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Old 04-23-12, 03:29 PM   #201
AC_Hacker
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Default John Siegenthaler on Wood-Fired Radiant Heating

There is a very interesting piece on wood fired hydronic heating by John Siegenthaler that is available HERE.

It is written for designers and installers so that they will understand the theory and best practices of a wood-fired hydronic system.

Along the way, the theory of hydronic design is explained pretty well.

The intended result is to sell their product, but for the innovative DIY person, this is a feast of information.

BTW if you like John Siegenthaler's writing, here is a partial list of articles he has written

...and he also does a "Glitch & Fix" column.

-AC

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Old 05-01-12, 10:04 AM   #202
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Default Radiant floors

Here is my radiant floor project:

I decided to put radiant floor heat when my house was already framed. I realized that I needed to do many changes like stair case rise etc. I started reading about radiant floor system construction and basically found 2 types:

1 Pex tubes buried in concrete
2 Under subfloor staple up

I didn’t want to deal with concrete in already framed house (3 store house framed without 1.5 “ layer of concrete in mind).
I realized many cons of staple up system like: a lot of drilling between joists (my joists are @ 12”). Also performance of this system is not the best and requires high temperature.

One day I was watching YouTube about radiant floor. Everything was concrete or staple up. Accidentally I hit one of the videos and I can see somebody showing how they sell MDF panels with grooves and one side is aluminum foil. The price for this MDF reinvention was just extreme and shipping made it impossible. I started thinking about what if I can buy MDF and router groove. At one point I think “why MDF???” MDF has ton of glue in it that has formaldehyde. Heating MDF inside your house is not a good idea.

So I ended up using just 1x2 wood strips (the actual size is 3/4x 1.5). They are:

1. As cheap as dirt
2. Can buy everywhere
3. Just plain wood, no glue
4. Thick enough to fit 0.5” Pex tub and will have gap on the bottom, so Pex tube will be suspended and will not touch the subfloor.

So, with this idea I started experimenting and here some pics to understand it better:



As mentioned before I used:

1. 1x2 wood strips
2. Aluminum foil HD 2' wide from Costco
3. Strips are stapled down and top layer of plywood is screwed down to subfloor through wood strips
4. I used Omega shaped aluminum heat distributing plates. They distribute heat and hold Pex tubes suspended from subfloor (omega shape helps holding Pex tubes in place while you install top layer of plywood. This is very critical)
5 Top layer of plywood is painted black from the bottom.

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Old 05-01-12, 11:09 AM   #203
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Default Performance

Now when winter is over I can say that floors performed perfect. My original heat loss calculation required 50k BTU for heating. This winter I used my HWT as heat source. My HWT is 34000BTU input @65% efficiency gives only about 22k BTU output. We still use it for hot water. Even on coldest days @ -10C HWT was never working constantly. It was working for an hour and stopped for half an hour. Because we used hot water at the same time it was useless to measure time periods when it was working.

I put some sophisticated controls to control loop temperature and flow according to outside temperature. On coldest days loop temperature was about 95F. I set TD(supply-return) 6F. Most of the time loop temperature is 85-87F. When outside is +10C system shuts down.

Here are some pics of "boiler room"

Manifold:



Controls and storage tank on the left :



Pumps and piping note white cube behind storage tank is a plate heat exchanger inside foam insulation (primery loop is DHWT secondary loop is storage tank. Water from storage tank runs under floor.) :


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Old 05-01-12, 11:16 AM   #204
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Default Main parts list:

I bought most of components from 2 web sites and eBay.....

Variable speed control for main underfloor loop circulator
157 - Tekmar 157 - Difference Setpoint Control - Variable Speed

This holds all copper piping on board. Very handy items. You just need to add pieces of 3/8" threaded rod and nuts.
81CT16 - Carpenter & Paterson 81CT16 - 1" Copper Split Ring
85CT06 - Carpenter & Paterson 85CT06 - 3/8" Copper Ceiling Plate

I added mixing valve on DHWT to keep safe temperature limit for domestic hot water.
AM101-1 - Honeywell-Sparco AM101-1 - 3/4" Female NPT Mixing Valves, 100-145F

This valve is part of the underfloor loop it controls supply loop temperature according to outside temperature and closes completely @ +10C outside
I050C2R-2 - Taco I050C2R-2 - 1/2", 2 Way Outdoor Reset I-Series Mixing Valve w/ Sensor
------------------------------------
SS pump for primary loop in HX (DHWT-HX)
https://www.pexuniverse.com/store/pr...ulator-pump-st

https://www.pexuniverse.com/amtrol-e...expansion-tank

This valve is creating pressure difference between return line( cold floor loop) and supply(hot) from storage tank. I could just put ball valve and adjust it to have some resistance. Otherwise return floor loop water would recirculate and "fresh" hot water from storage tank would stay in storage tank.
https://www.pexuniverse.com/store/pr...***-valve-3196

This two help to eliminate air in underfloor loop. I have 0 problems with air even my manifold located in basement and all loops above it.
https://www.pexuniverse.com/store/pr...o-400-air-vent
https://www.pexuniverse.com/store/product/415

Main pump for underfloor loop. More then enough to circulate water. Most of the time works 75% RPM or does nothing. If pump runs @ 75% speed for 5 min main control shuts it down for 5 min then starts it again @ 100% then if TD( floor supply-return) comes to 6F pump slows down step by step to 75% and cycle start over. I tried to go lower then 75% but pump start making humming noise. So I left 75% as a slowest speed for pump.
https://www.pexuniverse.com/grundfos...-pump-52722330

Secondary pump for HX (HX-storage tank. It has 3 speeds but runs @ 1 speed. More then enough.)
https://www.pexuniverse.com/grundfos...-pump-59896341

Manifold. Love it. Easy to install easy to adjust.
https://www.pexuniverse.com/store/pr...nifold-ssm0010

Pressure reducing valve for water supply. I keep 35 PSI pressure in underfloor loop.
https://www.pexuniverse.com/ds05c102...reducing-valve

The floor does have some warm spots and some colder spots but you can feel the difference only barefoot. Floor is actually cold when you touch it by hand. But this is enough to keep house @ +22+23C.

Now I realized that I don't need 110F-120F or even some authors say 130F supply water. It makes possible to use GSHP . I only need max 90-95F for heating and if for some reason(-20C outside for a week or two)

I can have an emergency set which will be a small SS pump and HX (even small tube in tube hand made will work). This can raise supply floor loop temperature if needed using DHWT if HP can't go that high temperature or if it is unreasonable.

This will be kind of 2 stage system 1 stage is HP heating "cold" return floor loop 2nd stage raises temperature to needed temperature using DHW. Domestic hot water will be recirculated back to DHWT.

I called this "emergency" because it can be a real emergency if HP brakes down or when outside temperature goes bellow expected limit, which is only happening a few times in whole winter.

I will draw and post the diagram to help to understand the whole system....

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Old 05-01-12, 12:49 PM   #205
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Default

Interesting setup you have there. Can you feel the difference in heat between the pipes?
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Old 05-01-12, 12:58 PM   #206
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Quote:
Originally Posted by Daox View Post
Interesting setup you have there. Can you feel the difference in heat between the pipes?
Can you give more info what pipes?
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Old 05-01-12, 01:11 PM   #207
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Between the pex tubing I mean.
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Old 05-01-12, 06:04 PM   #208
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Default

FYI, In 1995 i designed an in floor hydronic heating system for our conventional stick frame new home (2x6 outside studs, crawl space under TJI floor joists, ply sub floor), single floor, about 2400 + 2.5 car garage (also heated).

The house consists of 2 independent hydronlc zones, bedrooms carpeted, rest of the house lime stone tile. About 5500 or 6000 of 0.5 ID poly butylene tubing (pre PEX) was stapled to the sub floor at 6 spacing in approximately 200 lengths from and returning to the 2 plastic zone distribution manifolds, flow adjustable for actual loop lengths. This piping was covered with a pouring of 1.5 Gyp Crete, a very fluid gypsum based material that will flow to level. Sets up overnite but took weeks in the summer to dry the moisture out of it, no hindrance to conventional construction.

Pros: It has been a joy to live on for 15+ years now, absolutely quiet, constant comfort temp 24/7 during the heating season. Does take overnight to reheat when turned down for extended travel.
Cons: Not compatible with AC, two separate systems. But no need for AC at 4700 elevation on the E slope of the Sierras, always cools off at night in all but the hottest summer days.

The system is supplied from a heat exchanger within a propane fired high efficiency DHW heater. Why Im lurking here, need to add a W/WHP to the system. I am adjacent to an irrigation ditch running about 100 GPM all winter, never freezes completely even in extended sub zero temps. A 35 degree water source has to be better than a -20 air source!
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Old 05-02-12, 12:28 AM   #209
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Default

Quote:
Originally Posted by Daox View Post
Between the pex tubing I mean.
I still don't get it. But if you mean supply-return then control tries to keep TD @ 6F by modulating pump speed.

If you mean floor area where I have tubes and where there is nothing then yes you can feel the difference but only barefoot.
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Old 05-02-12, 12:37 AM   #210
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Default

I forgot to mention there is no insulation under pex tubes and there is no insulation under subfloor. The only "insulation" I have is aluminum foil that covers subfloor and air gap under pex tubes.

I was thinking about adding insulation but price was about 3000$ so pay back period for this kind of improvement would be 50 years if not more I guess.

As I posted before my gas bill is about 100$ higher than last year when we used only electric heaters. And we have got second baby so more hot water usage I just ignore.

This is not bad for 3000 sft and 65% efficient DHWT.

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