We just moved into a house (built in 1958) with a gas boiler, hot
water baseboard, with domestic hot water supplied through the boiler
as well. We have three zones of heating. 2 anomalies we've noticed:
1) During shower use the domestic hot water starts out lukewarm, gets
almost cold, and after about 10 minutes gets comfortably warm but
never hot enough to warrant mixing cold water in. I assume I can set
the water temp higher, but I wonder what would be causing the
2) The baseboards make some weird sounds. I've searched the newsgroups
and haven't seen the sound I'm hearing described; the best I can do is
it starts out as a fairly quiet buzzing sound, almost like the sound
of locusts in the summer, and gradually rises in volume over a span of
about 10 seconds. The other night it got so loud in my living room it
temorarily drowned out the TV! As far as we can tell this happens in
every room of the house but at different times.
My guess is maybe it's air in the lines, but it's not a "water
rushing" or clanking sound, more of a reedy buzzing sound.
Any ideas? I'll likely have a pro in to do any repairs but I'd like to
know what we're getting into ahead of time, to keep expenses down and
maybe to help direct the person in the right direction.
With a little luck, your problem is that the lower limit on your aquastat is
set too low so that the boiler does not come back on again until the hot
water has dropped significantly below the desired temperature. Try raising
the lower set point.
Or it could be that the boiler is not quick enough to keep the water hot
when the cooler return flow from the radiators mixes with the water in the
boiler. Try this: On a not so cold day, before taking your shower, turn
your thermostat down (in all zones) to 50 degrees, so that the circulator
does not come on. Then wait until the aquastat turns off your boiler. The
water in the system is now at the desired (set) temperature. Run your
shower. Is it warm enough? Does it stay warm? If this is the case, your
boiler is probably not sized correctly for both heat and hot water. It
might be a good idea to install a hot water heater in series with the boiler
(this will truly be a *hot* water heater). It will take the warm water from
the tankless coil on the boiler and heat it to the desired temperature and
store enough for your showers. This has the added advantage of allowing you
to turn off the boiler in the summer and use only the water heater to
provide the domestic hot water. This is more efficient than running the
boiler just to produce hot water.
Lastly, it could be that the tankless coil on the boiler is encrusted with
crud, thus making the heat exchange inefficient, and thus not getting the
domestic water warm enough. I *think* that there is now way to clean this,
so you will need a new tankless coil or you could just add the separate
water heater. HTH.
"Me" < email@example.com> wrote in message
A tankless boiler used as domestic hot water has a difficult time putting
out enough hot water to maintain any sort of temp for the domestic supply.
Think of it this way cold water from outside gets heated to be selectively
pushed through one, two or three zones depending on which zone is calling
for heat. Once that demand stops the water sits and cools, not only in the
boiler but in the pipes as well. So when you try to get hot water it takes
what is left in the boiler (probably a little warm) tries to heat water as
needed but it's pushing out newer water (cold) and then as the temp increase
you get your final temp (getting warmer)And with what sounds like air stuck
in your system somewhere it makes it that much harder to heat the water.
Shut down two zones, and check if the buzzing stops. Then rotate zones.
If you get the noise in all three zones then there it becomes fun to not
only bleed the system, but figure out where there air comes from.
When I lived in a house with zoned force hot water, I always bled the system
prior to the heating system.
Try to figure out where there first bleed valve is on your zones and work
around bleeding as you go.
I would add on a water heater strictly for your domestic supply, electric or
gas, they should probably cost about the same by the time the price stops
going up for gas. Or you can check into on demand heaters, just make sure
you do your research. So many out there don't meet today's needs
firstname.lastname@example.org (salbinak) wrote in
First, check your boiler pressure to make sure it's around 15 pounds or
so. Next, bleed the baseboards. Air can cause more than gurgles and
surges. It can cause vibrations that will drive you nuts.
Second, you need to check the aquastat on your boiler to be sure the
settings are correct. The "High limit" setting should be around 190 or
so. The "Low Limit" setting should be no lower than 160. What this
control does is to shut down your heating circulators in the event the
boiler temp drops below 160. Thus allowing enough heat in the boiler to
allow for your hot shower. Otherwise, the circulators would cool the
boiler off so much that your coil could not provide hot water. The 3rd
control knob is the "differential" setting. It can be set to around 10
or even 15 degrees. 10 is better.
Once you start a hot water use (shower, dishes, etc.) you draw the boiler
temp down. The burner starts so that the boiler heats up again. If at
the same time a circulator calls for heat, it'll only be allowed to run
as long as the temp in the boiler remains above that 160 degree setting.
If the temp in the boiler drops below that, it'l disable the heating
circuit temporarily so that your domestic water take precedence over the
heating. Check these control settings.
Third, your tempering valve located on the outlet of the domestic coil
could be bad. The thermo disk in these go to hell and need to be
replaced every so often. But don't waste your time on just the disk.
Replace the whole valve. Replacing just the disk seldom works. And I've
done hundreds of them. Better to go with the whole valve.
Forth, it's possible that you have a faucet leaking by internally if you
have any faucets that are the single handled type. Cold water will
always superced flow in a pipe since it's heavier. If a faucet is
leaking by, the cold water may not drip from it but it can trael down the
hot water pipe to the faucet you just opened for your shower. To check
this, shut the hot water down at the mixing valve on your boiler. NOT
the heating line. The smaller pipe coming away from the tempering valve
on your coil. Or shut off the cold water feeding this valve. Now, go
through your house and turn on the faucets to the hot water side. You
should get no water flowing. If you do, they you've go a single handled
faucet leaking cold water by. Locate and replace this bad unit. I
always prefer double handled faucets due to this malady of the single
That should do it. Try all of these in the order I posted them. With a
little luck, it might be nothing but the boiler setting. Post your
results so that others can see how you made out. That's why we're here.
Excellent info everybody. A couple of nights ago, before reading these
replies but after reading some other info, I went down into the
crawlspace and checked things out. What I found:
1) The "weird buzzing noise" is coming from one of the zone valves,
once I heard it up close I identified is as a solenoid noise, like you
get from a pinball machine flipper (a hobby of mine). When I rapped on
it with a knuckle it stopped, so I'm going to try blowing all 3 of
them out with compressed air, then replace if they still do it (they
don't look that old, and the ones they previosuly replaced are still
lying around so they may just be gummed up)
2) Hot water - I checked the aquastat, and the max was set a little
low, so I moved up both the min and the max. I was a little nervous
about it though, not sure what the practical max was but I remembered
reading somewhere previously that 190 or so was good, I know I don't
want it boiling!
The diff setting was on its middle setting, can't remember if that was
15 or 20, but I dialed it back. I wasn't sure how that related to the
min/max settings ad didn't want to set the min setting closer than
what the diff says.
Is there any reason not to set min to 180 and max to 190, for example?
And is there an issue if there's only 10 degrees difference between
the two, for instance, but the diff setting is 15?
The water still takes quite a while/too long to come up to
temperature, but at least when it does it's hot enough now.
I'll check the tempering valve as well.
Having come from homes with separate hot water heaters, like the other
poster I thought this was an unusual setup, but I see from researching
it that it's not really that bad. I would honestly consider a separate
hot water heater, except that the heating plant is set into a pit
inside of a crawlspace so there's no plave to put a hot water heater
unless we made the concrete pit bigger. Big work that I think I'll
avoid if possible.
Thanks again for the excellent info everybody!
We have hot water heating, but also a separate hot water tank. Never heard
of a furnace boiler providing hot water for washing, etc.. Am certain it is
against some building code or other. Doesn't make any sense except that the
original builder was trying to get off as cheaply as possible. Amazing that
a situation like that would go unremedied since 1958. They usually did
things better back then. Not so much trying to cut corners like they do
Someone else here recommended installing a separate water heater for
washing, bathing, etc.. I can't think of a better idea than that.
Using a coil in your boiler for domestic hot water is still used today.
There are more efficient ways to do the job, but using the indirect coil
saves space in some houses.
Oh, and it's not against any code to heat water that way.
Nope. It's perfectly leagal to do so. They tried to change the law some
years ago so that everyone with hot water heat would have to buy those
"hot water makers" for around $600 or install a hot water heater. I say
"BULL". With proper installation and temperature control, a boiler can
produce plenty of hot water for a famliy and there is very little standby
loss in doing it this way.
In the last 12 or so heating systems that I've installed, I've used the
existing hot water heater tank as a storage tank due to the family being
rather large. I can eleminate the tempering valve too. I simply install
a stainless steel circ pump on the outlet (hot) side of the existing tank
using a TEE with check valves at each end of the pump and then wire the
pump to the existing bottom thermostat on the electric water heater. As
the water in the tank cools, it kicks on the thermostat and thus the pump
and then is circulated through the boiler's coil that would normally be
used to the domestice supply hot water. It is then fed back into the
bottom of the hot water tank at the drain. I install a TEE there so that
the drain is still available obviously. The cold water for the hot water
heater is then rerouted to the outlet side of the pump where another TEE
is installed so that no matter what, the water must pass through the coil
before entering the hot water tank. It's virtually impossible to run
this thing out of hot water. I heat with a coal boiler fired boiler and
even on warmer days when the fire is light, I still have plenty of hot
water for 1 wife, 3 daughters, one son and me.
As they say, live and learn. Still it doesn't sound like a very good plan
to me. I would prefer the setup I have where the hot water for washing and
bathing is separate from the hot water for heating.
I live in a cold climate and perhaps having the hot water combined for two
uses would not be practical.
Called an Indirect water heater. The boiler heats the heat circulating
water, which goes into a tank with pipes. The heat carries into the domestic
water. The heater water and domestic water (should) never mingle.
I've worked on a couple of this kind of thing.
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