Need Help with Heat Exchanger Temperature Variances

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Jan 17, 2011
57
NE, Ohio
Hello everyone. I am new to the site. I’ve been using a pieced together outdoor wood burner for three years now. I will share the set up with everyone soon.

I’ve been dealing with a few problems most critical is temperature losses between OWB, Heat Exchanger, and Indoor Boiler.

I understand there are charts and calculators for sizing pumps for the system, but for the sake of keeping this simple, I know my temperature of OWB supply to the heat exchanger is 160° However, my heat exchanger is at a 30-40° heat loss because my indoor output from the heat exchanger is at 110-120°

I have the exchanger lines crossing properly on the heat exchanger.

The problem surfaced when I had a 1/25th HP circ motor and I was only getting 140° on my OWB supply but I could get 140° on my house system. I changed It to a 1/12 HP Bell & Gosset series 100 then it jumped to 160°+ depending how hot I run the OWB. But the indoor system will not rise above 120°.

What might be causing this heat variance?

Here is some data:

OWB Supply Indoor Boiler House Temperature
9:30am 145° 110° 58°
10:30am 145° 110° 58°
11:30am 145° 110° 60°
12:30pm 140° 110° 60°
2:30pm 160° 120° 62°

Any help to lead me down the right road is appreciated.

Thank you,

Adam
 
Just to let youk now you are not alone with a problem of this nature...I have a thread "OWB to Benjamin cc500 problems"....with exactly the same situation.

I am investigating other sources of info and will keep you apprised of anything I learn in the process...by the way hope uo have your longjohns on...62 degrees is pretty cold in the house....

Mike
 
Likewise. I am surprised I missed that thread. I will see what you have going on.

Longjohns are on. I have to get something going quick. Baby due Feb 22 not to mention the rest of the family is patiently waiting for a resolution under layers of blankets.
 
What is the actual flow rate on both A and B sides? What about the temperature drop on the B side. Is it possible you have that much load on the system keeping the temperature low?

If you throttle down the B side flow does the temperature rise on the A side. If you have the spec on the HX you should be able to troubleshoot the cause of the temperature you are seeing. Most HX manufacturers have software programs that they could use to determine what is going on with your system, but you need to provide some actual operating data.

Is it a new HX? Any chance of a flow restriction? Do you have strainers on the HX on either side?

hr
 
CountryBoy,

To much missing information to start any useful diagnosis.

Go to my website www.MurphysMachines.com and hit the "contact us" button to send me an email with your phone number and I'll call you. Or, just call the number on my website and it will go straight to my me. I'm located about an hour north of Detroit.

I talk folks through these kinds of problems every day.
 
Hey Country Boy....did you call Murphy 2000...? Paul was extremely helpful and knowledgeable....and reinforced the advice I had heard from other members...at least I now have a plan.....and feel a little bit better about getting my system working right.....

Good luck with your issue...

Mike
 
Thank you for the replies everyone. Here is my set up. It is not much. It is an old 1980 Steel King model 480B(H) indoor wood boiler in an old gas shed located about 150’ from my house. With it being an indoor boiler, I am seriously thinking of putting it in my basement and calling it a day, but I do like my current set up if I can get it to work in the colder periods. There is nothing fancy in my set up. Initially I thought this was a pretty straight forward. Get the hottest water I can to the exchanger and life would be good. I now know this isn’t the case.

I purchased my 1†pex from outdoor furnace supply with quadruple wrap. I am certain my lines are in good shape not saturated in water as I have about an estimated 15’ vertical elevation change. Boiler is at the top.

Heat exchanger is a HEX BL26-50. 50 plate heat exchanger. Q1- OWB IN / Q4 OWB OUT & Q2 House Line Out / Q3 House Line In.
Heat exchanger is 3 years old.

A & B flow rates – No clue and do not know how to check

Flow restriction- Yes I have a drain in the line by my heat exchanger. I’m finding a heavy sediment coming out of the line the side of find coffe grounds. I have no in line strainers. I did flush the exchanger by shutting a few valves. Needs more flushing, but I did see my OWB Supply line temp jump to almost the same temperature as my OWB gauge.

I know I have a slight amount of cavitation on inside system. I have to purchase a new in line vent as mine appears to be mal-functioning. I just bled all my base boards and did not find much air at all. Cavitation was still present afterwards.

At this point, I want to build the system right. I have no problem putting the money into it.

BTU requirements for the house are unknown at this time. I don’t think this is relavant for this situation.

Let me know what other information is needed and thank you all for your help.
 
I just wanted to follow up this issue so we all can learn from it. A couple issues I am working on.

1.) Line size is too small for distance. Would have been better off with 1 ¼†Lines
2.) Can be argued that pump is too small however since I have trialed a 1/25, 1/12, and 1/6th HP circ pump with similar results, I think it is safe to say my limiting factor is my line size.
3.) Removed my 50 plate heat exchanger and found it loaded with rust scale on the OWB side. I cleaned it out by back flushing and filling with muratic acid. Appears to be flowing properly.
4.) No in-line boiler strainer. Installed one along with a few ball valves so I can backwash and flush. So far I have pulled at least two cups of rust scale from the system.
5.) I still have a wide heat exchanger spread, but I am not sure if it is me being overdemanding. Water output of the heat exchanger is 160° and my process water is at 150°.

I spent most of the day yesterday bleeding the air from my process water, but by the end of the day house temp went from 52° to 64°.

I am also getting a constant 150°on my process water which is over the occasional 140° I was getting previously. Boiler water is becoming less contaminated with rust scale.

Thanks to those who helped and comments and suggestions are still welcome.
 
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