temperature problems-Delta T Issues

rsv101

Hello everyone. I am having problems with figuring out if my system is working correctly. My outdoor wood boiler temp is set to approx 180-185 degrees and the gauge if correct never drops below 170. My run from wood boiler to house is 160 ft and is 1 inch pex that is approx 4 years old. Coming into the house the water is hot to where you cannot hold the pipe. I have a 50 plate heat exchanger. The pump from wood boiler to house is a B&G PL-36 the runs 24-7. In the house I have a gas fired boiler with the gas turned off. I have a wraparound pump that runs 24-7 to keep the gas boiler warm, that pump is a Taco 007-F5. From there I have two zones, a baseboard hot water on the main level. Main level is 2000 sq ft with 16 baseboard units, each unit is approx 4 ft long. My second zone is my basement zone with radiant in floor 2000 sq ft. I keep the mixing valve set low about 85 to keep from drawing the hot water supply down and just the keep the water moving all the time. Both Zones run constantly and my gas boiler sensor reads under that load the water temp moving through the gas boiler is 118-122 degrees. Under no load the water temp moving through the gas boiler is 150-160 degrees. My domestic hot water zone is on priority so when i have a call for hot water it will turn the two zone pumps off and run the domestic zone only. It takes about 45-60 minutes to satisfy my 53 gallon storage tank which is set at 115 degrees. Under the domestic load gas boiler sensor reads 118-122 degrees. My main level baseboard zone is pushed with a taco 007-f5 pump, basement in floor with a grundfos 15-58 3 speed, and domestic hot water with a taco 007-f5. Does this all seem right? I wish i had temp gauges installed but i dont, I tried measuring temp with a heat gun and i am getting readings all over the place. If the water coming in is 180 degrees, what should be going back? What should the supply and return temps be on the house side of the exchanger? Are my pumps the correct size? I took the heat gun readings on the same material at the 50 plate heat exchanger, the reading are: Wood boiler side supply 180, return 125. House side supply 145, return 120. I also took some reading on my baseboard zone same material supply 140-145 return 125-130. Any ideas or suggestions would be great! Thank you and sorry for the long story.

hot_rod

Is it 160 feet to the OWF, so a total of 320 feet of 1" pex?

rsv101

Yes correct 160 feet from heat exchanger to wood boiler. So you would be right 160 ft of supply line and 160 ft of return line (320 total loop). I have the pump on the supply line mounted in the house.

Gordy

When you use an IR thermometer you have to put painters tape, or black tape on the surface. Other wise you won't get good reliable readings. Also hold the gun as close as you can to that tape spot otherwise the aspect ratio will pick up adjacent surfaces, and throw the readings off. Do that and get back with the readings.

Harvey Ramer

Take a bunch of pictures and post them as well. We would like to see the piping layout.

I assume your problem is that your house isn't staying warm?

With the B&G pump and the length of 1" pex and a generic 50 plate HX, you should be moving about 8-9 gpm in the wood boiler loop.

If the temp readings you took on the FP HX are anywhere near accurate, you are transferring approximately 233k BTU/h

I feel like something is really wrong here.

We definitely need more information to draw an accurate conclusion.

All the different factors, especially the length of time it takes to heat the indirect, makes me suspicious of a water leak in the hydronic system on the house side. It would have to be a fair sized leak though, and one would think it would be noticeable.

Give us pictures, temperature readings and all the info you can. We'll figure it out for you.

Zman

I absolutely agree with Harvey's calculations.
I think it would take one heck of a leak to eat that many BTU's.
Is there something going on on the wood boiler side of things that could be reducing flow?
Bad circ, blockage or other source of resistance.
Has this ever worked?

icesailor

That must be one big mother of a wood heater, burning a lot of wood to be providing all that energy to that house.

Some judiciously placed inexpensive tridicator gauges might show some really interesting features. As far as Delta T and pressure differential as to what goes into the system from the wood heater and what goes back.

For all the money spent on this system, skimping on some Tridicator gauges is penny wise and pound foolish.

hot_rod

All systems strive for and reach thermal equilibrium, basically saying the the heat emitters or load connected to the heat source dictates the operating condition.

Whatever the claimed output of the outdoor wood furnace, multiply that times 40% to get actual output, that's assuming you have good quality, dry wood to burn, and the unit is dialed in for airflow.

Green or wet wood the unit could be operate g in the 30% range, assuming it's not a gasification type boiler. So basically 60-75% smoke and emissions and the rest as useable energy minus the loss from the 160 feet of buried pex.

Some flow meters, gauges, or ideally a combination of both know as a BTU meter will tell the true store.

Either you are not exchanging the energy from the wood, or you have some big loss somewhere, or a roadblock along the way.

icesailor

@hot rod:

There's an interesting article in the November issue of P&M by Siggy about just that subject. About reaching Thermal Equilibrium. Sounds like that is what could be happening to him.

The article would make a interesting discussion.

hot_rod

Also hydraulic equilibrium where the energy added by the circ matches the energy dissipated by the emitters, piping, etc in the distribution loop.

Thermal + hydraulic equilibrium= system equilibrium

Zman

I think your water heater recovery time is a real indicator here. As a test you could turn off the pumps and fill the water heater with cold water Measure the temp of the cold water. Then turn the pumps on and see how long it takes to recover the tank to 115. Be sure no heat is allowed to escape into your heating system. From what you are describing, you are moving no more than 30k/btu from the wood boiler to the hot water heater. That is a slow recovery in DHW priority and not enough energy to heat a 4000 sq foot house.
It would be nice to be able to narrow down your problem a bit. I think you have a flow issue on one side of the heat exchanger, not a problem with the heating system itself. How does it heat using the gas backup only?
Pictures?

icesailor

Then, there's the raw potable water, heated in the HX that might be coating and insulating the plates. If it worked OK when it was first installed, and now doesn't perform as well, look for dirty coils and HXers.

Zman

Ice,
Possible, but with the high delta t at the exchanger and low temp at the gas boiler combined with the underperforming heat system, it sure looks like the problem is upstream.

rsv101

pics

rsv101

more pics

rsv101

more pics

rsv101

more pics

icesailor

@Hatterasguy:
and others:

Some of you all think of me as a giant negative PITA.

Whenever I see as much dissimilar metal put into a system like that with high energy and temperature swings, I know that there is going to be some serious electrolysis and rust somewhere.

It doesn't matter where you look. It is always there. You just have to look. I just watched an all day+ ship show where my next door neighbor (unbeknownst to me) had very low water pressure. Mine off a separate service riser does not. Understand that the development was built by one of the finest housing developers ever. They were so good that they even have a town named after them. So successful, they had to move to Florida to find more potential victims.

Their ability to find quality low bid contractors is legendary. Or so it appears. Each "Court" has a 2" Sch. 80 PVC loop around off a 4" PVC (I guess) main, so everyone has equal pressure off the circle/loop. They took a 2" cast iron saddle fitting, clamped to the 2" PVC and screwed in a 1" brass Corporation Cock into the cast Iron saddle. The Corporation Cock connected to Poly pipe, which went to another underground shut off, and all PVC and copper into the buildings.

A common problem is that the electrolysis between the cast iron saddle and the brass Corporation Cock, and the iron in the water completely occluded the opening of the 1" corporation cock, almost completely stopping the flow.

In the photos I looked at, there's more dissimilar there than the average metal recycler. Galvanized fittings are a good start. They use galvanize/zinc blocks on boat in the water as sacrificial anodes on boats.

Like we plumbers might see on a water service that that needed a brass Poly X Poly insert coupling but someone used a Galvanized Coupling and two Poly X MPT brass adapters. And there's a big chunk of iron/rust plaque built up inside the galvanized malleable coupling.

Harvey Ramer

Open those Y-strainers on each side of the FP-HX, pull the screen out and clean it. I would hazard a guess that both strainers are crapped up and restricting the flow.

If you don't get control of the corrosion issues in the system, they'll get control of you. As Ice pointed out, you have a lot of dissimilar metals in the system. I cringe when I see galvanized fittings. Every one I have pulled apart and looked inside was nasty.

I would recommend running a good cleaner through the system followed by a power purge. Then refill with desalinated water and add a corrosion inhibitor.

icesailor

I saw parts of a new system put in by a "Green Build" Contractor. All materials provided by some Internet Wholesaler, all non-barrier PEX, CI circulators, a SS Mod-Con boiler, and the whole system was a solid mass of rust chunks.

Harvey Ramer

icesailor said:

I saw parts of a new system put in by a "Green Build" Contractor. All materials provided by some Internet Wholesaler, all non-barrier PEX, CI circulators, a SS Mod-Con boiler, and the whole system was a solid mass of rust chunks.

It doesn't take very long either. I have 2 radiant systems under my care that have tubing without oxy barrier. They require careful attention and maintenance.

Zman

Good comments above, and very tactful.
I think gunk in the strainers, the fittings and maybe the gas boiler is very likely.
Can you confirm the 1" lines to the owd? They look 3/4" how are they insulated underground?
Some pictures from farther away would help. A drawing might be easier.
@icesailor‌ "a negative pita" does not come to mind. You are a refreshing mix of brilliantly insightful and possible escaped mental patient. Florida will do that to you.

icesailor

And the installer is no where around.

There were a few "Green Build" contractors that had their vans all tricked out with green build signs. Such failures they were that you can only see evidence of the signs upon close scrutiny. At least when I left.

I saw a lot of carpenters become "Green Building" Hydronic experts. I wish I had a record of all the derelict systems I have seen over the years. The wasted money spent.

Zman

The more I think about the dissimilar metals and the gunk, owb because they are open to the atmosphere and boil off a bit, have a tendacy to concentrate the nastiness. What does the water look like on the owb side look like? It may have plugged the exchanger.

icesailor

@Zman:

"" @icesailor‌ "a negative pita" does not come to mind. You are a refreshing mix of brilliantly insightful and possible escaped mental patient. Florida will do that to you. ""

Look no farther that the Strictly Steam part of "The Wall". Steam has been around since James Watt invented the steam engine to pump water out of coal mines. The technology hasn't changed that much in 100 years. Yet, I/we see one disaster replacement after the other of once working steam boilers. All solved by people that give a RA and studied and learned their craft well. They way I have tried to learn my own. They say that once you go into business, you really start to learn. That's because you don't have anyone to fall back on when you find yourself falling down the rabbit hole. If you learn what you are doing, its harder to fall down the rabbit hole. As far as being a escaped mental patient, they don't lock up mental patients. If you are lucky, they throw you in a private prison and give you no services.

What Florida does for you is to remind you of how many just know their craft by Rote and are clueless as to why whet they do, works. But they know how they are going to do it. Even if it is wrong.

Like my old friend Cooper said. "You can teach a monkey to run pipe. It takes brains to fix the mistakes."

I and others here have seen a lot of monkey work.

hot_rod

Zman said:

The more I think about the dissimilar metals and the gunk, owb because they are open to the atmosphere and boil off a bit, have a tendacy to concentrate the nastiness. What does the water look like on the owb side look like? It may have plugged the exchanger.

I think Harvey is on to the problem, or one of them. If it's an open system OWF, good chance you have some plugged strainers. Might consider a dirt separator on the open side, or clean the strainers a few times yearly.

rsv101

My wood boiler side is non-pressurized open. I would agree this system is a mess and the funny thing is the original home owner was a contractor and friends with a plumber. I moved into this house in 2008 and in 2010 I replaced the underground pipe with 1 inch pex wrapped with insulation in corrugated tubing. It is buried quite deep as well. I probably should have gotten better stuff but i didnt know any better then. I also replaced the heat exchanger from a 20 to a 50. I drain the water out of the wood boiler every fall and refill it and i also add the boiler chemical-inhibitor. I am going to pull the strainers out and clean them. Is there a additive or chemical that should be put into the pressurized gas boiler?

icesailor

Check your HX'ers. They may be dirty and not heating water fast enough now.

For a third world method that often works, get the flow going on the boiler/hot side with no flow on the other side. Turn the flow side on slowly. It should get hot. Increase the flow slowly to see if the flow side starts to cool. Then, turn off the flow side and with the boiler/hot side pumping/flowing, both inlet and outlets of the boiler side of the HX'er stay the same, fine. Open the flow side slowly again. Notice if the boiler side starts dropping. If it does, and the flow is low, the boiler side is dirty. If the water/flow side flows, and the boiler side doesn't drop, the flow side is dirty. Sometimes, it can be both. I hope I made sense. Sometimes I get confused in my back and forth directions.

You can use this method as effectively as a Infra-Red thermometer gun. If you have little baby Kiddo's, you are told to squirt the formula bottle on your wrist or arm to decide if the formula is too hot for the precious wonders to drink and not burn their mouths.

This method requires some playing around. But your problem is going to require some playing around.

If you have a quality Multi-Tester with a temperature probe, those can be helpful. Just be sure to use something to insulate the sensor. Really helpful if you have two because you can measure the Delta T in the same moment.

Don't count on the Contractor and his plumber friend knowing what they were doing. They might have both been going to school. Most bad outcomes were based on bad advice.

The fact that you went from a "20" to a "50" says a lot about the history.

hot_rod

yes you should consider a regiment of corrosion inhibitors. The OWF manufacturer should have guidance for that. Most of the hydronic chemical manufacturers have inhibitors that can be used. Rhomer, Fernox, Rectorseal are a few of the common brands. being open to the atmosphere you will need to add the inhibitors occasionally.


Determine if it is a plain steel type or stainless steel construction. The stainless versions may require a special inhibitor package.

Your system is salvable, you just need to learn the quirks of open system OWF operation and maintenance.

rsv101

So here is the update. I pulled the wye strainers apart. The house side was very clean, required very little cleaning at all. The outdoor wood boiler side was completely clogged. I cleaned the strainer and everything improved greatly. I will be cleaning that strainer more often than not now. Do you guys think it could have harmed the pump? It seems to operate fine but i dont know if it should be better. Right now i have good heat and my delta t has improved as well. Domestic water recovers faster as well. I am thinking when spring comes and i shut down the system i will give the flat plate heat exchanger good cleaning. Any other recommendations?

hot_rod

If it is just rust and gunk, pressure flush it. If it has hard water and lime or mineral build up, it will need a cleaner run thru it.

I have a customer that takes his DHW HX to a radiator repair shop. They drop it into their "hot" tanks and cook it clean.

Or buy one of those tankless cleaner tank/ pump devices.

If you pipe it back in with some Webstone valves it could be flushed yearly with a pump and coil cleaner,

Like this.

icesailor

You found chunky's in the strainers? Wait until you see what's in the HX and the hot water pipes after the HX. Blow the water out of the HX and piping through the inlet to the HX and have the water be blown into a 5 gallon bucket until there no more water. Let the air blow through for a while. Then, let the water in the bucket settle out for some time. Then carefully drain the water off. Look and see what is in the bottom of the bucket. That's the same stuff that the dental hygienists cleans off your teeth and gums.

You need the assistance of the pipe dentist.

hot_rod

I think the "A" side of the HX is just connected to the outdoor, open system boiler, or furnace as they are called OWF outdoor wood furnace.

OWF, pex, pump and HX.

The inside, heating side is a closed loop off the B side of the HX.

Some of those OWF manufacturers are in denial regarding the corrosion potential of an open system, steel tank, that sees fresh water constantly added to it.

You get one bottle of conditioner when you buy the unit. Sometimes:)

RobG

I didn't re-read the post but is the pump on the OWF bronze, stainless or iron?

rsv101

the outdoor wood boiler pump is a b & g pl-36 that is cast iron.

Zman

I think focusing on the cause of the problem is the key.
Have the water tested.
Reduce the amount of dissimilar metals as much as you can.
How hot is the outdoor boiler running? It may be boiling a bit as it tries to regulate it's temp. It is really difficult to maintain constant temp when you can only control the air and not the load or the fuel. If it is getting too hot, that will concentrate the nastyness.
I think I would try setting the temp around 160. That should keep you from condensing or boiling.
Thanks for the follow up. It is good to hear this site works.
Carl

Weezbo

While the strainers were found clogged then things worked better, that is far from the point of "Calling it Good" .
If you take the fittings off the boiler taps for the supply piping and the flanges and the recirc i think you are going to have fresh insight as to what is what.

I hope this helps .
replace the near boiler pipe etc and flanges maybe even the circ. you can post a pic or two of the tapped hole in the boiler and the first nipple coming away to clarify what i just said .

*~/: ) Weezbo.

p.s. i'd suggest upsizing the near boiler piping ... Oh and not all strainers are created equal.