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optimistic
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# Posted: 16 Jun 2020 07:50pm
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Hey all
I have 2x 30lbs propane tanks. The will feed my tankless, 68k btu and my cooktop - 21k btu. So about 90k btu.
They are about 2-5ft away from propane tanks. I will run 1/2 black gas pipe. I know how to work with that.
When I started the project I bought a two stage regulator with Pol. It is rated at 160k. I'm pretty sure it is fine but just wanted to make sure. The thing has been sitting unused for the last 4 years (hooked up to a 20lbs tank which I will disconnect of course)
Any thoughts?
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ICC
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# Posted: 16 Jun 2020 09:43pm
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optimistic
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# Posted: 17 Jun 2020 07:42am
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Thank you ICC.
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Brettny
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# Posted: 17 Jun 2020 08:09am
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Have you checked the vaporization rate for a 30lb tank? There not really good enough for what your doing. I have a chart on what temp a propane tank can supply what BTU, il see if I can find it. I guess if you want to try it out leave the regulator high enough that you can put a 100lb tank on it.
What is your location and/or what temp is the coldest you plan on useing this setup?
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FishHog
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# Posted: 17 Jun 2020 08:13am
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I run off 30lb tanks and have done so down to -33C for a week straight and had no issues so I think you will be OK. You might be slightly less efficient but I don't think you will notice.
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Brettny
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# Posted: 17 Jun 2020 08:14am
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So two 30lb tanks in parallel (pulling from both tanks at once) can support just your tankless at 60*. Unless your in the south that's a pretty poor output.
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optimistic
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# Posted: 17 Jun 2020 08:58am - Edited by: optimistic
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wow....
Fish hog do you run a tankless heater like mine?
Brettny - That is a major bummer. I am trying to get confirmation from tankless company about this. Then essentially I need a 100lbs tank min??? nice that I just spent $150 on 2x 30lbs tanks and propane
According to your chart no propane tank can supply you enough btu at 0 degrees? that doesn't seem right.
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optimistic
Member
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# Posted: 17 Jun 2020 09:01am
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I found another chart with very different numbers?
https://flameengineering.com/pages/propane-information
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optimistic
Member
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# Posted: 17 Jun 2020 09:20am
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I just got off the phone with a propane regulator store.
The guy said that a 30lbs propane tank will have between 200-250lbs pressure and that my appliances require 0.5psi so it needs to be dropped significantly - which is what the regulator does. Essentially he said that I am good to go with the 30lbs.
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Brettny
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# Posted: 17 Jun 2020 09:41am - Edited by: Brettny
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A regulator dosnt make the tank vaporize more. Your chart is for a 100lb tank and different amount of propane in the tank. The chart I showed is for each size of tank with 25* remaining in the tank. They are almost identical numbers of you look at the chart right.
I should clarify that a 20-100lb tank both have the same pressure. The 100lb tank has more surface area to vaporize this allowing you to remove more gas at a time. The colder it is the less propane you can remove at once from the tank.
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ICC
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# Posted: 17 Jun 2020 09:49am
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I messed up. Forgot about temperature effect. That must be a big capacity water heater. Is that the correct figure?
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optimistic
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# Posted: 17 Jun 2020 10:10am - Edited by: optimistic
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Brettny - so the guy at the store is wrong and I won't be able to support this tankless and burners with 30lbs tank? he said I am good to go
This is the tankless I got fyi
https://www.amazon.com/gp/product/B01N1ZM1TS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF 8&psc=1
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optimistic
Member
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# Posted: 17 Jun 2020 10:24am
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Just spoke with the manufacturer of the tankless unit. They also say that with my tank size and regulator I am good to go...
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ICC
Member
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# Posted: 17 Jun 2020 10:27am - Edited by: ICC
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I think you are good to go when the 30# cylinder is full and the temperature of the propane in the tank is summer-like. As the level falls and as the temperature falls the ability for the propane to turn from a liquid into a gaseous form slows and you will reach the point where the 30# cylinder cannot supply he required volume.
There would still be propane in the cylinder and it would still be able to supply a smaller demand, such as one burner on the cookstove.
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ICC
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# Posted: 17 Jun 2020 10:31am - Edited by: ICC
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At -40 F liquid propane remains frozen, will not vaporize at all no matter the size of the tank.
Also FYI, a horizontal tank of the same size capacity will have a larger surface area on the liquid content. That allows for better vaporization rate. However you cannot use a cylinder designed for vertical use in a horizontal position.
So to the original question, nothing wrong with the regulator.
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FishHog
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# Posted: 17 Jun 2020 01:14pm
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To be perfect, it might not meet the specs on a cold day. In the real world for me, I'm OK with not running my cooktop and having a shower at the same time if I find it isn't heating my water quite enough.
To each their own, its code to design for max demand with everything running on the coldest day. If you aren't worried about meeting code I think you will be fine. If your shower is a little cold stop cooking at the same time.
You already have the 30lb tanks, so try. If your not happy buy a longer hose and hook to 100lb tanks. I suspect you will never even notice a difference in the real world
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Brettny
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# Posted: 17 Jun 2020 01:25pm - Edited by: Brettny
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What temp do you plan on useing this setup down to?
O and 68kbtu is the output. It's not 100* efficient so you need to know the max btu input. Yes a single 30lb tank will work but you wont get 68kbtu output and at some point your just going to change the tank with propane left in it.
It's not really about code. It's about getting 68kbtu output of the heater. If your not worried about having cold water then why not just step down one size?
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deercula
Member
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# Posted: 17 Jun 2020 03:45pm
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Prior thread with some interesting info and opinions.
https://www.small-cabin.com/forum/7_7640_0.html#msg110140
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NorthRick
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# Posted: 17 Jun 2020 04:18pm
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That says MAX output is 68K btus. One of the knobs adjust gas flow and it looks like the other knob adjust water flow. Seems like in very cold weather you might have to settle for a warm shower at lower flow with no one cooking at the same time.
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optimistic
Member
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# Posted: 18 Jun 2020 08:20am - Edited by: optimistic
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interesting. Thank you everyone for great infromation. I wish I knew - I would have bought a 100lbs. but it is what it is.
I will test it out this winter and report back for others
btw, at 20f a 30lbs will provide 17.3k and a 100lbs is at 43.3k so that still won't be enough for max..
The good news is that I have an indoor tank and an underground tank for rain catchment - I fill up indoor tank then use indoor tank for my showers & sinks. This is the great mountain don design which allows you to use it in winter without needing to heat up the line between the indoor and outdoor source let it be a well or what not.
This means that assuming I will get there in winter in the am, fill up my indoor tank, then won't need to take a shower until much later in the evening - that water temp will get higher throughout the day... assuming my cabin will be in the 68-70f range - the water can be similar to that so the tankless will only need to raise by around 30 degrees or so? that shouldn't be that hard I hope.
If in frozen winter it still won't work well I will need to switch to electric. which sucks but it is what it is.
another idea - enclose tanks outside and insulate them really well then heat up that space a little bit. Once this winter ends i will decide which route to take... 100lbs vs electric tankless vs heated space for propane.
BTW... that chart shows that even a 400lbs tank at frozen weather won't work so this tells me that a household can't use this for main heat source if they are in cold weather like ny... wild.
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Aklogcabin
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# Posted: 18 Jun 2020 08:59am
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When it gets cold here. -30 , or so folks put a light bulb over their regulator to keep the gas flowing.
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ICC
Member
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# Posted: 18 Jun 2020 01:17pm
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Quoting: optimistic BTW... that chart shows that even a 400lbs tank at frozen weather won't work so this tells me that a household can't use this for main heat source if they are in cold weather like ny... wild.
That's when you need an underground tank. 1000 gallon underground tanks are fairly common around me.
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keystone
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# Posted: 19 Jun 2020 09:39am
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optimistic could you elaborate a bit more on your water system? Do you have any pictures?
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Champ7ac
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# Posted: 20 Jun 2020 09:29pm
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I went through something quite similar to your situation. I too thought that I'd use 2- 30lb tanks of propane to fuel my wall mounted heater.
Only problem was, that in really cold weather in the winter, the propane would get to 50% level, and my stove quit working.
Did some reading, and it was suggested to switch to a 100 lb tank. The new tank works great.
Problem resolved.
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Aklogcabin
Member
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# Posted: 21 Jun 2020 10:46am
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In Ak folks regularly use propane for heat. And it get 40 below. Ive never seen a buried tank.
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Brettny
Member
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# Posted: 21 Jun 2020 11:54am
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What size tank and what size heater do you see alot of?
That's the thing about heating with propane with a to small of a tank..the colder it is the more propane you need to burn yet the less the propane tank can supply.
A lightbulb on a regulator is a work around not having the regulator freeze up from a cold tank. It can even happen here in NY. I still dont see any light bulbs on regulators.
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NorthRick
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# Posted: 21 Jun 2020 12:19pm - Edited by: NorthRick
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Quoting: Aklogcabin In Ak folks regularly use propane for heat. And it get 40 below. Ive never seen a buried tank.
The coldest it has been at my cabin when I was in it was -28F. I can normally keep the cabin in the upper 60s but not that night. I have a 100lb propane tank that feeds a 30K btu heater. The flame on the burner was noticeably smaller and the heat output noticeably less. I'm quite sure at -40F the heater would have quit all together.
It's a recreational cabin and -20F and colder is not recreating - it's surviving. The area had temperatures in the -30s this winter and I stayed in town in my house heated with natural gas.
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Al Burton
Member
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# Posted: 21 Jun 2020 02:25pm
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Another option is to keep the tank warmer. It could be as simple as a well insulated box with a lightbulb or something like this tank warmer. You could even keep one inside and swap them back and forth. Tank heaters are also used a lot in the air conditioning service industry. Maybe you could find a used one.
https://www.briskheat.com/hotbelttm-refrigerant-jug-warmer.html
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ICC
Member
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# Posted: 21 Jun 2020 03:15pm
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Quoting: Aklogcabin Ive never seen a buried tank.
Ya' never do. 
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FishHog
Member
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# Posted: 21 Jun 2020 07:27pm
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Quoting: ICC Ya' never do.
Took me a second but LOL.
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