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Shop Off-grid heating

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PaulL

PaulL

Technologist at Large
Premium Member
We've just had a couple of days of heavy rain and just the wrong kind of cool to go with it - dropped below the dew point and I'm back in damage control mode in the smithy and in my woodshop - first time in 10 years that my jointer decided to flash over with rust :-(
So I'm thinking it's time to figure out a bit of heat for the shops, just to keep above the dew point.
My current thought is to use a propane through-wall unit in the smithy. The woodshop is harder, but I think I can clear a space on the one wall that would be eligible for such a heater. Running propane there doesn't look too challenging, probably 20' of line from the tee the kitchen stove is on.
So the real question: does any know of control systems for these that can manage a dew-point/humidity-based "thermostat"?
 
There are many high end hvac systems that can be programmed to run a heating system only when the interior conditions fall below the dew point, but they're mostly proprietary and very expensive.

IF it were me trying to set up a simple system on any fuel type, I'd use an arduino and a DHT22 humidity sensor. There are a bunch of programs that can calculate the dew point. It is simple to go from there to programming an output to close a relay that would allow the control voltage for whatever heater you wish to activate your heater.

cost under $30 perhaps.
 
TorontoBuilder said:
There are many high end hvac systems that can be programmed to run a heating system only when the interior conditions fall below the dew point, but they're mostly proprietary and very expensive.

IF it were me trying to set up a simple system on any fuel type, I'd use an arduino and a DHT22 humidity sensor. There are a bunch of programs that can calculate the dew point. It is simple to go from there to programming an output to close a relay that would allow the control voltage for whatever heater you wish to activate your heater.

cost under $30 perhaps.
Click to expand...
I built that circuit some years ago as part of my "haminator" which measured humidity, temperature and the weight of my hanging prosciutto, trying to keep a tight balance on all three as the weight reduced.
The ham came out well, but the haminator was all but useless.

Yeah, building the device myself has some advantages. Heck, I'm just now wrapping up prototyping on my new guitar-pedal midi controller. So much easier to use than the commercial units.
 
PaulL said:
We've just had a couple of days of heavy rain and just the wrong kind of cool to go with it - dropped below the dew point and I'm back in damage control mode in the smithy and in my woodshop - first time in 10 years that my jointer decided to flash over with rust :-(
So I'm thinking it's time to figure out a bit of heat for the shops, just to keep above the dew point.
My current thought is to use a propane through-wall unit in the smithy. The woodshop is harder, but I think I can clear a space on the one wall that would be eligible for such a heater. Running propane there doesn't look too challenging, probably 20' of line from the tee the kitchen stove is on.
So the real question: does any know of control systems for these that can manage a dew-point/humidity-based "thermostat"?
Click to expand...
If the Propane burner would be direct-fired it will actually add humidity to the Smithy and also Carbon Monoxide: please use caution.
 
PaulL said:
We've just had a couple of days of heavy rain and just the wrong kind of cool to go with it - dropped below the dew point and I'm back in damage control mode in the smithy and in my woodshop - first time in 10 years that my jointer decided to flash over with rust :-(
Click to expand...

I live in the worst part of Ontario's rust belt. I do not have a dual control system, nor do I want or need one.

There are some fundamentals about dew points and such that can be exploited to achieve your objectives without dual control. Please note that I am not going to explain the psychometric chart here, but can if you wish.

1. Simply warming a given space reduces its relative humidity.

2. Any dehumidification at all reduces relative humidity.

3. Circulating the air exposes more of it to the dehumidiying system (heating and dehumidiying) and reduces the likelihood of localized dew formation.

The other important aspect of relative humidity is its seasonal character. Totally independant of relative humidity, warm air can hold a lot more water than cold air can. So a few degrees of temperature change can make much bigger difference in relative humidity in the winter than it can in the summer.

My location in Ontario is the worst spot in all of Ontario even worse than Windsor and Toronto which are both horrible too! I have never had a rust problem in my shop.

I recognize that my shop has two seasonal high rust risk conditions. They are summer and winter. Therefore, my climate control system is set to address these two extremes as well as keeping me comfy.

1. The standard temperature setting for the heating in my shop is 42°F (6°C). This heating condition totally clobbers any winter humidity. But warmer is better. I simply increase the temperature temporarily when I am working in the shop.

2. I also have a relatively large Dehumidifier in my 40d x 80w x 20h shop. It is set to 60% and comes on during the summer to keep the relative humidity down. It could be a much smaller unit in a smaller shop.

As stated earlier, a dual control system is not required.
 
Susquatch said:
As stated earlier, a dual control system is not required.
Click to expand...
Thanks. I'll take that at face value, based on your experience. Getting a 50k BTU garage heater, vented appropriately, looks like it will do fine with my 400lbs propane bottle for the couple of months of the year where less than 6 degrees is normal.
And if I find out otherwise from experience, I'll look into more complicated controls.
 
ChazzC said:
If the Propane burner would be direct-fired it will actually add humidity to the Smithy and also Carbon Monoxide: please use caution.
Click to expand...
I'm looking at *direct-vented* units, exactly to avoid this problem. The typical garage heaters appear to take their combustion air from the room, but vent the exhaust outside. That's a good trade-off to the complexity of the ones with the intake air in the same line.
Paul
 
Susquatch said:
I live in the worst part of Ontario's rust belt. I do not have a dual control system, nor do I want or need one.

There are some fundamentals about dew points and such that can be exploited to achieve your objectives without dual control. Please note that I am not going to explain the psychometric chart here, but can if you wish.

1. Simply warming a given space reduces its relative humidity.

2. Any dehumidification at all reduces relative humidity.

3. Circulating the air exposes more of it to the dehumidiying system (heating and dehumidiying) and reduces the likelihood of localized dew formation.

The other important aspect of relative humidity is its seasonal character. Totally independant of relative humidity, warm air can hold a lot more water than cold air can. So a few degrees of temperature change can make much bigger difference in relative humidity in the winter than it can in the summer.

My location in Ontario is the worst spot in all of Ontario even worse than Windsor and Toronto which are both horrible too! I have never had a rust problem in my shop.

I recognize that my shop has two seasonal high rust risk conditions. They are summer and winter. Therefore, my climate control system is set to address these two extremes as well as keeping me comfy.

1. The standard temperature setting for the heating in my shop is 42°F (6°C). This heating condition totally clobbers any winter humidity. But warmer is better. I simply increase the temperature temporarily when I am working in the shop.

2. I also have a relatively large Dehumidifier in my 40d x 80w x 20h shop. It is set to 60% and comes on during the summer to keep the relative humidity down. It could be a much smaller unit in a smaller shop.

As stated earlier, a dual control system is not required.
Click to expand...
all so very true.

but propane isn't cheap and you can maintain lower baseline temp if you control for dew point rather than temp.
 
Maybe, but it can't be less than zero, so is there a significant difference between heating to 2, 3 or 4 versus 6 or 8?

In another climate, it might be worse in other seasons, but at my house in Toronto, I think fall is the worst. Because the air is still warm, but very damp, and progressively getting colder. Which precipitates out when i'm not watching
 
Princess Auto has a 50K btu gas shop heater on sale at the moment. A vented propane heater coupled with a dehumidifier would be my choice, as the warmed air will hold the water and the dehumidifier will strip it out.
 
TorontoBuilder said:
all so very true.

but propane isn't cheap and you can maintain lower baseline temp if you control for dew point rather than temp.
Click to expand...

That's true too. But I also have to prevent my water lines from freezing so temp seemed like a better way to do it. Besides that, I also like the barn sitting at a temperature I can actually tolerate till it warms up. I don't mind the gas bill. It's very reasonable.
 
Susquatch said:
That's true too. But I also have to prevent my water lines from freezing so temp seemed like a better way to do it. Besides that, I also like the barn sitting at a temperature I can actually tolerate till it warms up. I don't mind the gas bill. It's very reasonable.
Click to expand...
every person's design conditions are unique... the OP never said squat about water :p
 
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