System Design #1 Crested Butte, Co

billyboy

A.O. Smith with 3 port tank.

hot_rod

That is the exact drawing I was referring to a couple post up. In that DHW application, I think the diffuser (sparge) tube I showed above would also be used to stir the tank.

billyboy

Sensor location, I'm undecided between using the tank well above my proposed Hot inlet

OR placing it at the top of BT on the system supply outlet?

hot_rod

if the sensor needs to trip on the heat input, it needs to be at the coldest fluid location. I have seen some solar tanks with the sensor mid point and it limits the solar input by quite a bit. Essentially reducing the tank capacity.

Now in some instances two sensors are installed, the lower as the boiler on, he upper for load distribution. Several of our solar controls have applications that use this, and can even "share" a sensor across several functions.

In Europe there are a lot of hybrid systems that incorporate solar, wood or pellet, and oil fired input. Special control logic monitor the system and select on a priority basis. Or they monitor several levels of the tank and trigger input accordingly.

Zman

Are you doing continuous circ so it does not freeze? That is ridiculous.
What happens when the power goes out?
You really either need to keep the tubing well within the heating envelope or use glycol.
Then again, I would just install a properly sized mod con and be done with it.
The issues you have experienced with mod cons are symtomic of an improperly set up unit. Was a combustion analysis performed?
Most units I see are installed higher than Crested Butte and have few problems when installed and set up correctly.

billyboy

Fewer pumps on distribution.
ODR + constant circulation.

billyboy

Zman, U R invited to help someone else.

Rich_49

Billyboy ,

You are on a site that offers help to those who need it . The fact that you are here would suggest that you were looking for advice or peer review . You have heard many suggestions on your numerous discussions in the past few weeks . Some of the advice you receive or hear may not be to your liking and that is the nature of the beast . I get scolded for speaking what I know or opinion . Your tone and meaning is unmistakable in the above post . Mind your manners .
Now I feel like the social police .

Zman

billyboy said:

Zman, U R invited to help someone else.

Sometimes I forget some of the best advise I have ever received. "Never try to teach a pig to sing, it is a waste of time and it annoys the pig"
Sorry for the unsolicited "singing lessons", It won't happen again.
Best of luck with your project...
Carl

billyboy

I came to this website looking for good ideas & discussion from experts, which I got from HR & Hatterusguy.

Concerning constant circulation benefits read this article by Siggy, especially the Bottom line at the end:
[PDF]hydronics
www.bizlink.com › April2006

Tim Potter

Billboy, can't click on link, but what was the "jist" of the article?

Tim

billyboy

I tried to copy & paste on IPhone nogo, maybe when I get home from road trip I will be able to on desktop computer.
Along these lines:
Euro engineers amazed that USA still use bang/bang,
Continuous circulation=good for all emitter types, especially slab, prevents freeze up at cold shop doors, diagram that shows using 3-way zone valves instead of injection pump as HR talked about above.

billyboy

Also good for moving solar gain from one side of a zone to cooler side

billyboy

Winter solar gain through large South windows will be a big deal on my son's house Great room/ kitchen & master Suite zones

Zman

What are your emitters?
Seems like an important detail in the constant circ conversation....

Tim Potter

Here is a great article written by Mark Eatherton:
https://heatinghelp.com/systems-help-center/buffer-tanks/

SWEI

Great description of how TRV's operate, but it was written about a decade ago. Ignore the references to a pressure bypass and substitute "pressure-dependent ECM circulator" for "Wilo Stratos" and it comes pretty close to current.

billyboy

My Son won't listen to me whem it comes to emitters, (or much of anything) I much prefer a well insulated slab.

His house won't have any slabs, the main level is completely over a 6' crawl space. I don't like it, but the builder over priced the delta to make it into a full basement. (he didn't want to do it)

Son also won't let me do a light weight 1.5" slab over the subfloor. I did this with a neighbors main level with 2x4 sleepers for nailing Hickory hardwood floors. Looks & heats great.

He is set on doing suspended pex under the subfloor, as I have in my current house. I built this house 15 years ago & didn't know better. Most are 8" OC with some at cold edge of house at 4" OC

It works because the house is very well insulated in zone 5, all windows are tripple pane argon filled Low-E with a 4th layer of glass storm windows (wind storms). ICF basement & 7.5" SIP main level & upstairs walls.

Several sources show that we can get the required 30 btu/ft2 at design (-20*F) up through the R1.5 floor with suspended pex 4" OC in a 4" deep convection space with R23 Rolul insulation to the bottom of the 11-7/8" TJI's
Will need AWT of about 140-150*F

hot_rod

30 btu per foot from a suspended tube install? Sounds too good to be true. 30 is a high number for any residential radiant floor. Suspended tube is the least powerful heat transfer method, it's mainly convection, I'd guess more like 160 a- 180 supply, judging from my rubber tube days, and those had some conduction transfer.

Rule of thumb is 2 degrees for ever degree difference between room and floor surface. Some engineers suggest 1.7 a- 1.9

So for a 70 degree room temperature, the entire floor surface would need to be 85, is that doable? Any furnishings in the room that limit the heat flux? If so divide that out of the floor square footage. Now the floor output needs to increase.

85 floor surface is a high number 82-83 is a more comfortable number that home comfort gurus like Robert Bean recommend

Mid 20's is a more realistic number floor output number, unless you can be comfortable in 65F room temperature. Might think about some supplemental heat if that 30 BTU number is accurate.

njtommy

@hot rod
Would Hydroair work well as supplemental heat?
I guess the best would baseboard heat?
But I'm assuming he doesn't want to see or take up space with baseboard.

billyboy

The rear (North) 1/2 of the main level of house will also have heat contributed by the uninsulated radiant floor of the upstairs rooms.
This works well in my current house.

The 500 sqft space that I'm most worried about is above the unheated garage, cold on all 6 sides. I want to add baseboard or ceiling heat there.

billyboy

Notice I said AWT. 160*F supply is about right.

Bob Bona_4

Not a design I'd endorse.

billyboy

Months ago, somewhere, I found some data posted by Tim Doran on Wirsbo testing.

Suspended pex with convection plenum, 4" OC

Insulation below = R15, Floor = R1.25 (12:1 ratio)
Room MRT = 65*, Floor surface = 77*, Btu/ft2 = 24, AWT = 123*

Son's house: Insulation below = R23, Floor = R1.5 (better 15.3:1 ratio)

Wirsbo: AWT (123*) - MRT (65*) = 58* deltaT between AWT & MRT

So I set up a formula, hope it's correct:

X / 58 = 30 / 24 , X = 72.5*
+ MRT (70*) = 142.5* AWT

billyboy

Or another way to look at it:
123 / 77 = X / 85
X = 135.8*

billyboy

I will be using an Erie BB3000 injection ODR control, as I got it new on Ebay for under 1/3 of retail price.

I will be able to dial in the reset slope to match conditions.

So upon reflection, near-constant circulation using 4x zone valves & 1 Alpha or Viridian pump, is what I will do.

hot_rod

billyboy said:

Months ago, somewhere, I found some data posted by Tim Doran on Wirsbo testing.

Suspended pex with convection plenum, 4" OC

Insulation below = R15, Floor = R1.25 (12:1 ratio)
Room MRT = 65*, Floor surface = 77*, Btu/ft2 = 24, AWT = 123*

Son's house: Insulation below = R23, Floor = R1.5 (better 15.3:1 ratio)

Wirsbo: AWT (123*) - MRT (65*) = 58* deltaT between AWT & MRT

So I set up a formula, hope it's correct:

X / 58 = 30 / 24 , X = 72.5*
+ MRT (70*) = 142.5* AWT

24 BTU/ ft seems like a reasonable number, not sure about his MRT as opposed to wall stat temperature? I know the older I get the more I find myself bumping up the t-stat. 68 just doesn't feel so warm after a days work out in the cold, I bumped my t-stat to 72 a few times last winter.

But 60- 62F in my shop feels just fine.

Really, ideal comfort is a user defined scenario. What works for you or your son may vary from what the numbers or calculations define.

What I do know and have heard over and over from other owners and contractors here, is suspended tube and tube stapled to the floor are the lowest performing systems. I'd consider them more of a floor warming installation and on mild days a heating system or a mild climate system.

Once installed the only wiggle room is to increase supply temperature. That may take you out of the boilers best efficiency and produce uncomfortably warm floor surfaces on design or below conditions.

After a proper load calc, the next most crucial step is selecting the appropriate installation and emitter methods. It's not so easy to upgrade a radiant floor after the fact, many times.

billyboy

Simplified system:

billyboy

I have a system very similar to this in my current house & it works great.

billyboy

High temperatures are bad with a ModCon, but good with a cast iron boiler.

hot_rod

It sounds like this is the system you want and like, go for it.

Remember ALL boilers are more efficient at low operating temperature all things being equal. With non-condensing types, you just need to keep returns above condensing temperatures, so around 130F return.
Sounds like your 160F is needed for the emitters you have and to allow a 30 delta T through the boiler?

billyboy

HR, Thanks for all your input.

Tim Potter

Did I read you correctly, you are installing pex 4" on center? That seems like a lot of pipe to fit into the joist space, have you thought about plates & 8" oc?
Here is some info: http://radiantengineering.com/productsthermofin/

Tim