You need to tell us what size your greenhouse is. Its all about the greenhouse, not the heater.

You must fit the heater to the greenhouse then add some air, and bingo! It will work.

Orchiddude I didn't mention the size cause I have posted it so many times here in the past few months while you were not around. It's 8ft w x 17 ft l x 8 ft high. I just read Chris's post on radiant versus blue flame heaters in another thread so now I understand why a blue flame is better for the greenhouse.
The dealer I was talking to understood the size of my greenhouse. His advice was that a) the 20K should not have run out of air in there and b) since I'm planning on a larger greenhouse (at least 16 x 20) I should get the 20K instead of a 10K. He felt that the heater that kept snuffing out (and mind you I was in the greenhouse breathing comfortably several of those times) was probably faulty.
My thinking was that I'd rather buy another 20k locally than have one shipped though they're now dissappearing from the shelves so fast here I may have no choice.
Any logistical reason that the 20k at low settings wouldn't work in my gh? I need temps of minimum 50 at night (55 is better) and max of 75 day (they can take higher but it's not the preferred thing). Currently outside temps are in low single digits (and known to get in negative double digits). My main reason for the new heater is to get thermostat control of the heat. I currently have a 1500 watt electric (running full blast) and a Big Buddy (set on low) propane heater both running together. They keep it at 55 the coldest nights but the Big Buddy doesn't turn itself off when the GH gets hot. I want something that will turn itself off and on at 55 or so.

MollyD

A 20,000 Btu will work just fine. Just get one with some low, medium and high settings and you will be good to grow...LOL

It will work.

so you too believe that other 20k that kept shutting off was faulty?

MollyD

Well I'm picking up a 20K heater at Home Depot tomorrow morning. We'll see how that one works out.
A cold wave is heading this way and I want this thing in place before then.

MollyD

I think it was bad. These heaters dont use that much air.

Molly I dunno what kind of cold wave is coming but make sure to plan for the possibility of your propane supply running out. I had placed a remote sensor in our GH and set it to alarm at 33F indicating a failure, and it alarmed at the START of our nasty freezing rain problems here in TX. Thankfully it happened in the evening vs. the dead-of-night. Put-on the spare tank and also put an electric heater in there, to back each-other up.

Anyway make sure you have an adequate LP tank, and a full spare. The 20lb (grill-size) tanks don't last very long in our experience, and we have only a 10K heater.

Thanks laserfan. We have 4 tanks (100,40,and two 20's),and I'm keeping the electric heater in there set on low (it has a thermostat) just in case!
We had an ice storm this weekend but only got hit half as hard as you did. The bed of our pickup truck is still an ice rink! Now we have snow on top of the ice which surprisingly gives us better traction.
I sure hope things are getting better down your way. I'm sitting here listening to avalanches of snow and ice falling off the roof! We have an A frame so the roll is very fast.
We're suppose to get more ice and snow and very cold temps starting tomorrow. Today it's relatively warm at 32 degrees.
I'm heading out to the GH now to start the installation of the heater. This one (ProCom blue flame) didn't come with legs so I'll have to design something to hold it. After work hours Paul will do the gas part of the work.

MollyD

Hey MollyD,

I posted a reply to your other thread about the heater shutoff problem you've had... I don't think you have a bad heater; I think you have a well-sealed gh! I agree with Orchiddude; it *will* work with a blue flame heater. A 20k or a 30k should be fine for your size gh... Mine's 8x16x7 with a 30k (built-in thermostat controlled), and it could easily be handled by a 20k. Keep in mind, most of these heaters have two heat levels, determined by the heater automatically. My 30k heater kicks on with 15k of output, unless it's REALLY cold... then some internal setpoint kicks it into full 30k mode. You can see this yourself by getting the heater to turn on, and then crank it to the highest thermostat setting... and watch the flame get bigger!

Anyway, I'd venture that your heater is exhausting the oxygen from the air, at least as far as its overcautious safety system is concerned. Here's some pics of what I've come up with to fix the problem; maybe it'll come in handy for you too!

{{gwi:287014}}
The heater

{{gwi:287016}}
Duct tape is my friend for sealing off the front air vents. This way I don't pull oxygen from the air in the greenhouse.

{{gwi:287017}}
Duct tape, some machine screws, a forced-air heat register duct, and a dryer vent hose conspire together here as an air inlet which leads outside...

{{gwi:287018}}
...here, to a dryer vent cap. Inside, there's a flap that I've reversed so that air can only come in, when the heater needs it. Convection currents from the hot air that leaves the heater when it's on draws cold outside air in to be warmed...

{{gwi:287543}}
...leaving things comfortable.

I've gone through two 20lb grill-size tanks of propane per week here in northern CT when night temps are around 25 degrees.

Hope this helps!

Just in case anyone thinks I'm ignoring etravian I'm not. I wrote offline thanking them.I think that's a very interesting setup for the heater.

MollyD

MollyD,

I definitely didn't feel ignored -- I just posted my reply a few minutes ago after all! :) I just wasn't sure which thread to post to, and since I had a couple minutes and camera in hand to take the pics, figured a visual couldn't hurt.

And it's just that I remember the pain of having all my plants freeze to death that makes me want to help others with problems similar to those I encountered.

All the best,

-E

>We have 4 tanks (100,40,and two 20's),and I'm keeping the electric heater in there set on low (it has a thermostat) just in case!
>I sure hope things are getting better down your way.

You're in good shape Molly with your tanks!!! Good job!

Thanks for the kind words--today our temps got into the 40s and trees were dropping their ice so it was still nasty out there BUT unlike what I might expect (being from "up north" myself) after the freezing rain we did NOT have cold pour-in and winds pick-up etc. etc. which would have REALLY made this a disaster. I do feel sorry for the folks in OK, here we only have to worry about gutters coming down (they are heavily ice-laden) and amputating broken tree limbs.

Good luck w/your new heater!

The Oklahoma folks say their neighborhoods look like bombs exploded. National media isn't paying any attention to their plight.
Missouri got hit hard too.

We'll see how this new heater holds up. We got it installed tonight. Etravian gave me some good pointers on venting if this one snuffs out too.

Molly

Well it looks like my greenhouse is tighter than I thought. The new heater ran all night on low keeping it 58 degrees until about 5am when it began to drop. I went out at 5:30 and the heater had snuffed out so today I'll be trying out Etracians setup. I already have the dryer hose and only have to pick up the boot and dryer hook up.
Aside from that "little" problem this heater runs beautifully. It's a cheaper model with less bells and whistles to foul things up. In other words no blower or built in thermometer, no batteries needed cause the ignition isn't electronic. No legs either so we set it up on patio blocks.

MollyD

MollyD,

I'm sorry to hear that you had to be up at 5:30! But that's an A+ for dedication!

Are you saying that this new heater has no thermostat at all? Or does it have a numbered dial of some sort and the heater turns on/off at some approximate setpoint?

Having a heater with no electrical requirement is nice -- so even if the power's out, your gh has heat.

We've been really lucky up here in terms of weather. Last night brought not much more than a dusting of snow -- the most we've gotten all winter long, and we can still see grass poking through. I remember when we used to have *real* winters here...

Etravian,
It has a thermostat but not a thermometer that tells you the temp in the room. The other one gave your a temp display. It has the number type of dial.

I just got back from Lowes where I got the parts for that vent system you posted. How high up is your intake? I can't tell from the photos but it looks much higher than the heater. I don't want to make any holes till I know if there is a specific location I should place it. I want to get this done early in the day so I can test it before bedtime! I'm like to sleep a little later tonight not to mention avoid all those wakeups to check the temp.

MollyD

Good eye!

Yes, the intake is higher because what I didn't want was a natural convection current to develop from a low intake. My thought was that since warm air rises, a low intake would simply suck in cold air even when the heater is not running. Putting the intake higher (about 5 feet from ground) would mean the warm air in the gh would push out against the one-way flap (since cold air inevitably seeps in somewhere, usually down low near the base of the gh), keeping it closed unless the greater force of the air requirements for a running heater started pulling air in.

(The flap is just one of those dryer vent doodads turned in reverse, btw... $3.50 at HDepot)

I don't know if the low/high vent makes a difference, but I've not detected any warm or cold drafts coming in or out of the intake vent. It gives me peace of mind in any event.

Good to hear that the heater does have a thermostat. Once you get your heater up and running for a whole night, you'll start to learn your heater's on-off habits... which will require minor tweaking when temps outside go up/down a lot. The control is pretty good mind you, but the thermostat bulb can be pretty sensitive. I actually detached mine from the body of the heater and kinda have it sticking out in the air so it wouldn't be affected by conduction through the metal body of the heater.

Keep us posted on the install!

-E

You said Molly your GH was 8x8x17, but I wonder if you have a pitched roof and your cubic feet are something significantly less than 1088. On the surface those numbers should in theory support a 1088/50=21.76 meaning 21,760BTU heater, but have you measured Insided your GH and taken the roof pitch into account? Maybe your CuFt are much less?

Our HFGH is per specs "10x12x10" for 1200cuft but in fact inside is only about 940cuft. Should support 18,800BTU but I bought only a 10K heater just to keep the GH above freezing. In addition our doors and 4 roof vents have signifcant open gaps in them...

Anyway sounds like your first heater was OK after all--hope your combustion air vent does the trick for you, though you may ALSO need a flapper for air to escape. When you bring in outside air, it's gotta go somewhere, and it sounds like your GH is extraordinarily well-caulked.

Laserfan has a point. I have a kitty door for my four-legged gardeners and when the heat's on I don't feel any cold air coming in... presumably because the cool air near the floor is going out when the heater intake is drawing air in. You might need to to put in another dryer vent cap (a one-way flap, exit only this time) near the floor on the other side of the gh if the heater still kicks off at night.

more holes!
I just finished putting in the vent. Took me about an hour and a half to get it done. When I was finished (and is it ugly!) I hung a fan to blow the heat away from the heater towards the far end where I had found it to be cooler. I found that the temp felt more evenly distributed after I did all this.
The sun is out so it's hard to judge what the heater is actually doing. It's in the mid 70's in there right now. Normally with my old set up it would be around 55-60 on a cloudy day.
My heater's openings were different from yours so I placed the boot over the front vents and duct taped it in place blocking the extra openings along the sides. The intake is slightly higher but not much. There was no where to attach it if I tried to go higher. In the next greenhouse I will place it up around 5' or so and use rigid duct work instead of the dryer flexible stuff.
Laserfan I have a curved roof. This is a cattlepanel hoophouse. I'm not sure how much that impacts on the cubic ft. I don't mind parting with that other heater. This one weighs less (probably cause it doesn't have the blower but I can add one if needed)so it's easier for me to move around when necessary.
I couldn't find the dryer vent that could be reversed but I made do with what I could find and installed it backwards so the flap opened in instead of out.

Thanks!
MollyD

Well I'm happy to report that since making the modification that Etravian indicated my heater has been running correctly since! It keeps things a balmy 63 at night (and we dropped to 3 last night!). I think I'm in love (with this heater)!!!!!!!!

MollyD

Congratulations!!! Soooo happy to hear that things are working better now... I remember my relief when all was right with the [greenhouse heating] world!

Wow three degrees. If the heater can keep it in the sixties through that and not shut off, you are all set. Was the heater going all night or did it get a chance to turn off for a bit every now and then? (It's no problem if it's on all the time esp with those outside temps. I'm just curious)

Now what we all need are some pictures of your accomplishment!

Warmly,

-E

E,

No idea if it ran all night. How would I check that? I know I woke several times during the night and the temp was alright. Last night I slept straight through after two nights of doing that!
Now if I could find a way to know when my propane tank is close to empty. With a 20 # you can lift them but you can't do that with the 100#. Do they sell any gauges for this ? Right now the tank is covered in a layer of ice so i can't even see if there is a frost line.

I'll try to post pictures later.

MollyD

I know they make those tape-on gauges for the 20lb tanks, but I've not seen any for the 100lb tanks. I use a couple 20lb'ers and a 40lb tank so lifting/checking frost line is easy enough - I'd not be interested in doing the same for your tank!

Perhaps if you were to pour some warm water down the length of the tank to melt the ice off... and then watch for where it freezes first... you can tell the fullness of the tank?

As for watching the heater -- I figure if you go in there when it's dark out and cold and the heater stays on for more than half an hour without turning off, you can pretty much assume it's on all the time. Mine'll come on for 5, maybe 10 mins at a time and then stay off for a good 20 minutes before firing up again (at night). And as I mentioned before, I go through about 40lbs of propane every week (a little more now that the weather's turned colder).

Looking forward to the pics!

-E

E,

I don't fancy going out to the greenhouse after dark unless I have to! This is bear country and while they're on the rare side I don't want to tempt fate!!
I'm having trouble posting pictures. Last fall I had a virus on this computer. It went in for repairs and since then it's had a lot of trouble. I can't access my digital camera or printer. I can't run any FTP programs so I can't upload photos unless the page does it for me. GW doesn't do that so I'm stuck for now. I just spent a few hours installing different FTP software none of which would run for me. Ugh! I'm going to look for a web page host since I can't even access my web pages to make changes right now.
I turned my heater down a smidgeon today as yesterday it stayed at 68 all night and that's more than I need. Tonight it's hovering around 66. It tends to stay at the lowest so I have to assume that it stops running at some point when it's warm enough in the GH otherwise it would get warmer in there as the night when on instead of staying the same.
I had posted some over on Dave's Greenhouse forum but I think you have to be a member to access them. SB is this right?

MollyD

Okay I'm going to try and post pictures. I got hold of a new ftp program that seemed to work very well (ftp commander) and was free!

MollyD

{{gwi:287544}}

Here's are two shots of the inside of the greenhouse. I haven't gotten a new photo of the work on the stove so it's not in these pictures.

MollyD

and

MollyD,

Awesome greenhouse!

You have a lot of stuff started in there. I am jealous! It looks great!

You appear to have double layer plastic... one layer outside the cattle panels and one layer inside held back with wire... and then on the north side, maybe? you have a metallized insulation of some sort held back in the same fashion. Very inventive, and probably more efficient than the two layers of plastic inflated by fan that I have.

Thank you for the pics!

-E

E,

The outside is 6mm film, on the inside is a solar pool cover being held by the wire. On the north side is the same thing topped by foil faced insulation. The foil is to reflect light (as far as I'm concern!). It makes for a very cosy setup in there. The barrels hold water for heat retention. There are 4 of them (55 gals each). I'm adding a 20" bench down the middle next week cause I need more room. A lot of the plants in the small pots are ready to move into the 1 gal pots.
Next year I want lights over all the plants. We just don't get enough sunlight here in the winter for things to grow fast.
It's effective but not beautiful I'm afraid. Had to sort of throw it up in a hurry with winter breathing down my neck. Next one I'll start this spring. Paul wants to keep this one up and attach the new one. I want to remove this one altogether!

MollyD