Boiler Undersized???

[Bitz14]

I have a car wash 24'x30' with 2 12'x12' sunshine doors. The plumber sized my heating system with a 11kw electric boiler (in floor loops) as we have no gas in town. I am having trouble with he heat keeping up on very cold days even when I close the car wash and the doors don't open. I have temp set for 10C and it only gets to 4c. The sensor is not mounted in floor it is on the wall. The boiler only ever gets up to about 90-95F. I have the elements almost as high as they can go. I asked him if it was under sized and he says no. What are some thoughts. Also what would increasing the boiler size to a 18kw boiler do? Would this help or be worth the extra cost?
Thanks
Brent

 

[Jadnashua]

11Kwhr equals about 37.5KBTU...the doors probably aren't all that energy efficient, and without knowing what insulation is in the walls, ceiling, and underneath the slab, it's hard to say, but empirical evidence says it's not enough!

But, if you're using an air sensor, and there's a lot of hot water vapor floating around in the car wash, it may not be sensing things accurately. Maybe moving the thermostat might help, but in-floor sensors may work better.

 

[Sponsor]

 

[Bitz14]

So would going to an 18kw boiler solve my problem?

 

[Dana]

There are too many design details that would have to be known if simply putting 5-%+ more power into the slab would allow the system to hold the line at +10C even when it's -30C outside. You may be asking too much from the slab radiation, or you might not.

This could potentially be an issue of insufficient pumping rates. With 95F water out of the boiler and a room temp of 4C when it's struggling, not keeping up, what temperature is the surface of the slab? What is the entering water temperature at the boiler under those conditions?

Antifreeze in the system water lowers the heat transfer rates both at the boiler and in the embedded tubing, but going without it is a bit risky in your situation.

 

[Bitz14]

There are too many design details that would have to be known if simply putting 5-%+ more power into the slab would allow the system to hold the line at +10C even when it's -30C outside. You may be asking too much from the slab radiation, or you might not.

This could potentially be an issue of insufficient pumping rates. With 95F water out of the boiler and a room temp of 4C when it's struggling, not keeping up, what temperature is the surface of the slab? What is the entering water temperature at the boiler under those conditions?

Antifreeze in the system water lowers the heat transfer rates both at the boiler and in the embedded tubing, but going without it is a bit risky in your situation.

Thanks