OWB water temps

[ktm250rider]

Seems like I have some odd water temps on my woodmaster 5500. I have always questioned the incoming temps. The OWB is set to 170/180 and my inside boiler was always showing much less, between 150 and 160. I thought this was perhaps a dirty or poor heat exchanger. I installed a couple inline boiler temp gages with a couple T's. With our current cold spell, im showing 140 on the inline and return line temp gauges.
My feeling is that if the water temp in the underground lines was loosing 40° in transfer, id be going through a boat load of wood. Im not seeing that, my wood consumption is pretty stable over the past few years.
The unit was installed about 8 years ago using about 80 feet of thermopex.

I always hated thermodynamics in college, does it sound right that I would be burning through wood if im loosing 40° just in transfer.

Ive thought about just eliminating the HX and plumbing right into the inside boiler. I need to find out if the supply lines are the problem before making that jump.

 

[Poston5]

To be sure it's supply lines, Check the line temp leaving the boiler and check the line temp coming into the house. This is comparing the same baseline so you can see the variance.

 

[ktm250rider]

Got a good reliable way of doing that? I have an elcheopo IR temp probe but its not reliable enough for me. I don't know where the actual thermostat measures the water in the OWB but I figured that was accurate at the 170/180. When my damper failed it was reading above 200 and I could hear the water slightly boiling.

 

[ktm250rider]

So, i got a thermocouple from work. With the owb at 169, incoming copper is 164, outgoing is 150. Water going to boiler is 145-150.
Looks like i needa new HX or clean the current one. Any good or bad on removing the HX and going right onto the boiler from the owb?

 

[NSMaple1]

Assuming your indoor boiler & the rest of the system is pressurized, and the owb isn't - I wouldn't do that.

 

[Red97]

That does not sound too far off. Did you test on the outside of the pipe? You want to shoot for 10-15* lower temp coming out of the exchanger, back to the owb. The owb water should not be mixing with the boiler water. Boiler=pressurized OWB= vented to atmosphere.

 

[Iska3]

If I have my OWB set at 170 degrees and (after going 135 feet underground) I check the water temp inside the house before my plate exchanger for the HW and the air exchanger for my furnace, my temp will be around 168 degrees "IF" I'm not drawing hot water for the bath or washing and going back to the OWB after the funrace my water temp will be around 145 to 150 degrees. My furnace will draw off something like 20 degrees. When I installed my OWB, I also installed a pressure guage on my water line so I know if my exchangers are clogged. My 009 pump will pump around 22 pounds or I have something like 22 pounds of restriction with a clean plate and air exchanger... What type of insulation do you have on your in-ground water lines? How large is your water pump and is your furnace fan on low or Hight Speed for Air. It should be on Low. If your pump is large enough, you could show very little heat loss and still be dumping heat from your lines into the ground. It's best to go by your temp and how much wood you use. My friend have very little heat loss but burn 25 cords of wood per season. He had very little insulation on his lines and a larger pump so in the real world, his pump was pumping fast enough to make up of all his heat loss. I just cleaned my air exchanger today but not the water side. (I had to clean the vents with a Vacuum) I change my filters often but over the years the fine dust seems to work it's way in. I cleaned my exchanger, changed the filter and my house heats like before. Check your water lines first... If your exchanger is plugged so the ewater can not flow, your wood usage will be going down fast and your outside damper will never open as much.

So, i got a thermocouple from work. With the owb at 169, incoming copper is 164, outgoing is 150. Water going to boiler is 145-150.
Looks like i needa new HX or clean the current one. Any good or bad on removing the HX and going right onto the boiler from the owb?

 

[NSMaple1]

So, i got a thermocouple from work. With the owb at 169, incoming copper is 164, outgoing is 150. Water going to boiler is 145-150.
Looks like i needa new HX or clean the current one. Any good or bad on removing the HX and going right onto the boiler from the owb?

Might help to get some clarification on all the temps.

Where is 'incoming copper'? Is that OWB water as it enters the HX?

Where is 'outgoing'? Is that OWB coming out of the HX or is it 'indoor boiler' water coming out of the HX?

Water going to boiler - OWB or indoor boiler?

Key items are temps drops on both sides of the HX, along with temp drops at each end of your underground pipe.

If you've got thermopex underground, you should be good there. What is it pumped with?

With 8 years of use, your HX could very well be getting dirty/scaled up inside. It could also be undersized if you've always had this problem. There are a lot of dynamics & things to get right for proper HX sizing - flows on each side, heat output on one & heat load on the other....

 

[tawilson]

Air in the lines or the hx could affect your temps too.

 

[ktm250rider]

I have thermopex coming into the basement from the OWB through the foundation wall (about 12" above the floor). I transition to copper and go into the HX about 6' off the floor. OWB temps were taken about 2 feet from the HX on both incoming and outgoing for the OWB. So the OWB loop is 165 in, and 150 return to OWB. I have a drain valve on the incoming line and was able to measure the water temp at ~164 as well. Im not concerned about the underground lines anymore.
HX output to IB (indoor boiler) is about 4' of copper. I took another measurement about 1' from where the copper returns to the IB. I was only getting 150. I believe this is telling me I have 15° of "loss" at the HX. I have 165 coming into the HX but the HX can only extract 150.
I did not check the temperature on the incoming side of the HX from my heating loops.
The heating system is a combination of 3 zones for hydronic hot air, 1 for water heater and 1 for radiant. All pumps are taco but I don't recall the numbers, 009 sounds about right. The HX is supposed to be a 60 plate. I say 60 because it almost looks like someone overwrote the 5 with a 6. We live in NH and naturally have hard water.

 

[Oxford]

If your return temperature to the OWB is 150 and your supply temperature to the Indoor boiler is 150, the exchanger is transferring heat. I don't know what you're using for a pump, but the 5500 specs say that it's good for 650mBTUh, or about six times what a reasonable house should need. If you're using a 60-plate with 1 1/4 NPT connections, It should be good for roughly 240mBTUh, which you're surely not using, unless you've got a heck of a big house. If you want your indoor water warmer, I think you're going to need higher flow from the OWB. As an example, if your pump is something like a Taco 009, pumping at its max specified flow of 10 gpm and your delta of 15, you're moving about 75000 BTU/h. If you keep your same approach of 0, to cut your delta in half, you're going to have to double the flow. Even then, depending on how your indoor plumbing is configured, your supply water temperature is marginal for most hydronic hot water applications as the discharge air just wont be warm enough to be real comfortable.

Whatever else you do, do not put the oxygenated, poorly treated water from your atmospheric outdoor OWB into your pressurized indoor system unless you plan on replacing both of them instead of just the OWB due to premature failure from oxygen. At least you'll be able to stay warm while you weld if you keep them separate.

 

[ktm250rider]

Ok, I guess I was hoping that if I was getting 165 to the HX I should get something higher than 150 out.
i will check the actual pump models tonight.

That seems to be my problem, when its really cold, the hydro air isn't warm enough to heat the house. House is 4000 sqft moderate to good insulation. Ive been on a mission to stop air leaks and have made a huge improvement.

I just like to be reminded not to open up the system because Ive seen a couple installs done this way.

 

[tawilson]

Turn your owb temp up. I run mine at 190 when it's uber cold out. You might want to check the temps going out to your zones to make sure you don't have another piping issue on the ib side of things. I added my owb on to my existing system and had to play with things for a bit to get things working right.

 

[Joesell]

I usually keep mine at the factory setting, 180°. It's been super cold here lately and my house has felt really cold. I bumped it up to 190° and the problem is solved! 10° made all the difference.

 

[fixit1960]

I have mine at 175, I was tempted this past week to turn it up to 185 or 190 like I have run it in the past but man does it eat wood when I do this!!!! Seems like up it 10 degrees and you use 20% more wood.

 

[Joesell]

I have mine at 175, I was tempted this past week to turn it up to 185 or 190 like I have run it in the past but man does it eat wood when I do this!!!! Seems like up it 10 degrees and you use 20% more wood.

I agree, definitely more wood. However, I don't care how much more wood it takes. Gotta keep mama and the baby's warm!

 

[Mike Van]

Sometimes heat exchangers will get partly plugged too, or just coated inside rust, lime, calcium, I'd take it apart and try to flush it out before I spent a lot of $$$$$$ on other things. You need steam or muriatic acid [I believe] to really clean one. I used one of the Shark steamers [as seen on TV] It worked pretty good.

 

[Poston5]

I had mine at 165 with a 5 degree differential and it was struggling to recover when we were pulling domestic and the furnace was running @ the same time, so I bumped it to 185. I really have not noticed more consumption, when its zero it burns a lot of wood no matter what.

 

[Oxford]

If the OWB return temperature and the Indoor Boiler Supply temperature were radically different, I'd agree that the exchanger was fouled. They're not- according to the OP, they are the same, and that very small "approach temperature" tells me that exchanger fouling isn't the issue here. Turn your OWB temperature up. It'll smoke less and your house will be comfortable.

 

[Joesell]

Sometimes heat exchangers will get partly plugged too, or just coated inside rust, lime, calcium, I'd take it apart and try to flush it out before I spent a lot of $$$$$$ on other things. You need steam or muriatic acid [I believe] to really clean one. I used one of the Shark steamers [as seen on TV] It worked pretty good.

Last time I cleaned mine I used toilet bowl cleaner. Mine was totally plugged. Dumped the cleaner in, left it sit for a week. Flushed it out, and it was good as new!