Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: sceptre74 on November 05, 2014, 03:35:21 PM
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I'm about ready to hookup my in slab radiant heat in my shop for the first time. I have 6 loops of approximately 250 ft. I'm using a 50 plate off the bl 2840 and that will be hooked up to this manifold. http://www.ebay.com/itm/360791092709? (http://www.ebay.com/itm/360791092709?) Since this unit has adjustable flow rates built in, what should I be setting each loop at? I'll be installing a mixing valve so what should my supply and return temps be at the manifold? Sorry for all the questions. Not the least bit familiar with this kind of system. Thanks
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I would think you would want more heat by your doors. I am running mine at 80 in and have 75 coming back. Expect a lot lower return temps when you start. Takes my 28 x 40 shop 2 days to come to temp, that's when it's 40 outside. I have one ft on center in front of my doors and 18" in the middle.
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So the loop by the doors should be on a higher gpm than the others? I went with 12 inches on center for all the loops. Can the supply be warmer than 80? I was planning on setting it at 110. Like I said, totally clueless with this stuff so expect many more questions.
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If they are all evenly spaced and you have flow meters on each loop and can increase the flow at the doors then by all means do so, the lower the supply the better as long as you can satisfy the demand, 80 is low but no more than 130 F
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I at least have somewhere to start now. Thanks guys
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I Have my shop slab set at 120 on the supply line. and tubing spaced about 12" apart. This will work just fine for you also....
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I have my sidewalk set at 125F and it works just fine, indoor linesets can probably run a little lower.
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In the past when I installed (in-slab) the perimeter would get 6" OC spacing for the first couple feet or passes, then switch to 9" or 12" depending on size of slab. FUTURE RREFERENCE
OK, I will assume a few things and hopefully point out some pros & cons, along the way
1) Supply water temp of 80f (probably a bit low); in-slab can easily be run with 120f water going into floor (looking for a delta T across supply vs return, to reduce stirping and maintain an even heat across all of the slab)
*Use of a thermostatic mixing valve (purely MECHANICAL and only allows you to control the inlet temperature)
*Use of a powered or actuating mixing valve (may allows for out door reset, control of delta T & max temperatures) -> CAN GET COMPLICATED AND REQUIRE ADDITION ELECTRONICS TO CONTROL
2) You say all loops are approximately the same length, GREAT start
Now about the balancing, I would start off with all loops having the same flow (wide open as possible) and allow the system a few days to get up to temperature and see how the shop feels. Big question is do you know which loops feed which areas because it greatly affects the next step. If there are any noticably cold areas, what you can do is slow down some of the other loops that do NOT go to the cold area. Again give a few days between adjustments, as slabs have SLOW reaction times
***My shop is 48'x80' with an office off one end (4k sf), if I start heating early enough building comes up to temperature within a day. However the first year of heating that building we had a fwe hiccups in the system and did not get started until after it had been 40f outside for a week. Took 2 solid days of runing the OWB wide open to get that slab up to temp; but once it gets there, it stays there :thumbup: (other than some afternoon solar gains)
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All runs are with in 20 to 30 feet of each other in length and no more than 250. We ran them starting on the outside and worked our way in as we went. Looked around for plans on laying them out and never really found anything to go by. I will be using a mechanical mixing valve and running it around 110 to 120. Hope to have it up and running by the end of next week
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All runs are with in 20 to 30 feet of each other in length and no more than 150. We ran them starting on the outside and worked our way in as we went. Looked around for plans on laying them out and never really found anything to go by. I will be using a mechanical mixing valve and running it around 110 to 120. Hope to have it up and running by the end of next week
You get a star, for running loops from Outside of building to Inside (putting hottest water near largest expected heat loss)
You get a 2nd star for keeping loops so close in length (since you are in slab, probably would not even need to balance, but since you have the manifold its nice to use the flow valves as a good gauge of if system is working or not)
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Set all your flow meters to 75% then balance from there. Make your mix V easy to adjust. I was just servicing a greenhouse yesterday and they run 180 in and 150 out till it comes up to temp , then 150-155 supply.
Their MV was way too small so I put ball valves in instead.( homemade mixing valve) and will handle all the flow the pump can do at a quarter of the price of a MV that can handle the required flow. Now it only take 4-5 hours to come up to temp from a cold start instead of a week. They have 5/8" viega pex @ 9" centers. It's 15 years old and not a crack in it. Not sure if it's better Crete or standard 3000psi stuff. Anyways they now can run much lower temps and get fast response. Their pex is on chairs in the pictures so not at the bottom of the concrete and foam except for the ends of the greenhouse. They have some lag time. Double of the rest of the GH. The FLIR is handy for balancing
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Got things hooked up and running this morning. The temp inside and out was 40. I have a 26 99 on the boiler side and a 15 58 on the slab side of the hx. Speeds are set on high on both. The supply temp is set at 120 and the return is coming back at 80 right now. Flow is 3 gpm on each loop. Does all this sound about right?
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A delta of 40F is a bit high, but not unrealistic since from what you describe as a "COLD" slab to start with.
Question, you say you are getting 3gpm per loop??
That mean your floor is sucking up something like 360k Btu/Hr -> (3gpm x 6 loops) x 40f x 500
Combine that with what sounds like a 1500 sf building, 6 loop x 250' @ 12OC
(360000BTU/hr)/(1500sf) = 240BTU/sf :o- That is Snowmelt type numbers
**I am not saying any of your numbers are wrong, but they do seem HIGH! How has your OWB been reacting, has it been gobbling (could not hold back, so close to Thanksgiving ;D) up the wood!
There is nothing wrong with running with your the delta T that high, but a few draw backs are as follows;
1) May feel warm and cool spots in floor, or may notice heat striping
2) Your OWB my not be able to maintain its setpoint with water coming back so cold
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That's what I'm fearing. Is there anything I can do to improve my delta T?
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Generally you just increase GPM, but if you are at 3 gpm, you may not be able to go any faster.
How has you OWB been reacting, does it seem like it is struggling to keep up or has it been puttering along??
After a while does the return temperature start to come up or does it stay way down at 80f??
*If slab is "cold", it may take a while to before you start getting decent return temps; but once you get it there, it will only take small amounts of heat to keep a constant temperature
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It chewed through a fair bit of wood yesterday. I have it set at 195 with a 10 degree dif and sometimes it would dip down to 175. It would only idle for maybe 10 minutes at a time. The return got to 80 last night and I shut it down because the temp inside was at 55 and I'm away from the house for the day so not there to feed it. Outside temps are at 65 today but back down to the 30's tonight. I'll get it going again tomorrow and see how it goes from there
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So it's been a couple of weeks since I've been up and running and my delta really hasn't changed. I dropped my supply to 100 and the the return temp at startup is around 60 and never gets much above 80. I do have to say that there isn't a call for heat too often either. Maybe twice a day at the most so far. I'm assuming this is why the return temp is so low at start up. Do any of you see any issues in my future?
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Figured I'd add a pic of my setup incase I did something wrong.
(http://i1375.photobucket.com/albums/ag443/sceptre74/Mobile%20Uploads/IMG_20141208_112222_zps3c8f5d04.jpg)
(picture posting corrected by Sloppy. :thumbup:)
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So it's been a couple of weeks since I've been up and running and my delta really hasn't changed. I dropped my supply to 100 and the the return temp at startup is around 60 and never gets much above 80. I do have to say that there isn't a call for heat too often either. Maybe twice a day at the most so far. I'm assuming this is why the return temp is so low at start up. Do any of you see any issues in my future?
Sounds good, but u might have lag time on colder or windy days. It looks like the mixing valve is your limiting/choking factor. Find out what it's flow rate is......meaning I have replaced many of those due to lack of heat problems. They forget that they can only flow so many GPM before the head loss skyrockets. An the circ can't move anymore, even tho the circ will flow way more at lower HL. If it takes more than 6 hours for return temp to be within 10-20' of supply,and air temp is a problem, that's where u look. Good luck, looks nice
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Thanks sprinter. Without the help of members here I'd still be scratching my head. Lol. I'll check to see if I can find the flow rates on it. I seen another post you commented on that you used ball valves to maximize flow and still get the desired temp. I just may have to go that route if it becomes a problem
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I've been keeping an eye on my delta with the infloor and the best I've seen it get to is 36. So this is what I'm thinking of doing. All 6 loops in the floor have water flowing the same direction. Would it help or make any difference of I were to change the flow of 3 of them in the opposite direction? Loops 1 3 and 5 flowing the same way and loops 2 4 and 6 the opposite direction. Thanks
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1/2 gallon a minute is fast enough!!! any faster and the heat don't get a chance to deliver !! .. heat the "perimeter" 1st try for a D-T of 20 degs ! ....110 degs is what my 4way/w/outdoor reset, is feeding my floor rite now ..and its 30 below out !!
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Chatting with another member last night and he figures my pump isn't quite big enough. I'm sending it at about 1 gpm. Gonna try a bigger one to see if it tightens that number up. Thanks
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I have 2000' of muilt core 1/2" pex on the same pump u have ...just saying..
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Chatting with another member last night and he figures my pump isn't quite big enough. I'm sending it at about 1 gpm. Gonna try a bigger one to see if it tightens that number up. Thanks
1 GPM is plenty fast, like ATVALASKA -> don't sorry so much about GPM, focus more on your Delta T. As long as your delta T is less than 20f, you should be in the ball park.
My dad is running 14 loops of 1/2" - 300's off of an Alpha and each loop is seeing about 1/2 to 3/4 of a GPM, with no complaints of house being cold
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If I don't increase the gpm's how will I get my delta T lower? A return of 82 is the highest I've seen it so far.
The building is plenty warm but I'm worried about straining the boiler. I spoke with Robert at P & M and suggested I install a diverted valve to send supply water to mix with the return after it leaves the return side of the floor. Hopefully this will make it easier on the owb
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If I don't increase the gpm's how will I get my delta T lower? A return of 82 is the highest I've seen it so far...
When you say return of 82, do you mean at the manifold or on the OWB side of the FPHE??
C- If only the manifold return temp is 82, I would not worry too much
- If the water coming out of the Return side of the FPHE is 80, then I would get concerned
- What are the temperatrures on all 4 ports of the FPHE, after about 5 minute of the start of a call for heat??
...as long as the water going back to the OWB is at or above 140f, you should not see any long term issues (before 140f condensation can occur in the reaction chamber and lead to RUST -> and welding). May need to turn up the pump between the OWB and the FPHE.
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It's the return on the manifold that is 82 degrees. The return on the owb side of the hx usually doesn't go any lower than 165. When the boiler shuts back off at the 195 set point the return is around 175 to 180
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It's the return on the manifold that is 82 degrees. The return on the owb side of the hx usually doesn't go any lower than 165. When the boiler shuts back off at the 195 set point the return is around 175 to 180
Ok, glad you are not putting you boiler at risk, by having return water too low. ;D
Now I see no real problem with the Return manifold being at 82, but what is the approximate temperature of your Supply Manifold? ALSO, as long as the wife and OWB are both happy and working, GREAT JOB :thumbup: :thumbup:
If its much above 105 or so I would either; turn up your pump and see if delta T drops, or depending on where your Mixing Valve is set turn it up and see if that also brings up the return temps.
If the Delta T across the 2 manifolds is at or around 20f that is good; you can run with larger delta t's but beware you may get following HOT/COLD spots in the slab and/or heat stripping, and is generally not recommmend.
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The supply is at 110 and the pump us oh high already. I might still pick up a 26-99 to see if a little more flow tightens it up. I'm also figuring the diverter valve will restrict the flow somewhat so it might be necessary.