Water heater water to water heat exchanger install
« Reply #3 on: November 03, 2016, 07:54:27 PM »

The exchanger is the tube type from central boiler. Basically a one inch pipe carrying the water heater water, with a larger pipe around it as a casing carrying the boiler water.
Hope the pictures come out
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boilerman

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Re: Water heater water to water heat exchanger install
« Reply #4 on: November 03, 2016, 08:23:00 PM »

T28 is it a tube and shell or plate exchanger? If it's a tube and shell make sure it is not air locked on the domestic side. I use a tube and shell exchanger using just thermo-circulation and leave my electric water heater breaker off all winter while my outdoor boiler is running and never run out of hot water. Can you post a pic of your setup?
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slimjim

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Re: Water heater water to water heat exchanger install
« Reply #5 on: November 04, 2016, 02:42:15 AM »

First, your boiler water is backwards, the hottest water should enter at the top of the exchanger for countercurrent flow, next, I think I recall you saying that it is about 5 years old, check to see if it has plugged up with minerals in the bottom of the tank or even more likely in the bottom of your exchanger.
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willieG

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Re: Water heater water to water heat exchanger install
« Reply #6 on: November 05, 2016, 06:30:13 PM »

I'm going to make a guess here (by the photos)  your homes cold water supply is hooked to both your side arm and your hot water tank? if so, then I think your siphoning comes to a halt the moment you open the hot water tap in the house and the path of least resistance is sending cold water under the homes pressure up the side arm at a rate that there is very little heat transfer and you are in fact delivering cold water to the top of the hot water tank?

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T28c34

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Re: Water heater water to water heat exchanger install
« Reply #7 on: November 05, 2016, 06:51:12 PM »

Well the wife just came out of the bathroom very disgruntled, she stepped into a ice cold tub. The pilot when out on the water heater again. That's a whole different problem of why that goes out every now and then. As far as the incoming boiler water entering the exchanger, the book shows it entering the bottom. I did just open up the drain valve on the bottom that comes out on the right side (see previous pictures) It did sputter a bit like it was clearing out. I didn't notice if anything was coming out, you can see in the picture I was using a dirty bucket to begin with (duh). In studying the set up, I really have to cut things apart to be able to clean out the bottom of the exchanger tube.
So if I understand things, With this setup, you still need the gas operating to keep the water holding in the tank hot. If I wanted to take the using gas out of the system, I have to totally bypass the water heater at input of the water heater and directly into the heat exchanger. out the bottom and right to the mixing valve to the house. That about right?
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T28c34

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Re: Water heater water to water heat exchanger install
« Reply #8 on: November 05, 2016, 07:28:12 PM »

Willieg,
The installer had me tap into the water heater for the supply from the side where the pressure relief valve is at. I see what you are saying if it were hooked directly to the cold line. If it were hooked up that way directly,would there be enough time to heat the water as it goes though under house pressure. But being where its at on the side, when the water is turned on, flow is coming in the cold input of the water heater and not directly though the input of the side arm. and the outflow of house water is coming out of the hot side of the water heater. So water heated by the boiler is just siphoning through as water is used?
I hope this all makes sense, because I'm confusing myself.
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slimjim

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Re: Water heater water to water heat exchanger install
« Reply #9 on: November 06, 2016, 04:00:55 AM »

Somebody might want to alert Central that the drawing is wrong, any exchanger should be plumbed in counter current flow for the best heat exchange results.
A couple of more things to note, as with the drawing, the top of the exchanger must have a purge port in order to get the air out of the domestic side of the side arm heater or it will not thermally siphon, the side arm piping should have a ball valve just before entering the tank, if you close that ball valve and then open the purge port the water is forced under pressure up the tube , it carries sediment and air out the purge port clearing the way for good thermal siphoning and will bring the tank to the same temp as the wood boiler water.(be sure to use a mixing valve or you will burn somebody.
One more thing to note, some folks use the cold water inlet on the tank, if it is used, be sure that there is no dip tube that goes to the bottom of the tank or it will not siphon.
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willieG

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Re: Water heater water to water heat exchanger install
« Reply #10 on: November 07, 2016, 03:22:20 AM »

Willieg,
The installer had me tap into the water heater for the supply from the side where the pressure relief valve is at. I see what you are saying if it were hooked directly to the cold line. If it were hooked up that way directly,would there be enough time to heat the water as it goes though under house pressure. But being where its at on the side, when the water is turned on, flow is coming in the cold input of the water heater and not directly though the input of the side arm. and the outflow of house water is coming out of the hot side of the water heater. So water heated by the boiler is just siphoning through as water is used?
I hope this all makes sense, because I'm confusing myself.
no if it were hooked  directly it would not work, sorry for confusing you more. when you said earlier you had a tube and shell exchanger I took you meant a tube with a long coil inside it (mine has 50 feet inside)
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boilerman

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Re: Water heater water to water heat exchanger install
« Reply #11 on: November 07, 2016, 08:07:51 PM »

My water heater has been hooked up the way the diagram shows for 14 years including bringing the hot water line from the boiler into the low side port then out the top side port and I turn my electric breaker off to my water heater when my OWF is burning and never run out of hot water. Hitting the cold water in the tube at the lowest point with the hottest OWF boiler water probably makes domestic water thermocirculate up the tube exchanger better in this application. I agree with Slim that in your picture I don't see an air bleeder valve at the high point on the domestic side before returning back into your water heater. You're probably air locked or partially airlocked on your domestic side.
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T28c34

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Re: Water heater water to water heat exchanger install
« Reply #12 on: November 08, 2016, 08:11:23 AM »

Yes I like that idea of having a valve in between the side arm and water heater on the domestic side. I could then close that and purge. I can open the domestic side at the pressure relief valve to purge air out of the system. I did do that the other night and had a lot air come out. As nice as its been here in northern Illinois, I just might shut things down and put in that valve to clean out the sidearm.
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sabercat

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Re: Water heater water to water heat exchanger install
« Reply #13 on: December 07, 2016, 04:54:07 AM »

My water heater has been hooked up the way the diagram shows for 14 years including bringing the hot water line from the boiler into the low side port then out the top side port and I turn my electric breaker off to my water heater when my OWF is burning and never run out of hot water. Hitting the cold water in the tube at the lowest point with the hottest OWF boiler water probably makes domestic water thermocirculate up the tube exchanger better in this application. I agree with Slim that in your picture I don't see an air bleeder valve at the high point on the domestic side before returning back into your water heater. You're probably air locked or partially airlocked on your domestic side.

Me too, as soon as the wood stove is up and burning, the gas is shut off to the hot water heater.
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hrc200x

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Re: Water heater water to water heat exchanger install
« Reply #14 on: January 13, 2017, 01:31:37 PM »

Your saying he needs a bleeder just above the side arm on the domestic side? The top pipe looks level into the water heater, So as it is now if air is there wouldn't it just go into the tank, float to the top of the tank, then out the "hot" out to the faucets? I have a similar side arm set up, mine quit working end of last winter, I drained the water heater and it started working again, it must have been plugged. Like others I turn off the breaker to the water heater when the boiler is up and running, but I live alone and don't use much hot water, compared to what a family would.

From what I understand the side arm heater like you have isn't meant to heat up water instantly like a plate exchanger would. A plate exchanger would tap into the "hot" out to your faucets just above the water heater on 2 of the ports on the plate exchanger and the other two would be in/out for the boiler. As long as your boiler is up to temp and pump running you'd have infinite hot water at the faucets because the plate exchanger transfers the heat way quicker than a side arm heater does.
« Last Edit: January 13, 2017, 01:44:53 PM by hrc200x »
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