OWB with Geothermal radiant floors (New Build)

[Olinfarms]

Hey All!

Longtime lurker and a new member hoping to get some opinions/advice on a heatpump owb combo.

To start we’re building a large addition on a small house in western NY, the total sqft with basement is around 3000sqft. The addition will have radiant floor from the basement to second story and the addition retrofitted with radiant on the first and second.

The goal is to have an OWB run the main heating and DHW while I’m around and the Geo take over when I get shipped out of town for work.
I’m no stranger to simple setups and I designed and installed the geothermal that heats my shop, but it’s just a closed loop single zone deal.

I’ve seen some ideas around the forums but Has anyone set up something along these lines and had a good experience ?
My main concerns are avoiding freezing the OWB even with it circulating and the finite details of the changeover of systems.
And don’t be afraid to tell me there’s a better way! Thanks in advance

 

[peakbagger]

Have you reviewed the NY regs for OWBs? https://www.dec.ny.gov/chemical/51986.html

Have you read through the form that you would need to sign to even buy an OWB in NY? https://www.dec.ny.gov/docs/air_pdf/owbbuyer.pdf Dealers are going say its bunch of government BS but they are the ones making the profit when they sell them and dont have to live with them day to day. Yes they can burn clean when there is continuous heating demand but when there isnt, they rapidly become smoke dragons that ruin the nearby air quality and possibly the neighbors. There is also the temptation that folks seem to get with OWBs that they can adopt lazy habits of burning poorly seasoned oversized wood as the short stacks mean that creosote forming deposits are usually thrown up in the air rather than collecting in the stack.

Do you get the hint that NY (and myself) is not a big fan of OWBs? Just because people use them, doesnt mean they are the smart way to go especially if the owners ignore the need for properly drying wood.

If you are in the planning stage, NY paid to have a course on how to design a proper biomass heating system that is going to burn far less wood and have far less impact on the local environment https://www.heatspring.com/courses/...ficiency-biomass-boilers-sponsored-by-nyserda Note that the instructor lives in upper state NY and is generally regarded as the number one hydronics expert in the country. His designs concept using thermal storage tanks also fits well into integrated geothermal into the picture.

 

[EbS-P]

Are planning on AC with the geo thermal? How air tight are you shooting for (AHC50 #)?

 

[sloeffle]

Yes they can burn clean when there is continuous heating demand but when there isnt, they rapidly become smoke dragons that ruin the nearby air quality and possibly the neighbors. There is also the temptation that folks seem to get with OWBs that they can adopt lazy habits of burning poorly seasoned oversized wood as the short stacks mean that creosote forming deposits are usually thrown up in the air rather than collecting in the stack.

Do you get the hint that NY (and myself) is not a big fan of OWBs? Just because people use them, doesnt mean they are the smart way to go especially if the owners ignore the need for properly drying wood.

NY state only allows gasification OWB's for new residential installs. If they are so bad, why are Heatmaster OWB's rated at a higher efficiency than any of the indoor cord wood boilers ? The EPA numbers don't lie. The OWB's today are not the OWB's of yesterday.

As a wood burning community we need to give folks the correct information. All comments like these do is turn people away from burning a renewable energy resource that's grown right here on our soil.

 

[GrumpyDad]

Have you reviewed the NY regs for OWBs? https://www.dec.ny.gov/chemical/51986.html

Have you read through the form that you would need to sign to even buy an OWB in NY? https://www.dec.ny.gov/docs/air_pdf/owbbuyer.pdf Dealers are going say its bunch of government BS but they are the ones making the profit when they sell them and dont have to live with them day to day. Yes they can burn clean when there is continuous heating demand but when there isnt, they rapidly become smoke dragons that ruin the nearby air quality and possibly the neighbors. There is also the temptation that folks seem to get with OWBs that they can adopt lazy habits of burning poorly seasoned oversized wood as the short stacks mean that creosote forming deposits are usually thrown up in the air rather than collecting in the stack.

Do you get the hint that NY (and myself) is not a big fan of OWBs? Just because people use them, doesnt mean they are the smart way to go especially if the owners ignore the need for properly drying wood.

If you are in the planning stage, NY paid to have a course on how to design a proper biomass heating system that is going to burn far less wood and have far less impact on the local environment https://www.heatspring.com/courses/...ficiency-biomass-boilers-sponsored-by-nyserda Note that the instructor lives in upper state NY and is generally regarded as the number one hydronics expert in the country. His designs concept using thermal storage tanks also fits well into integrated geothermal into the picture.

As someone that lives in a valley, who hada neighbor about 1/2 a mile a way that burned garbage, I can say that everyone around me really doesnt like this person because it smokes us out. Summer weekend birthday parties, there's that smell. Fall walks, there's that smell.
The good news is, the guy sold his place and left about a year ago.
My neighborhood, you arent allowed to burn other than one day a month. That means indoors too. So everyone has a gas fireplace.
At my cabin, where Im next to many other cabins that sit on anywhere from 1/8 acre lots to 5 acre lots, and being in a valley, the valley will QUICKLY fill up with smoke early season around hunting seasons when the cabins are all mostly occupied. And mostly occupied for this community is probably about 1/3rd full. Imagine if everyone showed up and burned?
The smoke quickly subsides as the winter goes on, less people come in and less people want to go through the trouble of burning wood. When we first got our place I would dread making a fire. The deep snow, dragging wood inside that would last maybe a few hours at most, then having to do it all again - getting snow all over the place inside the house. Now I have a face cord rack in the back on the deck that I keep cleaned off, and then when that runs out I have a pull / trailer cart that I load up from the main stack and restock the face cord stack.

I think it is a beautiful thing to see smoke coming from my stove chimney and 25' over, my fireplace chimney. .

 

[sloeffle]

To answer the OP's question. I have geothermal forced air and I'm in the process of installing a Heatmaster G4000 OWB. Running water doesn't freeze so you could just run the pump on your OWB 24x7 ( that's my plan anyways ). You can also add 25% max ( you'd need to verify with the manufacturer ) to the system to give it a lower freeze point. The problem with glycol is that it doesn't transfer heat as well as straight water.

For my personal project, I'm going to setup a PID controller with a thermocouple. When the incoming water is above X point it's going to open up the circuit that kicks the geo compressor on. I'm assuming you could do something similar. If you want to hook up both your DHW and in floor heating to the OWB you'll need two HX plates in series to do that. The first plate should be for your DWH, and the second plate for the in floor heat. You'll definitely need a mixing valve so the water entering your floor isn't >100F.

There are some really smart folks on a Facebook group that I'm apart of. Feel free to PM me and I can send you the info over. I'm sure they've seen this done before.

 

[peakbagger]

The OP asked for a better way, I gave him my opinion. I am not the only one. https://www.health.ny.gov/environmental/outdoors/air/owb/purchase.htm A fairly good indication is an indoor wood boiler dealer does not have to have the customer sign a statement that they are aware that an IWB could be a nuisance. BTW even an IWB can be installed without thermal storage and be fed green wood and become a nuisance. NY state realized this and attached "strings" to the incentive program that only certified installers could install and went the extra step to subsidize and offer the course I linked to for free.

Efficiency ratings are based on steady state operation. I will not disagree that an OWB can be and are built with very impressive steady state efficiencies and if someone had a use for steady state heat like a manufacturing operation or power plant. I would recommend the boiler with the best efficiency. I tuned industrial and commercial biomass boilers (which are effectively large gasification boilers with staged combustion) for a decade or so, so my opinion is probably somewhat more informed. The reality is that typical residential heating loads are not steady state over a heating season. They start out very low, ramp up to peak winter and ramp down again. An OWB without a huge thermal storage tank is going to have to idle for much of the spring and fall and part of the winter with no demand for useful heat load and during that time the boiler is going to need to idle and there really is no good way to idle a boiler with zero heat load. Show me a plot of idle emissions and efficiency at no load and my guess is the efficiency is zero as there is no useful heat so any fuel being combusted is wasted as long as its idle. Emissions will be high as gasification requires a minimum temperature to burn CO and if there is no load on the boiler its going to emit CO.

IWBs also are rated for steady state efficiency but they tend to be designed for batch burns with lower mass than an OWB, that in combination with thermal storage means little or no idle load. They are started, run at full load and then shut down for a couple of hours when needed and then radiate what remaining heat from the mass of the unit into the space around it. Since the OP is going with low source temp radiant, his storage will be more effective as he can utilize the heat at a lower temp, thus his storage can be smaller.

 

[sloeffle]

I'll agree with you all day long that an IWB running at a steady state will definitely be the most efficient way to turn a lb. of wood into a usable BTU. The problem is, most folks don't have the room for a IWB and 1k or 2k gallons of storage in their basement, or they want the fire risk outside of their residence. Personally I was tired of the mess in my basement. I kept my basement clean but every time I opened up the door on my wood furnace it seemed like a plume of fine ash would come out. I think that's where a gasification OWB is a nice compromise. You have the mess and fire risk outside but you don't have the expense of having a building to put it in. If money wasn't an object, I'd have a Froling with 2k gallons of storage sitting in it's own building.

For my edification, how are the all of these OWB's passing the EPA test if they burn so dirty at idle ? What you said makes perfect sense but I have a hard believing they can pass the test if they are putting out a ton of particulate matter at idle. I know @brenndatomu and @JRHAWK9 have talked about the test for wood furnaces. As part of the wood furnace test, I believe the furnace has to burn at idle ( they will idle as much as OWB ) for so long and is only allowed to put out X amount of particulate matter.

 

[peakbagger]

I will let you do the homework and report back.

 

[sloeffle]

I will let you do the homework and report back.

I'm good. I don't care enough, and I don't have the time to dig into how the test labs perform their testing. Digging into government documentation seems like a never ending rabbit hole. The EPA test results are good enough for me.

 

[Olinfarms]

Hey all,

Not sure what I was expecting when I posted but it wasn’t this! Thank you all for your inputs.

First please let me tackle the functional points and then we can cover the environmental and situational issues raised above.

@EbS-P , yes I will be running chilled water air handlers off a separate manifold with switching valves when the reversing valve kicks. This side of everything makes sense to me since it is only one sided from the heat pump. But I may be missing some error here if you have any input!

@sloeffle , thank you for your offer and I’ll be messaging you in a bit, sounds like a great group!
Great point with the PID controller, initially I may just go with ball valves to prove concept and get things going. And I agree on glycol, I’m not a fan of the stuff, if only methanol wasn’t so explosive haha.
For the running water point, my concern was if the only mass in the system was the water in the OWB and not the floor (due to the HX)
Would the water reach whatever magical number that running water would freeze at?
My understanding of running water is that once all of its volume reaches below freezing it would still freeze. Please correct me here. Thanks in advance!

Now for the situational, moral, and environmental issues:
Situational:
214 acres of unfortunately 25% minimum dying ash trees. I will not bring in a logging company as there’s no real advantage for me, so that leaves all of those dying trees for me to clean, so for my lifetime I will never have a shortage of clean dry wood. I have no problem cutting and leaving wood to season, but the majority of the ash I drop is already dry lol.
Where I live I have about 10ish neighbors on top of a hill at 2000+ft. Almost the highest point in my county.
Of those neighbors I’d say 4 to 5 burn exclusively wood. Indoor and outdoor stoves.

Environmental:
I will be going with a gasification boiler, and I’m not going into the political deals of Ny and boilers at this time.
And as far as sizing this is not a new concept. I have a good bit of hvac coursework in my career and have sized the group in my shop so that the first stage runs almost full time when it’s zero out.

So the above is what brought us to the proposed OWB and geo setup. As it would be the most benificial cost wise and efficiency wise for us in my head, no number crunching went with the above statements, just from experience and searches online.

Ps, our current heat is an indoor stove, not boiler, and we just don’t want the mess or the fire inside the house anymore

Please let me know your thoughts!

 

[maple1]

The cost of Geo just doesn't pencil out for me, at all, in general. That would be even more so if it was going to be secondary. If I was going to burn wood, I would combine that with mini splits. Which might mean not doing in floor heat. Which would be fine with me.

 

[Olinfarms]

To me the idea of geothermal was always intriguing so I‘lol admit I burned more money than most would need to in order to install my shop heat, I figure about 8k all in for a 4ton geo system. But my electric bill for that setup has only hit 80 a month so I’ve been very happy.

For the house I know I could go mini split but I like the idea of the geothermal being a backup heat and an AC all in one as well as sharing the same radiant floor loops.

 

[sloeffle]

@sloeffle , thank you for your offer and I’ll be messaging you in a bit, sounds like a great group!
Great point with the PID controller, initially I may just go with ball valves to prove concept and get things going. And I agree on glycol, I’m not a fan of the stuff, if only methanol wasn’t so explosive haha.
For the running water point, my concern was if the only mass in the system was the water in the OWB and not the floor (due to the HX)
Would the water reach whatever magical number that running water would freeze at?
My understanding of running water is that once all of its volume reaches below freezing it would still freeze. Please correct me here. Thanks in advance!

I'm definitely not a fan of glycol either, but I think there are situations where it has its place. My geo system has methanol in it, my installer preferred it over glycol. I'm sure that I learned the equation for your running water question in college years ago. There are so many variables, that a hard one to answer. IMHO - for 180F water to completely freeze with a pump running that would have take a serious amount of time. You could put a thermowell on your lines and setup a Inkbird or something like that to send you an alert.

I have no clue how this would be plumbed in, what about using your desuperheater to feed warm water into a plate exchanger that's being fed by the OWB ? You could put some valves on it so it would only be used when you are gone.

214 acres of unfortunately 25% minimum dying ash trees. I will not bring in a logging company as there’s no real advantage for me, so that leaves all of those dying trees for me to clean, so for my lifetime I will never have a shortage of clean dry wood. I have no problem cutting and leaving wood to season, but the majority of the ash I drop is already dry lol.

I'm in a very similar situation except on about a quarter of the property. I haven't cut a live tree down in probably 10 years unless the top was blown out of it, or there was some other issue going on.

To me the idea of geothermal was always intriguing so I‘lol admit I burned more money than most would need to in order to install my shop heat, I figure about 8k all in for a 4ton geo system. But my electric bill for that setup has only hit 80 a month so I’ve been very happy.

That's cheap. I had about 15k into mine 12 years ago. I paid someone to install it though. I've met a few people that have done their own and they said it wasn't hard at all. I got a huge % back from the government in a tax credit though. My system is Waterfurance 4 ton multi-stage, with a DC ECM blower motor, desuperheater, and soft start.

With today's Air HP technology I'd agree that a geo system is a hard sell. Some of the new Air based HP's have higher COP's than what my system has.

 

[Olinfarms]

@sloeffle, the desuperheater idea is a good one, helps the compressor run more efficiently and I can rig it so the pump won’t kick on until the OWB/plate heat exchanger loop gets below 80ish degrees. Thank you for that!

And yeah it was definitely a good deal, I got it in just after they moved the rebates to 26% but that is still a huge incentive. The month it took us to run the 3200’ of ground loop was where all the saved costs went haha.

I’ll try and dig up some info on the running water issue in my text books and see what I can find

And I went with methanol as well in the ground loop, we had probably 40gal left from making biodiesel so it was already paid for and every inch of head I could save in the ground loop made it very worth it, as well as heat transfer.

 

[mtnxtreme]

I'm wondering if there is any real benefit to an OWB, I live in the Catskill Mts. of NY and anyone I know that's running geo thermal is not paying more than $100- $125 per month year round. And burning wood is a pain in the ass !

 

[sloeffle]

I'm wondering if there is any real benefit to an OWB, I live in the Catskill Mts. of NY and anyone I know that's running geo thermal is not paying more than $100- $125 per month year round. And burning wood is a pain in the ass !

If they are heating their house in the dead of winter using that little amount of electric with a geo system then they must have super insulated houses.

I was out of town last week on vacation and my house was set at 66 and it was in the 30's one day and my electric usage for that day was almost 50 kWh ( 8$ ). The house isn't set to 66 when I'm home so it would have cost even more if I was here. When my OWB is running and I'm home it's easily less than 20 kWh for the day. Your in a colder climate than what I'm in and you electric costs more than mine so that's another reason I don't believe those numbers.

$250 - $500 a month in the dead of winter sounds like a more reason figure based off my personal usage and what I've seen on geoexchange and from talking to friends with geo systems.