Double bubble trouble..... scrap or proceed with caution?

RNB716

Greetings All,

Thank you in advance for any insight to my issues forthcoming, also for the vast amount of information provided to those who have ventured here before me.

Rewinding back 13 years to 2007.... We built a 32'x48'(1500sf) two story pole barn kit with 4"slab on grade floor containing 7, 250' loops of 1/2" pex tubing in preparation of a future radiant floor. I was assured by the kit provider that their underfloor reflective double bubble product was just what I needed under my slab. The supplier does tons of these structures so unknowingly I agreed to use the product. A couple of kids later and fast forward to today..... I began my research on completing the heating system in the barn. Needless to say, I'm pretty disgusted with my findings and the effectiveness or lack thereof double bubble brings to the table.....

I've done multiple heat loss calculations and have a supply house shopping cart full of components ready to cash out. I'm at the point of "all in" or "bail out"! I'm not looking for 0*/70* design performance... more like 20*/60*... Is that even achievable at this point without owning our own NG well!? I live in Western New York in snow country where the temps are usually bearable outside of a few days in Jan/Feb which I would not likely be in the barn then anyhow. Perhaps a good blanket of Snow to insulate the slab edges. LOL with real tears.....

Advice????

Jamie Hall

No reason not to proceed. The bubble wrap insulation won't be doing much of anything for you, but you can still heat the place reasonably. You should do your heat loss calculations, though, to determine what floor temperatures and boiler you need.

Lack of insulation underneath with, however, slow the response down -- as the ground underneath becomes part of your heated mass. Bringing it up to temperature will take quite a while. Once there, not that big a difference.

One thing you may be able to do which will help a lot is to dig 2 to 3 feet down all around the foundation and put in 4 inches or so of blueboard (or pink board... whatever... rigid) foam insulation as perimeter insulation. It's the edges which are the real heat loss into the ground.

Zman

You are not the first to make this mistake. The good news it that you can still heat the space. The bad news is it will cost more in gas. I like Jamie's suggestion of insulation on the outside. That would make a big difference. You probably will need to come up with a flashing detail to protect the foam.

RNB716

Yes, thanks for the responses. Perimeter insulation is in the contingency plan! Along with raising the bumper on the mower and hiding the string trimmer from the Mrs.! I've been pondering the coverup details as well. It is board and batten over osb. Perhaps a 3' vertical steel bottom. My worksheet calls out 17kbtu@0* for the uninsulated floor alone.

RNB716

Up and running after some hard headed mistakes and 25% of a 250g Lp tank. Using Takagi tankless for heat..... Yes, I know!!! Piped home run assuming the flow charts were going to be as advertised.... Not!!! Repiped P/S as I should have done to start. Floor came up to temp within 36 hours after re pipe.  Can someone look at my setup. Q1.. does the orientation of close T make a difference? I have the valve throttled to bring the manifold inlet up just before the point which would reduce flow in loops. My gauges are pretty inacurate at best, good for a quick reference I suppose. 
Q2.... should I keep the zone circ pump running or cycle with the primary pump, does it matter? I can convince myself either way....  

Thanks for looking! Merry Christmas All!!!

hot_rod

really shouldn't need or want to throttle the valve betweens the tees. I don't like to even see a valve there.

Yes you need to run both circs to move heat from the boiler into the radiant distribution.
The boiler pump could be connected to the boiler relay, so it only runs when the boiler calls.
The relay box could take a heat call and and then send a call to the boiler.

RNB716

Thanks H-R, 

I run both pumps, I was refering to letting the zone circulate as the primary rests. I decided to keep it as is and cycle both pumps when called for heat.... If the fluid is not heating then it would be cooling as it circulates. 

  I have some fine tuning to do now that it actually cycles instead of running full time. My Q about the T is if it matters which side of the T is the primary heat source. Is it more efficient in either configuration? Thanks again

hot_rod

You have it correct, supply from boiler into the tees, on the left branch.
 Some say running the distribution constantly will even floor temperatures. It will cost that power consumption.
So constant circulation and the thermostat turns on the boiler and its circ.  Assuming you do not have zone actuators. Try it both ways.

RNB716

Thanks

Im pretty happy with it right now. No zone actuators as the slab is one zone. Im ready for expansion in the future and a 3 zone relay wasnt a huge leap in $ compared to buying another later. I may rewire to constant circulation but things are running so well Im hesitant to fix whats not actually broken.

hot_rod

I know large high mass slabs can benefit from constant circulation. I think constant circ was promoted by the europeans back in the early mid 90's when German boiler started arriving en mass. A side advantage is freeze protection. As long as you can keep the circs spinning.

https://www.pmmag.com/articles/100586-continuous-circulation-in-floor-heating-circuits

RNB716

Thanks again H-R!

This here is enough reason for me to make the adjustment

Constant circulation allows heat that is stored in the interior areas of the slab to be relocated to the high-heat-loss perimeter areas, such as just inside overhead doors in a garage-type facility. Think of the circulating water as Robin Hood — it steals from the areas rich in heat storage and gives to the areas in need.

I was thinking opposite.... that the cooler perimeter glycol mix would cool down the rest of the slab.... I guess that is true as well but the benefit of the mass warming the perimeter loops trump the thought.

RNB716

Please excuse my asking the same question over again... The close T has me wondering as most, not all, of the examples I see show the primary as in EX:1 on the image I've created here as opposed to EX:2. Is either way more efficient than the other.

hot_rod

Different opinions on primary secondary. Here is my opinion based on chatting with Dan and what Gil taught. Since P/S really started or got on the map via that brain trust.

Whichever loop has the expansion tank, that should be referred to as the primary loop.  And the choice of where to “place” the tank varies on the intent or components used.

For example where the indirect tank is connected when a hydraulic separator is involved?  Most times the tank is better located at the indirect connection if a high pressure drop boiler is used.

HomerJSmith

I was always of the opinion that the heat source was the primary and the heat distribution was the secondary, but the consensus was against me.

So now, I refer to the heat distribution as the primary and the heat source as the secondary. Definitions only matter so everyone knows what you're taking about.

hot_rod

HomerJSmith said:

I was always of the opinion that the heat source was the primary and the heat distribution was the secondary, but the consensus was against me.

So now, I refer to the heat distribution as the primary and the heat source as the secondary. Definitions only matter so everyone knows what you're taking about.

Confusing. It would be nice to get the industry on the same page.
By explaining the primary as the loop with the tank seems to clear up any confusion. So with multiple boilers, or tertiary piping, the primary loop is alway definable.

Here are a few examples.

kcopp

I have stopped calling it primary/ secondary loops...
I refer to them as Boiler loop and System loop...