Do you calculate Heat Loss every job?

Supply House Rick

New construction and renovation? Just doing research because I see here almost every time someone asks a question the next response is usually "have you, did you, the first thing you need to do is perform a heat loss. Just wondering...

Thanks

Charlie from wmass

not every job

I also install bathrooms so not heat loss when sizing tubs. Also not when replacing steam boilers there I figure the radiation. But for hot water yes every time.

Unknown

Rick,,, No I don`t,,,,

I do a standing-count,,,, usually that "weeds-out" the tire kickers,,,,  when we`re there you can kinda-tell if the people are serious or not, I take-it from that point.

Charlie from wmass

I do not share my heat loss calcs

unless I get the job. The slant fin program makes it fairly quick to do a heat loss. I do not do a heat loss for every bid we put out but I do for every installation we do.

The Steam Whisperer (Formerly Boilerpro)

Yes, all hot water and most steam.....

usually end up downsizing a whole bunch and can offer more economical options when dealing with smaller sizes.  Steam installations are alot easier when putting in 140,000 btu's with a single riser verses 300,000 btu with dual risers.

TonyS

What Dave said

I like to guess what it will be, then do the heat loss to see how close I get. Usually pretty close but every once in a while one throws me. Most times I guess the right boiler size though.

Matthew Grallert

Heat Loss

I do a heat loss for every water system I do, like Tony said, sometimes you get thrown and it's sorta fun to see how close my guess really is.  Sometime I'll think; really that can't be right but of course the numbers don't lie.  The results can be surprising.

Better safe then sorry:-)

mars_6

Yes to an extent.

On the new construction projects I do a manual J, on a boiler replacement I will get the lineal feet of base board and match that load, providing the customer has no complaints with the existing system. On CI rads I find the EDR of the rads and base the boiler load on that provided the customer has been comfortable to this point. Sincerely Matt Rossi 

EricAune

I do!

I do it for many of the reasons listed above. 



Another reason would be because other guys don't.  And that has gotten me the job more than once!

Mark Eatherton

Yeah but....

and there's a but in every crowd, ain't there. :-)



What really conts more than a heat loss calc is a real time firing test to see exactly how many btuH the HOUSE system is drawing, and let me tell you from experience, it's a LOT less than we think it is.



For example, here at the palacial Eatherton Estates, the forced error furnace that resided here when I moved in was rated at 150,000 btuH (96,000 btuH output). On a bet, I replaced that with a 40 KbtuH water heater (24,000 btuH output) and my casa was muy comfortable. But it seemed like it was running ALL the frikin time, so I replaced it with a modcon, and I have sen it running at steady state design conditions at its minimum capacity with a net output of 12,000 btuH, so my hourly heating energy consumption is around 11 btu;s per square foot per hour, and this castle ain't no show case home. Standard run of the mill tract home by a medium grade builder. Sure, we insulated, but you can only get some much R value into a wall stud cavity. I call it reality heat loss.



If you can't be there at "design " conditions, record what you can (should be below 40 degrees F) and extrapolate to design conditions. Add something extra if you aren't comfortable with significantly under-sizing the heat source, but I have done it time and time again, and it works great. Never had a complaint of no heat unless something was broken.



ME



What kills me is the Germans touting their 10 btu/sq ft/hour 12

The Steam Whisperer (Formerly Boilerpro)

What Mark Said.......

When I do a heat loss I use the gas bills and extrapolate from them.  I do a simple load calc using Weil Mclains oldheat loss forms (none of the Weil dealers use them around here) just as a check and look at radiation.  Nothing like a real world number.  It shocks most people how small their boiler needs to be to function efficiently.   Also, if the sizing is on the borderline of what is available and if it masonry construction I use the smaller boiler because the lowest outdoor temp at night does not hit the interior of the home until 2 to 3 days later, which by that time it is already warmer outside.

Supply House Rick

Thanks guys

I used to have a contractor doing 1200 sq/ft modulars in and he brought me the plans every other week with pretty much the same items. I stopped doing the heat loss after the 1st house. 3-section oil, he said "Rick, what you need to know about me is I don't install 3-sections, make it a 4" That told me everything I needed to know about him. I think my heat loss was 24,000 btuh. Woo Hoo 4-sections for everybody!!!