Hydronic heating load calculations

[Ggg]

I’m building a shop, & I’m trying to install hydronic heat on my own. The issue I have is inconsistencies in info I’m getting from different sources. I have had three different sources (all of which are HVAC engineering companies) give me specs on what size manifold, flows, and btu tankless water heater etc. to use. All three have radically different figures. All three were given the same information for their load calculations.
**Before boiler people pipe up saying I must use a boiler... I DO NOT have the money for a boiler. This MUST be done with a tankless water heater.**
Back to my calculation issues, here’s an example;
Water heater btu’s varied from 110,000btu, 160,000btu, and lastly 250,000btu plus a 50,000 make up heater.

So after getting such radically different answers I’m leaning toward doing my own load calculations. Are there any links or recommended software people have used for hydronic heating load calculations?

 

[whatuusay1]

What was the load calc parameters? Its pretty easy to do a manual J calc and estimate the required heat/cooling BTU's. Most typical spaces (1k sqft) are going to be in the 25-35k BTU. You do not want to oversize, thats a major mistake often made with heat sources in radiant designs. I have an 80k BTU boiler and its more or less the smallest boiler you can find (ensuring that the turn down rate can accomodate for the smallest load it might see). You can use buffer tanks to try and deal with a larger than desirable boiler but its much easier to plan it correctly up front, much cheaper design and operating costs.

I used LoopCalc to work up the Manual J, loop numbering, spacing, size, floor requirements etc. LoopCalc has a free trial that you can use to work everything up for free. I'd recommend just doing it yourself, do not assume these companies know what they are talking about.

 

[tricountytrail]

All three were given the same information for their load calculations.
You didn't post the info?