scalding water from indirect water heater on a steam boiler

jgd

Hi,



I have an indirect water heater connected to a steam boiler.During the winter (when the boiler is often making steam) the hot water gets scalding hot (at the sinks and showers) - much hotter than the setting on the aquastat (set to around 120F).

During seasons when the boiler is not making steam, the hot water temperature seems to stay close to the setting on the water heater's aquastat.



The indirect water heater is connected to the boiler as follows: 

Water from the lower side of the connection to the boiler's sight-glass goes to the inlet of a recirculator (controlled by an aquastat monitoring the water heaters temperature) then through a check valve and into the hot inlet of the water heater. The path just described is almost level, tilting down about an inch from boiler to water heater.

The water returns in a nearly level path from the water heater to the bottom of the boiler.

The boiler also has an aquastat that senses the boiler's temperature (near the water line).

I have researched this issue and have found references to:

- "heat traps", dropping the piping from the boiler down to near the floor and then back up to the inlet of the water heater

- tempering valves, mixing the hot water coming out of the water heater with cold water going in to reduce the resultant hot water temperature

My system does not have either of these. 

What seems to be wrong with my system as it stands, and what should I do to prevent the water from getting scalding hot in the winter?

Thanks,

Jeff

Charlie from wmass

Install a mixing valve

I like Sparco. Caleffi is also good.

jgd

is a mixing valve and tempering valve the same thing?

The guy at home depot said it was...

billtwocase

scalding water

I agree with Charlie. You need a mixing valve, but something else is going on there. The temp should be the same winter or summer. The tank has it's own thermostat, and should stop the circ when the tank temp (aquastat setting) has been reached. Somehow hot water is flowing thru that indirect coil when the heat is on. Pics might help here

EBEBRATT-Ed

gravity

Hotter water in the boiler is making the water circulate by gravity. Need a mixing valve on the domestic side, a flow check on the boiler side and check that the temperature control is operating the pump correctly

StevenB

check valve?

I think all water heaters should have anti scald tempering valves (Sparco AM 101 or equal) for safety's sake. But you have a more involved issue, like previously said, the water temp shouldn't change winter to summer. It's likely that your check valve is scaled and hung open, especially since you have a steam boiler.

jgd

here is a pic

I though that since I only get scalding water in the winter this was because the water in the bottom of the boiler stays hotter since the boiler runs more often to make steam for the radiators.

So, the hotter water from the bottom of the boiler is rising up into the heat exchanger in the water heater  - this water can rise up because the check valve might be stuck open which is what StevenB said below..

icesailor

Location:

Is it correct to supply/return the line to or from the boiler through the fitting that handles the LWCO and gauge glass? I'm no expert but I thought I read somewhere that it is not considered good form to do that.

Inquiring minds are asking:

billtwocase

not that way

This is not the way to pipe it, and although I can't see the check valve, it may also be a swing check, which is not the one to use. 

Charlie from wmass

please take this as being helpful not snarky

You need professional help. That is not how it is done or how to do it efficiently or well. 1/2" pipe is 1/4 the size you need. If 1" is not four times the size of 1/2" to the math of the installer you need a different install. That is a swing check which as stated is the wrong type of valve.

jgd

Is this the right kind of check valve?

I appreciate all the input. 

 



This system was installed "professionally". It was done by company that services the boiler.

billtwocase

wrong valve is clear now

That valve will not stop gravity feeding. It is a swing check valve. It only stops reverse flow. You need a flow check installed by a "pro". I must say, this is not a "professional" install. Keep us posted.

icesailor

Apples and Oragnes:

We're looking at one thing (photos) and talking about something else.

We're looking at the boiler side of the indirect piping but we're talking about the DHW being too hot and fluctuating.

A steam boiler with an indirect is like a hot water boiler with a tankless or a storage tank fed from a tankless, like I have. With the operating control on my boiler set at 145 degrees, if there is no heat call, the boiler is maintaining 145 degrees +/- and the DHW recovery is based on that. If there is a heat call and the boiler flips to 170 (or higher) degrees, the water coming from the boiler to the indirect tank.water heater will be hotter. If the operating control for a steam boiler was set at 150 degrees, or is set as a cold start, it would have a secondary high limit for off heating season DHW. During the heating season, the boiler water would be at least 212 degrees with a heat call.. Therefore, the water being heated in the tank will be hotter and internal circulation inside the tank will make it hotter at the top than if the boiler wasn't running, blah, blah, blah.

There is no photo of any mixer. A mixer will stop the fluctuation in domestic hot water.

We oil/tankless folks all know the trick of someone without a storage tank, and knowing that the coil never worked all that well, in spite of the customer insisting that it always worked perfectly (until someone futzed with the settings), know that if you tell the customer to turn up the thermostat for a period before you want hot water, the boiler will be hotter and the circulating hot water will improve heat transfer.

In my own home, I have clock thermostats. If I try to take a shower during an off period, I get plenty of hot water. I set my Symmons S96-1 shower valve with the limit stop set If it is an off time, the water is hot where I set the handle but I might want it hotter so I turn it up slightly. If it is 4:10AM when I get up, and the thermostat for that zone has come on, the boiler is running on high limit. The water at the same setting might be a tad too hot. At 3:00 AM, when all zones are off, it isn't as hot.

I still think that the indirect coil shouldn't be connected through the tapping's for the LWC. But what do I know. I think that there is a tapping for that indirect somewhere. The poster does not say what breed of boiler it is. I think that somewhere on the jacket, there is a knock-out with a plug behind it for that use. With the large amount of installers that have no need to read the installation instructions because they know it all, I can see a problem.

Post the brand of boiler so we can look it up and see.

billtwocase

Peerless

looks like a Peerless to me Ice. I will also say again, not the way to pipe it, and needs a mixing valve

icesailor

Water Port:

On the second picture, please note:

Someone didn't know what they were doing. That circulator probably stared out as a Taco 006B Bronze circulator. The steam boiler water killed it so it was replaced with a Taco 006 or 007 CI circulator motor assembly on the bronze body. They will fit.

The nipple coming out of the side of the boiler with the pencil line is the skim port. The pencil lines show the suggested water line that the boiler manufacturer recommends. Below and to the left, above the 4006 control, is another uncapped nipple. That is where the water too or from the Indirect belongs. The *006 control, being just below it is so that it will sense the cooler coming or going, depending on which way the water is being pumped.  I really don't think that the indirect should be piped through the LWC/Gauge Glass connections. But I defer to the real steam experts. I'm not one of them.

icesailor

Swinging Checks:

That is the correct type of check valve for the part of the application, to stop circulation from two bodies with different water temperatures. The upper connection is wrong.

All indirect's need a thermostatic mixer. I'm partial to the Honeywell AMX direct connect. It has checks and you don't need to heat trap it. On electrics, and other tanks, it is direct connect on the hot water outlet with unions. I replace 80 gallon electrics with 50's and run the tank hotter. I have never had a complaint of running out of hot water. I use them on ALL small storage tanks.

But the smart guys don't need them. Theirs work just fine. Until I install a mixer to solve the too hot/running out of hot water problem.

icesailor

Peerless

It isn't an EC/ECT or WB/WBV. I don't know about a JO/JOT. I never installed them. But the Peerless Website doesn't show either of those two boilers with the gage glass ports on the side, only the front. And it must be older judging by the older Beckett burner on it. I can't see enough of the front to make a decision. But those boilers do have a designated skim port and a tapping for an indirect. That install looks more like a hot water boiler that as an afterthought became a steam boiler. Like a lot of steam replacements.

Like something I wouldn't be asked to give a price on. Done properly, it cost money. Done wrong is a lot cheaper.

billtwocase

Peerless

those pipes sticking out of the jacket left side is a tankless coil Ice. This was and is a steam boiler from I see. Although there is copper pipe involved, it is a steam boiler. The bronze circ body is the only light at the end of this dark tunnel.  JMHO

icesailor

Then it's a JO

Then it's a JO/JOT.

There is an alternate place for the gauge glass and LWCO in the back of the boiler. There is also a 3/4" tapping below the two 1/2" taps for the LWCO. They should have gone in through there. Whatever kind of Indirect water heater that is, it has a 3/4" coil. At least the size would be continuous.

jgd

more info

boiler - peerless JOTTW1755PT

indirect tank - mega-stor

recirculator - Taco 007-F3



The threaded pipe sticking out of the side of the boiler (where the recirulator is) are the connections to the old water heater - this one pumped the domestic hot water into the heat exchanger in the boiler (I was told these connections should stay uncapped).



The new system pumps boiler water into the heat exchanger in the water heater.



There are two knock-outs on the back of the boiler (you might be able to see them in the picture)