Big fuel bill

Wayco Wayne_2

to look at a problem job with radiant floor heat. It's a big house but the nat gas bill is way out of proportion. $2400 in Dec and 1800 in Jan. Yikes. At the heart of it is a Buderus cast iron boiler with a primary secondary piping set up. The piping job was beautiful. At first glance you could only suppose the piper knew his craft and took great care to do it right. Then I started looking closer. The sequence of heat emmitters coming off the primary loop was Indirect water heater first, (that's good) radiant floor second, (what the...) and 3 fan coil loops one after the other, so the return of the first one cooled the hot water to the second and so on and so on. (holy cr--p!) The fan coils supplys coming off the top of the loop had flow control valves but the returns didnt and boy were they hot. Defineitely some mono-laminar flow going on there. The boiler had no cool water protection so when the radiant floor first comes on it would drag the primary water temp down, down , down. Really should have used a condensing modulating boiler, or at least a thermostatic bypass to protect the boiler. Then I inspected the slab itelf. It was 3.5 inches of concrete on top of a sub floor with R-19 beneath it. They filled up to the top of 2 x 4's around the perimeter walls with no perimeter insulation, however... wherever there were Windows and French doors (and there were a lot of them) they poured right up to the cinder blocks that were contigous to the outside. (Let's grow flowers in the Winter) I feel bad for the Homeowner. What a mess. At least the original contractor is still answering the phone. WW

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Brad White_9

Series versus Parallel

Good share, Wayne. Funny -but not amusing- how it is usually the violation of fundamentals that trip us up the most.

I suppose if the piping was parallel they would have better control (potentially equal or top-end supply temperatures) at the fan coil units. But that will not help the edge losses in the least.

I would fault the GC for not coordinating (not understanding really) the needs of floor construction (edge protection) in a radiant system.

Constantin

Note ideal, for sure...

... but is this the whole story?

Methinks that this house is afflicted by a bit more than just slab-edge losses and a mis-piped manifold or two. What is the size of the place?

Weezbo

What a shame.

One thing leads to another.

re piping some of rhe header may help protect the boiler and get the heat where it belongs buh the home must be rather diverse in its standards of construction "Techniques" you may find there is all kinds of problems with the sheet metal and its lack of insulation and sealing etc... on top of many other "corners" of the creative reality. Here again i would like to mention an Ultra sound from Go Pro. place one tone generator in a duct or plenum and you can track leaks broken fittings whatever....Vapor barriers and insulation both add to the mix....sounds real drastic $ in order to pull it out of its downward spiral of diminishing returns.

Good Luck. Spring is comming Snowed in the hills yesterday here *~/:)

Brad White_9

Spring in Alaska

Hey Weezbo,

Tell me. In Alaska do you mark spring on the calendar or with a stop watch?

hr

pull out

your HDS and laptop and run some numbers. It should be an easy, but time consuming task, since the home is up and running.

Was a heat load calc run in the first place? How does the equipment stack up to that figure.

Depending on the BTU load of the radiant it may not pull down the boiler return that much. If it is 1/4 or less of the total boiler output it shouldn't be a problem.

The edge loss could be a big number. Again, easy to calculate, it's a deolta T game. What about DHW overheating? This can keep a boiler running excessivly. it usually presents, to the homeowner, as too hot of DHW at the taps.

Short cycling? How does the boiler output match the actual load.

Sounds like a fun puzzle to work on.

hot rod

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Weezbo

*~/:) Brad ...

i have a Large round faced out door thermostat,it has "time" painted on it:) that seems like a New And Rennovative idea to be sure buh then again I am That kinda guy )

Brad White_9

Patent

that invention, Weezbo! My kind of guy.

Wayco Wayne_2

The house is

very contemporary. 6400 sq. feet and the 2nd floor is all lofts open to the first floor. The main ceiling height is about 30 feet. The boiler is not oversized, only 188,000 output but was cycling every few minutes due to mild outside temperatures. It probably runs all the time when it gets cold outside. I have not heard back from the HO. He probably just wanted some more ideas to throw at the mech. contractor. If he wants my help I think I would start with an infrared scan of the house at night, a blower door test, and a heat loss. After that, decide what to do and prioritize. WW

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