Preparing for OWB install

[i'mstihlaguy]

I have been asking alot of questions in preparation to install an OWB and have been receiving alot of good advice from people on this site. As a result, I am going to make my own underground insulated pex and I think I have the t-stat situation worked out for the OWB primary / heat pump backup scheme. I am very thankful to everyone for this.

Up until now, my questions have kinda been hit and miss about the different parts of the system. Mostly because I would read someone else's posting and that would cause me to have similar questions. I want to do the whole system right the first time so I have created a sketch based on what the OWB dealer told me to do and the advice I have received here. If anyone wants to ask questions, comment or make suggestions on any part of this setup please feel free. Again, I appreciate the help.

Here's some detail:
1. Heating two-story house with full basement (about 3200 sq. ft.)
2. OWB will be 75' from the house.
3. Currently have two heat pumps. One serves the basement and first floor. Second one serves second floor. Chose to only install hx in downstairs air handler for now. Can install second hx upstairs later is needed. We have a big room with vaulted ceiling open to second story. There are returns near the ceiling so I hope to pull heat from there with the upstairs air handler to distribute to the second floor.

 

[projectsho89]

I'd run the circuit to the air handler HX first, then to the water heaters in series, then back to the OWB.

Alternatively, run a separate loop just for the DHW via an HX with its own circulator.

Steve

 

[showrguy]

hi imastihlguy, i dunno bowt your owb but, i think you could do some control work to have your circulators come on only when your t-stats are calling for heat, some owb stove guys recomend running 24/7 to keep water in owb at a constant "happy" temp. ?? i see the point, but don't see the point of circulating your 185 deg. or so water constantly through 56 deg. avg. ground temp just for circulation purposes....... my buddies is set up that way, his unit is smaller, his house is ALOT smaller than mine and he burns about the same ammt. of wood i do in a year (he's wasting alot of btu's circulating that way)..... do ya know any HVAC control guys ?? that's who you need to talk to.. (in my opinion)
i was lucky, my brother in law is a wizzard with that stuff, we did alot of things that the dealer said probably would'nt work, it works flawlessly...
alot of times the guy selling the unit looks at it as "how easy/quickly would this be for me to do" ??
not like " how efficient can i make this thing be".........
hope i did'nt piss on yer cherrios or anything, was'nt trying to !! just give it some thought.........
good luck

 

[i'mstihlaguy]

I'd run the circuit to the air handler HX first, then to the water heaters in series, then back to the OWB.

Alternatively, run a separate loop just for the DHW via an HX with its own circulator.

Steve

Thanks for the comments Steve.

OWB dealer's logic was as follows:
1. The water heaters won't draw heat from the main loop too often. (Just the wife and me and no kids in our future)

2. BPE's will remove far less heat from the main loop (when there is a demand for DHW) than the water to air HX in the plenum when the t-stat calls for heat. If it were reversed, the water going to the BPE's would be much lower temp.

I have been pondering just having the two BPE's on a separate loop for DHW. I can change it pretty easily if I need too.

Thanks again.

 

[i'mstihlaguy]

hi imastihlguy, i dunno bowt your owb but, i think you could do some control work to have your circulators come on only when your t-stats are calling for heat, some owb stove guys recomend running 24/7 to keep water in owb at a constant "happy" temp. ?? i see the point, but don't see the point of circulating your 185 deg. or so water constantly through 56 deg. avg. ground temp just for circulation purposes....... my buddies is set up that way, his unit is smaller, his house is ALOT smaller than mine and he burns about the same ammt. of wood i do in a year (he's wasting alot of btu's circulating that way)..... do ya know any HVAC control guys ?? that's who you need to talk to.. (in my opinion)
i was lucky, my brother in law is a wizzard with that stuff, we did alot of things that the dealer said probably would'nt work, it works flawlessly...
alot of times the guy selling the unit looks at it as "how easy/quickly would this be for me to do" ??
not like " how efficient can i make this thing be".........
hope i did'nt piss on yer cherrios or anything, was'nt trying to !! just give it some thought.........
good luck

Showrguy,

Thanks for your comments. I have debated this as well. My lines from the OWB will be well insulated. From what I have read here, others have experienced only a slight loss in water temp. from the OWB to the house with well insulated lines. The pump running 24/7 is a necessity so the BPE's are always at the ready when there is a demand for DHW. Alternatively, I could put them on a separate loop but that would mean a separate pump that would run 24/7 as well. I thought about having an aquastat in the HW heaters kick on the pump for this loop. The HW heater's main thermostat would be turned down a few degrees. This is another thing I can always change later if things don't work out as planned. I eat grape nuts for breakfast not cherrios

 

[i'mstihlaguy]

Forgot to mention the first time, I am also looking for suggestions like, "you should put a valve there", or "you should put a temp. gauge here", etc.

Please keep the questions and/ or comments coming. I didn't explain the reasoning behind everything in my first post because I want to hear unbiased thoughts and opinions.

 

[Slick]

Honestly I'm still designing some of my house setup for my owb install but my CB dealer said for the main line to come into the my DHW side are exchanger first, then go to my baseboard radiators....I will have a zoning pump for the radiators though but like you said, you want the water flowing to the DHW exhanger all the time.
On the 24/7 circulation thing...I didn't understand it at first either but I've now heard from a couple people that Taco at least suggests it for their pumps, less on and offs equals longer pump life. You'll also get quicker heating cycles in your house this way, if your water is sitting in your lines when your house calls for heat you'll get colder water at first...my friend has an owb with a water to air coil in his forced air furnace, he has a zoning valve on it to only circulate when it calls for heat, he gets a cold blast from the furnace when it first comes on until the coil heats up.
I'm also not sure having your pumps switch on and off at the boiler saves and btu's....the water is either sitting in your boiler loosing btu's (where it could be very cold outside of that insulation) or it's loosing btu's in the ground going to and from your house (where it's much warmer than at your boiler), which one will cause more heat loss?....like I said, I'm not convinced you loose more heat just because your circulating all the time...mine will run 24/7.

 

[i'mstihlaguy]

Honestly I'm still designing some of my house setup for my owb install but my CB dealer said for the main line to come into the my DHW side are exchanger first, then go to my baseboard radiators....I will have a zoning pump for the radiators though but like you said, you want the water flowing to the DHW exhanger all the time.
On the 24/7 circulation thing...I didn't understand it at first either but I've now heard from a couple people that Taco at least suggests it for their pumps, less on and offs equals longer pump life. You'll also get quicker heating cycles in your house this way, if your water is sitting in your lines when your house calls for heat you'll get colder water at first...my friend has an owb with a water to air coil in his forced air furnace, he has a zoning valve on it to only circulate when it calls for heat, he gets a cold blast from the furnace when it first comes on until the coil heats up.
I'm also not sure having your pumps switch on and off at the boiler saves and btu's....the water is either sitting in your boiler loosing btu's (where it could be very cold outside of that insulation) or it's loosing btu's in the ground going to and from your house (where it's much warmer than at your boiler), which one will cause more heat loss?....like I said, I'm not convinced you loose more heat just because your circulating all the time...mine will run 24/7.

Thanks Slick. The lag in delivery of hot water to the water to air HX was a concern of mine as well. And it only gets worse the farther it is to the OWB.

 

[derwood91]

Forgot to mention the first time, I am also looking for suggestions like, "you should put a valve there", or "you should put a temp. gauge here", etc.

If you have not already, you may want to consider a strainer between the output of the OWB and the input of your first plate exchanger. This will keep any large scale or debris that the OWB may produce from plugging your plate exchangers. Easier to clean the strainer screen than it is to clean the exchanger!!!

 

[i'mstihlaguy]

If you have not already, you may want to consider a strainer between the output of the OWB and the input of your first plate exchanger. This will keep any large scale or debris that the OWB may produce from plugging your plate exchangers. Easier to clean the strainer screen than it is to clean the exchanger!!!

Is this a special component for this application or is this something like a cartridge type water filter you would buy at Menard's or Lowe's?

 

[derwood91]

I bought mine from freeheat4u on ebay along with all the other components for my owb. I think it's a standard plumbing part as my "Brother in law the plumber" was familiar with it. Pay attention to the flow arrow on the housing.

Let me know if this link works.........

http://cgi.ebay.com/OUTDOOR-WOOD-FU...photoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

 

[derwood91]

check out the pics in Scootermsp's post.......... You can see the strainer installed. Make sure you put it in a place where it can be easily serviced and consider valve placement to keep system drainage to a minimum while servicing.

http://www.arboristsite.com/showthread.php?t=76966

 

[Scootermsp]

strainer

Is this a special component for this application or is this something like a cartridge type water filter you would buy at Menard's or Lowe's?

It's called a "Y" strainer, I have one on my system.

 

[Laird]

Filter

I'm also in the process of installing an OWB and a filter kit came with the install pkg. I have found it sold separately on their ebay store (Hawken) and it is a bit pricey. You may be able to find something cheaper elsewhere. This one does appear to be well made, the filter screen is stainless I believe. I just assembled mine a couple nights ago.

http://cgi.ebay.com/Filter-Kit_W0QQ...photoQQcmdZViewItemQQ_trksidZp1742.m153.l1262

 

[Slick]

yep it's a y strainer, industrial supply houses will have many choices...my favorite is www.mcmaster.com McMaster Carr is the best place ever!! couldn't live without it...

 

[Biker Dude]

I am going to make my own underground insulated pex.

I did that for my OWB and if I had to do it again I would pass. Pulling 75 feet of pex taped up in bubble wrap through 4" corrugated tube is NOT fun at all. This stuff looks like the best way to go but it's $10/ft.

I guess it all depends on how much you have to spend on the project but I'll bet that expanda-foam makes for very little heat loss.

 

[mtfallsmikey]

My main concern: All the HX's are piped in series. by the time the HW gets to the water/air HX, it's not gonna be very warm!

I've always been a fan of primary/secondary piping. Use one loop to and from boiler, pipe each HX on it's own loop, and circ. pump, with flow control valves/IFC's on circ. pumps to keep out ghost flow.

 

[i'mstihlaguy]

check out the pics in Scootermsp's post.......... You can see the strainer installed. Make sure you put it in a place where it can be easily serviced and consider valve placement to keep system drainage to a minimum while servicing.

"Y" strainer - got it. I added it to my diagram last night. Valve placement for service wasn't on the horizon. It is now. Thanks.

It's called a "Y" strainer, I have one on my system.

Excellent photos! This has helped tremendously.

I did that for my OWB and if I had to do it again I would pass. Pulling 75 feet of pex taped up in bubble wrap through 4" corrugated tube is NOT fun at all. This stuff looks like the best way to go but it's $10/ft.

I guess it all depends on how much you have to spend on the project but I'll bet that expanda-foam makes for very little heat loss.

Looks like good stuff. Cost is a big concern. I think I can do it for half price and still have good R-value. I plan on using a silt sock (like you would normally use on the outside of perforated pipe) as a final layer around the insulated pex conglomeration. I am going to use 6" corrugated (non-perf.) so there's more room and hope the sock will make everything slide through easier. This will all be done before laying it in the trench. Don't know how well it will work but I gotta try it.

My main concern: All the HX's are piped in series. by the time the HW gets to the water/air HX, it's not gonna be very warm!

I've always been a fan of primary/secondary piping. Use one loop to and from boiler, pipe each HX on it's own loop, and circ. pump, with flow control valves/IFC's on circ. pumps to keep out ghost flow.

This is one of my main concerns as well. I am routing the pex inside so I can easily change over so the DHW is on a separate loop just as you described. The dealer's logic for putting everything on one loop is that we won't be pulling heat out of the loop very often since we don't have alot of DHW usage. Its just me and my wife and no kids in the future. She does most of the laundry in cold water. I am going to monitor temps at the water to air HX and change over if necessary.

As you all can tell, this system is pretty simple and I am trying to route everything so I can easily make changes after the initial installation if necessary. On that note, what kind of wire should I run to the OWB if I decide later that I want to control the main pump from inside the house?

Thanks so everyone for your input whether I responded directly to you or not.