2 stage gas heater a no brainer?

[Tizzy]

Is the 2 stage valve option a no brainer? The heater I plan on getting is either a 75 or 90 Sterling. Everything I read indicates 2 stage is the way to go. Run on 1st stage to maintain and 2 stage to recover or increase temp quicker.
I keep the shop at 50f 97% of the time and bump it to 70 when I'm working.
Sterlings website recommends a 90 for my size shop. Most everything I read others are running a 75 with my size shop.

 

[Jackfre]

I generally prefer to undersize equipment. I then find it is big enough in operation. If it isn't you work to seal things up enough to bring the sizing back to the load. Two stage is definitely the way to go, but ask the question, what are the stages? When I first began selling two sage equipment in '91 it was a wall furnace and max was 38kbtu. I assumed the low fire was about 50% but found that it was actually 10kbtu. Why, because it delivered better comfort. You had a longer run time. Many appliances are two stage but the low fire may be 75-80% of max capacity. If that is the case and there is a substantial up-charge for the two stage, buy the smaller single and run it. Know the specs.

 

[yeldogt]

When sizing a two stage you still size the upper stage to design temp ... since design temp for a heater is the highest temp you may want on the coldest day -- that output is rarely needed ...unless you live in a very cold climate where the design temp (outside) remains steady for many days.

Since WWII most houses have insulation and some type of storm windows -- the heat load calculations are easier to do vs many shops that have such a wide variation in construction.

That said -- most people oversize home units .. so garages with decent construction are even more off .. always to the bigger is better.

As Jack mentioned. Two stage can be many things and you see what the actual numbers are?

 

[wes73]

I have the Modine HotDawg 75K with a 2 stage valve. I can tell the difference when it is maintaining or bring up to temp when I adjust it from 50 to 70. My thought was to get all the options and not look back. Also went with a separate combustion chamber in case of fumes in the garage.

 

[Tizzy]

Hi guys, im back with a few more questions. Do I need a 2 stage thermostat for a heater with a 2 stage valve?

 

[Showkey]

In garage shop situation.........two stage is overkill and extra cost has little or no benefit.

70k btu for 1500-2000 sqft well insulated shop will recover and get to temperature from 50* in minutes.

Multi stage 96% furnace in home heating Situation is nice upgrade ( costly) to maintain/ recover provide even temperature, quiet Operation and very comfortable home.

 

[Soccer918843]

I’m in the same boat I have a 28x52 10’ walls and sterling recommended a 105k for me i am also trying to figure out if the two stage is worth it.

Here are some questions I asked sterling and there response on it
That is not accurate.
" they claim it doesn’t save u anything"
- A heater is more efficient the longer it runs between cycles. This is because less of the heating time is spent getting the heater up to its maximum temperature. A heater with less output will run longer to heat an area than one putting out twice as much heat. In much of the heating season, when temperatures are not extreme, the 50% output will be plenty to heat your garage.

" may cost you more and it would heat faster in a single stage if I’m just turning it up when I go out to the garage"
- Most 2 stage thermostats are setup to switch the heater to full output if the temperature setpoint it is set to is more than a couple of degrees above the ambient temperature. This is exactly what you will be doing if you turn it up from a low temperature to a comfortable one.

That being said, will the 2 stage valve and thermostat extra cost pay for itself? Eventually yes. How long it will take really depends on how often you use the heater.

 

[Showkey]

This has been hashed and rehashed many times..........2 stage is about comfort, no drafts, even heating and quiet operation. Run time is longer with unit in low heat mode. Run time is shorter but more fuel is used in high heat. Some guys around here are still pushing 78-80% furnaces for home. Typical hanging garage heater is 80-86%. Efficiency and two or variable stages are not linked. 80% units are usually multi stage.


The two stage or variable furnace is NOT more efficient than a single stage furnace. 90 plus is 90 plus.... It will not save you any money on your utility bills compared to a single stage furnace. In fact, it has most likely cost ( slightly) MORE to operate.

A 2006 study completed by ASHRAE (American Society of Heating Refrigerating and Air-Conditioning Engineers) said this: “…while the 2006 ASHRAE test procedure shows only a 0.4% decrease in fuel consumption. The electricity consumption of two-stage furnaces as opposed to single-stage furnaces increases by 11%…”.

This increase in electricity consumption was mostly from the blower motor due to increased running time. It is only recently that has changed.