Boiler for in-floor heat??

[caper150]

I am looking at a boiler to run the in-floor heat in my garage, I have a 40 gal hot water heater and is not sufficient to heat my garage, the garage is 32X40 with 10' high walls with R-11 in the walls and R-40 in the ceiling, and 2" pink styro under the slab.Will this boiler run or do what I need to heat my shop.
Heres the info the seller sent to me about the boiler.
It is made by Weil-Mclain and is a manufacturer CG Boiler
Model # is CG-4-SPDN
The imput BTU/HR is 105000
Max heating capacity is 88000
It has a Grundfos 1 phase circulator pump attached to it in working order.
It is a natural draft boiler and needs to be vented out to the exterior with a metal chimney.
I do have the 5" exaust electric damper that will come with the unit.
Right now it's natual gas and I do not have natural gas going to the house or garage but he says it can be converted to LP, will a 100lb tank run it or will I need something bigger?

 

[danski0224]

Only way to know for sure is to do a load calculation on the space.

Could be cheaper than installing that and trying it.

In floor heat is typically classified as "low temperature".

That cast iron boiler needs a return temperature over 140*F to prevent condensation on the heat exchanger.

Your supply temperature for the in floor heat will probably be around 120*F- lower than the required return temperature.

You will need to pipe the boiler with a mixing valve or primary/secondary loop to get the operating temperatures right.

The compression tank in the picture is a bad idea.

A modern condensing boiler that has built-in controls for in floor heat and a modulating gas valve is a much better choice, and you can achieve 98% efficiency. They are eligible for tax credits.

A typical natural draft water heater is 59% efficient: 40k btu input = ~23,600 btu output to the water. Rest goes up the chimney.

Good luck.

 

[caper150]

how about this think it will work
http://rmn.craigslist.org/mat/2001572536.html

 

[overdriv]

What size water heater did you have? I am just building a garage and will have radiant floor heat. Was planning to heat with a water heater.

 

[caper150]

a 40 gal and it ran all the time.

 

[Neighbor]

I'm 100 mi straight south of you.

I have a boiler for in floor heat. Expensive but works great.

 

[caper150]

I'm 100 mi straight south of you.

I have a boiler for in floor heat. Expensive but works great.

Expensive as in how, to run or put in?

 

[Neighbor]

cost a bit to install. I think about $7k. That's with me doing all the pex tubing myself. I told the plumbing contractor, funny that the materials were way more than his labor.
Fuel cost for last winter were very reasonable. Less than 250 gal LP

 

[HoosierBuddy]

I don't think 100 pound cylinders will do it. You're talking something on the order of 14 hours run time with those.

IIWY I'd be looking at a 500 gallon tank. at 80% full, that would be like 350 hours of burner on time. Might last you more than a year.

As a point of reference, that boiler you are looking at uses more gas/hour than the furnace I'm using to heat my 2 story house. You're going to need some fuel on hand to run it.

Phil

 

[danski0224]

how about this think it will work

That is only 32k btu.

You *really* need to do a load calculation of the space to find out how many btu's you need.

Just using a rule of thumb based on square footage, you need almost 39k btu for average typical construction in the midwestern USA. The rule of thumb does not take large doors into account.

Things like the absence of slab edge insulation will make a big difference on system performance, as will tubing layout.

Your space is too big for 1 standard natural draft water heater. You could do 2- maybe that will work.

A modulating and condensing boiler will be the better choice. It will cost a lot less to run than a water heater.

 

[Fastback]

Did you use PEX with an oxygen barrier?

 

[z28toz06]

im all ears here. need to heat 768 square feet myself with pex in concrete. where or how can i do heat needs study?

 

[dirttracker18]

Running my 1080 ft garage from an electric water heater with no issues . . . now.
Mine ran almost all the time at first until we dialed it in. You need the mixing value and it sould be nearly closed. When my system calls for heat it jsut adds a small amount of hot water from the tank to increase the temperature in the floor. I have found that just the moving of the water in the floor helps to bring the temp back up.
Once we got the system so that only a small amount of hot water came out of the tank the system ran way more efficiently. As well, my air temp in the garage is only at 12 C (55 f). Feels cold when you first walk in but after 5 minutes the radiant heat from the floor warms you right up. any higher and I find it too hot to work in for any length of time.
My $ 0.02

 

[KenB]

im all ears here. need to heat 768 square feet myself with pex in concrete. where or how can i do heat needs study?

Here is a quick and dirty calculator: http://www.h-mac.com/heat-load-calculator/heat-load-calculator.php


Ken