Hot water heating system questions

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 fluctuations.
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.
Thanks!
Steve
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Try bleeding the air out of the radiators. Are your hot water pipes insulated this may help for your showers.
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the buzzing sound is probably your pump noise

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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.
--
Peace,
BobJ


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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
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snipped-for-privacy@connext.net (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 handled variety. 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. Right??
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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!
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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 today. Someone else here recommended installing a separate water heater for washing, bathing, etc.. I can't think of a better idea than that.
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heard
is
the
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.
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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.
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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.
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You don't understand. The heating hot water and the domestic do not mix.
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That wouldn't be the first thing I didn't understand. That's why I like simple things.
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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.
--
Christopher A. Young
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alt-hvac Moderated posted for all of us....

But never fixed a dang one of 'em!
--
Tekkie

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Marilyn and Bob, and Doug, those were some of the most informative and courteous answers I've seen on a newsgroup. If the OP doesn't thank you then I do.
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