Seasonal issues with hot water

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Old 04-02-20, 07:15 AM
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Seasonal issues with hot water

Thanks in advance for reading:
We have a Weil McLain oil-fired boiler for our gravity steam heat.
Domestic Hot water is heated via a loop from the boiler as well.

Every spring, and occasionally throughout the summer, we are having issues with heating the water.
The hot water tank is calling for heat, the circulating pump turns on and often runs continuously, circulating boiler water that is not hot enough to heat the water in the tank, while the circuit from the aquastat remains open and the boiler does not fire. I want to reiterate that this is an occasional problem.

I made the assumption that the aquastat was likely faulty - (Honeywell L4006) and replaced it.
What I noticed after replacing the aquastat was that with the circulator pump activated, the hot water loop coming out of the bottom of the furnace was merely warm to the touch, but the actual well that fits the aquastat probe was quite HOT to the touch. Therefore, the circuit did not close.

I am enclosing pictures for reference, and would love some guidance on how to troubleshoot this issue.
 
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Old 04-02-20, 09:26 AM
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Does the circulator send domestic hot water through a boiler coil or does it send boiler water through a domestic water tank coil?

Is the water level in the boiler too low?

 
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Old 04-02-20, 12:41 PM
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Hi Allan, The boiler water circulates through the domestic water tank. The water level in the boiler is about three inches higher than the aquastat well. (Water fills half of the glass that you see on the front of the boiler.) Boiler water is fed automatically when it falls below this point.

The dom hot water tank calls for heat - that signal goes to a control on the side of the boiler, which separately sends a signal to the circulator pump and to the aquastat. The aquastat sometimes keeps that circuit open even when the boiler water temp is below set point.

For example, yesterday the boiler water temp was between 100 and 120 degrees - and the water tank was calling for heat. I have the aquastat set at 180 degrees. The circulator pump was engaged, running for hours, while the boiler never fired. I had to manually fire the boiler using the thermostat upstairs in order to get the boiler water hot enough to warm the dom hot water. This was the point where I installed the new aquastat (L4006 pictured above) - and this aquastat also did not close the circuit when the boiler water in the loop fell well below warming temps. I touched the well (behind the aquastat) and it was quite hot to the touch, perhaps as high as 180 degrees. I found this unbelievable, as the water in the circulation loop felt about as hot as a warm cup of tea.
 
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Old 04-02-20, 01:00 PM
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More info and pics of the tank and pump and controls would be very helpful. What turns on your boiler and what turns on your pump on a call for hot water. You should have an aquastat on your tank going into to a relay that turns on your boiler and pump on a call for hot water.

It sounds like you have an Indirect HWH heated by your steam boiler. Also where are your supply and return pipes from the tank to the boiler. If not properly located lines may get airbound which would prevent boiler water circulation to tank even though aquastat is calling which may be why pump is on but line is cold.

Hope this helps a little.
 

Last edited by spott; 04-02-20 at 01:28 PM.
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Old 04-02-20, 02:01 PM
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The supply comes out of the front bottom, and return is toward the top at the back of the boiler.

The relay is an ARGO AR822-II. It sends signal to both the burner control (through aquastat) and to the circulator pump.
 
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Old 04-02-20, 05:16 PM
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Hi, did this setup ever work correctly? Is there an aquastat on the water tank? It would seem to me that an aquastat on the water heater should be calling the boiler and circulator on, there would be another HI limit aquastat on the boiler that would control the boiler temp.
Do the conductors on terminals 5&6 come from the aquastat on the water heater? Itís hard to tell in the pics where the circulator is fed from, I would assume from terminals 1&4.
Geo
 
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Old 04-02-20, 05:59 PM
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A couple of thoughts. Do you have the manual for the boiler where you can see piping schematics.

I believe your supply and return lines are reversed. You generally feed from the top and return in the bottom. Another thing i the lines must both be within the water of tWhe boiler. If your boiler water drops below the top tapping you will get air preventing the water from circulating and lastly for the piping, I don't see any means of bleeding that coil. I believe you could be air bound.

As far as your control go. You should have an aquastat on the tank that goes to TT, What is on 5-6. Pump on 2-4. Where is your 4006 tied in. That is your high limit for the boiier.
 
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Old 04-03-20, 12:33 PM
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@ Geochurchi:
1) This setup has worked since we purchased the home in 2015 - with the exception of the intermittent problem in this discussion. Essentially, there are times when the circulator pump is circulating cool water and the boiler is not getting the call to heat the water. This doesn't happen in the winter, since the boiler is always warm.
2) There is an aquastat on the water heater which feeds into the ARgo relay at TT. The aquastat on the water heater is functioning as it should. The relay directs the circ pump via L2 and 4, (power supply connected to L2 and L1). 5-6 goes to burner via the aquastat (4006) on the boiler.

@spott
1) I'm interested in this notion that the setup is not proper. I hope this is not the case.
2) I've looked up the manual here: and there is no specified piping for this type of hot water loop, only for a tankless heater. It is possible to drain the boiler, we do this annually, at the lower left corner where the feed is for the water tank is a valve for this purpose.
3) We have an automatic system to replenish the water. I've never seen the water more than a half inch below the midpoint in the glass, and for five years have not had to fill it manually while in operation. The return port for the hot water loop is 2.5 inches below the water level.
4) See my note to Geo re: relay connections.

I am not sure what you mean by air bound... Are you suggesting that the hot water loop might develop air in it, or the boiler itself? The latter seems plausible, since when I changed the aquastat on the boiler, the probe well was extremely hot to the touch, while the water circulating in the loop was merely tepid. Nevertheless, this is an intermittent issue. For the last couple days the system has worked perfectly without the thermostat calling for steam.
 
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Old 04-03-20, 12:59 PM
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Hi, so there are 2 cables going into L4006 aquastat 1 goes to 5&6 where does the other one go? What is the complete number on that aquastat there must be a letter there.
What are the other controls on the boiler ? it’s hard to tell from the pics.
is there a temp gauge on the boiler?
if you were to raise the set point on that aquastat while the water heater was calling , would the boiler start?
Thinking out loud here a bit.
Geo
 
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Old 04-03-20, 01:39 PM
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Hi guys Ė

Is the L4006 meant to be used here as a low-limit? If thatís the case I think itís supposed to be an L4006A model. If itís the L4006B instead, then I think the contacts open when the temp drops below the setting (setting minus a differential) and close when the temp rises above the setting.

If the L4006 is being used as a high-limit controller then how did raising the house thermostat cause the burner to run? It seems that if the L4006 was actually broken and stuck open and acting as a high limit, thus breaking the burner circuit, then raising the house thermostat shouldnít have caused the burner to run. It would be bypassing the safety high-limit. At least it seems that way to me.

So instead maybe then the L4006 is in the configuration as a low limit? But I guess then if thatís the case - then why would the Argo be configured to pass a request from the DHW tank aquastat through to the burner, since the water temperature would always be hot enough to circulate if there was a low limit? Above my pay grade and anyway I might be out in left field Ė lol!
 
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Old 04-03-20, 04:34 PM
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RB,
Let's address the issues one at a time.

1) The water height in the boiler: The aquastat well must be submerged in water in order for the aquastat to sense the boiler water temp. properly. If your well was extremely hot while your water was cooler there is a problem. Automatic water feeders for steam boilers work well but they do operate off a signal from the LWCO and are only designed to get the water above the LWCO switch so you don't run the boiler without water. That works fine unless you have a tankless or an Indirect HWH where additional piping is installed at a higher location. In that case you must manually adjust the water level to the desired height to make sure the aquastat and piping are in the water.

2) 4006 aquastat: This should be wired and used as a HIGH LIMIT aquastat and not LOW. Set as high limit you run the boiler as a cold start application which is what you want. You only want the boiler to run on a call for hot water. If it was set fot low, the boiler would run to maintain a constant temp if you needed it or not which is defeating the purpose of an indirect.

3) Air bound: I am talking about the loop from the boiler to the coil and back. That coil must be air free and bled just like a hot water system or the water will not not properly circulate. Although I don't see any provisions for that, since you are getting hot water in the winter I wouldn't worry about that now because if that was the problem you wouldn't get it periodically.

4) Aquastat wiring: If you have to turn the boiler on with your heating t-stat and it doesn't resond with the 4006 then you have a wiring problem. You said 5-6 goes to aquastat. What goes to boiler to react from aquastat setting. Ordinarily 5-6 from your relay would go to your boiler to start the the burner because your aquastat would already be wired in to the burner circuit but in your case you have steam controls only for heat. What I think would help you in the off season is to eliminate the use of terminals 5-6 altogether and just use the relay to start the pump on a call for hot water and run a wire from the aquastat to the same location as your heating stat. That way what I believe would happen is on a call for hot water the pump will start and lower the boiler temp water which will activate the aqustat and turn on the burner. When the tank is satisfied the pump will shut down and the boiler will continue to run until it reaches the aquastat temp and shut down on high limit also and stay off until next time.

Since 5-6 are suppose to go to the boiler, ifI you want to use them then you must wire in the aquastat between the boiler and relay.

In that manual you found on pages 15-16 I believe it will show you the tappings and description. U2 I believe is what you have for your return and they want that for the supply and then return into the bottom. You always supply from the top and return to the bottom because hot water rises as it heats. That is common practice. If you can find your indirect manual the piping may be in there. If I can find it again I'll post it for you.

This is just a sample of your tank, don't know what model you have. Page 18 of the install instructions

https://www.supplyhouse.com/Weil-Mclain-633-600-003-Aqua-Plus-85-Pewter-Indirect-Water-Heater?gclid=CjwKCAjwvZv0BRA8EiwAD9T2VeZI0DBGcrjS-2b7QqWRb_5xVOG5WvyeHbZSHHeVihPSQFORE76n7BoCGRcQAvD_BwE
 

Last edited by spott; 04-03-20 at 05:04 PM.
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Old 04-03-20, 06:45 PM
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Regarding connections on the relay - 6 goes straight to burner control, 5 goes to burner control via the aquastat. The aquastat is an L6006C - I made a mistake above. [R-B Opens, R-W Closes on Temp increase] There is also a temp differential dial in this model. I've wired it just like the previous L6006C that I replaced. For the most part, it works. It would be nice to know if this wiring is correct.

On another note, the other two wires going to the burner control are from the house thermostat.

The LWCO is several inches above the aquastat well, and the water level in the boiler has never fallen as low as the well - using the visible level in the gauge glass as an example. I've kept my eye on that glass for the last five years. U1 - which is being used as hot water return, is also several inches below the LWCO level. I'm not sure about the anomaly with the hot well and tepid water - I'll certainly keep my eye on it and pull out my meat thermometer to test when I run into this problem again. Perhaps this is simply a problem with the temp differential at the top of the boiler and the bottom, which could be remedied if the piping were correctly done.

I can see the U1 tapping in the manual - explicitly for indirect hw supply and/or baseboard hw supply. Now I'm frustrated with the local company that installed this. What's not clear is where the water should return. There are some unused tappings on the side, so I'm guessing it should be at either U2 or U3, which are only slightly lower than U1.

I have the documentation for the boiler installation, I'll try to give a shout out to the company and see if they'll remedy this mistake. I don't have a lot of faith that they'll follow through on a faulty installation from 14 yrs ago, but I'll give it a shot.

Meanwhile, if anyone could confirm that I have the aquastat wired correctly, that would help me sleep.

The dom water tank is Weil Mclain Gold Plus 40, I'm looking for the manual.
 
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Old 04-03-20, 07:31 PM
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You have 3 terminals on your aquastat. You want your 2 wires on R & B. This will shut the boiler down on high limit. Set the differential at 10 or 5 if you need the boiler to come on sooner. Your aquastat sounds like it's wired in series with the relay and primary control so when the tank calls relay send a signal to aquastat and if boiler temp is below aquastat setting the burner will come on. You can test by turning up the tank temp and see what happens. If burner doesn't come on turn up the aquastat and it should come on. If not try eliminating 5-6 and just run wire from R & B to primary. That relay is for heating off of a stat. Your aquastat is the important control here to shut down the boiler on command.
 
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Old 04-04-20, 06:15 AM
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Thanks for the feedback. I've had some other ideas, as even though the supply/return lines for the hw coil are reversed, I don't think the boiler water level has ever retreated below the return line.
1) I'm wondering if the water in the coil is not circulating on tank signal; this could be one explanation for the low temp in the coil vs the high temp at the aquastat.
a) Could the circulator pump intermittently fail to do its job? I replaced this pump a couple of years ago when the previous one froze up, but have had no other reason to suspect this one - except it was unusually hot the other day during the times of system failure - i.e., the pump was running, but the water in the coil was not hot enough to do the trick. When it's running normally, it's about the same temperature as the water in the coil. This leads me to suspect a circulation problem, primarily.
b) Or could it be from possible air pockets in the heater coil? There is an auto relief valve in the coil, see page 16 in the manual. I assume that it generally does it's job, but I'll run a test to make sure this is working. Stuck at home to weather the current situation, so I'll be able to do the annual maintenance in the next few days.
 
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Old 04-04-20, 07:01 AM
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Hi, you said the system works fine in the winter, correct? so what changes in the Spring/Summer ?
where is the Hi limit aquastat that controls the boiler aside from the DHW tank?
you havenít answered some of the questions posed earlier.
Geo
 
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Old 04-04-20, 07:43 AM
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I presume the only change is that the boiler isn't running as often on calls for steam. Usually in the winter the boiler water is warm enough to circulate without the need to additionally run the burner. However, this may be a coincidence. Reason has led me to the previous post, since it doesn't seem possible that the aquastat well is not submersed in the boiler water. I believe that the aquastat is working as it should be, and from time to time the water does not circulate through the hot water coil. This could explain the temperature differential between the aquastat well and the supply feed to the HW tank. (See previous post)
I though I had answered all of the questions, though perhaps I missed some. The High Limit Aquastat is attached to the boiler, several inches below LWCO. The Argo control/relay takes the signal from the DHW tank and sends signal to burner via this aquastat, and at the same time starts the circ pump.

There is no temp gauge on the boiler.

Yes, I have in the past raised the aquastat temp and this has resulted in firing the burner. However, during winter months the water is generally hotter than needed due to the steam heat, so I've only tried this occasionally.

Other controls: The Argo relay mentioned above, and the burner controller, as well as LWCO.
 
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Old 04-04-20, 07:46 AM
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You said you replaced the circulator a few years ago. When circulating water thru a steam boiler, the circulator should be either bronze or stainless steel. Don't know what yours is or if it has any bearing on your problem. Just something that caught my eye.
 
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Old 04-04-20, 10:11 AM
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Hi, post #3 you say water temp 100-120 and you think the water at the boiler aquastat is 180, and the setting on it is 180 5*+_ then the circuit would be open, how did you determine the water temps if there is no gauge on the boiler?
Geo
 
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Old 04-04-20, 11:42 AM
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You are right, The pump should feel about the same temp as the boiler water it is circulating. That pump is called a wet rotor pump and the cannister that you are feeling has water in it which is why the temp should be about the same. It is not like the old style that has a seperate motor connected to a bearing assembly. If you remove that cannister you will get system water, unlike the older style. That is why it is good practice to install isolation valves on both sides of the pump.

It is hard to tell if those pumps are running sometime so the simplest way is to take a screwdriver and place the metal tip on the cannister and the handle end to your ear, like a stethascope? and call for hot water, You will be able to hear if the pump is running or not.

Page 44 & 45 of that manual you found pertains to your setup. They are for steam boilers to tanks specifically. If you read both pages it will tell you the proper way to install and tie together including the bronze pump and why and why they want the piping done as recommended and also NO manual air vent and why. Different rules apply for a steam boiler vs hot water.
 

Last edited by spott; 04-04-20 at 12:35 PM.
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Old 04-04-20, 12:35 PM
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This is a cast iron Taco 007-F5 pump. Any recommendations on what type of stainless steel or bronze pump I could replace it with? Here is the spec sheet. Perhaps this more powerful Grundfos here? Or this Taco (same model but with stainless steel construction)

I'll still look into re-piping the boiler so it at least meets the mfr recommendations, though I'm thinking more and more that the main issue in this thread has to do with a circulation problem.
 
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Old 04-04-20, 01:07 PM
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The Taco is fine. If you call them with your pipe size bronze might be cheaper and just as good for your purpose. They are very helpful over the phone.

Don't if you got my revised post but on pages 44 & 45 of that manual you found is all the info you should need including no manual air vent and other things.


 
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