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Author Topic: Flat plate question  (Read 12818 times)

wreckit87

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Re: Flat plate question
« Reply #30 on: December 06, 2017, 06:35:37 PM »

No heat loss calc was done. As far as the primary/secondary deal, that was my thought if the return temps end up being too low. The building will still require the same amount of flow P/S or not, so the way I see it there will be no benefit unless the return temps are too low but perhaps I'm missing something. Huge delta shouldn't hurt the boiler as long as return temps are above condensation right? The damper will probably be open forever, but if the same load is applied to the other end, I'm thinking the boiler is going to run just as often with P/S as it would in a single loop
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wreckit87

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Re: Flat plate question
« Reply #31 on: December 06, 2017, 06:39:21 PM »

Woodman has your question been answered? I only brought up my deal to say I might have an example in the near future- totally wasn't planning on hijacking your thread. I'd rather keep on your topic if you're still needing information
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woodman

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Re: Flat plate question
« Reply #32 on: December 06, 2017, 06:55:33 PM »

Woodman has your question been answered? I only brought up my deal to say I might have an example in the near future- totally wasn't planning on hijacking your thread. I'd rather keep on your topic if you're still needing information

I think I am good. I have a hx on order but will be out of town for a couple weeks so it may take a while before I can report back, between vacations and Christmas. It's fine with me to keep this thread going the direction it is. It will be interesting to see how this turns out. I too have a very large and complex heat load and am making changes to address some of the possible problems I think your customer may run into. It will be interesting to compare notes when both are up and running.
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E Yoder

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Re: Flat plate question
« Reply #33 on: December 07, 2017, 07:16:01 AM »

No heat loss calc was done. As far as the primary/secondary deal, that was my thought if the return temps end up being too low. The building will still require the same amount of flow P/S or not, so the way I see it there will be no benefit unless the return temps are too low but perhaps I'm missing something. Huge delta shouldn't hurt the boiler as long as return temps are above condensation right? The damper will probably be open forever, but if the same load is applied to the other end, I'm thinking the boiler is going to run just as often with P/S as it would in a single loop
My thought with P/S was that if the radiant ran at a lower temp than typical 180 furnace temp you could could mix down at the manifolds and supply in from the owb at 180, back at perhaps 120 or 140 (or whatever the return floor temps are). Your delta can double or triple and the primary loop prevents condensation. The huge delta reduces the required flow rate to move the same btu's.
But this is all depending on the mixed down radiant temps. So may or may not be of much use. Almost an injection mixing idea.
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wreckit87

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Re: Flat plate question
« Reply #34 on: December 07, 2017, 07:53:41 AM »

Yoder, I think we may be on different pages. My boiler loop here hits the domestic HX first, then to the A/W in the furnace, then to the 200k unit heater in the shop, then the 10x20" HX before going back to the boiler, all in series. If there is P/S at the boiler, the heat loss will be the same through the building as it is now, so the temps in the underground loop would be identical regardless of how it's piped at the boiler, right? The radiant is all run in a closed system (you know how I like atmospheric radiant) off of that 10x20 HX, with all 3 zones having their own pump and mixing valve. I'll start with all 3 zones at 100 degrees as a baseline and see how it performs, that way the flow rate through the boiler loop remains the same regardless of load. P/S inside the mechanical room may have a little benefit from a no-load flow standpoint, but P/S at the boiler would only be for boiler protection if the return temps get to be too low due to the huge delta T. With all 3 radiant zones pulling at once, say 100 degrees, while the boiler loop is hypothetically still 170 into the 10x20 HX at 7 GPM, we're still looking at only 6-8 GPM through the plate on the radiant side instead of the full 15 because much of the return water will be recycled. With that, let's call it 80 degree return temps from the floor. Doesn't take a ton of new heat to inject from the plate to make it back to 100 right? So even if I'm getting 130 off the plate, should still be great plenty to feed all 3 zones while keeping the boiler loop above condensing temps. This is why I push closed systems, to keep max flow in the boiler loop. I spent many a night awake designing this system to work with what he's got, and I'm fairly certain it'll work just fine. The unit heater in the shop will almost never run at the same time as the 21 loops of radiant in there, it's only backup if he brings a semi in and wants to heat it up quick- at which point the air temp would satisfy the radiant stat and shut it down, so that's a huge weight lifted right there
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E Yoder

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Re: Flat plate question
« Reply #35 on: December 07, 2017, 09:00:17 AM »

Makes sense.
I mentioned P/S at the owb for return water protection, not to change the BTU load.
The main loop to the building doesn't change temp or delta whether it's one loop or P/S like you said. And yeah, it would need the flow you mentioned to be enough for dhw and fan coils. I missed that, Duh Eldon.
You've got a good plan, sorry about the bunny trail.
« Last Edit: December 07, 2017, 11:02:26 AM by E Yoder »
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E Yoder

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Re: Flat plate question
« Reply #36 on: December 07, 2017, 04:13:01 PM »

Something more on subject-
I'd love to find a flat plate sizing calculator online to input various flow rates and temps and it would give you BTU rates, delta t, pressure drop. I can email our supplier but it's slow.
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hondaracer2oo4

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Re: Flat plate question
« Reply #37 on: December 07, 2017, 04:53:16 PM »

Yoder. Can the company  give you the equation they use?
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wreckit87

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Re: Flat plate question
« Reply #38 on: December 07, 2017, 09:37:05 PM »

That would be a fantastic option. I'd love to have it simplified vs guessing but I feel the variables may be too great?
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E Yoder

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Re: Flat plate question
« Reply #39 on: December 08, 2017, 07:04:30 AM »

I don't know what formula they use, there would be quite a few #'s in the mix. And flat plate sizes. Probably would have to buy a program.
Would be interesting to swap plate numbers , sizes and watch the output temps change..
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wreckit87

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Re: Flat plate question
« Reply #40 on: December 08, 2017, 07:37:33 AM »

Here is the cluster in question Yoder, just finished piping last night. Waiting on insulation and the OWB delivery before I can fire it up and put it to work
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E Yoder

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Re: Flat plate question
« Reply #41 on: December 08, 2017, 08:40:42 AM »

 :thumbup:

How many feet of the 1" Thermopex underground?
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wreckit87

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Re: Flat plate question
« Reply #42 on: December 08, 2017, 08:59:42 AM »

Too many. I think he said 170ft  :-\ Looking at some online calculator thing this morning, it's looking to me like even if I'm able to keep 7 GPM through the boiler loop and put 170 into the plate, the return temps will need to be down in the 110 range in order to get 130 out of the plate on the radiant side  :bash: Looks like P/S is in order. 15-58FC in the primary between supply and return ports with a pair of closely spaced tees and a 26-99FC pumping the secondary loop to the building? I can honestly say I've never done a P/S at the wood boiler before.
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E Yoder

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Re: Flat plate question
« Reply #43 on: December 08, 2017, 09:55:16 AM »

That's kinda the temps I was (very roughly) guessing would be if everything runs at once. I see why you wanted bigger piping, I'm sure it'll heat though. Post some temps when you fire up.
We did a 400'+ one way run with 1" Pex this year, less than 3 gpm with an NRF-25, got 130℉ domestic water by doubling flat plates in series, but ran a huge delta t during showers. Extra large heat exchangers were cheaper than larger pipe.

I've never done P/S in the back of an OWB either.
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wreckit87

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Re: Flat plate question
« Reply #44 on: December 08, 2017, 10:51:29 AM »

That's kinda the temps I was (very roughly) guessing would be if everything runs at once. I see why you wanted bigger piping, I'm sure it'll heat though. Post some temps when you fire up.
We did a 400'+ one way run with 1" Pex this year, less than 3 gpm with an NRF-25, got 130℉ domestic water by doubling flat plates in series, but ran a huge delta t during showers. Extra large heat exchangers were cheaper than larger pipe.

I've never done P/S in the back of an OWB either.

You got 3 GPM out of an 800+ ft loop of 1" with an NRF-25?!?! That's incredible! It'll be a couple weeks before I get this contraption fired up probably. Sounds like they're going to start insulating next week sometime and sheeting the lid toward the end of next week. Overhead doors are 2 weeks out yet, but I think he's going to double poly the openings until then if we need heat. Kind of a cluster, because I need water to fill the boiler but the well guys need heat to turn the water on lol. Once it's insulated I think we'll Nipco heat it up for a day and get the water on, then I can get the boiler fired and at least run the unit heater for awhile while I purge the floors and whatnot. As far as the P/S goes I just ordered parts a half hour ago here, I think a 1" copper loop between the supply and return ports at the boiler with a 15-58 in 3rd gear, and a pair of closely spaced tees with a 26-99 in 3rd gear running the building loop. Temp gauges on the supply and return lines of the building loop and another gauge on the return port of the primary loop to keep an eye on the mixed return water. Should keep everything in check, I hope
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