Clogged Heat Exchanger?

swampfox1 Posted By swampfox1, Nov 12, 2017 at 8:35 AM

  1. swampfox1

    swampfox1
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    Nov 12, 2017
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    I have a Nature's Comfort 250,000 BTU Wood Boiler and I can't seem to get it to work. The boiler burns the wood with no issues but the water just doesn't flow to the heat exchanger inside the house. The pump on the boiler works but I think the brazed plate heat exchanger is clogged. I have done some research into a shell and tube type heat exchanger but I don't know if they are too inefficient..

    There was some corrosion inside the boiler and that probably made its way to the brazed plate heat exchanger and clogged it. I also am considering an in-line filter but not sure if this will restrict flow even more.

    Thanks for your help!
     
  2. maple1

    maple1
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    Sep 15, 2011
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    Could be plugged. Could be an airlock. Assuming the circ is running right. One of those things we'd likely have to be there to sort out.

    The HX should be plumbed for easy flushing - isolation valves at all HX outlets and hose bibs between the valves & the HX. So all you have to do is close the valves, hook a hose up to one bib & let the flushing water come out the other. So if your setup doesn't have that you should add it if you end up needing to take things apart. And you should have at least a simple wye strainer up stream from your circ. Maybe another at the HX inlet. Also set up for easy cleaning - iso valves on each side. Maybe a ball/drain valve on the filter plug so you can just open the valve to let trapped crud out. You should also have hose bibs at places that will allow you for force water through your lines also with a garden hose hooked to domestic water supply to get air out if needed.

    Don't switch out a plate for a shell & tube - much less heat exchange potential.
     
  3. TCaldwell

    TCaldwell
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    I️ second maples advice, not sure how long it’s been since you have cleaned the hx, but i have made it a annual necessity at the beginning of the heating season.
     
  4. Bob Rohr

    Bob Rohr
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    Jan 9, 2008
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    If it worked in the past, recently, I'd suspect an air lock. did it boiler over? Sometimes that will lock them up.

    Re-install it with Two Webstone valves. These allow you to shut it off and pump a cleaner thru the HX.

    If you have a radiator shop nearby, they can cook them out, it will work like new.
     

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  5. salecker

    salecker
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    You should be able to flush both sides,so if you are going to install 2 valves you should install them on the other side so it can be flushed as well.The webstone valves look nice...and expensive.
    I used a iron Tee with a ball valve next,and boiler drains on the bottom of the tee.
    I have a y strainer before the HX on each side.I also have a side-stream filter for the glycol side of my system,the first filter in the side-stream lasted about a month after i started my sytem for the first time,second one lasted a year.Havn't had to change one since.All my copper was used and most of the fittings were used that i had salvaged from a apartment i tore down.
    I have had zero issues with mine.
    I keep wanting to flush the HX but i never get to it on my list in the fall.
     
  6. Bob Rohr

    Bob Rohr
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    Really shouldn't need a strainer or flush valves on the closed loop side of the HX. Unless you are adding fresh water that side should stay clean ad scale free.

    On open systems water gets added and there is a constant ingress of O2 that causes corrosion and rust, scale, etc.

    The cost of the Webstone is reasonable as compared to buying and assembling 3 components to make your own, and nothing to leak.
     
    Chris Hoskin likes this.
  7. salecker

    salecker
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    I figure better safe than sorry.I always try to make the "really shouldn't" redundant
    If you are going to be adding stuff to the system,may as well do both sides,that way should there ever be a problem it is an easy fix.Especially where i live,100 miles to any plumbing parts or heating tech's.Fancy parts like the Webstone valves are all special order and cost a butload more than off the shelve parts.If there is an issue and i am not home the travel cost for a tech is close to $500.00 just for them to come look at something.
    If you use hemp for your threaded connections there is very little chance of leaks.When i built my system i had close to 200 threaded fittings,i have yet to have a leak either on startup and since. That was 8 years ago.
     
  8. warno

    warno
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    I'll second the webstone valves. It take 3 different fittings to make up what one webstone is. That's ALOT of leak potential. They are costly but i can say with having 8 of them on my system i have yet to see a problem with them. If you are a "what if" type of person buy a spare webstone to have on hand. The initial cost once again would still be worth the piece of mind in a leaky situation.

    With all that said, i put wye strainers in upstream on both sides of my plate heat exchanger. It's a quick and easy way to see if there is crap headed that way, then you can assume if the HX is clogging or not.
     
  9. salecker

    salecker
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    Aug 22, 2010
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    With properly installed threaded fitting using hemp there is virtually no leak potential.
    Using hemp if you do have a leak it will seal up as soon as liquid gets to the hemp,it swells when it gets wet.
    It takes a little extra time to install hemp properly,but the piece of mind knowing you don't have to redo any threaded fitting is worth it.
    I am not saying to not go with the Webstone valves.If they were available off the shelve here i probably would have used something like that as well,but i went for the K.I.S. approach so if i need any parts they are in my shop,not on order 100 miles away.
    Where i live if you can't do it yourself it's gonna cost you a bunch of $$$$
     

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