Boiler choice

Gene Davis_2

We are on a budget, so please don't recommend expensive high efficiency boilers. We are spec builders, not heating contractors.

New construction, tight quarters. Walkout basement living space with mostly ICF walls will be heated via RFH, tubing in the 4" concrete slab with 2" rigid foam underneath.

Limited space in the mechanical room. It is 5/0 wide by 7/9 deep, and by the time we subtract out door swing space and that needed for the 2/0 diameter electric HWH, we only have a footprint area of roughly 4/0 deep x 5/0 wide for the boiler, its controls and manifolds, etc.

We've got 866 sf of slab area to heat with RFH, and roughly 750 sf of mainfloor space above it, to be heated with HW baseboard units.

Fuel is LP.

We are wondering if a W-M CGa-5, or a size up or down, will do this for us. There is a nice material savings versus a GV or an Ultra, and the CGa is a quite compact unit.

Our heating contractor has the plans and specs, and will size and price up the package.

ALH_4

small load, tight space

That is a pretty small load. You might use a Bradford White Combi2 to kill both the space heating and domestic with one stone.

Al Letellier_9

which boiler

If I may say so, any Weil will do the job, if properly sized for it. Make sure a proper heat loss is done and size accordingly. I understand budgets and used to do work for spec builders, but no longer do. I just couldn't convince them that spending a little more would add so much value to the home. Buy the best boiler you can afford.
Did you say electric water heater??????? Ouch. Unless you've got really cheap electric rates, use an indirect. Sure it's more money, but progress is passing you by using equipment like that.

Jeff Lawrence_25

You said

not to suggest a mod-con boiler, but look at the efficiency of the system. A mod-con will use much less gas to heat the space and give you the option of using an indirect water heater.

I'd set myself apart from the other builders by going for the high efficiency equipment.

Ken_40

Without a real heat load calc...

You're pissing in the wind lad.

ICF's are notoriously efficient envelopes. The W/M is a fine boiler. The "5" will be grossly oversized! The Munchkin T-50, as nice - and even smaller (wall hung). I prefer the W/M branded indirects to the Munchkin/HTP, but they are both stainless, and not at all pricey.

The size of the boiler is NOT determined by your boiler-room space requirements. It is sized based on design day load.

Almost all the "canned" heat load calulators that are free, take a lot of tweaking by a pro to come up with a legit load number. The ACH (air changes per hour) with an ICF house are off the charts in most cases. We find SIPS and ICF's to typically be 1/3 of standard stick-built for infiltration factors; e.g., one-sixth AC/H, not one or one half AC/H.

Hope this helps

Gene Davis_2

I know about the heat load req to size boiler, but . . .

Thanks for the reply. I really wasn't asking for help sizing a boiler, but for info as to whether one of the WM CGa boilers might be right for the heating needs.

The gross space figures were just for conversation. They give a very broad brush idea of where we are headed.

The house has an ICF foundation, but it is a walkout, thus two of the four downstairs rooms have woodframed exterior walls.

All the rooms in the 750 sf of mainfloor above the foundation are built with wood frame construction.

Uni R_3

People like you...

People like you are what's wrong with North America. So you're skimping on the boiler, skimping on the indirect, no doubt you'll be skimping on the controls for the radiant all so that you'll get more profit selling what could have been a far more efficient house. It's all so shortsighted. What a waste!

I'm surprised the "professionals" here are helping you on your skimp-quest!

ALH_4

smaller mod/cons

With a design load that is *probably* in the neighborhood of 30,000 btu/h or less, I think the Combi2 is an appropriate choice, for lack of smaller mod/cons. Given an 8-40MBH mod/con, the choice might be different. I guess the smallest Munchkin Contender is close. I dont think a cast iron boiler is appropriate for this situation because of the amount of additional equipment needed to accomplish the same thing at 3-5% more combustion efficiency. That money would be better spent on spray urethane foam.

These small loads are a little tough. What do you think?

Al Corelli_2

Door Swing?

Um, according to the code I go by, the boiler room door is supposed to swing OUT. What's your code say?

For such a small load, why not use the combi water heater? It surely must be cheaper than the WM and the electric tank. And it would leave you all that room in the boiler room. You should even have enough money left for some decent controls.

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kevin coppinger_4

I would not use...

the CGa...the air exchange is so small and tight that the CGs is the better unit...higher AFUE to...kpc

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ALH_4

dreaming

Like outdoor reset for the basement with a Tekmar 362 and the indoor sensor, constant circulation, no thermostat needed.......

Oversize the baseboard for the main floor to run the Combi2 at a lower temperature, one zone, and run it with a 356 connected to a 507 thermostat....

Back to reality....make sure you get a tempering valve on the water heater if you go this way.

Mike T., Swampeast MO

Seems a shame to use an inefficient boiler in a highly efficient shell.

If value pricing is your goal, I'd consider the "Contender" by Heat Transfer Products.

Design with reasonable care and you'll likely find little need for the Vision 1 option that allows for outdoor reset.

As others have mentioned, ICF structures usually have extremely low heat loss per square foot and in a home that size DHW needs are likely to exceed space heating.

Use HTP's stainless steel indirect (fine match for their boilers) for further true value as in all likelihood it will outlast many stand-alone "water heaters".