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[atvalaska]

I got the house tied to the shop ...both have the same set up, both slabs are 1200sf shop at 69degs an the house @60 ...so we can hang the VB ,and rock...last winter I burned just a hair over 4cords to keep the shop happy from 4oct to mid April...in the last 22days I have burned 2 cords never split a  piece last year or this , they burn great whole !!! That's from start up to now ...them 1st 4 days bringing the house slab from 28 to mid 60degs  sure ate some wood !!! I'm hoping that is what took most of the wood....other wise I'm going to be in the logging business next spring ! ...like I have said before I burn a mix of wood and coal - and I just started my coal mix last weekend here is what I found  a gallon or two of coal mixed in works great /keeps the fire going to much coal = all your wood gone in a hurry !.... I did try a burn that  went like this I gathered the hot charcoal that was left from  a wood burn and slide it to the back of my boiler than I added coal about 5" deep and 14" wide all the way to my door /so the fire would burn like one of those  black 4th of July snakes or a cheap cigar .. well it worked somewhat …. it lit on the far end but it would not get hot enough to shut the fans off -it just hung at 145 to 150 . test over as I was running of  time and needed the fire going as it is/was 5below outside…...so I added wood and stirred it up ...well it got hot> and burned the wood “quick like”…..like I said above ...my next test will be with more coal ;burning the same way  using…… maybe two 5gal buckets worth of coal end to end ……… that may keep up… but I’m a bit worried if all the coal got going I would be wrecking something/no where for all the heat to go  !  >>> btw  the temp at the boiler... and  the shop and house  "loop" are the same  maybe a deg off on the coldest of dayz

[cartod]

bringing a slab to temp will burn a whole bunch, especially if the slab is not insulated properly. 

[atvalaska]

It does 4" foam under and 2" on all sides...another 2" around the whole  premierer..cold has some work to do to get to me!

[U.P. Doug]

I rented a house here for a year. They had a Woodmaster 4400 installed in a new cape cod and they had radiant heat in the basement. The house had r-60 in the roof and r- 30 in the walls as well as insulation under the basement floor. Loved the warm floor, but whenever it called for heat the boiler had a hard time keeping up and I had to feed it tons of wood. I ended up turning the thermostat down to 55 as the basement was used for storage for us. My wood use went way down just heating the plate in the house boiler and my domestic water.

[hondaracer2oo4]

Once the slab got up to temp it should have not been hard on wood usage to keep it there. Were you changing the room temp served by the radiant? They say you have to keep slab radiant bassicly at the same temp all the time, can't knock it back at night and bump it up during the day

[U.P. Doug]

I had set it to 70 degrees and left it there. When the slab called for heat the boiler could not keep up with the demand. If I remember right the water going into the loops under the slab was 170 going in at the loop pump and 125 when it returned to the main loop.

[hondaracer2oo4]

How many loops in the slab? Should have had less then 20 degree drop in each loop in the slab.

[U.P. Doug]

Testing my memory here, but I believe it had a copper manifold around 2" diameter and there were around 8 to 10 per feed lines coming from that going under the slab running the length than returning down the other side to a similar manifold then returning to the main loop. There was a pump for this loop and he had temperature gauges on the feed side and return side.

[hondaracer2oo4]

You were heating the slab with straight 170 degree water??

[atvalaska]

120 water for me ...170is killing something IMO , I have the slab floor at 60  it is going well now ....I did a coal test this weekend and  it ran thu 90 pounds of coal in 12hours 

[hondaracer2oo4]

i don't have radiant, but from what I have read you want to run the slab at just high enough temp to allow the slab to meet the demand of the thermostat and not over shoot the temp. I see people running 80-110 degrees through their slabs.

[willieG]

the lower your feed water into the slab the less btu of output the floor has. I have no real idea but I would agree that you want to be able to meet the demand for the room and have the loop "idle" some but not too much. I start my loop at about 100 and as winter sets in I bump it to 110

most charts indicate water temps going into a slab at 90 degrees will output 10 btu per square foot...110 degrees, 20 btu, 130 degrees 30+ btu and 150 degrees will emit 40+ btu per square foot (this is if spacing for the size of pipe in your slab is followed per normal spacings)

[intensedrive]

Yes I suck... My whole system is a mess.. Probably gallons of water in my lines.  Fired up the boiler October 15... I burned approx 2 1/2 cords until now. I'm trying to figure out heat lose from the boiler to the home.  My only test is to feel the lines before entering the furnace.  They feel much colder than normal.  I can also base the heat of the lines by feeling the register heat which feels colder , and it feels modishly warm.  Also if you ran a boiler long enough you can judge time between furnace blower cycles.  If some one can help me temp the system from boiler to air heat ex-changer.  The pex does create a insulated problem, meaning you can temp the outside of the pex but not the true temp of the water flowing through them.

[hondaracer2oo4]

IR guns when placed with the sensor right onto the pex have been very accurate at reading the actual temp of the water. Make sure that before you test the temp on pex that you peel away the pipe insulation and test that spot.

[mlappin]

Guess I must be mislead, but I thought much over 130 water in a slab was a no-no.

Went to birthday party a few weeks back, was in a friends new shop, has been set at 65 for weeks before that, was 67 in the shop, hated it the whole time. 5 minutes after I was in there my feet were sweating something horrible, even had thin socks on. I don’t get cold feet though, have even stepped outside in barefeet in the winter for something and walked on hard packed snow.