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Author Topic: Flat plate question  (Read 12815 times)

E Yoder

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Re: Flat plate question
« Reply #45 on: December 08, 2017, 02:37:02 PM »

I'm guessing it was about 2.5. According to the charts the resistance dropped off dramatically when the velocity got that low. So I tried it, through two flat plates, close tees for house blower coils loop  and back to the owb.
And I didn't measure the flow, just what I calculated on that distance with the NRF-25 pump curve. A 26-99 would have gained a bit more than 1 gpm if I remember right. Would have never gotten air out except it's all uphill to the OWB.
Customer says it's heating well and has good hot water, but I'll bet the delta t climbs to 80+ degrees at times. A new house so the heat load isn't very high. Domestic water is the big one. First flat plate pulled the domestic up to maybe 100, second up to 130-ish. Not as hot as normal, but it'll do.

That sounds like a fun one, juggling everything. With new construction seems like its always hurry up and wait.  :)
« Last Edit: December 08, 2017, 02:40:42 PM by E Yoder »
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RSI

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Re: Flat plate question
« Reply #46 on: December 08, 2017, 04:24:29 PM »

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.
I would put the new 15-58 pump from supply to return at the boiler but only connect the main loop into the return and leave both pumps drawing directly out of the boiler. That would get you more hot water to mix before it goes back into the stove return and also won't lose heat if the extra pump dies.
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E Yoder

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Re: Flat plate question
« Reply #47 on: December 08, 2017, 04:31:50 PM »

  :post:
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schoppy

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Re: Flat plate question
« Reply #48 on: December 08, 2017, 11:44:27 PM »

Been busy on a friends install. Not sure what you were disagreeing with after my post on page 2 wreckit? No plates are 100% efficient, check the manufacturer specs.  My 10 plate (5"x12") produces hot water temps in excess of 145 with single use drawing from it. It drops if multiple faucets are used at the same time. My set up is a primary 1 1/4" pex line in the basement with secondary 1" pex lines using monoflo tees to feed each of my loads, DHW is first load. I only have 1" pex coming from the OWB and upsized to 1 1/4" in the basement and shed once indoors. Would have buried 11/4'  but got some ill advice on my first install.   
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schoppy

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Re: Flat plate question
« Reply #49 on: December 08, 2017, 11:59:33 PM »

One more thing. As I mentioned my 10 plate is in the hot discharge of my water heater. If installed in the cold inlet to use the w/h as a storage tank you usually have to leave the water heater on or the temp drop in idle time, i.e. overnight or gone at work all day, will leave you with tepid water when you go to use it. I shut my breaker off to the w/h for additional savings during the heating season.   
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wreckit87

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Re: Flat plate question
« Reply #50 on: December 09, 2017, 08:34:08 AM »

My disagreement schoppy, was that temps can absolutely be matched across a plate if properly sized. With my 40 plate at home, I checked it a couple weeks ago to have this discussion elsewhere and with the shower running, I had 168 coming off the plate into the tank. At the same moment, I had 168 coming into the plate from the boiler. Exact temp match. That's my residential example. I work commercially as a pipefitter and build hydronic systems every day, and I can assure you that there are thousands of commercially installed exchangers out there that match temp as well. Most are shell and tube design, but there are a handful of gasketed plates out there as well. As for the storage ordeal, that is a very common misconception. I fill my tank with 160-170 degree water, but it'll last a week in there without firing up the burner. To prove this point, I shut the gas valve off to my water heater last year and used a ton of hot water the day before I left for Aruba. I was gone for 6 days, and had enough hot water left to shower when I got home. I think having my plate below the WH allows for some thermosiphon, because the line is always hot.


RSI, I don't see how that would be of any benefit? First, it would eliminate hydraulic separation. Second, if the 15-58 dies the 26-99 will still pull the same water from the boiler right through the 15-58 while piped with closely spaced tees. What am I not seeing?
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E Yoder

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Re: Flat plate question
« Reply #51 on: December 09, 2017, 08:43:23 AM »

I think in most residential applications cost dictates that the exchanger is sized to not attempt to match temps during a load. Maybe that's what we're missing each other here?
How would the 26-99 pull through through the 15-58? Wouldn't it just recirc back through the tees? With the assumption the goal was higher return temps, not hydraulic separation.
« Last Edit: December 09, 2017, 08:45:08 AM by E Yoder »
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RSI

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Re: Flat plate question
« Reply #52 on: December 09, 2017, 09:09:19 AM »

I thought the point of adding the pump was for a higher return temp. Why does hydraulic separation matter. If setup like I suggested, you could even put a sensor on the return pipe and only need to run that pump when the return temp drops way down. If there is some other reason than simply not wanting cold water being returned into the boiler then primary/secondary setup may be better.
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wreckit87

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Re: Flat plate question
« Reply #53 on: December 09, 2017, 09:33:54 AM »

I guess my thought behind the close tees/ hydraulic separation is that if the 15-58 would die, the 26-99 wouldn't recirc through the tees because it is hydraulically separated. But then again as RSI pointed out, there really is no need if piped in that fashion. Very good points guys, thanks
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hondaracer2oo4

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Re: Flat plate question
« Reply #54 on: December 13, 2017, 06:51:09 PM »

Will this work for you Eldon for a flat plate sizer?
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E Yoder

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Re: Flat plate question
« Reply #55 on: December 13, 2017, 08:08:53 PM »

Hmm.. I'll check it out. Thanks.
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E Yoder

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Re: Flat plate question
« Reply #56 on: December 16, 2017, 09:23:27 AM »

Trying to figure out their model #'s but this is very useful. Thanks, Honda.
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hondaracer2oo4

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Re: Flat plate question
« Reply #57 on: December 16, 2017, 06:30:50 PM »

No problem. Took a little digging to find it again but that is what I used when I sized mine.
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E Yoder

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Re: Flat plate question
« Reply #58 on: December 16, 2017, 07:39:44 PM »

What I'm seeing is they size their models that don't quite fit the dimensions I use.. but it's a good place to start.
I actually already had a password, but forgot I had used it in the past. My brain's getting fuzzy in my old age I think.
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schoppy

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Re: Flat plate question
« Reply #59 on: December 23, 2017, 10:04:38 PM »

Just getting back from Texas where it was almost as cold there as here in Wisconsin before this weekend anyway.

Well wreckit87 if you want to put in a 40 plate heat exchanger that's rated anywhere from 250,000 to 400,000 BTUH at close to twice the price for a 40,000 BTUH water heater you could probably keep incoming and outgoing temps very close to the same. But installing it in the cold inlet to the w/h you still need to keep your water heater on to prevent tepid water during prolonged off cycles. Extreme overkill in my opinion.

E Yoder you hit the nail on the head with properly sizing equipment to loads. 
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