47,000 btu's to heat 1.5 car garage

Hi All,
Is this amount of btu's overkill for this space?
Had heating company #1 recommend a "toaster" and 1/2" insulated pex tube run from basement boiler to garage.
heating company #2 said that the btu's in a toaster would not be sufficient to heat a 1.5 car garage- they are recommending Modine HSB- 47, a 47,000 btu hot water unit w/fan coil/ blower with 1" pipe run from boiler to garage and then glycol in the system.
Price is twice as much for company #2, but if this is the correct installation for this job I would go with it.

Thanks in advance for any info and recommendations.

 

Too many variables to say...

What is the outdoor design temp where you live ?
What is the indoor design temp in the garage ?
What type of construction ?
How much insulation (walls and ceiling) ?
How many exposed (to the outside) walls ?
How many (and how well insulated) doors and windows ?
Unheated space above ?
etc ...

47K doesn't sound out of the question though...

 

Interspersed below

 

This is a tough one... (keep in mind that I'm no expert... I'm like Xiphias, on an accelerated learning curve!)

I'm assuming that you will have the heat OFF when you aren't in the shop?

That being the case, also assuming it's a slab floor, nothing you do is going to keep your feet warm, short of doing radiant, with an overpour of concrete, and turning the heat on 24 hours before you intend to work out there, and warming up the slab. You are going to have a pretty steep temperature gradient from floor to ceiling.

Another assumption: at least one of those 3 doors is an overhead garage door? That may or may not be opening and closing when you are in there ?

Something to also consider: Is your existing boiler going to be capable of supporting the extra heat load ?

Have you thought about a wood stove ? or a direct vent gas furnace installed in the garage. either might be cheaper than your proposed plan.

If you give me the dimensions of the building and doors and windows, type of floor (uninsulated slab?), amount of insulation in (and height of) the ceiling, I'll run some rough numbers on your heat loss and see how close to 47K this program comes.

-[edit: I made some "worst case" assumptions and ran the program to see what I came up with. I used a 20x30 building, with 150 sq ft of window/door, uninsulated glass, no storms, no weatherstripping, R13 in the ceiling and walls, uninsulated slab floor, and I'm coming up with slightly over 40K. But I'm skeptical, cuz I just found what I think could be a bug in the program. I massaged one number just a little bit, and the heat loss went to 60K ... I'm gonna start a new thread about that]

 

IMHO, your boiler and anything having to do with hydronics should not be involved in this application. Go with a dedicated unit that will jack up the temp quickly and doesn't involve hot water piping, controls, yada yada yada from a separate structure (your house).

I also strongly doubt you have a spare 47k of BTU output from your boiler to get the garage up to and maintain temp without freezing your house.

Get a Modine HD-45 or HD-60, or if you're going to be cutting a lot of wood, making dust or spewing chemical fumes, get an HDS-45 or -60 which draws combustion air from outside. Run your gas and electrical and you're done. Build a nice wooden boat in this toasty warm space and I'll come help!

Good luck.

 

Xiph, since yer here... do me a flavor if you would please and tell me what you think is going on with this program

I used these numbers for namaste's garage

10* outdoor
10 ft ceiling
20 x 30 room length and width
150 sq ft doors/windows
1.13 glass factor
100 ft exposed wall
.07 wall factor
.81 floor factor
.054 infiltration
70* indoor

should come up with 40K +

now, manually change the floor factor from

0.80 note the btu then,
0.81 " " " " ,
0.82 " " " "

what's up with that ya think ????

 

NJTrooper: Looks like a bug to me. It only wants to see values from the list (regardless of whether you pick them from the menu or enter manually). Probably has to do with how they look up values in whatever underlying indices they have, but I only dabble in programming. I never noticed that before, and I think I'll go back to my heat loss and see what gives. There are a couple places I entered "custom" values but never noticed the kind of inconsistent behavior here. Does it happen for the other things like ceiling?

 

Thanks to all for the feedback. I'm hoping that this new EK2 system I just had installed can handle this extra zone.

I purchased this unit with the intent of adding on 3 zones (for a total of 5 zones- one which will be a pool heater and used only seasonally)
To that end, I would like to also run the pipe for the pool heater now while I have the trench open.

If I put in extra lines for a pool heater to be installed in 3yrs will the empty pipes be okay laying unused underground for 3 yrs?
If okay to run pool heater lines now, should I run 1" pipe for max flow?

If adding on to this hydronic system in the manner I am envsisioning is a "pipe dream" please let me know, I'd hate to spend the $$ and then not get the results I am expecting.

All replies and advice would be greatly appreciated.

 

Sounds like you need a pro who can do the load calculations, pipe sizing, flow rates, etc. etc. for all that stuff.

 

Xiph, I haven't tried that yet, but will. That kind of behaviour makes me mistrust the results.

nam, hopefully, the boiler was sized with the extra zones planned for, and you do have the capacity. With proper planning, you would also have had the future connections "stubbed" in and capped off, minimizing the work needed to add these zones.

I'm sure the pipes will be fine, just cap the ends well so no foreign (or domestic!) debris can find it's way inside.

As for the size of the line, as Xiph said, it's just not possible for us to guess with any accuracy with the limited info that we have. You really should have your installer do the calcs for you. I would also insist on some kind of performance warranty.

 

Thanks for the info.

I called a pool heater supplier who recommended I run 1 1/2" pvc underground for the pool heater lines. I guess it will be 3/4 from the boiler then expand to 1 1/2 on the way out of the foundation wall?
This is all greek to me, I'd like to take care of this while I have the trench open so as not to have to re-excavate.

Does 1 1/2" pipe sound unusual for an additional (pool) heating zone coming off the main boiler?

 

PVC is not used for hot water heating of this sort. You probably misunderstood. Get a real pro who understands hydronic heating of homes, pools, etc. to design your system. Doing all this wrong will be very painful to correct. Doing it right will not. It might cost a bit more up front, but the right people typically don't come cheap.

 

I'm pretty sure that your pool heater will require a heat exchanger at the boiler, and glycol in the lines out to the pool, where there will be another heat exchanger. This keeps the glycol out of the pool, and out of the boiler (while you _can_ run glycol in the boiler, there's no need to).

So, you may end up with 3/4 lines to the heat exchanger at the boiler, and larger lines out to the pool. But, PVC as Xiphias sed, is definitely NOT the correct answer.

If I was in yer shoes, I'd be looking long and hard at using solar to heat the pool.

Why not google pool heaters, and look at some installation manuals ?

-

 

I'll definetely have to do more research on pool heater requirements...
As for the garage heat, I told installer #1 I was passing on his install of 1/2" flex pipe from boiler to garage - sounds skimp for a 47,000 btu unit.
He insists that is THE correct way go...
why would I want 1/2" flex pipe across a 23 foot underground span when I have 3/4 pipes coming out of the boiler?
Think I'll go with installer #2 and 1" pipe w/glycol in added to the system - and the hot water / fan coil heater in garage.
Thanks for the good info.

 

No, those all work as expected, here's what I've realized though:

In the FLOOR FACTOR sub menu for Concrete floors, the first two are special cases (didn't you say that ?) . They refer to the heat loss per LINEAL FOOT of EDGE, not sq ft of floor space. So, I'm guessing that's the difference...

 

[QUOTE=namaste524;1085968]

why would I want 1/2" flex pipe across a 23 foot underground span when I have 3/4 pipes coming out of the boiler?

Think I'll go with installer #2 and 1" pipe w/glycol in added to the system - and the hot water / fan coil heater in garage.[QUOTE]

I wouldn't be surprised if you could move 47KBTU through 1/2" pipe, ya think Xiph ?

What kind of 1" pipe ? There is INSULATED PEX that is used commonly for outdoor wood boilers that sounds ideal to me. REHAU is one manufacturer, I saw that on the AquaTech website (wood boiler manf) Your guy wants to run glycol in the whole boiler ? or is he planning on a heat exchanger ?

Based on what I found with the heat loss program, 47K may be a fairly reasonable number.

 

Even if you could move 47,000 btu's thru 1/2" pipe, why would you if you had 3/4" coming out of boiler?
I have 206,000 btu hydronic system, and was skeptical about reducing the flow lines by 1/4" because of possible pressure build up.
To have to put in a flow reducer would be counter productive
Also, why would I want to reduce to 1/2" pipe for the pool heater lines?? I need all the outflow I can get...
Am I missing something here??
Thanks for your feedback - it will help steer me to the correct decision on all the various methods currently proposed - for what I originally thought was a relatively simple project...
IMHO, I've already done a signifcant portion of the work digging the 23' trench and drilling through the concrete

 

Think of it this way... you've gotta move 47KBTU of heat through the pipe, forget about pressure buildup, it's not an issue. Forget it's even water, or how much water it is. You are moving heat.

1/2" pipe you might be able to move say 3 GPM of water at design specs for hydronic heating pipe. That's 180 Gallons per hour. Your homework is to figure out how many BTU's of heat are carried by 180 Gall of water at say 180*F . That will tell you why you can probably use 1/2" pipe. Not saying 3/4 or 1 inch won't work, it just may be over kill. Why spend bux on over kill ?

In other words, you only need to move enough water through that pipe to transfer 47K BTU of heat to the air in your shop.

I don't think I said to reduce to 1/2" for the pool heater...

-

 

NJ
I did not mean to imply that you indicated 1/2" pipe for the pool heater. I was given that spec from my installer #1, which made me think that I was not going in the right direction...
Installer #1 said 1/2" pex tubing and added insulation around pipe was fine for the lines for garage heat

For pool heat he just ran 1/2' pex w/o insulation - this made me skeptical...

Installer #2 recommended 1" of Wirsbo Multicore polyethylene with an aluminum lining - then insulate, for supplying heated water to the fan coil in the garage which seemed more appropriate.
Did not discuss req's for pool heater lines with installer #2 yet...

Is installation #2 overkill? or a better job that is worth paying up for?

I need to make a decision soon before the ground freezes.

Thanks.

 

OIC, I thought you thought I said that! so solly!

I agree, 1/2" uninsulated for the pool "feels" like not enough, but what I know about heating a swimming pool is nothing. I just envision that huge mass of water, and how much heat it's gonna take to raise it a few degrees, and then envision that little pipe... naaahhhh, can't be right.

Is this pool heater going to be summer use only ? or is it an enclosed pool you will use all year ?

I don't know if 1" is appropriate for the garage either! I haven't done any ciphering on that at all... it depends on a number of factors. The recommended flow rate of the fan coil you are using, the circulator pumps' capacity, etc., for example. These are the things that determine the proper pipe size, that's what I'm trying to say. Thinking more about this, your installer #2 may have realized that there will be signifiant "head" on that fan coil that your circ will have to overcome. By sizing the pipe larger, he's minimizing the amount of head the pump will see. (think friction), but again, these are the things the pros know instinctively, and we as mere homeowners have to think about and study in order to understand. What seems simple on the surface is but the tip of the iceberg.

Have your looked at the insulated PEX they sell for "heat transfer" purposes ? It's designed specifically for ground burial. I didn't shop prices, but it's something to consider. Ask your installer if he is familiar with it, and if he thinks it would be a good idea... They use it mainly for installing outdoor wood boilers. Google it up. (and make sure it is O2 barrier tubing!)

I would still look at solar pool heating...(which by the way can also be used to _cool_ an overheated pool in mid-summer by circulating water through the collectors at night)

or, you could add it later when you get tired of paying $60-$100 a month to heat your pool with oil! or swimming in water that's as warm as ... (have you looked at the "blankets" they sell for heated pools yet ?)

-

 

Solar would definetely be cheaper than heating the pool w/ oil. Will have to research.
Thanks again, I'll let you know how it all turns out.