Extremely short above-ground pex run?

[danjayh]

Hi guys,

I'm about to get my first boiler (a used Maxim M175 pellet boiler) used off craigslist. I plan on putting it ~4-6 feet from my house, so I was wondering - is it even worth burying the pex for such a short distance? I was considering three possible options:

1) Buy commercial insulated pex, run it above ground
2) Same as above, but burying it (probably only ~3 ft would be buried, since it would need to come up by the boiler and by the house)
3) Using uninsulated pex, and wrapping it in that black foam insulation that is used for air conditioner coolant lines. I like this option because I already have uninsulated pex, but I'm not sure how well the air conditioner insulation will work.

Any thoughts?

 

[stee6043]

Ohh my...there are a few red flags in your post. First, I'm not aware of any time it would be up to code to place a wood boiler within a "few feet" of a house. Second, if it can freeze - it will. Not burying your pex to proper depths will eventually lead to bad, bad days. Read on!

 

[goosegunner]

I would research those pellet boilers as much as you can.

So even if you go 20' away the trench would be pretty short. I don't understand why you wouldn't bury it?

The only reason I could see not putting it in the ground would be if you think you might not keep it and just want to try for the winter.

gg

 

[danjayh]

Ohh my...there are a few red flags in your post. First, I'm not aware of any time it would be up to code to place a wood boiler within a "few feet" of a house. Second, if it can freeze - it will. Not burying your pex to proper depths will eventually lead to bad, bad days. Read on!

I suppose I'll have to double-check with the township. Insurance company said I have to be at least 3' from the house. There is nothing about setbacks from the house in the township's OWB ordinance, but I'll call and ask to be sure. The maxim is an outdoor/indoor boiler, and one of the cleanest burning machines that money can buy. Many of the installation photos that I've seen show it installed even closer to a structure than I plan to put it. Examples:

The last guy is obviously an idiot because his chimney isn't high enough (note the blackness on his soffit) ... but you get the idea.

As far as the pex freezing goes, I plan on running my circulation pump constantly, so the only time I foresee a problem would be if the power goes out, in which case I'll be hauling out a generator faster than you can blink anyway (Two reasons for this - the Maxims have a problem with burn-back when the power goes out, and can destroy themselves if you get unlucky, and I do not have an indoor wood burner, so no power = no heat, in which case all of my house plumbing will also be freezing in short order).

goosegunner - The reason I was thinking of doing it above ground is that given the minimum bend radius of the insulated pex, and the fact that I'll only be 4' from my house (assuming the township OKs it), it seems like I'd come out the back, dive underground for 2-3 feet, and then come up to go in the house. It just seems kind of pointless to me for a run that short.

stee6043 - Have you had problems with freezing in the past?

 

[goosegunner]

I guess that makes sense then to be above ground. How about using some insulated pex in a tile. and then also building a box to the house you could super insulate to with batts and then foam board on all sides. That would reduce heat loss and also max out time for a freeze.

Even if you use the in tile insulated pex above ground your heat loss would be minimal because of the short distance. It also would be easy to replace if you had a problem.

My first boiler was a OWB. I bought the stuff in a tile that was insulated. The company said you could lay it on the ground and snow would stay on it. Well I did that for the first winter because it was a late fall install. There was a 12" tunnel around it through the snow. I used it one winter and sold everything and put in a indoor Econoburn 200. I used Logstor and buried it well below the frost line. I can travel and leave my system without worry or the need to have someone babysit my boiler.

gg

 

[Tennman]

Well, I self named myself the "poster child for stupid underground installs". Read the sticky.... you did read the sticky right?.... but..... but.... I'm always amazed as I drive around on the very large NASA/Army installation where we do work to see the ABOVE ground steam lines running everywhere heating buildings on the Arsenal. If the run was short, then it is entirely possible if great care in insulation is taken that the thermal loss will be minimal. It's just physics. Energy is like a blood hound aggressively looking to move to a lower energy state. So 180 deg water with ~50 deg soil temp is way better than 180 deg water and 10 deg outside air. Given the same insulation it's clear which application loses the most energy in transit. BUT... if it's short and you use LOTS of good insulation, in theory, it's possible to make an above ground better than a standard underground. Let's not complicate the discussion about what happens when the water stops moving.

OH Pleeeeeze read about how I used that black stuff and how I wrung water out of it like a sponge when I dug it up to redo my underground.

 

[stee6043]

I suppose I'll have to double-check with the township. Insurance company said I have to be at least 3' from the house. There is nothing about setbacks from the house in the township's OWB ordinance, but I'll call and ask to be sure. The maxim is an outdoor/indoor boiler, and one of the cleanest burning machines that money can buy. Many of the installation photos that I've seen show it installed even closer to a structure than I plan to put it. Examples:

The last guy is obviously an idiot because his chimney isn't high enough (note the blackness on his soffit) ... but you get the idea.

As far as the pex freezing goes, I plan on running my circulation pump constantly, so the only time I foresee a problem would be if the power goes out, in which case I'll be hauling out a generator faster than you can blink anyway (Two reasons for this - the Maxims have a problem with burn-back when the power goes out, and can destroy themselves if you get unlucky, and I do not have an indoor wood burner, so no power = no heat, in which case all of my house plumbing will also be freezing in short order).

goosegunner - The reason I was thinking of doing it above ground is that given the minimum bend radius of the insulated pex, and the fact that I'll only be 4' from my house (assuming the township OKs it), it seems like I'd come out the back, dive underground for 2-3 feet, and then come up to go in the house. It just seems kind of pointless to me for a run that short.

stee6043 - Have you had problems with freezing in the past?

My installation is indoors so no, no freezing problems. I suppose this also means you should completely ignore my potentially irrational fear of pex being installed above ground. I have no experience with it.

You mention this particular model of boiler has a "history of destroying itself" in certain circumstances and you're still okay with putting it so close to your home? Hmmm....

 

[danjayh]

My installation is indoors so no, no freezing problems. I suppose this also means you should completely ignore my potentially irrational fear of pex being installed above ground. I have no experience with it.

You mention this particular model of boiler has a "history of destroying itself" in certain circumstances and you're still okay with putting it so close to your home? Hmmm....

Seems counterintuitive But ... from what I've gathered, they can burn-back and overheat, resulting in electronics that are melted into goo. I haven't seen any reports of huge infernos that could catch a house on fire. Even the burnback problem only happens to units that don't have the correct weekly maintenance performed. They've also released a kit that fixes the burn-back problem even on poorly maintained units by dumping water into the system if it starts to get too hot, which I plan to install.

Interestingly, I went to go buy it last night, and the guy who was selling it couldn't lift it onto the trailer. He claimed he used the same tractor when he removed it from his old house, but it wouldn't lift it last night.

 

[harttj]

Hi guys,

I'm about to get my first boiler (a used Maxim M175 pellet boiler) used off craigslist. I plan on putting it ~4-6 feet from my house, so I was wondering - is it even worth burying the pex for such a short distance? I was considering three possible options:

1) Buy commercial insulated pex, run it above ground
2) Same as above, but burying it (probably only ~3 ft would be buried, since it would need to come up by the boiler and by the house)
3) Using uninsulated pex, and wrapping it in that black foam insulation that is used for air conditioner coolant lines. I like this option because I already have uninsulated pex, but I'm not sure how well the air conditioner insulation will work.

Any thoughts?

I have mine about 30 feet from the house. I would not recommend it 3 ft as it does smoke at start up and a very light smoke at idle sometimes. Not sure where you are at. I have 15 feet of thermopex left that is rated for above ground installation. Send me a message if interested. I'm in n.w. Ohio.

Tim

 

[700renegade]

I'd run it above ground. The first 18" in the back by the pump is out in the air regardless.
Put a 6" PVC pipe between boiler and house, wrap pex with black foam. If you want to get real exotic add a few feet of nylon hose to a can of Geocell foam and slowly draw it out while filling remaining cavity.
The loss of BTU to dry cold air is a whole different animal than the loss of BTU to soil via direct contact of a wet insulator. Don't care if the air is -10 and the soil is 50*.

Unless you are going to be away from the system for extended periods of time I wouldn't worry about freezing as long as you have a generator and a spare circ. Moving water cannot freeze. Worst case, you throw the drain valve open and drain out 80 gallons of water on the ground before it happens ( another benefit of above ground pipe sloping back to boiler ).

 

[stee6043]

Moving water cannot freeze.

Water freezes at 32 degrees F whether it is moving or not. This is a certainty. Find a river with 31 degree water still flowing and you, my friend, have likely also discovered the fountain of youth.

 

[infinitymike]

[quote="danjayh, post: 1162586, member: 23300"

Interestingly, I went to go buy it last night, and the guy who was selling it couldn't lift it onto the trailer. He claimed he used the same tractor when he removed it from his old house, but it wouldn't lift it last night.[/quote]

Hmmmm maybe its not meant to be? Any reason why you're are not going with an indoor unit?

 

[katman]

I'd go for a good foam in ditch job for a short run if you are too close to bend thermopex(or similar quality preinsulated product)and run it underground. You do need space to bend thermopex. I would not even consider your option 3.

 

[BoilerMan]

The company said you could lay it on the ground and snow would stay on it. Well I did that for the first winter because it was a late fall install. There was a 12" tunnel around it through the snow.

gg

It's like those ICF insulated concrete forms. I was talking to a rep when i was building my house trying to convince me to buy his product and said "oh these have an R rating of around 50." I said "well it looks like 2" of foam, some concrete, and 2" of foam my math says thats less than R20". Granted the tightness of the house, but thats a different thread. Salesmen.

TS