Rinnai Heater Sizing Question

[boulderz]

Looking for advice on sizing a Rinnai for my 24 x 20 well insulated garage in VT. I am wanting to buy a used unit and install so can consider different options. I currently have an Empire DH 25 or 35 which smells awful (had mice in it in the past and no matter how much I clean it I can't get rid of the smell, I'm over it).

The most common ones I seem to see for sale are the Rinnai 556F (8200 - 20700 BTU) and 1004F (10500 - 36500 BTU). Would these be good options or too large? I do plan an addition to the garage at some point. Anyone offer advice? Maybe a smaller unit is better. I am not worried about anything freezing in there, I usually just turn on the heat when I know I'll be in the garage.

 

[fitter30]

Empire are 25& 35k btu's recheck ur empire then choose. I'd go with the larger since they vary the input. On the low btu their only 2 k difference.

 

[Jackfre]

The 556 will take care of the job. Now, the caveats. How is the insulation? Does the door seal well? Fitter is correct in pointing out the low fire difference of 2k, so your choice is the high end and size of the unit. The 556 will heat the place. The 04 will do it faster. Both have the programmable stats built in and use the same vent. I doubt you will have problems finding a used unit in VT. We estimated that at one time almost 5% of the homes and apts in VT had Rinnai DV’s. One suggestion prior to installing. Clean the blower wheels. The ‘04 is easy to reach with the cover off. The easy way (?) on the 556 is to do it from the back with a small brush and your air compressor. You will be happy you did this and so will the unit

 

[boulderz]

Thanks for the replies. The space is overall pretty small being 24 x 20 and only 7' ceilings. Don't know why they built it with 7' ceilings, has barn style slider doors. I plan to jack it up and put garage doors in. I have 4" of polyiso foamed in to the ceiling and 2" in the walls. But as I said, I hope to expand at some point so don't want to go with a small unit. I thought I read somewhere that a smaller unit would run constantly and that would be better to control heating?

 

[Jackfre]

They will both run constantly unless both are oversized for the load. By doing this they deliver the best even temp. If they cycle on/off regularly you end up with the heat, then cooler, then heat. Essentially an oversized heater runs like a single stage unit. Rinnai’s have seven stage burners and blowers. If you look at the 1004 it fires from 10.5kbtu-38000 (36.5 LP). The 556 will fire 8kbtu-21 (20.5 LP). The 1004 will step in 4k increments Approx 10,14,18,22,26… The 556 8, 10, 12, 14, 16, 18, 20. I heated my 30x34x10 shop with the EX22, the 556’s replacement. It did an excellent job. Rinnai came out with the 1005 and sent me a prototype to test. I put it in it too heated the same space. The only difference is that it brought the place up to temp faster. Beyond that I had excess capacity. The 556/22’s are smaller and quieter. Given your new doors, insulation package and sq footage I would go with the 556. Get a 22 model if you can.