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Author Topic: Configuration advice for new system  (Read 3162 times)

greasemonkoid

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Configuration advice for new system
« on: January 07, 2018, 12:38:52 AM »

First, much thanks to those who take the time to donate your knowledge and experience. I've got a NCB-175 on the way (and sacrificed dearly for it) and a lot left on the parts list. I'm having trouble arriving at a solid conclusion on number of pumps and loops to meet the heating needs, so any responses could potentially save me hundereds on the parts list along with wasted time so - thanks in advance!


Here is the application:

VERY leaky 2500 sq/ft house, 2 floor, and built in '72. Air handler for the heat pump is in the attic - I refuse to put a HX in the plenum (for a number of reasons, including my peculiar logic ???)

I had hope for the NCB-175 heating the entire house on a 0*F day comfortably, doubt it will happen, but might get close. Of all the online calculators I get an average of 240k btu requirement on the worst possible day.

1. Primary HX, manufacturer claims 200k btu, it is a unit heater with big fan. This is overkill I'm sure, had plans of changing fan motor to 3 phase with an eaton motor drive to have full rpm control. This will basically be replacing what the wood stove was doing and in same vicinity.

2. Second, HX air will be pumped through the floor, center of house, the unit claims 100k btu, the inline blower pulling the air is 440 cfm and can't (doesn't need to be) changed.

3. Third, domestic hot water,, already configured in an unorthodox (but proven effective) manner. The details are probably irrelevant, but it does have a circ pump and differential temp controller from previous setup. A plate HX will be used along with another separate pump - water heater tank cannot overheat this way.

4. Low priority so lower performance is acceptable - shop HX. The unit I have is a 150k (claimed) and way overkill because the small (affordable) units have all been sold out, so I went BIG.


Being mindful of the implications that exist with the way I wanted to set this up, I see the status quo seems to be leaving the pump running 24/7, >150* return temps, and ~20* deltaT. There seems to be an obstacle with every good configuration that I've come up with, but here is my best thought -


1-2 and 3-4 are within close proximity to each other, and all entering the house at same location.

1 and 2 will need total loop length of about 150'. 3 and 4 will need total loop length of 70'

OWB feet are 7' higher than 1,2,3,4.

The underground pex I have is 1"

My math shows up as an estimated 12.5' effective head. Flow through 1 and 2 need to be 15gpm combined (according to my math). I was thinking it may be best to run a grundfos 26-99 through two loops paralleled coming off that same pump to feed #1 and #2. By some means a filter would be nice to add here.

3 and 4 may best be together on same loop (1") due to their location being within a couple feet and priority level the same. A grundfos ups15-58 for these?


OR


Would it just be better to run a 15-58 for #1, and another for #2, and another for 3 and 4, then another 15-58 for a backup (since they are cheap). Now how do you put filters on all these affordably? :-\


Well, this turned into a book. My apologies. I will stay awake for nights to come thinking about this until the heat blows in this house again.

Big thanks.
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wreckit87

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Re: Configuration advice for new system
« Reply #1 on: January 07, 2018, 08:27:30 AM »

This is a bit confusing; will you be running 2 pairs of underground lines from the boiler to the house, entering next to each other? Or were you planning to run a single lineset and split once inside the basement? The primary HX, is it a shop-style unit heater? 2nd HX, like a fan coil perhaps? I'm not grasping the scenario very well. Some more information would be great
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RSI

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Re: Configuration advice for new system
« Reply #2 on: January 07, 2018, 08:48:35 AM »

If you really have a 250K btu heat load then you should have gone with a 325G or larger. I can't see a 175 working good at all for that.
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greasemonkoid

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Re: Configuration advice for new system
« Reply #3 on: January 07, 2018, 09:21:31 AM »

Thankyou gentlemen.

I wish a larger unit were possible, unfortunately beyond my budget, will have to make his do the best it can.



At the moment no pex lines have been installed, but was thinking about running two sets of line to HX #1 and #2, whether to tee them into the same pump or just run one pump per HX is what I'm uncertain of.

*All heaters are of the hanging, modine type with the fan.

3 sets of 1" line will be entering the house at the same location. How to configure , pump, and filter them is my uncertainty.
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wreckit87

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Re: Configuration advice for new system
« Reply #4 on: January 07, 2018, 04:00:19 PM »

Please correct me if I'm still misunderstood, but is there a reason you couldn't run a single pair of 1-1/4" Thermopex (actual 1-1/4" ID) lines from the boiler to the house with a single pump and serve everything from secondary loops? A BTU load like that is incredible- I think the poor boiler is going to be empty at all times. The way I see it, a single 1-1/4" Thermopex primary loop served with a 26-99 on high should yield you 12-14 GPM at 150ft total length. If you were to then add closely spaced tees in that primary loop for each HX with a separate 15-58 on each one, (water heater first, if possible) starting with all on low speed and adjusting higher if needed, you could theoretically feed all 4 from the same primary loop and only have to bury 1 set of lines at a fraction of the cost of 3 sets of 1". Perhaps I'm just looking at this the wrong way or not seeing what you want to do, but the picture I have in my head points toward primary/secondary.
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willieG

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Re: Configuration advice for new system
« Reply #5 on: January 07, 2018, 05:54:19 PM »

240,000 btu required for a 2,500 square foot home?  that would be about the same as living in a screened porch! (96 btu per square foot)

I am going to guess your current heaters a rated at that number but you never use the full capacity ?

if you required a heater rated at 100,000 btu  and you were using them all, the heater would never shut off

certainly your heaters don't run non stop?

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hondaracer2oo4

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Re: Configuration advice for new system
« Reply #6 on: January 07, 2018, 06:02:35 PM »

What have you been heating with currently? How many gallons of fuel have you been going through per year?
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greasemonkoid

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Re: Configuration advice for new system
« Reply #7 on: January 07, 2018, 09:04:02 PM »

Please correct me if I'm still misunderstood, but is there a reason you couldn't run a single pair of 1-1/4" Thermopex (actual 1-1/4" ID) lines from the boiler to the house with a single pump and serve everything from secondary loops? A BTU load like that is incredible- I think the poor boiler is going to be empty at all times. The way I see it, a single 1-1/4" Thermopex primary loop served with a 26-99 on high should yield you 12-14 GPM at 150ft total length. If you were to then add closely spaced tees in that primary loop for each HX with a separate 15-58 on each one, (water heater first, if possible) starting with all on low speed and adjusting higher if needed, you could theoretically feed all 4 from the same primary loop and only have to bury 1 set of lines at a fraction of the cost of 3 sets of 1". Perhaps I'm just looking at this the wrong way or not seeing what you want to do, but the picture I have in my head points toward primary/secondary.


This is an excellent idea, probably common practice in the industry I imagine? Will be brainstorming over this. :thumbup:

Reason being, two sets of underground line were significantly cheaper than one 1.25" set and still yields more flow. Dollar per gpm goes much farther - That was my thinking anyway.



Now that I've thought about it a bit, that 240k btu is over the top. So much for online calculators... Up until a few week ago a large wood stove was the main source of heat. On a cold day the doors had to glow to keep up. A chain of circumstances occurred and now the woodstove is gone - insurance company said I had to have a new stove "professionally" installed to be covered. The new stoves are fragile and of low btu output it seems.

So now it's a pair of heat pumps maxed out and and yes, it is cold in here, but we like it 80, not 60
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wreckit87

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Re: Configuration advice for new system
« Reply #8 on: January 08, 2018, 10:11:35 AM »

The Thermopex, last time I encountered it, the customer said it was about $14/ft. Not to be confused with 1-1/4" Rehau or 32mm Logstor which only have a true 1" ID and are typically in the $12-14 neighborhood also. There is the cheap 3 or 5 wrap line available like I assume you were looking at, in the $5-7/ft neighborhood, and usually encased in corrugated drain tile. Given that open cavity in the drain tile, these lines are subject to either cracking during backfill or potentially leaking water from one end or the other into the casing. That water will pull a ton of heat from your 1" lines if there is water in them, and waste a pile of BTU heating the ground. If there is no horseshoe in the line that water can sit in it, perhaps if your entry to the basement wall is the low point and water can just drain to the basement floor if it gets in, one can get away with it. If it were mine I'd spend the extra few bucks (I thought you had 3 sets of lines) and get the foamed pipe both for water infiltration and insulation value, even resilience to damage. The wrap style is called "do-over pipe" for a reason. Nobody likes doing it twice! You'd also probably want a pair of pumps at the boiler with 2 pair of lines. How far away will the boiler be from the entry to the house?
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greasemonkoid

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Re: Configuration advice for new system
« Reply #9 on: January 08, 2018, 01:02:03 PM »

oh boy... :(  Wish I would have found this site sooner. Welp, no turning back on the line now, I've got do-over line, and enough to add a line to the auto shop on the far end of the house - in the future. BUT, this doesn't mean I can't cut that corrugated drain line off and put the wrapped Rehau line in 4" pvc pipe.

Fortunatly, the furnace only needs 29' of line to get in the house, and the house is downhill. And yes, there's enough line to make 3 runs and then some. I'll know enough about this when I get done to stop wasting money.
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E Yoder

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Re: Configuration advice for new system
« Reply #10 on: January 08, 2018, 01:45:19 PM »

A few thoughts-
Putting a coil in a plenum is standard practice.. but you can do as you like. My thought is that if it's in the duct the heat would be distributed evenly. I'm sure there are more details I'm not aware of. the domestic water definitely should be first as wreckit said, otherwise the domestic will fluctuate in temp as the heat kicks on and off.
I'd pump a loop to a flat plate at the water heater, then do a secondary loop or loops pulling off of it through the blowers. My guess is one 1" line will pull all the owb can handle but I'd bury a second for the garage just to be safe.
« Last Edit: January 08, 2018, 02:41:08 PM by E Yoder »
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wreckit87

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Re: Configuration advice for new system
« Reply #11 on: January 08, 2018, 04:23:32 PM »

This brings a thought to my little noggin... Was the wood stove in the basement and ducted by any chance? That a guy could just place a big 200k HX under the duct where the stove used to be and an air handler to send it through the house? As for the underground, I wasn't aware you had already bought it. Sliding it through a 4" PVC is a great idea or you could even leave the corrugated sleeve on it and pull it all through a 6" PVC if you wanted. Heck, maybe a single 6" PVC and lose the corrugated pipe and pull both linesets through it? With 300k worth of exchangers on one pair of 1" lines, even in primary secondary fashion, I'm afraid your return temps are going to be scary low if they both happen to run at the same time. Not to contradict Yoder or anything, as we tend to have a similar mindset on most things, but in this case I would lean toward a straight loop from boiler through the 200k unit using the 26-99 at the boiler, and the 100k unit as an individually pumped secondary loop off of that loop with something small like a 15-58. Then a second underground lineset with another pump, another small one like a 15-58 at the boiler for the DHW and garage. Keep in mind that 7 feet of downhill pipe also needs to come back up so it will cancel itself out.
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E Yoder

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Re: Configuration advice for new system
« Reply #12 on: January 08, 2018, 07:21:52 PM »

 :post:
Good stuff, you're thinking it through better than I..I was just concerned about pulling more heat than the owb could put out.
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greasemonkoid

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Re: Configuration advice for new system
« Reply #13 on: January 08, 2018, 08:03:48 PM »

300k worth of heat exchangers - ha! That sounds ridiculous! Maybe it is. The 200k unit will probably be fitted with a 3 phase fan to throttle it down via Eaton motor drive, the 100k unit will only have ~400 cfm being pulled through it, the shop - mmmm not sure on that one. I see where this is going - limitations are going to be in the return temps as I suspected.

Here is is the previous setup, it worked well, even the boiler that served as a heat exchanger for the hot water. The blue inline blower (rated at 440 cfm) dumps the hot air in the hallway floor, the center of the house and right under the plenum inlet of the air handler which is in the attic. The air handler blower can be set to circulate and it does an decent job at distributing the heat throughout the upstairs. The limitation is however, that air handler fan will only run in low speed when in circulation mode - it is a variable speed fan.  Shame on those engineers  >:(.

So the blue inline blower and everything downstream remains, everything else has been removed. The 200k HX will be mounted in the ceiling in the corner where the washboard is.

Thinking about it now, wonder if that blower could be ducted to suck air out of the 200k unit when the lady calls for heat upstairs. The house is loose as a sieve, most of the heat is sucked up the stairwell. It will be interesting to see how a convection-only system works.

The better half says all that "junk" is an eyesore, personally I could give a crapola what it looks like as long as it works.

You guys are really helping me out here, I owe ya one ;)


« Last Edit: January 08, 2018, 08:17:07 PM by greasemonkoid »
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