Heating My Shed/Office off Solar

Eaks77

New Member
Joined
Jul 19, 2021
Messages
28
I've recently converted my shed into a small office (~100sq ft). The shed is now insulated with OSB walls and will be somewhat offgrid as I have ~2000W of solar going into a 24V 320AH battery bank, with a Growatt all-in-one 24V inverter. Yes, I know the 320AH batteries may be overrated.... I'm actually still waiting for them to arrive.

It's starting to get cold here in Northern Canada and I'm in need of some heating advice. While the shed is supplemented by grid tied power, I'm ultimately looking to heat the shed with as little power as possible, as efficiently as possible. I plan to have a couple GPU crypto miners running to provide some heat, but I know I'll need something more substantial for those -25^C days.
Some considerations:
Wood burning furnace - Not realistic as I need to have it heated at all times while being unmanned throughout the day
Propane wall unit - While I'm considering it, the units are a little expensive and likely overkill.
Electric - My only Option? If so, what are the most efficient/best heaters for this small space?

I just installed THIS HEATER, because of it's lower power consumption (either 450W or 1000W), but I immediately noticed this wasn't going to do the job. It was 0^C today and it struggled to keep shed at 20^C. Within 5 hrs, it burned 2.3KWH. My thinking is I'd rather have a higher powered heater on for shorter periods of time, than having a lower powered unit on for longer..... any logic with that?

With that said, I'm leaning towards an oil filled heater, such as THIS (De'Loghi) as it should require the element (consuming power) to turn on less once at temp. Thoughts?

Otherwise, I was thinking about getting the 1500W Version of the heater I just tried in hopes it might do better.

Anyone out there with similar challenges? Any advice?
 

labeeman

Solar Enthusiast
Joined
Jun 2, 2021
Messages
220
Location
Carencro, LA
mini split, inverter based may help here
They are only rated for -22 degrees F and it gets much colder where he is at OSB (oriented strand board) where I am at does not offer much insulation unless it means something else there. Insulation would be my choice first.
 

squowse

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Joined
Jan 4, 2021
Messages
283
Have you considered a Chinese diesel heater? They're very economical especially if you can get fuel that's not road taxed. (Heating oil /kerosene or red diesel in the UK).
I've installed several and had no problems with them at all.
 

Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
Joined
Oct 29, 2019
Messages
5,605
Location
Rural NE Ontario Canada
-3 This morning, yep the chillies are coming. But what else could I expect here in the Algonquin.
A Propane unit is certainly an option, I heat my powerhouse with a recovered RV Furnace, direct vent, Propane runs off 12V and is more than sufficient. Cost me $350 CAD for the Suburban NT20S Furnace, the thermostat, dual tank regulator and the fitting. Got it from an RV Vendor / Repair shop, they had 3 newer trailers (insurance write offs) and I scored it out of one of those. I keep the powerhouse at 10C/50F which keeps the batteries very happy and my 50 Gal. Water Pressure Tank safe. Check out Kijiji and any local RV Trailer/Camper vendors & repair shops.

For insulation, use Roxul, it's hydrophobic unlike fiberglass, mice & bugs hate it as well.
 

Wellbuilt

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Joined
Sep 14, 2020
Messages
795
A Williams propane heater would work i not sure if they make one with a pilot light any more
but a spark ignition could work .
 

OffGridInTheCity

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Joined
May 23, 2021
Messages
556
Location
Southern Oregon
I just installed THIS HEATER, because of it's lower power consumption (either 450W or 1000W), but I immediately noticed this wasn't going to do the job. It was 0^C today and it struggled to keep shed at 20^C. Within 5 hrs, it burned 2.3KWH. My thinking is I'd rather have a higher powered heater on for shorter periods of time, than having a lower powered unit on for longer..... any logic with that?
I recently did a 7 x 14 cargo trailer -> camper with 1" silverboard insulation all sides - e.g. 98sq ft. The mini-split takes about 6kwh/24hrs to maintain 60F/16C with a 32F/0C outdoor temp. I also tried a small ceramic / electric - and it burned 5kwh in just 12hrs to keep 70F/21C with a 40F/4C outside. Mini-split a very efficient *electrical* heat source in my opinion - but I agree it has ambient limitations.

My camper has 1200w of solar but that only produces 1.5-2kwh in winter.
At 2000w of solar I would think you'd max out at 3-4kwh / day in winter? - that kind of power won't heat 100sq ft at temps you describe.

Some thoughts:
1) Insulate as much as you can - every sq inch. Even if you have a small area like 1ft by 6ft up near a corner or a poorly insulated door it can make a big difference.
2) Can you increase solar? - 4000w is better than 2000w etc. I'd maximize solar as you can.
3) Obviously - cooler max temp with warmer clothes will use less power
4) Can wait till daylight / warmer - and only use a mini-split during with higher ambient?
-----
5) I do believe (but don't have math to prove) that short periods of heat w/cool-down will use less power. Can you let it stay colder most of the time but only heat a few hours a day - e.g. to point #4 above.


Conclusion: Maybe some kind of mixed system - direct heat for night-time to maintain minimum + mini-split for afternoons with warmer ambient to maximize efficiency?

I'll be interested to follow your comments on this topic
 
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Rednecktek

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Joined
Sep 8, 2021
Messages
789
Have you considered a Chinese diesel heater? They're very economical especially if you can get fuel that's not road taxed. (Heating oil /kerosene or red diesel in the UK).
I've installed several and had no problems with them at all.

This and insulation. I run 2 of them at my camp and have no concerns about walking away from them for hours and they get me from the 10F to a nice 68F in just a couple of hours.
 

ghostwriter66

"Here - Hold my Beer"
Joined
Nov 13, 2019
Messages
1,663
Location
From LA -work in South Texas/New Mexico region
This and insulation. I run 2 of them at my camp and have no concerns about walking away from them for hours and they get me from the 10F to a nice 68F in just a couple of hours.

This is what we have in all the work trailers -- and most of the truck drivers out here use these while they are parking ... fricking little jet type heater ... I think on full blast a 5 gallon diesel tank running 24/7 will last about 2.5 days if I remember correctly (but don't quote me) .. going to say that it just running a few hours a day in a well insulated room it will do much better. It puts out enough heat to melt plastic.

now of course I would rather you use Solar BUT heat is energy and heaters require ALLOT ... while working a project in Nome Alaska we had to keep a security shed warm(ish) for 10 hours a day and ran a 1200watt heater which required a 6.4 kW PV systems or (16) 400W solar panels at a minimum fudge factor involved at all - so the diesel may be your best bet ...
 

Eaks77

New Member
Joined
Jul 19, 2021
Messages
28
Hi Everyone... Thank you for the response! Great advice!

IMG_20211024_161540.jpgIMG_20211024_161628.jpg(@OffGridInTheCity - thank you, some answers below)
  • The walls have been insulated with Rockwool R14 (2"x4" thick walls). The interior OSB wall joints/gaps have been filled in with caulking, while the majority of exterior OSB joints/gaps were sealed with BlueSkin weather striping. I also used spray foam wherever possible. I like to think this shed is airtight.. which brings on other concerns haha :sleep:
  • The interior walls are OSB because the shed isn't on a concrete foundation. It's being held up by a couple 4"x4" length wise and it shifts throughout the seasons. Drywall would have easily cracked. The OSB is also painted with two coats of oil based primer and two coats of SafeCoat -> a latex, fire resistant paint. = Peace of mind
  • Before receiving any grief about the lack of a foundation, this was a previously standing shed that I've converted. Although, I tore down about 30% and rebuilt.
  • Due to the unstable foundation, the floor is not level and does shift throughout the season. As you can see, one of my last steps is flooring, of which I have questions, but I'll start up another thread (HERE) for that since everyone has been exceptionally helpful!
  • PV System = 4 x 445W Bi-Facial Solar panels, south facing on a pergola. The 445W does not include the bi-facial wattage.
  • Waiting (after scammed twice already) for 8x320AH LifePo4 cells. This will be connected to Growatt 24V all-in-one
HEATING
I really appreciate everyone's input!
I'm coming to terms that electric heaters will not suffice. Are oil filled heaters not even an option?
Objective is to keep the shed between 18^C->21^C while occupied and ~10^c when not occupied


@Steve_S - Great to hear from you again! I'm considering a propane unit and a used one is a great idea! My only hold up is the price (less so if a find a used one) and the fact I'll need to put a hole in the side of the shed. Doable, but something I'm reluctant to do. I've also heard from propane wall users that their output is less than expected. Also, I'm also reading that the price of Propane is supposed skyrocket if it hasn't already.

@squowse - I had not considered a diesel heater till now! :) This might be the answer! However, questions/comments:
  • Could this actually keep a well insulated space to my desired temperatures?
  • What __KW is recommends for the space? (100Sq Ft / 770 cubic ft)
  • I'm thinking about installing a diesel heater in the attic and venting the heat through the ceiling while venting exhaust through the roof soffit, but:
    • I'm worried about storing diesel in the ceiling.. any leaks would not be good! I'd also want a fairly large tank ~30L so that I don't have to consistently refill.
    • Fire! How reliable are these heaters? I know diesel is not exactly flammable, but still a risk, right?
    • Alternatively, I could get a all-in-one unit such as THIS, but it would have to be stored outside, which can be done between the shed and garage (protected from elements). I'd then be concerned with it operating in extreme cold, having enough cable to get the control/thermostat into the shed and I'm back to drilling a hole through the side of the shed... It may be smaller than propane unit, but not something I want to do.
 
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Smokin

Solar Enthusiast
Joined
Sep 8, 2021
Messages
152
The door on the ceiling needs to be sealed. Heat will draft out like crazy.
 

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Eaks77

New Member
Joined
Jul 19, 2021
Messages
28
The door on the ceiling needs to be sealed. Heat will draft out like crazy.
Great suggestion. It's sealed with some window gasket tape and has Rockwool on top of it as well. It's a tight seal to begin with and is not fully shut in the picture
 

ghostwriter66

"Here - Hold my Beer"
Joined
Nov 13, 2019
Messages
1,663
Location
From LA -work in South Texas/New Mexico region
Hi Everyone... Thank you for the response! Great advice!

View attachment 70029View attachment 70030(@OffGridInTheCity - thank you, some answers below)
  • The walls have been insulated with Rockwool R14 (2"x4" thick walls). The interior OSB wall joints/gaps have been filled in with caulking, while the majority of exterior OSB joints/gaps were sealed with BlueSkin weather striping. I also used spray foam wherever possible. I like to think this shed is airtight.. which brings on other concerns haha :sleep:
  • The interior walls are OSB because the shed isn't on a concrete foundation. It's being held up by a couple 4"x4" length wise and it shifts throughout the seasons. Drywall would have easily cracked. The OSB is also painted with two coats of oil based primer and two coats of SafeCoat -> a latex, fire resistant paint. = Peace of mind
  • Before receiving any grief about the lack of a foundation, this was a previously standing shed that I've converted. Although, I tore down about 30% and rebuilt.
  • Due to the unstable foundation, the floor is not level and does shift throughout the season. As you can see, one of my last steps is flooring, of which I have questions, but I'll start up another thread (HERE) for that since everyone has been exceptionally helpful!
  • PV System = 4 x 445W Bi-Facial Solar panels, south facing on a pergola. The 445W does not include the bi-facial wattage.
  • Waiting (after scammed twice already) for 8x320AH LifePo4 cells. This will be connected to Growatt 24V all-in-one
HEATING
I really appreciate everyone's input!
I'm coming to terms that electric heaters will not suffice. Are oil filled heaters not even an option?
Objective is to keep the shed between 18^C->21^C while occupied and ~10^c when not occupied


@Steve_S - Great to hear from you again! I'm considering a propane unit and a used one is a great idea! My only hold up is the price (less so if a find a used one) and the fact I'll need to put a hole in the side of the shed. Doable, but something I'm reluctant to do. I've also heard from propane wall users that their output is less than expected. Also, I'm also reading that the price of Propane is supposed skyrocket if it hasn't already.

@squowse - I had not considered a diesel heater till now! :) This might be the answer! However, questions/comments:
  • Could this actually keep a well insulated space to my desired temperatures?
  • What __KW is recommends for the space? (100Sq Ft / 770 cubic ft)
  • I'm thinking about installing a diesel heater in the attic and venting the heat through the ceiling while venting exhaust through the roof soffit, but:
    • I'm worried about storing diesel in the ceiling.. any leaks would not be good! I'd also want a fairly large tank ~30L so that I don't have to consistently refill.
    • Fire! How reliable are these heaters? I know diesel is not exactly flammable, but still a risk, right?
    • Alternatively, I could get a all-in-one unit such as THIS, but it would have to be stored outside, which can be done between the shed and garage (protected from elements). I'd then be concerned with it operating in extreme cold, having enough cable to get the control/thermostat into the shed and I'm back to drilling a hole through the side of the shed... It may be smaller than propane unit, but not something I want to do.
doesn't matter if its a 1500W oil filled Radiator or 1500W Electric Heater, Radiant Heater, Infrared Heater, Fan Heater, Halogen Heater, or 1500W Ceramic Heater.... they all pull the same amount -- 1500 or 1250 or 800 depending on setting...

As for the diesel heater -- go to YOUTUBE ... millions of videos ... I would put the heater outside and just vent it in ... we actually have 50 gallon diesel drums we run ours from ... but once you watch video you will understand better
 

squowse

Solar Enthusiast
Joined
Jan 4, 2021
Messages
283
Hi Everyone... Thank you for the response! Great advice!

View attachment 70029View attachment 70030(@OffGridInTheCity - thank you, some answers below)
  • The walls have been insulated with Rockwool R14 (2"x4" thick walls). The interior OSB wall joints/gaps have been filled in with caulking, while the majority of exterior OSB joints/gaps were sealed with BlueSkin weather striping. I also used spray foam wherever possible. I like to think this shed is airtight.. which brings on other concerns haha :sleep:
  • The interior walls are OSB because the shed isn't on a concrete foundation. It's being held up by a couple 4"x4" length wise and it shifts throughout the seasons. Drywall would have easily cracked. The OSB is also painted with two coats of oil based primer and two coats of SafeCoat -> a latex, fire resistant paint. = Peace of mind
  • Before receiving any grief about the lack of a foundation, this was a previously standing shed that I've converted. Although, I tore down about 30% and rebuilt.
  • Due to the unstable foundation, the floor is not level and does shift throughout the season. As you can see, one of my last steps is flooring, of which I have questions, but I'll start up another thread (HERE) for that since everyone has been exceptionally helpful!
  • PV System = 4 x 445W Bi-Facial Solar panels, south facing on a pergola. The 445W does not include the bi-facial wattage.
  • Waiting (after scammed twice already) for 8x320AH LifePo4 cells. This will be connected to Growatt 24V all-in-one
HEATING
I really appreciate everyone's input!
I'm coming to terms that electric heaters will not suffice. Are oil filled heaters not even an option?
Objective is to keep the shed between 18^C->21^C while occupied and ~10^c when not occupied


@Steve_S - Great to hear from you again! I'm considering a propane unit and a used one is a great idea! My only hold up is the price (less so if a find a used one) and the fact I'll need to put a hole in the side of the shed. Doable, but something I'm reluctant to do. I've also heard from propane wall users that their output is less than expected. Also, I'm also reading that the price of Propane is supposed skyrocket if it hasn't already.

@squowse - I had not considered a diesel heater till now! :) This might be the answer! However, questions/comments:
  • Could this actually keep a well insulated space to my desired temperatures?
  • What __KW is recommends for the space? (100Sq Ft / 770 cubic ft)
  • I'm thinking about installing a diesel heater in the attic and venting the heat through the ceiling while venting exhaust through the roof soffit, but:
    • I'm worried about storing diesel in the ceiling.. any leaks would not be good! I'd also want a fairly large tank ~30L so that I don't have to consistently refill.
    • Fire! How reliable are these heaters? I know diesel is not exactly flammable, but still a risk, right?
    • Alternatively, I could get a all-in-one unit such as THIS, but it would have to be stored outside, which can be done between the shed and garage (protected from elements). I'd then be concerned with it operating in extreme cold, having enough cable to get the control/thermostat into the shed and I'm back to drilling a hole through the side of the shed... It may be smaller than propane unit, but not something I want to do.
You can keep the diesel outside unless the fuel waxes? It depends on the local fuel and the temperatures.
Normal installation is to cut a 5 inch hole in the floor or a wall that the diesel heater mounting plate covers. The exhaust and combustion air pipes are then sealed to the outside. Personally I'd stay away from the all in one units. Not a fan.
 

Eaks77

New Member
Joined
Jul 19, 2021
Messages
28
You can keep the diesel outside unless the fuel waxes? It depends on the local fuel and the temperatures.
Normal installation is to cut a 5 inch hole in the floor or a wall that the diesel heater mounting plate covers. The exhaust and combustion air pipes are then sealed to the outside. Personally I'd stay away from the all in one units. Not a fan.
I think I need to setup the diesel heater in the attic, with a fuel tank. I anticipate seeing -25^C for a couple weeks this winter and keeping things in the attic will keep it out of the elements and a little warmer
 

Rednecktek

Solar Addict
Joined
Sep 8, 2021
Messages
789
That would probably work great. Jump on Amazon and get the rubber 3" - 4" ductwork adapter and you can connect up some dryer hose to pump the hot air to wherever you want it.

As an example, here's what I did with mine at the camp to feed the hot air into the back bedroom and into the living room. An adapter, some insulated ducting, and flashing tape made it SSSSOOOOO much nicer in the main part of the cabin.

Normal installation is to cut a 5 inch hole in the floor or a wall that the diesel heater mounting plate covers. The exhaust and combustion air pipes are then sealed to the outside.
In my case since the utility room is only "Mostly" enclosed I just had to run the 1" exhaust pipe out the side. Plenty of fresh air in there for the burner. Just mount it on a shelf inside, put the 2 1" hoses right out the side of the shed and it'll use a LOT less fuel since it'll be recirculating the air in the shed thus not having to heat as much.

Also for reference, and I can't do the conversions off the top of my head, but that 1 little 5Kw heater, once I got the floor insulated, kept the inside at a nice toasty 68F (20c?) when we had highs outside of 10F (-12c?) and lower at night.

As for attending it, before I got the insulation in I checked it every 3 days when it was starting to get low on fuel. Last time I didn't even look at it for almost a full week. I just drop the fuel line into a standard 5gal/20l diesel can and turn it on.

At long periods of low load I sometimes have to open them up and clean out all the soot and gunk that didn't burn off, but if you search YouTube or ping me you can get step-by-step instructions on that. It's surprisingly easy.
 

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Rednecktek

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Joined
Sep 8, 2021
Messages
789
Wood stoves were already ruled out as he'll need to be able to leave it unattended for periods of time.
 

squowse

Solar Enthusiast
Joined
Jan 4, 2021
Messages
283
That would probably work great. Jump on Amazon and get the rubber 3" - 4" ductwork adapter and you can connect up some dryer hose to pump the hot air to wherever you want it.

As an example, here's what I did with mine at the camp to feed the hot air into the back bedroom and into the living room. An adapter, some insulated ducting, and flashing tape made it SSSSOOOOO much nicer in the main part of the cabin.


In my case since the utility room is only "Mostly" enclosed I just had to run the 1" exhaust pipe out the side. Plenty of fresh air in there for the burner. Just mount it on a shelf inside, put the 2 1" hoses right out the side of the shed and it'll use a LOT less fuel since it'll be recirculating the air in the shed thus not having to heat as much.

Also for reference, and I can't do the conversions off the top of my head, but that 1 little 5Kw heater, once I got the floor insulated, kept the inside at a nice toasty 68F (20c?) when we had highs outside of 10F (-12c?) and lower at night.

As for attending it, before I got the insulation in I checked it every 3 days when it was starting to get low on fuel. Last time I didn't even look at it for almost a full week. I just drop the fuel line into a standard 5gal/20l diesel can and turn it on.

At long periods of low load I sometimes have to open them up and clean out all the soot and gunk that didn't burn off, but if you search YouTube or ping me you can get step-by-step instructions on that. It's surprisingly easy.
It's very easy and much safer to mount the heater in the way it's designed - so that the bottom pipes (combustion air and exhaust) are outside. If you're mounting it on a wall then the fuel pipe needs to be on the high side (air flow from right to left).
 
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