Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: tbone on February 28, 2012, 09:49:54 AM
-
What's an exceptable number? I know its all relative, but I believe I read somewhere that you typically lose x amount of degrees per 10 feet for 1.5 inch pex. Not the triple wrap or the best that money can buy....just the standard insulated pex.
-
Just temperature drop along without knowing the flow rate doesn't mean much.
-
Per 10ft, well that would have to be a fraction of a degree no matter what.
Some people on here have several hundred feet and would only be looking at a few degrees.
-
I am at 100 feet and loosing about 15 degrees...I'm guessing I need a redo.
-
RSI, not sure what my flow rate is...Ill check when I get home.
-
I should probably add that my circulator pump in non continuous, and I recently added a thermometer to my supply line, inside my house where I change over to copper. I used electrical tape and with some insulation to attach, not sure how accurate it is, especially with the pump not running all the time.
-
15 degree loss in 100 feet of pipe and you are still able to heat the house i would guess flow would be in the 8 to 10 gpm and if that is right you are losing enough heat to heat your home at least half of the days of winter
ill bet that if someone was only heating their home (or at least heating thier home before anything else) that if the heat loss was measured at the outlet (return) of the exchanger in the plenum when the house was calling for heat and the blower was running that the heat loss between feed and outlet would be no more (likley less) than 15 degrees
-
Can't find my gpm...but its a taco 0011-f4. Its an eighth hp @ 3250 rpm....amp 1.76.
-
Does the temperature drop stay the same when the pump runs for a while or does it slowly go up?
If you just have the thermometer on the pipe I would take it to the other end of the pipe and see what it reads there. It is real common for thermometers strapped on a pipe to read low.
-
Does the temperature drop stay the same when the pump runs for a while or does it slowly go up?
If you just have the thermometer on the pipe I would take it to the other end of the pipe and see what it reads there. It is real common for thermometers strapped on a pipe to read low.
I'm not sure...its been so mild my pump doesn't stay on for long....I'm going to check it in the early morning after my pump has been running continuously throughout the night. I was guessing that my reading might not be very accurate.. I used my old thermometer from my stove that I replaced with the led. I placed it on an elbow (just guessing that would be the most accurate). I know I'm at least loosing 10 degrees as I checked it with a buddies heat gun not long after instal and that was the difference.
-
tbone check what the temps are on both sides of your heat exchanger for the furnace when the house is calling for heat. compare this difference to that of your underground pipes...this shoudl give you an idea of what you are losing
-
Infrared thermometers are hard to get an accurate reading on pipes too.
If you can use the same thermometer on the same type surfaces it will be fairly accurate. If you can, insulate around it to keep the air temp from giving a lower reading. If you just compare the offset from the thermometer on the boiler should get you close.
-
Infrared thermometers are hard to get an accurate reading on pipes too.
If you can use the same thermometer on the same type surfaces it will be fairly accurate. If you can, insulate around it to keep the air temp from giving a lower reading. If you just compare the offset from the thermometer on the boiler should get you close.
ok I see what you are saying...good idea. I'll check my pex temp before entering the ground versus my pex temp where it enters my crawlspace exiting the ground.i
-
tbone check what the temps are on both sides of your heat exchanger for the furnace when the house is calling for heat. compare this difference to that of your underground pipes...this shoudl give you an idea of what you are losing
no heat exchanger....I'm h2o heat throughout, cental ac only
-
Anyone know an equation for calculating gpm that doesn't involve knowing BTUs?
-
You can get close going by length and size of pipe (total round trip) number and type of heat exchangers and number of fittings and elbows.
If you list what you have we can try getting a close estimate.
-
You can get close going by length and size of pipe (total round trip) number and type of heat exchangers and number of fittings and elbows.
If you list what you have we can try getting a close estimate.
8 is pretty close, used a drain valve on my supply line about 20' from my pump to fill 4 gal jugs in 30 secs. While running the pump. Low tech but it worked...credit willieg. Thanks for the reply rsi...I was going crazy googlen gpm calculations.
-
You need really accurate temperature readings to get a good estimate on heat loss. How far is it from the boiler to the house?
-
100'....taking several readings from each side to get an average
-
Im going 150ft. and i didnt use the expensive insulated pex. I simply used 1" foam insulation the wrapped with foil backed insulation then put inside a 4" sewer pipe. and buried it . Im only 1 degree diffirent from my boiler to the end of my 150ft. Seems like 15 deegrees over 100' is a bit high, but alot of variables. How is it heating? I have got a 20X28 HX in my furnace and a 12X12 in my garage and also a 20 plate on my hot water heater. Boiler is set at 180 and with shower going/washing machine/ dishwasher/ aand both furnace running my return line temp is between 18-20 drop. It works great... plenty of heat. House is at 74-75, garage is at 70... and hot water never runs out.
-
your pump must be moving a lot of water
-
Willie, if your speaking in ref. to my post here are my pump specs... just a cheap pump.. but seems to be working great:
Three Speed High Performance Circulating Pump
•Removable Integrated Check Valve
•Built-in motor protection for longer life
•Quiet and low power consumption
•Prevents thermal siphoning
•Pump Housing: Cast Iron
•Voltage: 115 V, 60 HZ. Power: 100/70/55w. Motor: 2 Pole, Single Phase
•Min Fluid Temp: 36° F (2° C). Max Fluid Temp: 230° F (110° C). Max Flow: 21.9 (U.S. GPM). Max Head: 19 feet (head). Max Working Pressure: 145 PSI
•Insulation Class: H 356° F (180° C)
Vendor: Stiebel Eltron
-
you are heating your home...your garage and your hot water and when you say they are all running you lose only about 20 degrees, that equals good water flow
-
you are heating your home...your garage and your hot water and when you say they are all running you lose only about 20 degrees, that equals good water flow
.....Or very slow moving air handlers. I'm seeing close to 20* loss in my plenum and almost 7* from my gravity fed side arm.
-
you are heating your home...your garage and your hot water and when you say they are all running you lose only about 20 degrees, that equals good water flow
.....Or very slow moving air handlers. I'm seeing close to 20* loss in my plenum and almost 7* from my gravity fed side arm.
lets say the hot water is being used and it is going through the domestic side at 2 gpm and is only drawing down the water 20 degrees first off lets say the water is 50 degrees goin into the exchanger and is coiming out at 150 that is 100 degree rise in temp and we know to raise 1 pound of water one degree is 1 btu so we are getting 2 gpm so we are getting (for easy figures) 16 pounds of water, so to raise 16 pounds of water 1 degree we need 16 btu to raise the same amount of pounds 100 degrees we need 1600 btu x 60 min. = 96,000 btu per hour ... to keep our heat loss at around 20 degrees in the delivery from the OWB to the return line we would need almost 10 gpm of 180 degree water, lets say we need another 10,000 btu per hour to heat the house and10,000 more for the shop .that would be another 2 gpm so we need 12 gpm to keep up. 12 gpm is about the max recomended for 1 inch pex
-
unless of course, it is late and my figuring is way off (can happen)
-
Air handlers are running high speed fan( as if AC was on) seem to have plenty of air movement with both. pump is 3 speed and i have set on highest speed. just looked at it again this morning. Its 30 degrees outside and house is at 74 and garage at 71 and right now with no hot water being used and furnaces running it 12 degree drop.... but keep in mind when its 25-30 degrees out. My furnaces may only lick on 3-4 times during the day. If i dont turn my blower on in the garage it keeps it 60 just with heat radiationg of the coil. House is same way. It stays 68 with blower off. Amazing how much radiant heat they put off without blowing air.
-
TBONE talks about his pump not running 24/7?? I think that would be a lot less efficiant cycling the pump. Isnt it better to keep that water moving and keep everything hot. that way when blowers kick on or demand for DWH then you have instant heat? I would think with it cycling like he is that just getting everything heated up would take alot of heat away. I can fully understand why hes having such a temp drop. He should try letting pump run 24/7. Im guessing he will see a huge improvement. Tbone.. what are the depth of your lines. I know someone on here posted that it doesnt help to have lines real deep in ground but in my case im at 5 1/2 ft. but im also inside a 4" PVC. Just wondering. anybody think running it 24/7 be better?????
-
Yes running it 24/7 is best. Many reasons for that. Back in the old days before good insulated line they all wired the pumps to the inside thermostat so that they wouldn't lose heat to the ground all the time.
Did u get my email? U can private message me on the board
-
TBONE talks about his pump not running 24/7?? I think that would be a lot less efficiant cycling the pump. Isnt it better to keep that water moving and keep everything hot. that way when blowers kick on or demand for DWH then you have instant heat? I would think with it cycling like he is that just getting everything heated up would take alot of heat away. I can fully understand why hes having such a temp drop. He should try letting pump run 24/7. Im guessing he will see a huge improvement. Tbone.. what are the depth of your lines. I know someone on here posted that it doesnt help to have lines real deep in ground but in my case im at 5 1/2 ft. but im also inside a 4" PVC. Just wondering. anybody think running it 24/7 be better?????
I use a lot more wood running 24/7...maybe when I get new lines I will try it again. I was off work yesterday and checking my temps. I forgot to turn my pump off and and went to cut a load of wood. I only had a few pieces of wood in my stove but plenty to get me through the day as the temps were mild here yesterday. When I returned home, I checked my stove and It was out of wood.. Then I figured out what had happened.
-
WOW... really. I can get 18hrs burn time when it 30+ degrees out. When its 10 degrees and under it will burn easily 12 hrs on a fill. How big is your firebox?
-
WOW... really. I can get 18hrs burn time when it 30+ degrees out. When its 10 degrees and under it will burn easily 12 hrs on a fill. How big is your firebox?
I can go 16hrs when its in the 30s with a full firebox...when its mild during the day I usually just add a few pieces in the morning which carries me through until nightfall. That is if me pump isn't running continuously.
-
I figured out my average temp lose is about 12 degrees with the pump running, I agree I could probably shave a couple of degrees off this by running 24/7...however I would consume more fuel.
-
WOW... really. I can get 18hrs burn time when it 30+ degrees out. When its 10 degrees and under it will burn easily 12 hrs on a fill. How big is your firebox?
firebox is 3'X28"....I can go 24 hours if I add coal to the mix.
-
Have you moved the thermometer to both ends of the pipe to make sure you are getting accurate readings? Also you should do the same on the return because some of the heat is probably going back into the return instead of the ground. If you have the pex touching together all the way then you could get a few degree temp drop just from that.
-
Yup better listen to RSI on this one. Based on what I'm reading there still hasn't been an accurate way of testing the temps. There are a lot of variables
-
i do agree that if your pipes are wet there will be a heat gain in the return line but even so if you were losing only half of 30 or 40,000 btu per hour you are losing enough heat to heat your home on many winter days...you are losing too much
-
Have you moved the thermometer to both ends of the pipe to make sure you are getting accurate readings? Also you should do the same on the return because some of the heat is probably going back into the return instead of the ground. If you have the pex touching together all the way then you could get a few degree temp drop just from that.
RSI,
I have, I measured an 8 degree difference on average at the back of my stove (pex supply line before entering the ground). This gave me an average temp drop of 12 degrees. I will check my return temps..the pex are touching inside the pvc.
-
If your using good piping , you should see less than 5* loss over 150-200' run. I have seen 3 degree loss in 300' runs, with velocity at 3 feet per second. Speed it up to 4.5 fps and it is less. If your using good pipe there will be virtually no heat transfer between the 2 headers as they will be isolated, not touching. If you have less than 15* differential on boiler side (S&R) of plate then velocity is too high, more than 25* and its too slow