#31 DHW recirculation, in a perfect world?

There are a lot of boxes to check to install and maintain an ideal DHW system.  Don't worry!  The guys can walk you through it.  How do you verify a DHW system has been balanced properly?  Which circulators pair best with thermal balancing valves?  How do you find out if you are meeting your minimum flow rate for a point of distribution mixing valve?

In this Episode, Greg breaks down the components needed to operate the perfect DHW system.  Pipe size, recirculation pumps, balancing valves, point of use and point of distribution mixing valves all play a role.  Dan will tell you where to find the proper piping diagram for various systems.  Dual tank, parallel mixing valve installs, the guys have seen it all.  They also share stories, straight from the phone lines, where they had to put on their detective hats to help figure out how to modernize a 70-year-old system and also work through a tricky dual-temperature recirculation piping project.      

Transcript

0:05
welcome to ask caleffi the podcast that
0:08
dives into real life problems that
0:10
plumbing and hvac technicians face in
0:12
the field we're your hosts from the
0:14
caleffi tech support team i'm greg tubbs
0:17
and i'm dan ferkus welcome we look
0:19
forward to sharing some stories from our
0:21
tech calls and using our background and
0:23
expertise to make your days a little
0:25
easier
0:27
[Music]
0:29
hey there welcome back to the ask caleffi
0:32
podcast
0:37
here in milwaukee in the studio today
0:40
how are we doing dan oh i'm doing great
0:42
today greg how about you oh can't
0:44
complain it's fall phones are ringing
0:47
eaves are falling phones are ringing yes
0:51
lots of halloween candy being passed
0:53
around oh yeah
0:55
even long after right
0:57
so
0:58
what do you uh what are you seeing
0:59
coming in on the phones lately oh man
1:02
phones have been busy
1:03
um a lot a lot of calls you know one one
1:06
call we get a lot of is about domestic
1:09
water research and mixing valves we sure
1:12
do and it seems like it's after the fact
1:14
once
1:15
either
1:17
i think mostly it's mixing valve related
1:19
it's
1:21
nine times out of ten it's going to be
1:22
because
1:23
our product has been installed right
1:26
with the recirc line right something's
1:28
not acting or performing right right
1:31
yeah and i mean we we don't sell pumps
1:34
we're not a pump manufacturer so
1:36
you know as far as like recirc lines and
1:38
recirc pumps we don't get involved with
1:40
that but when we get but our mixing
1:43
valves you know when you start putting
1:44
in a mixing valve into a project a
1:46
recirc line becomes a really critical
1:48
part of the performance of that mixing
1:50
valve yeah it certainly does you know
1:53
the pump has to be properly sized
1:56
and
1:57
let's hope
1:59
and we can hope but it doesn't always
2:00
happen
2:01
that the piping is also properly sized
2:03
for the velocity that's going to be
2:05
moving through it right yeah there's a
2:06
lot to consider there you know you start
2:08
looking at flow rates and pipe sizing
2:11
and pipe material yes especially pipe
2:14
material when you start looking at
2:15
velocities in in domestic water research
2:18
systems there's limitations that you
2:20
can't exceed right all not all piping is
2:23
created equal no i mean for example you
2:25
look at copper you don't want to exceed
2:27
five feet per second in copper no
2:29
because then you have to worry about
2:30
erosion corrosion right but then you'll
2:33
get
2:34
like size packs yeah and guys think gill
2:37
packs hey i'm going to run pecs because
2:38
pex is going to be really easy i'm going
2:40
to put it in staple it up run it back
2:43
um but boy two feet per second in packs
2:47
yeah that's pretty rough that's it's a
2:49
very
2:50
very major decrease in velocity yeah i
2:53
mean it definitely changes the pipe size
2:55
requirement you know if you're looking
2:56
at a
2:58
three-quarter inch copper line or a
3:00
three-quarter inch pax your flow
3:02
capabilities are going to be
3:04
quite a bit different certainly are and
3:06
then you have some jobs where it's cpvc
3:08
where they can flow more
3:10
but it's not always the nicest to work
3:12
with right right well what happens when
3:14
you exceed that velocity
3:16
you exceed that velocity
3:18
no matter what the product is you have
3:21
to consider that
3:22
potentially you're going to have a
3:23
problem with erosion corrosion
3:25
absolutely it's going to eat away at
3:27
that piping with copper
3:29
it turns into a miniature sprinkler
3:31
system you know over time like it might
3:33
start pinholing
3:35
in certain areas maybe where the
3:36
velocity picks up around an elbow right
3:38
you see that a lot well and that's
3:40
really why pipe sizing and system design
3:43
is so important and you know because you
3:46
so many guys think oh boy i'll just
3:47
change the pump you know i don't have
3:49
enough research i'm not getting the
3:50
performance i want i'll just put a
3:52
bigger pump in yeah more cowbell yeah
3:54
exactly
3:56
but that's going to change your velocity
3:58
and you're right you're going to start
4:00
to have pinholing or
4:02
you know the pipe's going to degrade
4:04
they certainly will it's not going to
4:05
last long yeah especially pax you know
4:07
pex says that low velocity very low
4:10
velocity
4:11
so in a perfect world ideally
4:15
to
4:16
really wrap your head around it a
4:18
perfect
4:19
research system would i i don't know i
4:22
just i think of what i would want to see
4:24
in a perfect research system
4:26
properly sized piping
4:28
properly sized and calculated pump yep
4:32
system balancing system balancing that's
4:35
very important the right size mixing
4:38
valve because most of this
4:40
most of these systems have a master
4:41
mixer in them right yeah you'll see that
4:44
especially commercial properties
4:46
commercial buildings you know you're
4:48
going to see a master mixing valve
4:49
you'll see a domestic research system
4:51
you know and face it when you start
4:53
getting into a hotel or a hospital or
4:55
something of that size you know you put
4:58
in a
4:59
one master mixing valve assc 1017 mixing
5:02
valve
5:04
to be able to achieve and
5:06
provide the maximum flow rates you need
5:08
at an acceptable pressure drop that
5:10
valve's going to have a pretty high
5:11
minimum flow rate it will yeah in order
5:14
to keep the velocities down you have to
5:17
have a big enough valve to to be able to
5:19
handle it right right exactly
5:22
what about balancing i mean
5:24
we make a lot of different balancing
5:25
products
5:27
but
5:28
there are cases where
5:30
some balancing valves are better than
5:31
others yeah there are or even just
5:33
having a balancing valve is better than
5:36
not having one at all right well and if
5:38
you have your system designed
5:40
um and calculated right i mean you can
5:43
put in we have you know like our flow
5:45
cals our 127s where very popular you can
5:48
pick a set flow rate for that mixing
5:51
valve and it's
5:52
you know pressure dependent i mean it's
5:54
going to provide that exact flow rate
5:57
within a
5:58
pressure differential range right a lot
6:00
of systems like what we're talking about
6:04
in cases they have to be that that flow
6:06
rates got to be confirmed
6:09
you know so then you got to add pt ports
6:11
right
6:12
another great option would be like the
6:13
132 yeah 132 is easily adjustable yeah
6:18
it's a pull pin and you can and make the
6:20
adjustment and you don't have to really
6:23
that's your verification right balancing
6:26
guy can pull that pin and see where it's
6:27
at yeah anybody a balancing guy an
6:29
inspector a maintenance guy can come
6:32
come around pull the pin check your flow
6:34
rate has a flow rate indicator that you
6:36
can
6:38
position when you set the system up so
6:40
that anybody trying to verify flow knows
6:42
what it should be set for
6:44
right
6:46
and then
6:47
i think one of my new favorites has got
6:48
to be that 116 that thermal setter the
6:51
fact that it
6:52
essentially self modulates as the risers
6:54
heat up and cool down it opens and
6:56
closes as needed allowing
7:00
it allows that water to continue flowing
7:02
because water's lazy and push onto those
7:04
further
7:05
risers that aren't maybe getting as good
7:07
of flow yeah you're right i mean when
7:09
you start balancing based on temperature
7:11
water is lazy you set it water takes the
7:13
path of least resistance so you know you
7:16
might have shorter risers that are going
7:17
to come up the temperature relatively
7:19
quick and they're always going to have
7:20
flow through them you know and then
7:23
risers that are further away that are
7:25
going to have more restriction more
7:26
resistance
7:28
and they're not going to come up to
7:30
temperature as quick or balance out so
7:32
the thermostatic
7:33
bouncing valve the 116 thermal setter
7:36
you know as soon as that
7:38
riser comes up to temperature it's going
7:40
to start to modulate the flow down never
7:42
close off all the way but modulate the
7:44
flow down and then push that on to the
7:46
next riser right so properly balancing a
7:49
system however whatever product you want
7:51
to use as long as it's being properly
7:54
balanced
7:55
that's going to save a lot of energy
7:56
yeah well i mean
7:58
boy you talk about the thermal setter
8:00
being one of your favorites yeah you
8:02
couldn't agree more you start looking at
8:04
today you know with all the variable
8:05
drive pumps
8:07
what better
8:08
okay so you put in a a variable speed
8:11
pump and it can modulate its speed based
8:13
on pressure differential right and then
8:16
you pair that with a
8:18
temperature or thermostatic balancing
8:20
valve that can modulate its flow rate
8:22
based on the temperature of the loop
8:25
how much more efficient could you get i
8:27
don't know how you can get much more
8:28
efficient but we see things often or not
8:32
more often than not
8:33
that are kind of the fly in the ointment
8:36
this size piping
8:39
incorrectly set up pump or
8:41
you know wrong size pump
8:44
piping is probably the biggest thing
8:46
though yeah absolutely is you know not
8:48
only size but just how the system is
8:51
piped
8:53
i mean that's a that's a rabbit hole we
8:55
can jump down and i think it's worth
8:56
jumping down but i just took a call
8:58
today
8:59
where
9:00
it was a
9:02
assisted living complex
9:05
and they had had problems with another
9:08
set of thermostatics that they had put
9:10
in okay um
9:12
the uh the contractor said oh we'll put
9:15
this legio mix in and it'll make
9:17
all your problems better well they put
9:20
it in they had a little more control
9:23
okay over the old thermostatic like they
9:25
couldn't get below 130 and this
9:27
this facility gets inspected regularly
9:30
okay
9:31
not to exceed 110 degrees out of the
9:34
faucets and they don't have anti-scald
9:36
in place okay but they weren't able to
9:38
control it both 30. so
9:40
originally with the old ones not below
9:42
130. sure
9:44
now with the new mix valve they got it
9:46
down to 120
9:48
but it was fluctuating a bunch okay
9:51
so
9:53
talked to talked to the guy on site and
9:55
happened to be the maintenance guy who's
9:57
who we most of the time end up talking
9:58
to because the plumber installs it and
10:01
you know his job is done he moves on
10:04
right well the guy that's on site the
10:06
maintenance guy is constantly monitoring
10:07
this he's in charge of this this is his
10:09
baby
10:10
so
10:11
he
10:12
is monitoring it and
10:14
you know he calls and says hey this
10:16
thing's just not doing what it's
10:18
supposed to do
10:20
so one thing leads to another going
10:22
through some things find out what size
10:24
valve it is so okay we know it's an inch
10:27
and a half all right an inch and a half
10:29
valve has a minimum flow requirement of
10:31
6.6 gallons per minute
10:34
all right do you know what size your
10:36
recirc is
10:37
well it's piped in three-quarter okay
10:40
do you know what your pump curve is
10:42
telling you what what what can that pump
10:44
handle you know on speed x because it
10:46
wasn't a variable speed pump it was a
10:48
fixed speed pump sure and it turned out
10:50
it wasn't speed adjustable it was one
10:52
speed and that was it
10:54
um
10:55
he didn't know
10:57
you know and you can go digging and
10:58
there might be four variations of that
11:00
pump and it's hard to know which one it
11:02
is right we know it's one with either
11:04
stainless or bronze veloute or a brass
11:06
flute but we don't know we don't know
11:09
which variation it could be sure
11:11
so that's the tough part
11:13
is knowing if your pump is
11:15
too big or not big enough right in some
11:18
cases yeah absolutely you need to know
11:19
that you can provide sure the flow rate
11:22
to meet the minimum and you know what
11:23
one one great test if you are on site
11:26
and you have a mixing valve that's
11:28
hunting around and it's not meeting
11:29
minimum
11:31
is to shut the recirc line off
11:34
shut the pump off valve it off
11:37
and then go out into the building and
11:38
open enough fixtures so that your and
11:41
confirm that you're flowing more than
11:42
your minimum flow rate and if that valve
11:44
steadies and
11:46
controls it's not a valve problem it's a
11:49
research problem right so here's the
11:52
here's the icing on the cake with that
11:54
this pump was wired in with all the
11:56
boilers on a master kill switch along
11:58
with several other pumps throughout why
12:00
they did that way i don't know okay so
12:03
he could not shut the pump off without
12:05
shutting the boilers off and sending
12:06
some sort of an alarm
12:08
which was kind of frustrating okay
12:10
so
12:11
i said all right let's discuss what the
12:13
piping looks like i said you should have
12:16
from the from the research the research
12:18
return past the pump downstream of the
12:20
pump it should go to two places
12:23
one it should go back to either the cold
12:26
supply of the tank or a dedicated
12:27
research port in the tank right
12:30
and two
12:32
into the cold
12:33
inlet of the mixing valve sharing the
12:35
cold feed okay right check valves need
12:37
to be in place isolation valves highly
12:39
recommend it yeah and good thing about
12:41
that is in every one of our installation
12:43
manuals we provide that pipe drawing we
12:46
do
12:47
for those who
12:48
are good at looking at installation
12:51
instructions it's there yeah we make it
12:53
easy it's in every every one of our
12:55
mixing valves has that drawing in the
12:58
installation manual certainly does and
13:00
we have other variations that if you
13:02
call here
13:03
dual tank dual valve we have some
13:05
drawings that we can share sure
13:07
so
13:08
the fly in the ointment here
13:12
the only place the recirc return was
13:14
going back to was the tank yep
13:17
he had the valve set on set one
13:19
temperature
13:20
down as low as he would want to go with
13:22
it at 104 degrees sure he was still
13:25
getting 126 degrees out at the faucets
13:28
over time okay
13:31
the system was creeping yeah the system
13:34
was creeping so that's why and it has no
13:36
way of dumping hot water once it's
13:39
creeped up unless someone opens a faucet
13:41
for a period of time to dump that hot
13:42
water out right it has no way of of
13:45
cooling off oh exactly and you know when
13:48
you're not
13:49
that's why the problem got better with
13:52
the legio mix than it did with the
13:53
thermostatic because it closes off but
13:55
it takes time to close off right right
13:57
yeah the the legio mix will close off
13:59
hotter cold 100 percent where
14:01
thermostatic typically won't right
14:04
um but you're right it ha it had he had
14:06
that mixing valve coming back on the
14:08
cold side of the valve
14:10
once his recirc line was up to
14:12
temperature it would resurf through the
14:14
mixing valve right through the cold port
14:16
back out through the mixing valve add a
14:18
little hot as it needs to to maintain
14:21
the desired mix temp um and the valve
14:23
would perform well for him yeah so now
14:26
he's calling his plumber back and he's
14:28
going to have him tie that bridge in
14:30
sure right to right to that cold inlet
14:33
of the mix valve
14:34
so that way they're you're not
14:36
deadheading your pump
14:38
you know if you were just tied into the
14:39
cold side of the mix valve it wouldn't
14:42
deadhead if you had
14:43
check valves in place like you're
14:44
supposed to right keep water from
14:46
flowing backwards where it shouldn't go
14:48
yeah i had an interesting one as well
14:50
did you um so again it was with the
14:52
legio mix and the problem the contractor
14:55
was having is that
14:57
he had his mixing valve set to deliver
15:01
115 degree supply water out to the
15:04
building
15:05
but he was getting 140 degree water out
15:08
to the building oh
15:10
so we started diving into and it's like
15:11
okay
15:12
you know hold on you have the mixing
15:14
valve and it's set to deliver 115
15:17
degrees out to the building yeah but
15:19
your building loop
15:20
is 140 degrees
15:23
how's that happening and what we
15:25
determined is he had this was a
15:27
commercial building
15:28
where they had a high temperature
15:32
line
15:33
and a mixed temperature line so the
15:35
mixed temperature line fed the rooms in
15:37
the hotel the high temperature line fed
15:39
the kitchen
15:41
but they had a research on both and when
15:44
we looked at where the research were
15:45
tied in he had it tied in right to the
15:47
cold side of the mixing they were
15:48
sharing the return weren't they yeah he
15:50
had oh no he had
15:52
a high temp recirc and three
15:54
mix temp research all tied into a
15:56
manifold
15:57
and then it split and one side went to
15:59
the cold side of the mixing valve and
16:01
the other side went back to the tank so
16:02
he had it piped right sure except
16:06
what happened is so you're bringing that
16:08
high temp recirc back and keep in mind
16:10
that high temp should have its own pump
16:12
and the mixed
16:14
low temp we'll call it mix the mixed
16:16
temp research should have its own
16:19
dedicated right well and they each had
16:21
their own pump but the problem is they
16:23
were all tied into like a manifold
16:25
and then came back to the cold side of
16:27
the mixing valve in the tank so what was
16:29
happening is the mixing valve said okay
16:32
i don't have you know we don't have any
16:33
use in the building
16:35
i need 115 degree water
16:37
and it's seeing 140 degree water from
16:40
that high temp research coming in on the
16:42
hot side and it's saying okay i need
16:44
more cold i need more cold so it's
16:46
dumping it's shutting the hot off coming
16:48
into the mixing valve but the cold side
16:51
which is the recirc water coming back is
16:53
140 degrees because that high temp
16:55
research is coming back on the cold side
16:57
certainly is and it's dumping in yeah so
17:00
with that they had to actually split
17:01
that high temp recirc
17:03
and pipe that back to the tank on its
17:06
own
17:07
and separate that from the mixed return
17:10
so that now the mixed return is able to
17:12
run through the mixing valve and the
17:14
high temp returns always going back to
17:15
the tank
17:17
well
17:18
it's tough to try and keep everything
17:19
straight for these guys in the field too
17:21
because
17:23
every job is different
17:25
and a lot of this a lot of our stuff a
17:27
lot of our product legible mix
17:29
especially is going in as a replacement
17:31
for old thermostatics that are very
17:33
expensive to replace or rebuild right so
17:37
you're kind of
17:39
as the plumbing contractor in the field
17:41
your back's up against the wall to do it
17:44
as inexpensively as possible
17:47
and to do it quickly right get the
17:49
building back up and running oh sure and
17:51
sometimes you're out on an existing
17:53
building existing research
17:56
you know
17:57
you don't know where where it's coming
17:58
from right you don't know if it's even
17:59
hitting half the building exactly
18:01
doesn't have balancing valves don't know
18:03
you don't know you need to find out yeah
18:05
yeah i talked to a guy with a 70 year
18:07
old building
18:08
today
18:09
this morning and
18:11
he he's like i'm pretty sure there's no
18:14
balancing to be had in here right there
18:15
definitely isn't anti-skull but they
18:17
want to do legionella control
18:19
and that's another subject for another
18:20
day we can we'll jump down that rabbit
18:22
hole another time but right
18:25
whole new set of requests
18:27
a whole new set of requirements that
18:29
we'll we'll talk about maybe another
18:31
time and i'm sure we've covered some of
18:32
it on on previous podcasts but
18:36
yeah there's certain
18:37
components that got to be
18:39
installed in order for that to to work
18:41
properly without someone getting sued or
18:43
killed or hurt yeah that that's
18:45
a challenging retrofit because there's
18:48
so many additional pieces that need to
18:50
be added
18:51
recirc line is super important with
18:54
thermal disinfection i mean that's how
18:56
you're
18:57
achieving thermal disinfection and
18:59
proving it's complete right um again
19:02
this that's a whole podcast on its own
19:05
but you start getting into existing
19:06
buildings
19:08
where research was marginal to begin
19:10
with
19:11
you know you really need to look and see
19:13
what you can do to to make sure that
19:15
that's going to be adequate with your
19:17
new mixing valve or new pumps
19:20
thermostatic balancing valves that work
19:22
great in that application they certainly
19:24
do
19:26
well i think we had some pretty good
19:28
information on research hopefully it's
19:31
helpful to you guys
19:33
we hear about it several times a week
19:36
and i think it's always a good topic to
19:38
to cover
19:39
so i don't know if you want to hear
19:41
something
19:42
more about recirc or any other topic hit
19:45
us up on our tech email yeah anything
19:47
you guys can think of that you want to
19:48
hear us talk more about or you want to
19:50
learn more about please send us an email
19:52
yeah
19:54
thank you for tuning in if you ever need
19:56
help please feel free to contact our
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tech support team anytime at
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or call us during our business hours at
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at 414-238-2360
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[Music]
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you