Need advice for heating a room addition: options?

kiwanda

Hello-



I've asked my question in a few forums and have had three HVAC companies visit my house, but I'm still looking for options. I have a ~275 sq ft addition (bedroom, bath, hallways) that was built to code ten years ago; it is currently heated/cooled by a PTAC that is noisy, ugly, and leaks cold air in the winter. I live in central MN so we see -25F occasionally each winter.  The room hovers at 40F with no heat on in the winter as it shares two walls with the heated part of the house.



I'd like to replace the PTAC with an alternative and do not necessarily need AC. The addition is on a slab and due to location we cannot connect it to the main house HVAC. We have gas and power accessible to the addition, but the mechanical room for the house is in the basement so it would be hard to run lines and impossible to runs ducts from their without, say going through the unconditioned garage.



Options I have considered:



-baseboard electric: cheap, inefficient, ugly, noisy

-hydronic: costly, complicated install, space too small to justify adding a boiler

-room-sized gas furnace: HVAC pro says the space is too small for product

-electric thermal storage (Steffes): bulky, costly, but qualifies for discount electric rate

-small gas furnace in attic: ducted to this space, but will cost $3K+ by best estimate

-small direct vent gas "stove": costly, questionable safety as main heat source



Anyone have other ideas? Or recommendations from among these options?  Right now I'm leaning toward removing the PTAC and putting in electric hydronic baseboards, largely because I know we can drop 240v from the attic and the materials will be relatively inexpensive. Operating costs will be high, but this option seems like 1/3 the cost of the others. I'd really like a gas room heater (wall unit) of some sort, but two HVAC guys have told us the space is too small.



Thanks,



Kiwanda

lchmb

have you

Has anyone discussed using a Rinnai space heater? Sounds like a good spot for one and as long as you have an outside wall and can get ng/lp to it and have power in the room it may do exactly what you want quietly...

http://www.rinnai.us/direct-vent-wall-furnaces/

you can also look up clearance requirements to see if you can use one..

BTW, I believe the smallest unit is 11,000 btu. That's pretty small and they modulate so they keep the temp very close to what you set it at...

moneypitfeeder

fireplace?

I have a friend that uses a gas fireplace to heat a basement all day long every day through the winter, their rec room is down there. Its set with a thermostat and the doors are kept closed, so no fears of open flames when no one is home. I couldn't honestly tell if it was a vented or unvented fireplace, but its pretty to look at and they've said its efficient.

kiwanda

Rinnai is too big, fireplace too dicey

One of the contractors I called in is a Rinnai dealer and he claimed the company told him their smallest unit was still too large for the space.



Re a fireplace, it seems like there would be a big efficiency hit in addition to the safety factor. A gas "wood stove" might work, but again the smallest one I found locally was like 24K BTU which was still too large.



I can get a gas line to the room, so am looking into a Toyo heater now: http://www.toyotomiusa.com/products/LaserVentedHeaters.php  My family in Alaska swear by them but I can't find a local dealer.



-kiwanda

James Day_2

Mini Split

What about a ductless heat/ac unit.  Alot of companys make them  fujitsu, mitsubishi, samsung.  All make heatpump units that are good down to about -5 degrees and sould be good for a small application.  They make units down as low as 9000btu I believe.

CMadatMe

Try This

May be perfect for this application. I'm not recommending the brand but the product does fit the application. I use to sell a similar product called Orbis. Worked very well for these types of applications.



http://www.eskabeusa.com/

icesailor

Rannai Too Big?

I've put in a few Rannai's. A couple in smaller spaces than yours. Like over a finished garage where the roof is part of the ceiling. The smallest Rannai was not over sized. They modulate.

They have thermostats. The worst thing that can happen is that they cycle off.

I have an electrician friend from Minnesota who has an expression. "They're smart, we're not". I guess I'm not smart enough to understand why the smallest Rannai is too big for this room when it is -24 degrees outside. But I'm teachable.

lchmb

I'm with

I'm with Ice on this one. The smallest Rinnai is 11000 BTU's and it modulates down to 5500 BTU's.. That's almost a candle burning...what less could you want?

Jack

Smallest Rinnai is the EX08

It will modulate from 2k-8kbtu. The EX11 was proving to be to large for an average bedroom. 5500 being the low on the 11 at 82% you are netting out to about 4k min. That is a lot of heat in a small room. We asked Rinnai to give us the smaller capacity unit and it has worked out well. One thing on the 08. You cannot add vent extensions as withthe other units

Jack

Smallest Rinnai is the EX08

It will modulate from 2k-8kbtu. The EX11 was proving to be to large for an average bedroom. 5500 being the low on the 11 at 82% you are netting out to about 4k min. That is a lot of heat in a small room. We asked Rinnai to give us the smaller capacity unit and it has worked out well. One thing on the 08. You cannot add vent extensions as withthe other units

lchmb

thanks Jack

I missed the 08 unit..my bad..:) Not thinking you could get much smaller than that though...

icesailor

Heat Loss Calculation?

Has anyone done an accurate heat loss calculation on this room? A room around 16'X16' with three outside walls and a ceiling? How many BTU's?

The room I am sitting in is around that size and I have more radiation installed that 10,000 BTU's and I'm not in Minnesota.

Someone has something against Rannai's

kiwanda

Re heat loss calc

I asked the Rennai dealer to do one; he took the room dimensions at least. Called back after a few days and said the mfgr told him they were too big; he actually said I should call an electrician and just go with electric baseboards. He agreed that the $3-4K price tags on things like the Steffes electric thermal storage unit was unrealistic.



I guess I'll call in another contractor and ask them specifically to do a Manual J for the addition before I ask about options.



Thanks!



-kiwanda

lchmb

maybe

maybe he looked at the wrong estimate...I would get a heat loss done, and see what your actual needs are. Then you can look at getting the proper unit for your needs...

icesailor

advice

YGTBK!!! That dealer told you that? What a lazy (whatever). He's probably complaining about how slow sales are.

If someone calls me on the phone, they want to spend money. It's my job to help you do that.  Does that turkey think that customers will drive up to his door with a wheelbarrow full of cash and drop it off so he can figure out what you need?

Post your room size, outside dimensions, window areas/sizes, wall insulation, exposed areas. etc. I'm sure that someone here will help you.  

icesailor

More Advice:

I just went on the Rannai Web Site. They have a heat loss calculator that you fill in the blanks with your information. I just filled it in with generic information based on a 16'X16' room and they had a recommendation for you. (It wasn't an electric heater.)  Go to the Rannai Web Site and click on warm air furnaces.

My generic estimation of this room was 6,000 BTU's. I just threw in window sizes. Remember, these heaters modulate. There are a ton of these Rannai heaters where I work and in the winter, it blows so hard, it will blow the feathers off of a crow bar. They listed all kinds of areas in Minnesota. You said "central Minnesota". I checked Mankato. That sounded cold.

I'll need to do an IBR calculation with my Slant-Fin program.

Call another seller or check their web site for dealers.

If I didn't live in Massachusetts, I'd be knocking in your door tomorrow at 8:00 AM. 7:30 AM if you'd let me.

I also get a lot more than 6,000 BTU heat loss in the room you describe with my heat loss program. Because it modulates, I'd go with a bigger unit. But that's my opinion. Give us accurate measurements of the room.

MNPLUMBER

Rinnai

I have two Rinnai units. One in my home and one in a cabin here in Northern Minnesota. They are both the 1004F direct vent units. They have both been installed for over six years with continuous use, they are very easy to install and are bullet proof. The cabin is only about 1000 sq. ft., this unit is using propane and it's so efficient because of the modulation it hardy uses that much gas.

The unit I have at home is a natural gas unit and does a great job also.

kiwanda

Room, insulation, and climate details

OK, here are the details of the space we need to heat, in case someone feels like doing a rough calculation:



-space is 252 sq ft of floor, with ceilings at 8' 5", so about 2,150 cubic feet



-rooms are bedroom 153 sq ft, bath 38 sq ft, closest 11 sq ft, and hallways 50 sq ft



-there are two windows on the exterior (north and west) walls, 19 and 14 st ft, so 33 sq ft total. These are double pane casements that I assume meet MN energy code (U 0.35)



-there is one 32" insulated steel exterior door



-there is ~42 lin ft of exterior wall; the balance are shared with conditioned interior or unconditioned garage spaces (the garage is insulated and sits at about 40F in the winter)



-the space is built on a slab and framed with 2x6 as the rest of the house. I assume it was also built to MN energy code in 1998, so expect R44 ceiling, R20 walls, R10 over slab.



-we are on the border of IECC climate zone 6/7. Average lows in January are slightly below zero. Our heating degree days average about 8500 per year. The neatest city is St. Cloud, MN 56303.



If there's any other info I can provide please let me know.



Thanks,



Kiwanda



-

Jack

Check Rinnai.us

go to DV Furnaces and the heat loss calculator is listed in the left hand margin. You can run the numbers yourself. A straight manual J is inaccurate for a Rinnai as they typically add a factor for duct losses which the Energysavers, being net to the space do not have.

kiwanda

Comes up about 6,400 for the heat load

Ran the Rinnai calculator and it came up with a heat load of 6,381. It appears that their calculator may be out of date as it recommends a model that doesn't show up in the product line (RHFE263). Looks like that may now be equivalent to the EX11C in the current line.



The only dealer near us is the outfit that already said Rinnai doesn't make anything small enough for this space, so I guess I'll go looking for another dealer and try again.



Thanks!



-Kiwanda

lchmb

when your done

Make sure to come back and let us know how you make out.

Jack

You are correct in the

263 vs 08 line-up. they changed the model numbers to reflect max btu input a while ago. Call Rinnai at 800 621-9419. Tell them you are having difficulty finding a local dealer and you'd like to talk to the area rep or regional mgr. Let me know if that doesn't work for you. These are slick little units and they last! I estimate that 90+% of those I sold in 1991 are still in the field.

icesailor

Rannai Heaters:

They are tough little units. People that have them, love them. You won't be sorry.