calculating head question

mustang_gt_350

I know this is a new guy question, but I am new. I looked around and couldn't find the answer. If my run is 50ft from the outdoor boiler to the house. Do i double that since the run has a feed/return line and say it is 100ft? Or doesn't it matter since it evens out the same way the rise isn't calculated because it returns?

Ironman

It's two lines, so that's 100' of pipe. It doesn't even out with dynamic head since every foot of pipe adds more resistance to flow.
Static head deals with gravity and since two columns of water of equal height weigh the same, they cancel each other when connected in a closed loop.

hot_rod

Add all the fittings, valves etc in the loop also.

mustang_gt_350

Thanks. I thought it was to be added for total pipe length but i wasn't sure. Noted, on the valves and fittings.

What is generally added for a radiant floor manifold?

Ironman

Check the manufacturer's specs on the manifold.

You're not planning on connecting the floor directly to the wood boiler, I hope?

mustang_gt_350

ok, I'll have to see if i can find a few manuals and download them.

Not sure i understand what your meaning about connecting directly to the boiler. If your meaning with no thermostat, zone valve(s) or means to control the temp, no.

I'm just trying to learn and plan out a future project. Nothing is currently in place, and I came here because the local "genius" outdoor furnace guy said I didn't need anything larger than a 1" line between my house and the furnace (80ft one way). That was after he told me that my heat loss he thought was considerably low at 75k, and that he recommends doubling that and that should put me right where i need to be. My house is/will be around 1500 sqft (2 story with basement,and the 2nd story being a low ceiling at 6'3") when i add the sunroom into being part of the living room in the next few years. So he expects me to push 150k btu's through a 1" run with a taco 0011 pump

because of this reason:

"Just my 2 cents..........don't waste your money on the 1.25 pex. The fittings are out of hand and in my experience you can flow a lot of BTU through a one inch pipe with a high head, high flow pump, like a taco 0011. I heat my entire house ( 6 zones of radiant heat plus domestic heat exchanger and one on my hot tub ) with one set of 1 inch pex lines and a taco 0011. Radiant usually does not require as much BTU due to the lower operating temps."


Now I'm not going to argue his experience with heat loss in older homes, mine was just a on line calculator guesstimate, along with the lack of a blower door test. I know my house is pretty drafty due to its 1940's construction, along with the same time period single pane windows that rattle when the wind blows. I am currently replacing them as i get time and $ to do so. I am a little over half way on the replacements. I am also gutting and replacing the spray foamed post construction train wreck with R20 and the same with the uneven blown in in the attic area that varies from 3"-10", with R38.

I have a few more sheets of drywall to hang and then i can try to get a blower door test done, or DIY and come up with a way to a try it myself so i can get a rough idea and locate my major leaks. before this years heating season (which is coming fast)

Sorry if its a little scattered. I usually work nights and have been daylight/2nd shift the last few days and I just woke up so I'm a little groggy lol

Ironman

mustang_gt_350 said:

"ok, I'll have to see if i can find a few manuals and download them.

'Not sure i understand what your meaning about connecting directly to the boiler. If your meaning with no thermostat, zone valve(s) or means to control the temp, no."

The radiant floor will need to be pressurized. You cannot directly connect it to an unpressurized ODWB. You'll need a heat exchanger between them as well the necessary ancillary parts.

"I'm just trying to learn and plan out a future project. Nothing is currently in place, and I came here because the local "genius" outdoor furnace guy said I didn't need anything larger than a 1" line between my house and the furnace (80ft one way). That was after he told me that my heat loss he thought was considerably low at 75k, and that he recommends doubling that and that should put me right where i need to be. So he expects me to push 150k btu's through a 1" run with a taco 0011 pump"

A 1" pex line is good for carrying about 8 gpm which = 80k btus at a 20* delta T. The head and velocity is off the charts if you try to push 15 gpm through a 1" line as you local genius is proposing.

Download SlantFin's heat loss calculator and you can perform an accurate calculation of the loss of your house. The load calc is the foundation for designing EVERYTHING. You've got the cart before the horse if you're trying to select a system and its components without knowing the ACTUAL heat loss. How do you know what size ODWB you need or that a radiant floor will produce sufficient heat without an ACCURATE heat loss calc?

"Radiant usually does not require as much BTU due to the lower operating temps."



A house requires the exact same amount of btus to heat it no matter what type of emitters are employed. Your local guy is clueless if he made that or the other claims.

mustang_gt_350

Yeah i realize pretty fast when he said about the btu requirements are lower, and that i can push that much btu through a 1" pipe that he didn't know as much as everyonethinks he does.

Just google to find that heatloss calculator?


My other question. Not questioning that it should be done, just doing so that i can learn the reason. Why must it be pressurized and separated from the Outdoor boiler?

Ironman

mustang_gt_350 said:

Yeah i realize pretty fast when he said about the btu requirements are lower, and that i can push that much btu through a 1" pipe that he didn't know as much as everyonethinks he does.

Just google to find that heatloss calculator?


My other question. Not questioning that it should be done, just doing so that i can learn the reason. Why must it be pressurized and separated from the Outdoor boiler?

To remove and keep air out. O2 is the enemy of any hydronic system.

I realize that some ODWB manufacturers have diagrams showing the floor directly connected, but they're trying to keep the installation costs down so you'll buy their ODWB. You'll pay a whole lot more doing it twice than if you did it right the first time.

Think about it: If house hydronic systems did not need pressurization, why has the industry been doing it for nearly 100 years?

mustang_gt_350

Thanks for the help/info. I will try to get the heat loss done tonight and maybe start a new post with my needs.

mustang_gt_350

new post is up