OWB not transfering heat into oil burner

[Mahoney86]

Now here is where the frustration sets in each time.

I pushed water from house to OWB. I opened the purge valves inside and drained 10’gallons of water to see if any other air could be trapped.

It’s now 8:03

OWB reached its high point of 192 and is now idle.
Temp reading at the supply line into HX is now down to 170. So my OWB temp has increased 9 degrees but my temp inside went down!

My thermostat inside is still calling for heat and everything is circulating

 

[Mahoney86]

That is an improvement.

I'd be most concerned about the 12 drop between OWB and OWB supply though? Are you sure the water leaving the OWB is 183 or close to it?

Yes that is extremely concerning to me. Went I take a temp reading at the pump casing it is 180 degrees. When I remove the pipe insulation and shoot a temp reading on the pex it is low 170s

My outside temp right now is only 39 degrees.

 

[Mahoney86]

1 hr later update

830pm


OWB temp at display -180


OWB supply - 163
OWB return - 152

Oil in - 143
Oil out - 156

 

[Mahoney86]

Did another quick check and display on OWB is reading 185 and OWB supply is at 168 climbing and my house system is still circulating so I feel like if any air was present it should likely be gone now.

Now it seems the next item of concern is the massive temp loss from the OWB to the house. There is a 7-8” run on the supply side that is not insulated in my basement, other than pipe insulation I have not insulated anything else on the OWB itself.

 

[maple1]

Simple question.

What is the temp of water right where it enters the pipe leaving the OWB, vs what the OWB display says, vs what is entering the HX from the OWB, at any one time? I couldn't discern that from your posts.

 

[Mahoney86]

Heat loss continues to grow if I raise the hi point as well. I raised to 195 and the OWB immediately went to 202 degrees. Inside supply at HX is 184 now

I guess the bright side of it all is I now know why my oil burner runs all night when set to a high of 170. Clearly the OWB heat loss is making it unattainable for my oil boiler water lines to get even close to 160 never mind 170.

That also explains why the OWB fire continually goes out because there is no need for it to heat water as the oil boiler is running consistently to keep up with the heat demand. I can lower my oil boiler hi point to 150 but then cold showers will be instore

 

[Mahoney86]

Simple question.

What is the temp of water right where it enters the pipe leaving the OWB, vs what the OWB display says, vs what is entering the HX from the OWB, at any one time? I couldn't discern that from your posts.

Display right now reads 202*

The metal elbow directly outside the boiler reads 197*

The area where the water pushes the circ pump reads 200*

The pex piping below reads 190*

 

[maple1]

Heat loss continues to grow if I raise the hi point as well. I raised to 195 and the OWB immediately went to 202 degrees. Inside supply at HX is 184 now

I guess the bright side of it all is I now know why my oil burner runs all night when set to a high of 170. Clearly the OWB heat loss is making it unattainable for my oil boiler water lines to get even close to 160 never mind 170.

That also explains why the OWB fire continually goes out because there is no need for it to heat water as the oil boiler is running consistently to keep up with the heat demand. I can lower my oil boiler hi point to 150 but then cold showers will be instore

I would lower that 170 to at least 160 when running the OWB. Mine would make enough DHW down to 140 or less. Do you have a tankless coil or an indirect?

I'm at a loss on the temp drop to the HX. If water wasn't flowing you'd see a big temp drop thru that side of the HX.

 

[maple1]

You said above you purged 10 gallons. Not sure your setup for doing that or how you're doing it - but is there a way you can run the OWB circ with the return running into a bucket so you can measure the gpm it is pumping? Not sure if even possible.

Or maybe before that, measure temp of OWB water as it exits the HX, vs its temp right before it enters back into the OWB.

 

[warno]

I just quickly went back through the pages on this thread. Could we get a picture of the back of the OWB? I'm curious if you are pulling OWB supply from the top or bottom of the water jacket.

 

[Mahoney86]

I just quickly went back through the pages on this thread. Could we get a picture of the back of the OWB? I'm curious if you are pulling OWB supply from the top or bottom of the water jacket.

Water is being pulled from the top where central boiler indicates hot water supply. Return from HX is at the bottom

 

[warno]

I guess the temp probe must be higher than the supply port then. But that's irrelevant now if you're pulling from the top port.

 

[warno]

@Mahoney86 I'm alittle worried you might still have a lack of flow to your FPHX. I looked up the pump curve and it's definitely a high head circ but at best you're going to get 10 gpm.

Did we ever get a good estimate head loss on your OWB side of your system?

 

[maple1]

@Mahoney86 I'm alittle worried you might still have a lack of flow to your FPHX. I looked up the pump curve and it's definitely a high head circ but at best you're going to get 10 gpm.

View attachment 238457




Did we ever get a good estimate head loss on your OWB side of your system?

I woke up this morning thinking about this thread (arrrghh) - and I think you could be right. If the lines are all well insulated, and temp readings are accurate, that is the only reason I can think of for the apparent loss between the OWB & the HX. And now after seeing it, that isn't an overly impressive pump curve for decent flow.

We also haven't seen many if any pics of the whole OWB loop - particularly of the boiler/circulator area & plumbing of it. If the circ is close to the top of the OWB, there might also be some cavitation potential.

I think it is also hard to fully get a read on things, from the HX temps, because the HX is also likely quite undersized (20 plate?). So what looks from the temps like decent flow, might actually not be because the HX isn't big enough to transfer out a lot of heat.

And we also don't know how well the indoor side of the HX is doing. Or circulating. I think I remember one pic showing the HX on its back - not sure how much that impacts, but pretty sure mounting in that position isn't recommended. Might be for scaling reasons. But if that side isn't flowing a lot, that could also make for misleading temp readings.

 

[stee6043]

It's a shame we don't all live in NY/NJ. I'd love to see this thing running in person.

You guys might be right on this pump thing but I've been struggling with the idea of "not enough flow" since the beginning of this thread. Mahoney isn't pumping this water particularly far...and only through a single HX. I feel like there is something plumbing related still going on here.

Mahoney, if you were to let the oil boiler run and isolate the OWB what would your supply and return temps be at the OWB? With no heat load you should be able to send water to your house and back and only lose a few degrees. Did you potentially install a bypass that would enable you to do this kind of recirc into the house and directly back into the OWB? Any chance your thermopex is waterlogged or crushed/restricted? Just for kicks have you opened up a spigot on your OWB loop inside the house to confirm you're getting "very good flow" from that thermopex?

 

[warno]

@stee6043 if I remember correctly the underground run was 75 feet I believe one way. So that's 150 feet of 1" pex. plus i remember seeing alot of pex 90s in the other pictures on the OWB side. 75 feet isn't far but, correct me if I'm wrong, my findings say that's alittle over 12 feet of head in the underground alone.

 

[Eureka]

I just read through all of this, but was the circulator loop added from the plate exchanger to the oil boiler to keep the temperature up? Without doing that I simply don't see how this will ever work without your oil boiler constantly firing to maintain it's temp. The oil boiler might not ever get up to temp just by circulating through the plate exchanger when there is a thermostat call for heat, especially given the fact that the load will always be sucking up all the heat.

You keep losing fires in your OWB because there is hardly ever any load on it because the oil boiler is heating your house most of the time. Without a circulator always pushing water through the plate exchanger you're really only heating up the first couple feet of the oil boiler copper piping right next to it. You want to be pushing water in and out of your oil boiler water jacket to keep it heated and up and ready for a call for heat. The constantly running circulator will then heat the jacket right back up to near OWB temp as soon as the heat call is satisfied and the existing oil boiler circulator shuts off. This would mean always having DHW water ready too.

My take at least. Seems like it should work just fine after that.

 

[Eureka]

I forgot but also wanted to add that I REALLY wouldn't count on an IR thermometer to get accurate readings of water temps. You really need to have a temperature gauge placed in a tee so it's seeing actual flow. I have learned this first hand. Sharkbite makes a handy temperature gauge that's easy to slip in but very $. I just used cheap Watts gauges in black/brass pipe tees so the thermowell is right in the middle of the flow. Works perfectly.

I have just learned that an IR gun reads all over the place especially on different surfaces, black paint/tape or not, of different materials that transfer heat differently. They're really only good if you have a known actual baseline temperature to set a differential from.

 

[maple1]

I just read through all of this, but was the circulator loop added from the plate exchanger to the oil boiler to keep the temperature up? Without doing that I simply don't see how this will ever work without your oil boiler constantly firing to maintain it's temp. The oil boiler might not ever get up to temp just by circulating through the plate exchanger when there is a thermostat call for heat, especially given the fact that the load will always be sucking up all the heat.

You keep losing fires in your OWB because there is hardly ever any load on it because the oil boiler is heating your house most of the time. Without a circulator always pushing water through the plate exchanger you're really only heating up the first couple feet of the oil boiler copper piping right next to it. You want to be pushing water in and out of your oil boiler water jacket to keep it heated and up and ready for a call for heat. The constantly running circulator will then heat the jacket right back up to near OWB temp as soon as the heat call is satisfied and the existing oil boiler circulator shuts off. This would mean always having DHW water ready too.

My take at least. Seems like it should work just fine after that.

Yes, that may be at play too. But seems from the postings that the heat isn't making it from the OWB to the HX the way it should be. Which should be the first thing to get sorted & working right.

 

[Eureka]

I guess I just think the temperature readings might not be close to actual and maybe are mistakenly being focused on. It seems like the OWB side is pretty straightforward as long as the supply/return are correct. I'm using a similar OWB circulator going through two plate exchangers, a Caleffi thermostatic valve, and another 40 feet of underground, and even if I put it on low speed, it still transfers plenty of heat (albeit with a huge delta T).
I could see a different circulator making it run more ideally but it should still function at some level which it doesn't seem to be doing now.

 

[maple1]

I guess I just think the temperature readings might not be close to actual and maybe are mistakenly being focused on. It seems like the OWB side is pretty straightforward as long as the supply/return are correct. I'm using a similar OWB circulator going through two plate exchangers, a Caleffi thermostatic valve, and another 40 feet of underground, and even if I put it on low speed, it still transfers plenty of heat (albeit with a huge delta T).
I could see a different circulator making it run more ideally but it should still function at some level which it doesn't seem to be doing now.

Without being there we are all doing a bit of guess work, and relying on the OP for info to try to help. Temp readings are about all we have, and should be good info if accurate. Pictures sometimes help too but we don't have many of those.

How big is your underground? What do you have exactly for a circ? Even if the same, there could be other varying factors at play here that might show in a picture. Layouts can differ quite a bit & influence if something gets overlooked or not done right.

A good dual probe BBQ thermometer can also be really good for this work. Tie each probe onto a pipe entering & leaving something, under some pipe insulation, and you get a pretty accurate read of temps. I have a Maverick on my tanks, it is very accurate. One thing I don't think that has been done here yet, is measure the temps of water leaving the OWB, and coming back to it - both with the oil side not circulating, then with it circulating. With the oil side not circulating, there should not be a big difference around the whole loop, with good OWB flow and well insulated piping. That would be my step 1 - then work towards the indoor stuff.

 

[warno]

I guess I just think the temperature readings might not be close to actual and maybe are mistakenly being focused on. It seems like the OWB side is pretty straightforward as long as the supply/return are correct. I'm using a similar OWB circulator going through two plate exchangers, a Caleffi thermostatic valve, and another 40 feet of underground, and even if I put it on low speed, it still transfers plenty of heat (albeit with a huge delta T).
I could see a different circulator making it run more ideally but it should still function at some level which it doesn't seem to be doing now.

A similar setup in plumbing with a different circulator makes all the difference in the world. I don't believe the Taco 009 that the OP said they just installed is a multi speed pump. When I looked up the manual to get the curve it only showed one speed and a flow of 10 gpm max. Which isn't a whole lot when trying to heat a house, essentially, through a 20 plate HX.

And @maple1 made a good point earlier that the OWB circ may be cavitating. Any cavitation will create lack of flow also.

 

[Eureka]

I'm late to the party and just trying to be a fresh set of eyes to help this guy stay warm and enjoy his investment of money and I'm sure lots of time as well. I like to make sure the basics are covered first and that recirculating loop through the oil boiler seems like a basic component of his system.

I still agree with what everyone else is saying and much of what I have learned in the last couple years has been from some of the fine minds in this thread. My trial and error building two systems has taught me even more. I've also learned that it's easy to focus on the wrong things when they're the only things available to look at.

I use Steibel Eltron circulators that are basically a Grundfos 15-58 3 speed. 1-1/4" underground lines but it all transitions to 1" inside my buildings. The one to my house I run on high to keep around 20-30 delta T and one to the shop is on medium. I have very few elbows and fittings and come into and out of my plate exchangers straight rather than directly into elbows, thanks to my research here.

So yes my situation is different, but I still think something very basic is missing in this system because it doesn't work at all. We can only help the OP as much as they are willing to help themselves by providing lots of info and pictures.

 

[warno]

@Eureka nothing wrong with another set of eyes. I'm basing all my experience of my system in the past 4 years and alot of reading here. I know that when I redid my plumbing and went to a much larger HX everything fell into place. When I dropped more than half the head losses and the addiction of a bigger 90 plate, vs. My 20 plate I had, I arguably dropped all my problems.

 

[Mahoney86]

Thank you for all the help in this everyone I’m truly blessed to have all of this input.

As suspected came home from work today to the fire completely out and wood barely even charred.

My indoor boiler is set to 150 and my OWN temp display is showing 148 right now.

I took some photos of the indoor setup. Disregard the small 3/4” pex lines. Not really sure what anyone wants to see so just let me know and I will take pictures.

I have no installed any circulator from the HX to my domestic water loop or anything like that. Before I even go down that road i need to solve other issues. Regardless I am likely going to disconnect my DHW from the oil boiler and install a natural gas tank heater as we just got natural gas installed at our house for free as an incentive from the gas company as they recently ran lines in the street. We can talk about hooking that heater in at another time.

All the pex is 1”. I have (2) 90* elbows on each owb line for a total of 4 elbows. The inlets on the HX are 1 1/4” and the HX is rates to 280,000 btu according to the spec sheet. Amazon will let me return the 009 series pump so if I need to upgrade to an 011 then it is what it is at this point.

I will be out of town this weekend at my camp and there is a central boiler dealer local. If I need to grab any supplies I can easily do so