OWB circulation/pump question

[Jacampb2]

Hey folks, it's been a short while. I hope all of you are doing well. It's heating season again here and I have more questions for the hive mind.

I have a Frontier 150 OWB, it's manufactured somewhat locally by a machine shop called "Carson City Machine Shop". I mention this because it's nearly impossible to find information on this stove. It has a 150 gallon jacket, and is very similar to a Woodmaster.

My loop is about 320' of 1" pex counting both supply and return. It has a rise of about 15 feet, 12 feet after it leaves the boiler. It goes up through my shop and then back down underground again and into the house. The heat exchangers in the house are 3/4" copper and there is a water to water HX for domestic hot water and there is a 17x22 air to water for forced air heat. The HX's are in series with the domestic water first, then the forced air, then the loop goes back out of the house and I have a unit heater next in the shop and then back down and to the boiler return.

When I got the boiler it had a taco 0007-xxx. The boiler didn't have any pressure gauges, but it seemed like the pump was struggling. The local OWB dealer thought I probably needed to step up to a taco 0011-xxx, so I did.

All year last year I had a lot of water loss. If I tried to run the jacket at 165°F, the was constant stream from the boiler vent and I had to add about 30 gallons a week. Many times I felt like the pump wasn't working correctly, but I had no pressure gauges. There were several times where the boiler was hot and neither the supply or return felt particularly warm, and I'm talking right at the pump. If I cycled the return side valve, the pex would get scalding hot in a heartbeat, but it would cool back off. I don't think the pump was priming.

This year I cleaned out the boiler jacket and installed pressure gauges on the supply and return. The loop has less than 4psi even with the return closed and the pump essentially deadheaded. If I cycle the return, the pump will briefly hit 50psi, then fall back off again. I get flow from a drain on the return, but it's just barely above a trickle.

I worked at a chemical plant for 22 years and have operated hundreds of centrifugal pumps. I'm 99% sure this thing isn't primed, but it doesn't sound like it's cavitating and it does produce some flow. I have tried every trick I know from my days operating a chemical plant, and I can't get it to prime.

The pump does not have a valve immediately at it's discharge. I'm picking one up from the big box store today. I've been trying to get it to prime using the return valve, but that's a lot of line to pressurize. The pump also does not have a strainer in line, and if I can find one, I'm putting one in as well.

The pumps suction side goes into a dip leg in the jacket. I've blown it down with compressed air to ensure it's not restricted. There is a check on the return side, which I think based on pump location below the water line and the checks, that once the jacket is full the pump should essentially be below the water line and should be completely flooded. It makes no sense that it will not prime.

I'm really looking for any advice you folks can give. I know this is long winded, and I apologize, but I'm trying to give the most accurate picture with the greatest amount of pertinent data as possible. I've also considered putting the old 0007 in the return line, but from the pump curves it sure seems like the 0011 should be more than capable of this loop.

Thanks in advance folks. I really appreciate your time.

Jason

 

[nedsim]

A couple questions:

Is the pump on the discharge or the return side of the boiler? From your description it sounds like it's on the hot side, but that's not typical.

What's the the check valve's cracking pressure? Could be anywhere from nil to 10 psi or more depending on the type of valve. Is it actually in the loop, or is it in the feed?

Is there a pressure reducing valve in the boiler feed? If so, is it set high enough to pressurize the highest point in the loop?

Bleeders at all high points in the loop? Do you get a stream of air-free water (no sputtering) when you open them?

It's not clear to me where the gages are in relation to the pump. Are they close enough to the pump to measure the delta P across the pump when it's running?

 

[blakey]

My understanding is that these pumps don't draw, they must be fed with water. On my Central Boiler it is fed from the higher port to get the hottest water.

 

[Jacampb2]

A couple questions:

Is the pump on the discharge or the return side of the boiler? From your description it sounds like it's on the hot side, but that's not typical.

What's the the check valve's cracking pressure? Could be anywhere from nil to 10 psi or more depending on the type of valve. Is it actually in the loop, or is it in the feed?

Is there a pressure reducing valve in the boiler feed? If so, is it set high enough to pressurize the highest point in the loop?

Bleeders at all high points in the loop? Do you get a stream of air-free water (no sputtering) when you open them?

It's not clear to me where the gages are in relation to the pump. Are they close enough to the pump to measure the delta P across the pump when it's running?

The pump is the very first thing in the supply line. There is a 1" bung towards the top of the boiler shell. I've made the assumption there's is a dip pipe inside, but that could be incorrect. Immediately following the 1" bung it makes a 90° downward, there is about 6" of pipe, a ball valve, another 6" of pipe, and the pump with the discharge side toward the rest of the loop. Before yesterday it made the entire loop, then there was a check valve, about 6" of pipe, a ball valve, then the return bung on the shell. I purchased this boiler at least second hand, so I suppose it's possible people have messed up the flow direction/port positions over the years.

I added a pressure gauge right at the discharge of the pump, and another immediately before the return ball valve in the return line. Physically they are right next to each other, as the water flows they are 300+ feet apart.

Today I added a ball valve right after the supply pressure gauge I added yesterday. Deadheading the pump here gets the pump to build about 6psi.

I also added a drain tap in the supply and return today to check flow. It does have more flow than I initially thought. I'd like to find a flowmeter that's safe for these temps, but I've not found something affordable yet.

I don't know the check valves opening pressure. I know it must be open, but I've wondered if it's stuck open.

No pressure reducing valve anywhere in the loop.

I put a vent about 1' higher than the highest point mid winter last year. My intention was to put a air trap up there. I have it, but I've not had time to install it yet. I have manually opened it though and if the loop is all valved for normal operation, I get nothing at all out. I believe because this high point bent I added is immediately before the loop falls back 15' to the ground and is also physically quite close to the boiler. I've seen this before in process piping where the liquid is falling and with very little restriction the high point vent never gets hydraulically full. If I put some restriction in the return, I get water that appears to be free of air out of the high point vent.

The gauge location allows me to see the ∆P across the entire loop, not the pump. That said, I bought one 100psi gauge and one 200psi gauge since I had no clue what these pumps discharge pressure was supposed to be. I'm so far down on the bottom of the scale with both gauges, that it appears they are reading nearly identical. I have swapped the two gauges to insure one want faulty.

My understanding is that these pumps don't draw, they must be fed with water. On my Central Boiler it is fed from the higher port to get the hottest water.

The suction of the pump is the highest port on the boiler. I made an assumption that there is a dip pipe because the high point is so high that even a slight drop in water would seem to starve the pump inlet. I understand wanting to draw the hottest water, but it seems it would make way more sense to pull from the lowest point in the boiler. I've actually considered plumbing the pump in place of the low point drain.

 

[blakey]

You shouldn't be losing that kind of water and it shouldn't be boiling. If you set it at 165 do you get an actual water temp reading that is much higher? If it is much higher do you have an air leak around the door?

 

[blakey]

My lines also go up and across my shed and I had a heck of a time bleeding the air out when I first installed the system. I ended up cutting the pex at the highest point and installed a T with a shutoff and a 1ft length of pex. I finally got the air out and now I close the valves at the OWB when I shut it down for the season to prevent drainback.

 

[Jacampb2]

You shouldn't be losing that kind of water and it shouldn't be boiling. If you set it at 165 do you get an actual water temp reading that is much higher? If it is much higher do you have an air leak around the door?

It's not boiling, not unless the fact that the water is falling and the psi drop as it falls is causing it to. I've read that the pressure drop can cause boiling much below atmospheric boiling point.

I installed a taco 0011 last year about a month in when I initial suspected the loop wasn't flowing properly. It hasn't had the 0007 installed in as long time.

I have a analog temperature gauge that's stabbed in at the top of the jacket just to the upper left of the door. It agrees with the aquastat that runs the blower. I replaced it this fall, just to rule out out, but it reads pretty much exactly the same as the RTD stabbed in the thermowell at the rear.

The blower is supposed to blow open a hanging damper, but one of the first things I did last year to try to slow the water loss down was to install a servo operated damper that pretty much totally shuts air down when it's not calling for the blower.

I've also replaced the door seal twice. Once from the local boiler supplier who thought the original looked like ¾", it went bad again inside a month. Then I managed to get a hold of the machine shop that built it. He sold me a new seal which was actually 1" rope. At the same time I took the entire door off and welded up some cracked welds around the perimeter of the door itself(not the stove). That seal has gone a few months and is still in great shape.

 

[nedsim]

The pump is the very first thing in the supply line. There is a 1" bung towards the top of the boiler shell. I've made the assumption there's is a dip pipe inside, but that could be incorrect. Immediately following the 1" bung it makes a 90° downward, there is about 6" of pipe, a ball valve, another 6" of pipe, and the pump with the discharge side toward the rest of the loop. Before yesterday it made the entire loop, then there was a check valve, about 6" of pipe, a ball valve, then the return bung on the shell. I purchased this boiler at least second hand, so I suppose it's possible people have messed up the flow direction/port positions over the years.

I added a pressure gauge right at the discharge of the pump, and another immediately before the return ball valve in the return line. Physically they are right next to each other, as the water flows they are 300+ feet apart.

Today I added a ball valve right after the supply pressure gauge I added yesterday. Deadheading the pump here gets the pump to build about 6psi.

I also added a drain tap in the supply and return today to check flow. It does have more flow than I initially thought. I'd like to find a flowmeter that's safe for these temps, but I've not found something affordable yet.

I don't know the check valves opening pressure. I know it must be open, but I've wondered if it's stuck open.

No pressure reducing valve anywhere in the loop.

I put a vent about 1' higher than the highest point mid winter last year. My intention was to put a air trap up there. I have it, but I've not had time to install it yet. I have manually opened it though and if the loop is all valved for normal operation, I get nothing at all out. I believe because this high point bent I added is immediately before the loop falls back 15' to the ground and is also physically quite close to the boiler. I've seen this before in process piping where the liquid is falling and with very little restriction the high point vent never gets hydraulically full. If I put some restriction in the return, I get water that appears to be free of air out of the high point vent.

The gauge location allows me to see the ∆P across the entire loop, not the pump. That said, I bought one 100psi gauge and one 200psi gauge since I had no clue what these pumps discharge pressure was supposed to be. I'm so far down on the bottom of the scale with both gauges, that it appears they are reading nearly identical. I have swapped the two gauges to insure one want faulty.

The suction of the pump is the highest port on the boiler. I made an assumption that there is a dip pipe because the high point is so high that even a slight drop in water would seem to starve the pump inlet. I understand wanting to draw the hottest water, but it seems it would make way more sense to pull from the lowest point in the boiler. I've actually considered plumbing the pump in place of the low point drain.

 

[nedsim]

The pump should develop about 15 psi deadheaded.
https://www.tacocomfort.com/documents/FileLibrary/101-034.pdf
If you trust the gauge reading, I'd be looking at the pump inlet -- the pressure and whether it's flooded, both deadheaded and open. Can you tee in a homemade manometer at the pump inlet?

Since you don't get water out of the vent until you restrict the return, I'd also be suspicious of the check. Either, as you said, it's stuck open, or doesn't have a high enough cracking pressure to overcome your 15 foot (approx 7psi) static head.

 

[Jacampb2]

The pump should develop about 15 psi deadheaded.
https://www.tacocomfort.com/documents/FileLibrary/101-034.pdf
If you trust the gauge reading, I'd be looking at the pump inlet -- the pressure and whether it's flooded, both deadheaded and open. Can you tee in a homemade manometer at the pump inlet?

Since you don't get water out of the vent until you restrict the return, I'd also be suspicious of the check. Either, as you said, it's stuck open, or doesn't have a high enough cracking pressure to overcome your 15 foot (approx 7psi) static head.

The gauges are both new and when I swap their places, the respond accordingly. I've also removed each gauge and made sure my tees I just installed aren't somehow plugged already. They flow water out and I don't think they are restricted.

I can't easily change the suction side piping on the pump. It is either 1" or 1¼" black iron pipe and while I am fairly sure I can get it apart, it's spent a lot of years threaded together out in the weather. I'm be a little bit nervous I'll twist something off or strip out a fitting. If have to do the work with the boiler running and just let the fire burn a long ways down and work quickly. Any time I need to work quickly though, nothing cooperates!

I will say that I'm fairly confident the suction piping is submerged in the boiler. Pump off, discharge side valve closed, and drain I installed between the pump and the discharge valve open, water runs out steadily.

I took down the markings of the side of the check today and I just looked it up. Apparently it should have a tag on the end cap with it's ratings. I've never noticed one, but I'll look it over now closely tomorrow now that I know it should be there.

Thank you,
Jason

 

[blakey]

It's not boiling, not unless the fact that the water is falling and the psi drop as it falls is causing it to. I've read that the pressure drop can cause boiling much below atmospheric boiling point.

I installed a taco 0011 last year about a month in when I initial suspected the loop wasn't flowing properly. It hasn't had the 0007 installed in as long time.

I have a analog temperature gauge that's stabbed in at the top of the jacket just to the upper left of the door. It agrees with the aquastat that runs the blower. I replaced it this fall, just to rule out out, but it reads pretty much exactly the same as the RTD stabbed in the thermowell at the rear.

The blower is supposed to blow open a hanging damper, but one of the first things I did last year to try to slow the water loss down was to install a servo operated damper that pretty much totally shuts air down when it's not calling for the blower.

I've also replaced the door seal twice. Once from the local boiler supplier who thought the original looked like ¾", it went bad again inside a month. Then I managed to get a hold of the machine shop that built it. He sold me a new seal which was actually 1" rope. At the same time I took the entire door off and welded up some cracked welds around the perimeter of the door itself(not the stove). That seal has gone a few months and is still in great shape

It's not boiling, not unless the fact that the water is falling and the psi drop as it falls is causing it to. I've read that the pressure drop can cause boiling much below atmospheric boiling point.

I installed a taco 0011 last year about a month in when I initial suspected the loop wasn't flowing properly. It hasn't had the 0007 installed in as long time.

I have a analog temperature gauge that's stabbed in at the top of the jacket just to the upper left of the door. It agrees with the aquastat that runs the blower. I replaced it this fall, just to rule out out, but it reads pretty much exactly the same as the RTD stabbed in the thermowell at the rear.

The blower is supposed to blow open a hanging damper, but one of the first things I did last year to try to slow the water loss down was to install a servo operated damper that pretty much totally shuts air down when it's not calling for the blower.

I've also replaced the door seal twice. Once from the local boiler supplier who thought the original looked like ¾", it went bad again inside a month. Then I managed to get a hold of the machine shop that built it. He sold me a new seal which was actually 1" rope. At the same time I took the entire door off and welded up some cracked welds around the perimeter of the door itself(not the stove). That seal has gone a few months and is still in great shape.

Did you purchase this unit brand new and are there many of these in service? I couldn't seem to find it in a Google search. Did it ever work correctly without losing water out the top? Could it be a design issue? It just doesn't make sense if it is not going over temp. I can go a whole season or two without adding water.

 

[Oxford]

Unless you’re above 212*, you’re not boiling, unless you’re below atmospheric pressure. Since your boiler is open to atmosphere, you’re not boiling- unless your temperature gauge is wrong.

I will bet that you’re either air bound or the pump suction isn’t flooded/is obstructed. How do you know the water level is correct in your boiler? Here is what I would do:

1. Stick a garden hose in the vent and fill it to overflowing. That way, you know the pump suction is full.
2. Start the pump.
3. Measure amp draw of the pump and compare it to full load, found on the nameplate. If it’s way low, you’re not moving water.
4. Take a blow nozzle on an air hose and stick it in the vent, then pack around it with a shop rag or similar.
5. Give it a couple squirts of air. This will temporarily and very lightly pressurize the suction, which should help the system purge the air in the line and get a full column of liquid through it. You should hear the pump change note when it catches.
5. If it takes off, cycle the pump several times to make sure the check holds.
6. Measure amp draw again to verify it has increased, but not past full load. If it has, you’re out of the curve and you need to throttle the return at the boiler to keep it in its curve.

 

[AnniesDad]

Fun read and takes me back to my OWB I called the monster.
First off these are not pumps. They are circulators. Need to be installed at lowest point in your system. If running any tacos make sure you have back up cartridges cause they will fail when it’s least convenient. I was partial to the 3 speed Grundfos. I had less problems with them.
As for hydro lock I tapped into the existing water supply for the house and had a ball valve for on/off. IF the system needed water or was air locked the well pump pressure was enough to push air thru.
Not sure if this would help here but just a couple things I did with my OWB that made my life easier.
Loosing that much water though would be a red flag. Where the heck is the leak if not boiling over?

 

[miller755]

I agree, pump should be at the bottom, i believe mine pushes hot water away from the boiler

 

[Jacampb2]

Well folks, I'm back at it again trying to understand what is going on with this cork stuffing thing. It runs well enough to heat the house and every year I mess with it and every year I give up and just deal with the quirks until heating season is done. I always think I'm going to really tear into it in the summer, and fall always tools back around while I still have a million things on my plate.

Anyhow, I finally got a little more prepared before fall. I built some thermowells to allow me to put a rtd in both the boiler discharge and return lines. It puts the tip of the thermowell pretty much dead center in the flow path. I also installed a strainer at the pump discharge, some additional isolation valves and a flowmeter in the return line. I then sat down for a week and wrote software to read all of my rtds and the flow meter, mounted the electronics with a backlit display in a ip68 enclosure and for ease of checking I also added a webserver and the microcontroller serves a webpage with the data live streaming on my local network.

So, I have been seeing some crazy stuff and I really don't know what to make of it. I added my own rtd up in the jacket thermowell where the blower controller has its rtd. Right now I'm not controlling anything with my shop but hardware, just gathering data. My hardware and the ranco controller seem to be within about 5° of each other. I think this is pretty close to accurate as the ranco probe is deeper in the thermowell.

My pump is flowing about 300 G/hr. Idk how accurate this is, but I wanted the flow meter mainly to tell if the strainer is plugged and just for a comparative data point.

So far the most bizarre thing is that sometimes my outlet temp is much, much hotter than the jacket temp but also there are times when the jacket temp is much hotter than the outlet temp. Like a lot. Right now it's reading 175° for the jacket and 155° at the pump discharge. Earlier the pump discharge was above 200° but the jacket was reading about 165°. I'm pretty sure that the wild variation in the jacket temp readings are all due to the pretty crappy probe location. It doesn't seem like the rtd notes very deep into the jacket and may actually not go into the jacket at all but butt up against it. The end of the stove with the probe faces south and we get a lot of wind out of the south. It used to go crazy any time there was a breeze but I stuffed it all with fiberglass bay and that stabilized it a lot. I think that in still seeing some impact from external factors.

I'm seeing about a 40°F ∆T across the loop without the shop heater running. If I turn the fan on to the shop heater the return temp plummets and I see as much as 85°F ∆T and oddly the outlet and return both start falling but the jacket temp stays fairly high, almost like the flow path internally is short circuiting from return to suction without having any residence time in the boiler. I replaced the HX in the unit heater this year because it was a homemade job with a old truck radiator and the tank started leaking. I bought a 27x22x3 just because that's the size of the opening in this thing. I think it's probably a hundred thousand BTU over what used to be there. I do not really think it's causing any issues, but I bring it up because I think it really hammers the loop temps harder than what I had. Intuitively it seems as if as long as the jacket is maintaining temp, I should be able to suck as much heat as I want out of the loop. I'm really not trusting the jacket temps though...

So, some things I've thought about experimenting with are as follows:

1) move the ranco probe to my pump discharge thermowell and control based on loop temperature.
2) temporarily move the loop return to the drain hose bib.
3) add a second pump mid point in the loop to assist overall flow, I'm not sure if 5gpm is good or bad really.
4) buying a central boiler

I'll post some pics of my thermowells and completed instrumentation project.

Thanks,
Jason

 

[jblnut]

I use an InkBird BBQ thermometer to monitor supply/return temps on my stove. The red/green lines are supply lines, orange is the house return and blue is shop return. The shop has two zones hence the two different temp drops. Not saying this is the best but it shows me temps and gives an alert when the temp goes outside parameters I've setup. Posted a pic to show you the drops I see when the circulators in the house/shop kick in. Around 300' of line total to each between the stove and house/shop.


The house is downhill from the boiler approximately 5' and the shop is uphill approximately the same. Both circulators are in the boiler because younger less smarter me thought that was the right way. My circulators pull hot water from the lower ports and dump back in the top ports. It's how it's called out on the back of the stove to do it and it makes sense to me. The water temp down there should be more consistent and it should have time to mix and not be crazy hot.

Every year I have issues with bubbles in the house line but I give it a blast of well water from my add water port and it solves it in a hurry with zero additional issues during winter.

In reading your replies I haven't been able to gather if you've moved the circulator to the lower port in the stove or not. All OWBs I've seen have the supply coming out the bottoms. I should say I've only seen inside the back of three other than mine so my sample size is small but they're all the same.

Not sure if any of that helps but there it is. Good luck !

 

[blakey]

Well folks, I'm back at it again trying to understand what is going on with this cork stuffing thing. It runs well enough to heat the house and every year I mess with it and every year I give up and just deal with the quirks until heating season is done. I always think I'm going to really tear into it in the summer, and fall always tools back around while I still have a million things on my plate.

Anyhow, I finally got a little more prepared before fall. I built some thermowells to allow me to put a rtd in both the boiler discharge and return lines. It puts the tip of the thermowell pretty much dead center in the flow path. I also installed a strainer at the pump discharge, some additional isolation valves and a flowmeter in the return line. I then sat down for a week and wrote software to read all of my rtds and the flow meter, mounted the electronics with a backlit display in a ip68 enclosure and for ease of checking I also added a webserver and the microcontroller serves a webpage with the data live streaming on my local network.

So, I have been seeing some crazy stuff and I really don't know what to make of it. I added my own rtd up in the jacket thermowell where the blower controller has its rtd. Right now I'm not controlling anything with my shop but hardware, just gathering data. My hardware and the ranco controller seem to be within about 5° of each other. I think this is pretty close to accurate as the ranco probe is deeper in the thermowell.

My pump is flowing about 300 G/hr. Idk how accurate this is, but I wanted the flow meter mainly to tell if the strainer is plugged and just for a comparative data point.

So far the most bizarre thing is that sometimes my outlet temp is much, much hotter than the jacket temp but also there are times when the jacket temp is much hotter than the outlet temp. Like a lot. Right now it's reading 175° for the jacket and 155° at the pump discharge. Earlier the pump discharge was above 200° but the jacket was reading about 165°. I'm pretty sure that the wild variation in the jacket temp readings are all due to the pretty crappy probe location. It doesn't seem like the rtd notes very deep into the jacket and may actually not go into the jacket at all but butt up against it. The end of the stove with the probe faces south and we get a lot of wind out of the south. It used to go crazy any time there was a breeze but I stuffed it all with fiberglass bay and that stabilized it a lot. I think that in still seeing some impact from external factors.

I'm seeing about a 40°F ∆T across the loop without the shop heater running. If I turn the fan on to the shop heater the return temp plummets and I see as much as 85°F ∆T and oddly the outlet and return both start falling but the jacket temp stays fairly high, almost like the flow path internally is short circuiting from return to suction without having any residence time in the boiler. I replaced the HX in the unit heater this year because it was a homemade job with a old truck radiator and the tank started leaking. I bought a 27x22x3 just because that's the size of the opening in this thing. I think it's probably a hundred thousand BTU over what used to be there. I do not really think it's causing any issues, but I bring it up because I think it really hammers the loop temps harder than what I had. Intuitively it seems as if as long as the jacket is maintaining temp, I should be able to suck as much heat as I want out of the loop. I'm really not trusting the jacket temps though...

So, some things I've thought about experimenting with are as follows:

1) move the ranco probe to my pump discharge thermowell and control based on loop temperature.
2) temporarily move the loop return to the drain hose bib.
3) add a second pump mid point in the loop to assist overall flow, I'm not sure if 5gpm is good or bad really.
4) buying a central boiler

I'll post some pics of my thermowells and completed instrumentation project.

Thanks,
Jason

What is the actual issue now that you

Well folks, I'm back at it again trying to understand what is going on with this cork stuffing thing. It runs well enough to heat the house and every year I mess with it and every year I give up and just deal with the quirks until heating season is done. I always think I'm going to really tear into it in the summer, and fall always tools back around while I still have a million things on my plate.

Anyhow, I finally got a little more prepared before fall. I built some thermowells to allow me to put a rtd in both the boiler discharge and return lines. It puts the tip of the thermowell pretty much dead center in the flow path. I also installed a strainer at the pump discharge, some additional isolation valves and a flowmeter in the return line. I then sat down for a week and wrote software to read all of my rtds and the flow meter, mounted the electronics with a backlit display in a ip68 enclosure and for ease of checking I also added a webserver and the microcontroller serves a webpage with the data live streaming on my local network.

So, I have been seeing some crazy stuff and I really don't know what to make of it. I added my own rtd up in the jacket thermowell where the blower controller has its rtd. Right now I'm not controlling anything with my shop but hardware, just gathering data. My hardware and the ranco controller seem to be within about 5° of each other. I think this is pretty close to accurate as the ranco probe is deeper in the thermowell.

My pump is flowing about 300 G/hr. Idk how accurate this is, but I wanted the flow meter mainly to tell if the strainer is plugged and just for a comparative data point.

So far the most bizarre thing is that sometimes my outlet temp is much, much hotter than the jacket temp but also there are times when the jacket temp is much hotter than the outlet temp. Like a lot. Right now it's reading 175° for the jacket and 155° at the pump discharge. Earlier the pump discharge was above 200° but the jacket was reading about 165°. I'm pretty sure that the wild variation in the jacket temp readings are all due to the pretty crappy probe location. It doesn't seem like the rtd notes very deep into the jacket and may actually not go into the jacket at all but butt up against it. The end of the stove with the probe faces south and we get a lot of wind out of the south. It used to go crazy any time there was a breeze but I stuffed it all with fiberglass bay and that stabilized it a lot. I think that in still seeing some impact from external factors.

I'm seeing about a 40°F ∆T across the loop without the shop heater running. If I turn the fan on to the shop heater the return temp plummets and I see as much as 85°F ∆T and oddly the outlet and return both start falling but the jacket temp stays fairly high, almost like the flow path internally is short circuiting from return to suction without having any residence time in the boiler. I replaced the HX in the unit heater this year because it was a homemade job with a old truck radiator and the tank started leaking. I bought a 27x22x3 just because that's the size of the opening in this thing. I think it's probably a hundred thousand BTU over what used to be there. I do not really think it's causing any issues, but I bring it up because I think it really hammers the loop temps harder than what I had. Intuitively it seems as if as long as the jacket is maintaining temp, I should be able to suck as much heat as I want out of the loop. I'm really not trusting the jacket temps though...

So, some things I've thought about experimenting with are as follows:

1) move the ranco probe to my pump discharge thermowell and control based on loop temperature.
2) temporarily move the loop return to the drain hose bib.
3) add a second pump mid point in the loop to assist overall flow, I'm not sure if 5gpm is good or bad really.
4) buying a central boiler

I'll post some pics of my thermowells and completed instrumentation project.

Thanks,
Jason

What is the current issue that you are trying to solve? Lack of heat? Do you still have water loss?