
Have we forgotten to make heat traps? (2012) - vq
https://www.esbe.eu/it/en/news/have-we-forgotten-to-make-heat-traps
======
mcmatterson
I designed and installed a complete hydronic heating system in our house last
year, replacing a conventional forced air system. It being the first time I'd
ever done such a thing (and indeed, the first time I'd ever really been
exposed to hydronic heating at all) I learned everything through reading
(mostly the excellent idonrics series at [https://www.caleffi.com/usa/en-
us/technical-magazine](https://www.caleffi.com/usa/en-us/technical-magazine)).
I went _really_ deep on the reading so while I had/have a pretty solid
theoretical understanding I was/am a complete novice on the craft side of the
field.

Overall, the practice seems to be very heuristic based, with every
installation being a bit different and rules of thumb being the norm. Our
system seems to work fairly well in practice, but I've been curious to get a
professional's opinion on it (the only pro that's seen it was the gas guy who
did the final hookup, who seemed impressed but didn't really offer any
specific criticisms).

Repo at [https://github.com/mtrudel/boiler](https://github.com/mtrudel/boiler)

I've since added an elixir based graphing system to it, at

[http://mat.geeky.net/boiler](http://mat.geeky.net/boiler)

~~~
jetbooster
That's interesting, as Hydronic heating is the standard heating method over
here in the UK. Reason its not done in the US I image is we don't often ever
need AC, so we only need to be able to turn the temp up.

~~~
LeoPanthera
UK hydronic systems usually use radiators. US systems are almost always under-
floor.

~~~
gxx
I once had a new house with hydronic under floor heating - the worst heating
setup I've every had - horribly slow to respond and expensive to operate. We
turn down the heat to sleep and finally I just shut off the heat to the
bedrooms and heated them a different way.

Our initial experience with the system was even worse than it might have been.
The people who installed it including the thermostats were plumbers and did
not realize there was a switch inside the thermostat to choose among three
types of heating systems. They left all the thermostats at the default forced
air heating setting. We suffered for two years with terrible overshooting and
undershooting of temperatures before my own research revealed that the hidden
setting existed and that it was set incorrectly. This helped but it was still
not great.

We were glad to get back to a forced air heated house. I do believe however
that hydronic heating with radiators is somewhat better than underfloor
hydronic.

~~~
m463
I wonder if better PID tuning would help, maybe adding stuff like ambient
outside temperature or weather prediction as a system input.

I know the nest thermostat does a lot of systemic learning and understands the
outside temperature. (I'm not recommending that system, just that a little
modern control theory might make things workable)

~~~
xattt
I have a 2nd gen Nest thermostat since they first came out in 2012 or so with
a hot water system, so I can speak from my experience.

There is a setting on the thermostat (True Radiant) that takes into account
the long heat-up times of radiant systems. With this setting off, overshoot is
real. On cold days, True Radiant does start the system earlier. For example,
it take about 2-3 hours in the deep of winter vs 30-60 minutes now.

However, it seems to be based to on a look-up table rather than an algorithm.
It doesn’t take into account forecasted conditions, such as a temperature rise
overnight, strong winds or decreasing/increasing radiance of the sun over the
season. Those latter factors do make a difference in whether the house reaches
the target temperature on time or whether overshoot occurs, and whether I am
slightly uncomfortable.

As far as I can tell, there is an automatic set-back for heat pump systems. I
wish this was given as an option for manual scheduling in True Radiant mode.
To this day, I can’t tell whether there is an effect on efficiency (based on
run-times which the thermostat dutifully displays).

I also wish the thermostats (in a dual-zone system with a single boiler) be
“genlocked” or run on common firing times with demand prediction for
temperatures to make use of boiler run-time, rather than running the boiler
just when there is a request for heat in one zone.

------
gowld
Simpler article:
[https://en.wikipedia.org/wiki/Heat_trap](https://en.wikipedia.org/wiki/Heat_trap)

~~~
Groxx
It also largely answers the question in the first paragraph:

> _Newer water heaters have built-in heat traps._

So it's "no, they're just done by default and hidden". Seems like a reasonable
thing to do.

------
thefourthchime
Seems like something trivial to make with PEX these days. I have no idea if
it's regular practice or not. The only downside I can see is if there was
recent hot water, it might take slightly longer to reach the faucet.

~~~
gregmac
My water heater has one made from PEX. From memory, I would guess it adds
about 18".

With 3/4" PEX at a relatively slow 1.5 GPM flow rate, that adds about 1.4
seconds to 'hot water delivery time', though that's not entirely accurate,
because the loop itself has some heated water trapped in it.

~~~
gpm
Shouldn't you also adding the length of pipe/water you are preventing from
being heated to that 18"?

~~~
gregmac
I actually don't think so, because you end up with only a gradient of
lukewarm-to-ambient temperature water, which you still have to purge in order
to get actual hot water. Even if you're going for just warm water, you still
have to purge some of it, then after a few seconds start continually adjusting
cold until the hot water from the tank gets to you.

------
dqpb
> _it saves you time and hazzel_

~~~
kazinator

      - '-'---'---,---- '-'---'---,--- ...

------
sctb
Since the submitted link has a download disposition we've updated it from
[https://www.esbe.eu/it/en/~/media/ESBE%20Public%20web_BRserv...](https://www.esbe.eu/it/en/~/media/ESBE%20Public%20web_BRserver/Documents/News/Heat%20traps/Heat%20traps%20in%20installations%2020120508.ashx)
to the abstract.

~~~
floatingatoll
This could use a (2012), per the article date.

~~~
sctb
You got it. Thanks!

