Heat will not shut off. Burnham Boiler

I have a Burnham Boiler model # 204NCL-TEI2. In the last few days it has failed to shut down when thermostat is not calling for heat or is off. The system is a single zone. The system has a Taco circular and a Taco zone valve. ( the zone valve was installed when the system was installed because of potential for a second zone someday). The boiler is firing until the boiler temp is satisfied (set at 180 degrees), the circulator never shuts off, the zone valve opens and closes in reaction to the thermostat set point. The zone valve is the only thing that is keeping the system from constantly heating the house. My first reaction was to suspect the thermostat was malfunctioning since it is 22 years old. I installed a new thermostat and nothing changed. Next I suspected the relay switch was malfunctioning. I purchased a replacement (model # Honeywell R8222U 1006 (3) ) I replaced the entire unit. (relay along with transformer) and nothing changed. Next, I wanted to isolate the thermostat wires to make sure there wasn’t a short. I took the original thermostat to the basement and wired it directly to the system so I could experiment without running up and down the stairs. The direct wiring to the thermostat in the basement did not yield any improvement. I’m unsure what to try next. On another note – the aquastat (model# L4080D 1234 or Burnham # 100189-01 ) is passing 180 when it heats up and stops at 195. Before all this the system was running terrific. It was installed in 2010 and has been maintained yearly. I would appreciate any help with this problem. I can provide additional information and pictures as needed.

Thank you,

The circulator pump is not stopping when stat satisfied.

The boiler is running properly on its aquastat.

Therefor you are overshooting the stat's set point temperature.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

when the t-stat calls for heat the zone valve opens. the open zone valve sends a signal to another control to turn on the circulator. when t-stat is satisfied then the zone valve closes thereby stopping the signal for the circulator to run. (unless there are multiple zones calling at the same time)
the boiler aquastat senses the boiler water temperature and turns the flame on or off according to the temperature the aquastat is set at.

have a read here..

[inspectapedia.com]

packy is correct

sounds like your zone valve is 'stuck open'

the boiler itself fires to maintain water temp (controlled by the aqua-stat) REGARDLESS of the 'room temp' stat's 'call' for heating so that when the stat DOES call there is hot water available to heat


sequence of operation:

boiler has available supply of hot water controlled by the boiler aqua-stat

room air temp stat 'activates' call for heat

zone valve(s) opens

switch on zone valve activates circulator pump

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Thank you and packy for your reply. I don’t think I accurately described my problem.
Sequence:
- thermostat is sending a signal to turn on
- within about 30 seconds I can hear the zone valve open
- within about a minute I can hear the circulator pump switch on.
- If the temp of the boiler is below aquastat setting the burner will start
- Note: I have turned the aquastat set point down to 140 since it is currently overshooting the limit and it stops a 175. I did this because it was previously set at 180 and kept going to 195.
- Once the thermostat is satisfied I hear the zone valve close.
- The circulator and the burner with continue to run – sometimes the circulator will shut in about 5 mins. Sometimes not – the burner will shutdown only when the aquastat set point is reached.
- As I mentioned, this is a new problem – everything was working well prior to this.
- I would like to replace the aquastat but the part # have been discontinued. When Resideo took over for Honeywell the stop making this part.
- Any suggests for an alternative.

I was thinking it must be a relay problem but I tried that route yesterday but I may try again.

Thanks, Mike

the circulator should/is controlled by the zone valve

the boiler firing is controlled by the aqua-stat / the firing should be independant of the room stat and/or the zone valve and/or the circulator

the room air stat controls the zone valve which in turn calls for circulation


replace the aqua-stat - it is NFG anyway


replace the zone valve or its 'electronics'


if this does not solve the issue you will need an on-site pro to troubleshoot/replace the 'main board' if any

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Thank you for the reply.
I will purchase a zone valve head and go ahead and replace it.
I am having problems getting the appropriate aquastat. I’m very disappointed it’s not longer available. the aquastat (model# L4080D 1234 or Burnham # 100189-01 )
Do you have any recommendations for a replacement aquastat. (range 140-240)
There is no mainboard with my setup. I have a transformer relay setup :
Honeywell R8285D 5001 with stand alone aquastat.


I have attached a link for pictures. As you can see it is a stand alone aquastat (not bundled with transformer and relay)


[postimg.cc]

Thank you ,

Mike

aqua-stat may be replaceable with: Weil-McLain SKU: 510-312-250

you may need a new relay assembly


but


replace/rebuild the zone valve FIRST - the room stat controls the zone valve and if the zone valve does not close/signal properly ......................................

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

before i would replace the aquastat, i would lather up the bulb with heat transfer paste (PUT PLENTY) and stick it back into the well. might just solve the overide problem.

[www.homedepot.com]

worth a try

? since it worked well previously, where did the ORIGINAL go ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I’ll go ahead and replace the zone valve first and update the post when I do.
Hopefully I’ll be able to get it within the next couple of days.
Just took a look at the Weil-McLain SKU: 510-312-250
It looks nearly identical to mine. I would imagine it will be like for like. As far as dealing with the relay assembly, I did suspect the relay assembly and purchased a replacement. I installed it yesterday and there was no change to my issue so I swapped back the original.

Thank you.

j/i/c you are interested: [inspectapedia.com]

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

I just returned from Home Depot. I purchased a zone valve head. I will give it a try this evening if I get the chance. I did not see packy’s note about heat transfer paste before I left so I’ll have to make a return trip tomorrow if needed. I thought it was interesting that there wasn’t any heat transfer paste on the aquastat probe to begin with. Not sure if it comes that way from the factory or was it my plumbing contractors decision. Either way – thank you for the advice.

Not going to have an opportunity to try the zone valve head this evening. I'll give it a go tomorrow.
Thank you all for your assistance today.

I changed out the zone valve head this morning. I turned the thermostat on and set the temperature above room temperature. It was music to my ears to hear the system react normally! The zone valve, circular and burner all worked as they should. I am literally thrilled! I never did suspect the zone valve as the problem – to me it seemed to be working fine – it opened and closed when it was supposed to – I did not consider the electronics of the zone valve failing.

I am going to spend today evaluating the aquastat before considering any changes.
I will post once I’ve done that. If you have an opportunity to provide feedback on my observations I would appreciate it.

Thank you very, very much!



Edited 1 times.

ps.

unless the room air stat is turned off the aquastat should ITSELF be cycling the boiler to maintain water temperature independantly/regardless of whether the room stat is 'calling' for heat

when the room stat 'calls it opens its associated zone valve - said zone valve upon opening fully then calls for the circulator pump (which has hot water IMMEDIATELY available because of the aquastat's operation


now you know 'what' as well as the typical piping tradesman - the trick is 'making it so'

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

the aquastat (model# L4080D 1234 does not maintain temperature.
it is simply a high limit control to shut down the fire when the water reached the control set point.
once the zone thermostat is satisfied, the boiler goes to 'cold start'..

that would be a real real cheapo pos system


do you mean that every time the room stat 'calls' the boilert must 'cold start' ?????????????!!!!!!!!!!!!!!



Hot Water Boiler Sequence of Operation Aquastats
hot water boiler sequence of operation
An Outside Boiler

Hot Water Boiler Sequence of Operation Aquastats - As boilers go, there is not a single sequence of operation for any hot water boiler out there, but there is a typical sequence of operation for most boilers. We will start off by describing the typical hot water boiler without domestic hot water or an indirect-fired hot water tank. In other words, this will be the typical boiler used for heating in the winter with either single-zone radiators or baseboards for heating rooms.

Boiler Sequencing and Considerations
The house is a comfortable temperature, but as the temperature outside drops, so does the temperature inside. It is a result of heat loss from the structure. So the thermostat drops below the setpoint, and the switch for heating inside the thermostat closes. This completes a control circuit to engage the relay for the circulator pump. The coil on the circulator pump relay energizes closing the contacts for the relay, and the circulator comes to life and begins circulating water through the loop. That circulates hot water from the boiler to the single zone (the entire house).
The water inside the boiler is 180 degrees Fahrenheit. As the circulator kicks on this hot water, leave the boiler and are circulated throughout the loop where it passes through several radiators or baseboards, and it heats the rooms. Since the heat left the water through the radiators or baseboards, the water returns to the boiler with less heat than when it left the boiler.
How a Boiler System Works
For a properly sized boiler under normal loads, the temperature should never be more than 30 degrees Fahrenheit (always check the manufacturer’s guidelines on the differential temperature as these temperatures can vary) from the leaving water temperature to the returning water temperature. It is possible for boiler thermal shock to occur if this temperature is exceeded. If the temperature exceeds 30 degrees the boiler system could be undersized or there is a problem with the loop somewhere. As the water temperature inside the boiler drops the cut-in temperature switch fires the boiler to reheat the returning water.

Hot Water Boiler Sequence of Operation Aquastats
Aquastat, Circulator Pump, and Burner Controls

The temperature switch (aquastat) has a temperature probe inside a thermal well placed strategically inside the boiler by the boiler manufacturer. These temperature switches with probes inside the boiler thermal well are aquastats. There are different types of aquastats from the very simple aquastats to the newer electronic aquastats with several different control strategies for economizing the use of the boiler based on different programmable parameters. Either way, the temperature switch or aquastat will turn the boiler on and off. It does that based on the temperature of the water inside the boiler.
Aquastat Variations
Again, some complex aquastats use different control strategies and settings. Still, on a simple boiler system, the aquastat will turn the boiler on and off based on the temperature settings of the aquastat. The cut-in temperature is the temperature at which the boiler fires at a low temperature reading by the aquastat while the cut-off temperature is the temperature at which the boiler cuts off as demand has been satisfied.

The demand has usually been satisfied after the circulator pump cuts off. The cut-off for the circulator pump is based on the room thermostat temperature setting. Once the thermostat setting is satisfied, the switch inside the thermostat opens, and that kills the power to the circulator pump relay, so the circulation of hot water throughout the system stops. Prevention of the migration of hot water throughout the boiler loop when the system is off, a flow valve has usually been installed the system somewhere in the near boiler piping loop.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 2 times.

To: bernabeu (SC)

Thank you for the explanation of the heating system.
My aquastat: model# L4080D 1234 or Burnham # 100189-01
Operates in the following manner.
Thermostat calls for heat.
Circulator turns on – zone valve opens.
Boiler will fire if temperature in boiler is below 165
Boiler will fire until stop temp of 180 is reached.
This cycle will continue until thermostat is satisfied.
If heat is not called for a considerable amount of time (at night for example) the boiler temperature will continue to drop until the thermostat requests heat.
In the morning for example my boiler will often be below 110 when I first call for
heat.

Do you feel this is not a well functioning design? I obviously do not want a design that may cause thermal shock or is more inefficient than it should to be. The system is set up as installed in 2010.

I have some other thoughts – if you have any time to address any I would appreciate.

Another subject:

Now that my system is running I wanted to address the following:

I took a look at the aquastat performance for a range of temperatures

- setpoint = 140,
o boiler heating off at 160
o reheat at 145

- setpoint = 160
o boiler heating off at 170
o reheat at 155

- setpoint = 180
o boiler heating off at 185
o reheat at 170

Obviously my aquastat is not very linear – I left it set at 180.

While I was doing my tests I wanted to ask your opinion about the aquastat setpoint.
It seems that 180 is the most common for hydronic baseboard heat. Do you agree?

Another subject:

At this time I feel the aquastat is a doing a good job keeping the temperature where I need it. Since my aquastat model is not longer available, if I decide to change it out for the Weil-McLain SKU: 510-312-250 - will the fact that it has a 30 degree temperature differential be a concern? My current aquastat has approx. 15 degree differential.


Another subject:

I have a 1000sq. single story home with a basement. As discussed earlier I have a zone valve on my system although I am running a single zone. Since the trouble I had stemmed from a failed zone valve would I be wise to disconnect the zone valve from the system – basically, manually leave it open mode and disconnect all wiring?
If doing so, I would need to wire the system differently.
Here’s an outline of my system. (see picture)

[postimg.cc]

Would I just wire the thermostat wires directly to the relay box?


Another subject:

Strap aquastats : what is your opinion on strap aquastats?

I have a approx. 1 ¼ inch black pipe exiting my boiler that would make a good mounting point.


Another subject:

My thermostat has an option which allows for the use of “C” wire to power the thermostat from a 24volt source. Can you offer any guidance where the best place to tap this source would be?


Another subject:

On a historical point, when I was troubleshooting my system I realized my thermostat was 14 gauge bx wire. At the thermostat end and the basement end they were connected to 18 gauge thermostat wire to allow proper connection. I was curious why would there be such wire for a thermostat and then I wondered it there was a need when the house was built in 1953 to use this type of wire. Any idea?

Thank you,
Mike

Quote

..... Circulator turns on – zone valve opens. .....

Nope - the stat activates (opens) the zone valve - then the zone valve ITSELF calls for the circulator !

You have a one zone valve system allowing for the easy addition of additional zone valves (each added zone valve would be controlled by its own stat) any of which would activate the circulator AFTER they open.

The zone valve also acts as the 'anti gravity circulation' check device which would have been otherwise required in a single zone system w/o a zone valve.

Quote

..... If heat is not called for a considerable amount of time (at night for example) the boiler temperature will continue to drop until the thermostat requests heat.
In the morning for example my boiler will often be below 110 when I first call for
heat. .....

You 'may' have some sort of 'smart' electronic / timed control, or, if you are turning the stat to OFF at night the system is working as designed.

180 off - 165 on by the aquastat is perfect for hydronic heat, you could try 160 off - 145 on in cold but not severely cold weather.

If you are comfortable with the existing system now that the zone valve was fixed you are good to go.

Anything further will require on-site design by a heating specialist.

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

Thank you for your time and expertise. I appreciate you taking the time to help me and educate me more about my system.

Take care.



Edited 1 times.

"check device which would have been otherwise required".


on a single zone system, i wouldn't care if there was a flow check or not.

OP,

Installation manual: [documents.alpinehomeair.com]


see page 17



Packy,

like i said, a zone valve eliminates any need for a flow check

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

The calculator pump was installed with a flow check.

excellent

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

why would you install a circulator with a flow check if you already have a zone valve?

thats like wearing a belt and suspenders.

I know! I just realized that as I was troubleshooting my problem. I wasn't paying enough attention when the plumbing contractor installed the system in 2010. I do not thing it poses any issues - just no purpose.



Edited 1 times.

My thermostat has an option which allows for the use of “C” wire to power the thermostat from a 24volt source. Can you offer any guidance where the best place to tap this source would be?

you are in MA

a licensed bonded insured plumber who specializes in heating systems is required

you need to find the 'system' 24 volt transformer (if any)

however

if it is presently 'powered up' 120 volt and apparently operating properly DON'T FIX IT, IT AIN'T BROKE


stop putzing - your issue is fixed

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Advice taken - well stated.

My thermostat is 24 v - but it is wired in the wall with 14 gauge bx wire from 1953 - still a mystery to me.

Thank you once again.

'may be' similar to a doorbell transformer wall box



[th.bing.com]




or (probably)



they 'hid' the low voltage wiring from a transformer on the boiler control 'system' itself




................... over and out

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638