I Want to ADD a 4-wire GVD Vent Damper to Thermopile-powered DHW Hot Water Heater

Larry Weingarten · February 2

Hi, Have a look here: https://www.greenbuildingadvisor.com/question/make-up-air-for-dryer I see @DCContrarian is part of that conversation. Maybe getting a HP dryer could go a long ways towards solving this problem? 🤔

Yours, Larry

DCContrarian · February 2

https://forum.heatinghelp.com/discussion/comment/1839771#Comment_1839771

Thanks Larry.

I usually caucus with the mad scientists, but I've been trying to follow this thread and I just don't get what the OP is trying to accomplish.

But three years in, I'm still happy with my ventless dryer.

109A_5 · February 2

You have provided no pictures of the situation and/or the ratings of the equipment. For all I know the window now providing the combustion air is on the far side of the basement away from the heating equipment providing the most blending of the outside air with the basement air. I would think an 8 inch square opening very near the heating equipment so the blending with the rest of the basement air is minimal would provide plenty of combustion air. An insulated duct could be used to bring the combustion air to the equipment too. The breach area needed can be calculated if the equipment ratings are known.

Personally I think the issue you are conveniently ignoring is on the coldest days of the year when you need to run the heating equipment the most (coldest air, coldest water) and you want to duty cycle limit the use of the heating equipment due to limited combustion air. I believe this is doomed to fail and someone is going to be cold and/or have to take a cold shower due to lack of the need heating equipment run time.

In other words you are trying to repair a flat tire on a car by adding an onboard computer. The computer may be able to detect the flat tire and stop the vehicle movement but it can't repair the flat tire (the actual problem).

Larry Weingarten · February 3

Hi @DCContrarian , I have a pretty snug SIPS house and use a ventless washer-dryer. It's an Ariston and could do a better job with drying, but isn't hard to live with. I always opt for simple as it's so much more durable than complex. I'm thinking the problem here can be broken down and dealt with in some simple ways, but a better understanding of the entire situation would help 😽

Yours, Larry

Martial_7erran · February 3

Letter to Honeywell, Bradford White, and AO Smith:

Here's a draft of a letter you could send to these manufacturers, focusing on safety and user-friendliness:

[Your Name]
[Your Address]
[Your Email]
[Your Phone Number]
[Date]

Subject: Request for Enhanced Safety and Control Features in Thermopile-Powered Domestic Hot Water Heaters

Dear Honeywell, Bradford White, and AO Smith Engineering Teams,

I am writing to express my strong interest in seeing enhanced safety and control features in your thermopile-powered domestic hot water heaters (DHW). Specifically, I believe there is an unmet need for easily accessible and reliable means to integrate these systems with vent dampers, carbon monoxide detectors, backdraft detectors, thermal cutoff switches, and centralized combustion air management systems. (all of which are available for gas boilers adjacent in the same room as the DHW tank)

As a homeowner and BSEE with extensive experience working with gas appliances, I recognize the importance of safe, efficient operation. Current designs present several challenges for those looking to optimize energy efficiency and overall system safety:

Lack of External Burner Control: Current thermopile-powered DHW units do not readily provide a means for switchable external control over (delay of) the burner valve firing, which is necessary for optimal operation of automatic flue dampers and fresh air dampers. This limits the ability of users to prevent heat loss up the chimney during idle periods and to integrate with centralize combustion air systems and safety systems (e.g. carbon monoxide detectors).
Limited External Safety Integration: There is also a need for easily accessible control wires that would enable the addition of various safety interlocks, such as interlocks with other gas appliance operations and or with fresh air supply dampers.
Complex Internal Control Circuits: The control circuit boards within Honeywell and other DHW gas valves are complexified by the use of a microprocessor, and not intended to be directly modified or improved by end users, although that might be necessary to add a simple, external, safety interlock.

Proposed Solutions:

I propose that future generations of DHW with Honeywell or similar gas valves include the following:

External Burner Valve Control Wire: At a minimum, there should be an external (5 Volt or external relay NC/NO pins) wire(s) that can be used to safely detect activation of the burner gas valve only and interrupt the activation of the burner gas valve only. This would not affect the operation of the pilot light. Ideally, the burner signal voltage would be made easily accessible for external switching through external switches such as the End Switch of a flue damper, a fresh air damper End Switch, and a carbon monoxide detector alarm relay,
Flue Damper Control Wire: A dedicated wire (e.g., a NO/NC relay) that responds to the burner operation signal and can be optionally wired to activate a motorized flue damper damper.
Fresh Air Damper Control Wire: A dedicated wire (e.g., the same NO/NC relay for the Flue Damper Control) that could be deployed to activate a fresh air damper on a common intake to the mechanical space.
Internal Flame Detector: Ideally, an external output or control signal from a dedicated internal "flame" sensor could be used to verify complete combustion in absence of direct or reflected flame from the pilot,
Open Access to Control Signals: All output signals (including the thermopile output) could be wired to an external connector (such as the existing serial port on the PCB board) to enable system-wide monitoring and fault analysis (by optional external monitoriting circuits like Home Automation software, thermostats, AI-enhanced security devices ) in case of normal operation and in case of any partial or complete burner operation shutdown.
Clear Documentation for Safety Interlocks: Clear wiring diagrams for how to use these control features are important for enabling third-party safety interlocks.

By incorporating these features, you would:

Enhance Safety: Provide options to prevent carbon monoxide and back drafting issues related to shared flue spaces.
Increase Efficiency: Enable users to reduce wasted energy from heat loss up the flue.
Facilitate Integration: Make it easier to integrate DHW systems with home automation systems, vent dampers, central combustion air management, and safety devices (e.g., CO sensors), zone valves, staged DHW systems etc.
Improve User Experience: Make your products more adaptable and usable in a wider range of residential settings.
Reduce Electrical Component Failures: By standardizing and providing external circuit ports for commonly deployed relay interlocks, you could reduce customer-induced hardware failures or circuit defects (that void warranties).

I believe that these changes would represent a significant improvement to your current DHW models. I urge you to seriously consider these suggestions for the benefit of homeowners and the environment. I would be happy to discuss these further with your engineering teams, if that would be helpful.

Sincerely,

[Your Name]

Martial_7erran · February 3

Quote [No pictures] You want to solve an equation like Fresh-Air minus combustion air out, minus air forced out by dryer fan. I don't want to solve an equation. I want to modify the House and the equipment to prevent undesirable conditions (carbon monoxide accumulation, inefficient combustion, cold air coming down the chimney, warm air escaping up the chimney)

I will try to present a verbal picture with the essential information. I am not sure why it is relevant.

One room in basement containing two identical independent Utica natural gas boilers ("INPUT BTUs specified as 75000) and formerly two independent DHW (now only one piped into two units), and in adjacent room in basement, there is a washingmachine and a natural gas dryer with an exhaust vent ported through a hole in concrete block foundation wall (used to be piped out through glass pane of basement window, but window was upgraded to doublepane glass with vynil frame). In boiler room (below full bathroom) basement window is very close to many domestic water/hydronic pipes and is kept closed in winter, and is also upgraded to vynil double pane, The gas appliances seem to work with all the doors and windows closed. Adjacent door to outdoors is cracked open, with a plastic sheet covering top 5 feet, to conserve warm air at top, and to intake fresh air at the bottom. The idea is to keep the winter fresh air away from water pipes while providing fresh air to boilers and DHW tanks.

Chimney in boiler room is concrete block (clay tile lined, which could fail any day an block the chimney, hence I am also adding a Carbon Monoxide Detector and relay switch) all the way up to roof. There is an apparent air gap between chimney and the interior walls and subfloors, and it seems that significant air from the unheated vented (cold air) ATTIC space can flow down two stories along the exterior of the Chimney blocks and into the boiler room in basement. (likewise, warm or heated air in basement can apparently exit through attic along the chimney). Plans include that this vertical air passage along chimney down through uninsulated walls in center of house will be closed at top (attic) and at bottom (boiler room) with firestop material and metal foil.

Because the plan is to air-tighten the basement and boiler room. the preparations to add an 8-inch tall external (damper) fresh air vent through block wall of basement with ducting towards and down to floor level at boilers and DHW, and maybe add a short shetrock wall around to contain the cold air. There is currently no way to activate this Fresh Air Damper because and while the one or two convection-driven gas DHW (and/or the gas dryer) are operating. (I am aware that some fresh air dampers come with differential pressure-sensing switches. I have not seen a document that indicates that this is reliable for convection-operated gas DHW or gas boilers)

109A_5 · February 3

Well, I'm just not going to type what I am thinking about your first sentence in the last post.

I will say if your chimney is that dilapidated that you feel it is a safety hazard it should be repaired, replaced or relined.

Martial_7erran · February 3

109A_5

Quote "Well the ADC conversion time is rather fast compared to a relay change of state and contact bounce." I realize this. It is possibly something that will make the use of switched decoy resistors ineffective (at least without having a way to do "make before break" type switching. which would be awkward and an expense to implement here) But, because the PCB is a low power device running off of a thermopile, there is a chance that they do not send measurement-current through the thermistor (and through the burner solenoid coil) all the time, but rather pulse the current/measurements a few times a second….

Your idea to manipulate the dial potentiometer resistance (using a switch) is interesting. That would mean essentially "turning down the set temperature of the DHW" during the time you want to keep the burner flame off. That seems like it could be mostly successful (using SPDT relay to: substitute the potentiometer resistance with a Decoy resistance or 2) swap in an additional resistance). I would note however that this approach represses the voltage call (at the Burner valve PIN) for burner FLAME-ON itself, thus interfering with production of the expected fire-on signal (which was going to be used to open the 4-inch damper) or otherwise in the external control circuit. But, such would only DELAY the generation of the burner FLAME-ON voltage at the valve PIN while the external control mandated that delay, so maybe it is not detrimental.

It seems likely that "vacation mode" is PILOT FLAME ONLY? That mode PILOT ONLY of operation is the result sought to be obtained in the burner flame-ON DELAY control mode that I have specified. So, simulating the "Vacation Mode" Voltage may be a solution. (Assuming that there is not "supervisor" ADC sampler there to complain about a momentary irregularity of infinite resistance during the flying of the pole in the relay.) Thus, it seems probable that you have identified here a necessary piece of the overall solution.

109A_5 · February 3

With the user control voltage examples I used above. This is rather simple. The actual circuit may be different.

" I would note however that this approach represses the voltage call (at the Burner valve PIN) for burner FLAME-ON itself, thus interfering with production of the expected fire-on signal (which was going to be used to open the 4-inch damper) or otherwise in the external control circuit. "

This need to be thought through much better, since the burner (with normal or modified control) should be locked out UNTIL the damper is proven open. The control side modification (user control or thermistors) has nothing to do with the damper functionality.

Martial_7erran · February 3

Quote: ["I will say if your chimney is that dilapidated that you feel it is a safety hazard it should be repaired, replaced or relined."] I have not indicated that the chimney/liner is dilapidated. The tile liner is visible at the top at the roof and last time I looked down the chimney hole (to replace the hood) it was looking fine. I am simply aware that the house is over 60 years old and I have seen older houses where the tile liner broke apart and blocked the gas appliance vents. There are also youtube videos of such. Maybe when I am 80 years old it will start to slough. I am simply illuminating the various scenarios and risks that can be mitigated by the modifications to the DHW that I am attempting to practice.

109A_5 · February 3

Yeah, you did, " which could fail any day "

" Chimney in boiler room is concrete block (clay tile lined, which could fail any day an block the chimney, hence I am also adding a Carbon Monoxide Detector and relay switch) all the way up to roof. "

HVACNUT · February 3

@Martial_7erran , you keep mentioning Carbon Monoxide as a concern for needing a vent damper. Can you explain how the addition of a flue vent damper will "enhance safety" or "prevent undesirable conditions" concerning CO? Thanks.

Also, I'm pretty sure a response to your letter to the manufactures would gently steer you to literature on the extensive lineup of power vent, indirect, solar, tankless, electric, and heat pump water heaters. Besides, the pointy heads at Honeywell, etc. are wired the same way as you. Do you think you're the first person in the world to ponder this query? It's not here because it's not feasible. Yet.

I admit, a lot of the posts on this thread are way over my head, but I believe the general issue here is combustion air. And even I can do that math. As mentioned by others, that's where things should focus. Without the water heater as a solution.

Martial_7erran · February 3

HVACNUT
Quote: [you keep mentioning Carbon Monoxide as a concern for needing a vent damper. Can you explain how the addition of a flue vent damper will "enhance safety" or "prevent undesirable conditions" concerning CO? Thanks.] Adding a powered damper implies intercepting the Fire-ON Call to the burner Valve (derived from Thermostat on PCB board) and delaying that Fire-ON Call from arriving at the burner Valve. Once you have this external control over the burner Valve, it is easy to add a CarbonMonoxide relay to shut off the burner upon/while detecting CO. Opportunity Created → Opportunity Accepted.

It is very common for clothes dryers and kitchen vent fans (and improperly installed power vented gas boilers that I have seen) to create negative air pressure that pulls down the chimney gasses and accumulates combustion air within the area of the gas burner, creating a CO risk, and a fire risk.

A DHW heater, even properly installed, can begin generating much CarbonMonoxide simply because of pet hair or dust or anything clogging up the air intake at the bottom. [Vendors now provide dust screens at bottom which does not entirely mitigate this.)

Hundreds or thousands of people die in homes and hotels and dormitories each year, from carbon monoxide poisoning due to water/air heating (many reports do not accurately distinguish between gas boilers, tankless, DHW tanks).

"Christmas tragedy: 4 found dead at vacation home from apparent carbon monoxide poisoning

Minnah Arshad Joanna K. TzouvelisUSA TODAY NETWOR

WAKEFIELD, N.H. — A Massachusetts community is mourning the deaths of four family members after an apparent exposure to carbon monoxide at a New Hampshire vacation home on Christmas Day.

https://www.usatoday.com/story/news/nation/2024/12/27/family-dies-apparent-carbon-monoxide-poisoning-christmas/77270439007/

Model-actress Dayle Haddon found dead after suspected carbon ...
Dec 28, 2024 — Dayle Haddon, model and actress, found dead after suspected carbon monoxide poisoning in Solebury Township, Bucks Coun...

abc7NY
Water heater blamed for carbon monoxide leak that killed family of 4
May 13, 2019

"Carbon monoxide poisoning kills 400 people in US each year
According to the Centers for Disease Control and Prevention, carbon monoxide poisoning kills more than 400 people each year in the United States on average and causes more than 100,000 Americans to visit the emergency room."

https://www.usatoday.com/story/news/nation/2024/12/27/family-dies-apparent-carbon-monoxide-poisoning-christmas/77270439007/

It is extremely EAZY to add a CarbonMonoxide ShutOff to an existing 24VAC gas appliance (simply by extending the wire through a rollout switch TCO through the NC relay pole of a FIRST ALERT Relay controlled by an 120VAC Carbon Monoxide Detector). In my view, the failure of an INSTALLER (of a 24VAC gas appliance) or HomeBuilder, or a Flipper, to install a CO-shutoff switch in 24VAC and 120VAC gas appliances is negligence or criminal recklessness for which they should have liability in a wrongful death lawsuit. No reasonable person would hinder the effort to add this safety feature to a standalone milivolt gas DHW tank. But, you point to the fact that Honeywell and the DHW manufacturers have not in fact facilitated this safety feature in their cheapest products (e.g. milivolt pilot-powered gas DWH sold to poorer people in older homes who cannot afford high end DWH and maybe who can't maintain their ancient chimneys. Quote:[Also, I'm pretty sure a response to your letter to the manufactures would gently steer you to literature on the extensive lineup of power vent, indirect, solar, tankless, electric, and heat pump water heaters.] That salesmanship does not obviate the problem in existing DHW also being sold and in already-installed gas appliances.

Quote: [It's not here because it's not feasible. Yet. ] This is false, and is disproved by the technical analysis provided in this discussion. Entirely feasible upon slight modifications, same as in the adjacent gas boilers, and other gas products, just not implemented by the valve PCB-maker.]

HVACNUT · February 3

https://forum.heatinghelp.com/discussion/comment/1839968#Comment_1839968

Ok… I'm just gonna walk over here now. Good luck with all your endeavors.

Martial_7erran · February 3

Another risk is that a chimney will fail, blocking the exit of flue gasses from the house (and slowing the convection of fresh air to the gas burners, generating carbon monoxide). Quote: Yeah, you did [imply deterioration] , " which could fail any day "" Chimney in boiler room is concrete block (clay tile lined, which could fail any day an block the chimney, hence I am also adding a Carbon Monoxide Detector and relay switch) all the way up to roof. "

I am rather alluding to the possibility that a clay liner, in any condition on one day, can fail the next day. This risk includes the fact that a gas burning appliance generates mostly WATER VAPOR that in some weather circumstances can CONDENSE inside the chimney or on the Cap above the Chimney, causing liquid water to accumulate (e.g., in or behind the clay liner and a cement block). If this occurs due to happenstance weather conditions, followed by a cold snap that freezes the water accumulated in or between the clay liner and the concrete block (or brick chimney) there is a risk that the clay liner will spall or flake or crack, and unexpectedly block the gas flue (e.g. at the bottom where the gas appliance enters the chimney). While there might exist in many cases some visible evidence (of prior deterioration) to increase the probability of this occurring. In my view, the risk of this occurrence should be assumed with or without evidence, and thus mitigated where possible.

No doubt that visible deterioration can precede clay tile chimney failure, but this is not always the case.

"Corrosion from combustion fumes together with moisture leads to the gradual breakdown of chimney flue tiles. However, poor craftsmanship in building a chimney can result in quicker deterioration of your clay flue tiles. On rare occasions, lightning strikes have been known to cause chimney liners to crack."

https://www.chimneysolutions.com/blog/why-do-chimney-flue-tiles-crack/#:~:text=Corrosion%20from%20combustion%20fumes%20together,cause%20chimney%20liners%20to%20crack.

P.S. I have personally seen the aftermath of a cementblock/claylined chimney that was struck with and damaged by lightning. I have personally seen where natural gas combustion products are chronically causing ugly icicles to form on the underside/edge of a stainless steel chimney cap, and then make a pile of ice on the masonry below, or fall down, causing damage to the masonry of the chimney below.

Martial_7erran · February 4

109A_5

You have provided a circuit diagram which I presume is a model of: The potentiometer (user control dial) as-configured on the PCB board of the Honeywell gas valve at issue. It shows the pontentiometer (max 10K) integrated into a voltage divider connected between the boosted board voltage (presumed to be 3.3 per the Texas Instruments microprocessor maximum input voltage) and PCB ground with a connection of that voltage divider node to the ADC (through a pin of the TI microcontroller)

Additionally, you have a light-blue circuit that is switchably connected to the same node (ADC) that I interpret as a proposed addition of a pull-down resistance to alter the voltage divider (dropping the voltage at the ADC). This has the feature that there is always continuously a voltage at the ADC sampling node (no disconnected state during the fly of the throw of the relay switch). You have proposed a resistance value 18.2 Kohms through this pull-down circuit.

I notice that the user-accessible dial (potentiomter) is not "locked out" while the pull-down resistor is switchably-connected to the node ADC. Thus, there can be some variation at ADC-sampling node depending upon the position of the user-accessible dial (potentiomter). I have not tried to compute to see if there is a safeharbor value for the pulldown resistance that prevents the pulled-down voltage (at ADC sampling node) from exceeding the required "PILOT" or "Vacation" mode level.

It is presently undetermined whether the voltage must be at a particular one of "PILOT" or "Vacation" to prevent burner firing. I assume that "PILOT" is the required voltage level.

To prevent the user-accessible dial (potentiomter) from introducing uncertainty, I envision connecting the "PILOT" resistance through the relay switch in a different manner,

Because the measured value to be switched (relay) is a VOLTAGE (at a voltage divider including potentiometer) it is easier to provide a glitch-free switching. (Easier than if we are switchably providing a different resistance or a current). My proposal is to construct a parallel voltage divider (having total resistance on the order of 20K ohm or 30Kohm (between Vcc and ground) that has its ADC-sampling node invariably fixed at the "PILOT" voltage. This parallel voltage divider will only and definitely provide the required "PILOT" voltage regardless of the position of the user-accessible dial (potentiomter). This approach requires cutting the connection between the ADC and the node of the original Dial voltage divider, (permanently connecting the ADC sensor to the common node of the NC/NO throw of a singlepole relay). Thus the ADC sampler will only be connected to one of the two voltage dividers at steady-state. A simple way to prevent switching glitch is to attach a small capacitor to the ADC node to prevent any erratic swing or change in voltage when the throw (ADC sensor) flies between NC and NO poles. Alternatively, two relays can be configured to construct a Make-Before-Break relay switch that will momentarily connect the ADC to BOTH of the voltage dividers (and connect both of the voltage dividers to each other at their ADC nodes). [This requires one double-throw relay to make NC connection to the "PILOT" voltage divider and exploits the time of closing the second pole (24VAC) NO contact to delay-activate the second 24VAC relay (which then opens the connection between ADC and the UserDial voltage divider).

This approach enables at least the desired external-control (OFF or delay of flame-ON) of the burner valve using an external signal (e.g., a 24VAC). Thus, this approach solves the aspect requiring turn-off of burner firing when Carbon Monoxide Detector issues an alarm (or the other gas appliances are firing and have priority)

The 24VAC control voltage for the above can be obtained from the PCB burner valve signal by sensing the FIRE-ON voltage applied at the PIN of the burner gas valve and sending that to a 5v opto-isolated relay to turn on the 24VAC control signal. This assumes that the "milivolt" voltage applied to the burner valve is really the boosted 3.3 voltage available (maximum) to the TI microcontroller. A 5v relay should trigger "ON" upon application of a 3.3v volts. (It does when a 3.3v arduino tries to control a 5V relay), But there is an apparent circular feedback loop here (valve turn off the Dial Call, turns off the valve). So a microprocessor (e.g., Arduino) would be needed here to intervene remember the Finite States and arbitrate if the burner valve voltage is the signal used to initiate a 4-inch damper opening)

109A_5 · February 4

Well there are many ways to modify the control of the water heater gas valve PCB. The example I posted is a simple method from about 1 minute of observation of the user control potentiometer with two obviously visible resistors and two capacitors. The circuit I drew is based on guesses and only a few facts. I have done no real reverse engineering of it.

If I wanted (and I don't) to have total control I would simply buy a second PCB (plenty out there), reverse engineer the whole board (not much there), buy a new microcontroller, remove the original microcontroller and write my own embedded code so it does what I want it to do. But there really is no practical point to do that, so I won't.

Also adding a damper would probably let the chimney cool down even more, acting as a catalyst to its dilapidation.

Your CO detector relay should interrupt the Power Pile circuit, not alter the temperature control circuit.

Martial_7erran · February 8

Quote: "Your CO detector relay should interrupt the Power Pile circuit, not alter the temperature control circuit."

That is very true. That can be done by adding the NC First Alert CO-alarm-activated relay in series with the easily-accessible TCO (flame rollout switch) at bottom of the DHW and would be easily removable also. That would easily shut down the pilot and the burner upon detection of CO. And, it is easily reproducible in any home to do it that way (no burden of modifying the connections on the PCB inside the Honeywell).

However, I am not sure that putting the NC First Alert CO-alarm-activated relay in series with the thermopile (or flame sensor) of a boiler of furnace in winter time (creating a house/pipe freeze risk following a temporary atmospheric inversion and downdraft of chimney) would be equally desirable. I should do some market research to see how CO-shutoff is implemented in existing gas appliance consumer products. The TCO (rollout switch or "spill valve") installed in gas boiler/furnace generally only cuts power to the burner valve? not the pilot?

109A_5 · February 8

Most modern boilers and furnaces don't have pilots. The pilot may not make enough CO to kill someone anyways, and frozen pipes is better than death IMO.

I prefer the natural draft it simply keeps the air moving, dryers and water heaters kind of have a limited run time anyway.

Say all the appliances except for the dryer have dampers and then there is a temporary atmospheric inversion and downdraft of chimney with dryer use, and some CO builds up in the basement with everything dampened it will never self purge. At least with the minimal heat loss with a un-dampered water heater tank there is a draft the will always move fresh air through.

To me there is a balance between reasonable safety and energy savings. I would not want to bet my life on a CO detector that may never work and with the consumer grade units the CO levels are pretty high for a period of time that it may require a trip to the hospital by the time they alert.

Martial_7erran · February 9

109A_5,

Quote: " I would not want to bet my life on a CO detector that may never work and with the consumer grade units the CO levels are pretty high for a period of time that it may require a trip to the hospital by the time they alert."

But, if all consumer grade units have such high threshhholds, then all consumers are at risk. Also, people die of heart damage and heart attacks from long-term exposure to small (not acutely lethal) quantities of CO gas. So, a low-threshhold CO detector with low-threshold alarm should be available.

Do you know of a CO-detector that measures and displays the PPM of Carbon Monoxide and has a user-configurable alarm setting that can be used to detect (smaller) CO accumulation (in the basement of a house). This resource would obviate the general concern that in consumer grade units the CO levels are pretty high for a period of time that it may require a trip to the hospital by the time they alert.

Martial_7erran · February 9

People have expertly studied this issue and have identified boiler-lockout (requiring manual reset) as the proper risk mitigation strategy upon detection of Carbon Monoxide:

Wiring for CO interlock/lockout for gas boiler?
https://forum.heatinghelp.com/discussion/157293/wiring-for-co-interlock-lockout-for-gas-boiler?utm_source=community-search&utm_medium=organic-search&utm_term=CO+relay

"My plumber says that NYC code requires new boiler installs to have a CO detector with interlock to boiler that forces a manual reset if CO is detected. My electrician is an idiot and has never done so and isn't interested in attempting. So I purchased a First alert combo detector with interconnect, a BRK RM4 relay .... If anyone decides to wire a CO detector interlocked with their boiler, using a First Alert combo smoke/co alarm along with a BRK RM-4 relay wired to the same breaker as boiler works a charm and is an easy install. Brown/Grey was the correct combination to the Manual Reset, which must be installed when boiler is off. I'd have liked to have invested in a smart CO that gave me an alert/notification when it tripped, so will look into that going forward."

If the CO relay has SPDT (both NC and NO), then you can use the NO (normally open) switch to activate a custom alarm or to activate/power an Arduino programmed to send you an email or TXT message alerting you to the fact that the CO-Detector has alarmed (and the boiler is OFF). Arduinos can be easily programmed for this using ChatGPT or Google Gemini (Generative AI) to tell you exactly how to wire and program them for this or a similar remote-alarm application.

Kidde has a NC/NO SPDT relay for CO-Detection alarm activation:

Carbon Monoxide Relay Module CO120X
"The Kidde CO120X can be used to activate auxiliary warning devices such as external bells and sirens, hallway or stairway lighting. This relay will only activate when it receives a CO signal from an interconnect Carbon Monoxide Alarm."

https://www.kidde.com/home-safety/en/us/products/fire-safety/safety-accessories/auxiliary-devices/co120x/

USER GUIDEs:
https://www.shareddocs.com/hvac/docs/2001/Public/0A/1201-7209-01.pdf.pdf

https://www.shareddocs.com/hvac/docs/2001/Public/09/CO120X_UserGuide_EN.pdf

DESCRIPTION:
"This module is only activated by a Kidde Carbon Monoxide Alarm interconnect signal [on one or more "red interconnect wires" of specific models of Kidde 120VAC-wired CO Alarms]."

[To use this Kidde relay itself to turn-OFF a pilot or the burner, the "yellow wire" connected to the "normally closed contact" (NC) pole of the relay and the Blue Wire (Common Contact) of the relay are wired in series with the thermopile wire, or in series with any of the installed TCOs such as "rollout switch" at bottom, or "spill switch" at the flue? or in series with the thermostat 24VAC call wire.]
"ADDITIONAL INSTALLATION INFORMATION: If the desired function is to switch off a device when the alarms sound, connect the yellow wire (NC) instead of the orange wire (NO) to the supply side of the device. Be sure not to exceed the relay contact ratings of the module. This
module should not be used to control inductive loads with inrush currents that will exceed the maximum contact ratings"

[Non-Latching relay switch, will not itself keep OFF the relay-controlled appliance after detector goes out of alarm]:
"Residential alarms do not latch in the alarm condition and they are self-resetting. If an alarm connected to a module has the test button pushed or the alarm momentarily activates, it will activate the module for as long as the unit is in alarm. If more than one alarm is connected to the module and the module is tied to a control panel there will be no way of knowing which unit caused the alarm."

"ATTENTION: The wiring connecting the module with the external devices is not supervised. Be sure to test the operation of all the devices controlling the module or controlled by the module. Devices controlled by the module can be tested by pushing the test button on the alarms and verifying that the controlled device responds in the desired manner"

"The model CO120X module is for use with the following interconnectable models: Carbon Monoxide Alarms: KN-COB-IC, KN-COB-IC-CA, KN-COB-ICB-CA, KN-COP-IC and KN-COP-ICCA, and CO/ Smoke Combo Alarms: KN-COSM-I, KN-COSM-IB, KN-COSM-ICA and KN-COSM-IBCA, all with red interconnect wires.

"Outer packaging is blue, in order to distinguish from Smoke Relay Module, Model SM120X, which has black outer packaging. This device will only activate when it receives a CO interconnect signal from a compatible device. When in the activated mode (as a result of a CO signal), this device will deactivate if it receives a smoke interconnect signal from a compatible device."

"NOTE: Only the Carbon Monoxide portion of the: KN-COSM-I, KN-COSM-IB, KN-COSM-ICA and KN-COSM-IBCA combo alarms will activate this module. If activation is required from the Smoke Alarm portion of these alarms, use the SM120X module."

"Compatible with [CO or Combined Smoke-CO] alarm models: KN-COSM-I, KN-COSM-IB, KN-COSM-ICA, KN-COSMIBCA, KN-COB-IC, KN-COB-IC-CA, KN-COB-ICB-CA, KN-COP-IC, KN-COP-IC-CA"

"This relay module can be used to activate auxiliary warning devices such as external bells and sirens, hallway or stairwell lighting. It provides isolated, (no internal connection to 120 volts AC) normally open, and normally closed contacts."

READ INSTRUCTIONS CAREFULLY AND COMPLETELY BEFORE INSTALLING.
Electrical Rating [to power the PCB and internal relay]: 120VAC 60 HZ 0.08 AMP

Contact [Relay switch] Rating: 10 AMPS @ 120 VAC
NON INDUCTIVE 5 AMPS @ 30 VDC

"Do not exceed the temperature or humidity limits of +40°F (4.4°C) to 100°F (37.8°C) (such as garages and unfinished attics) and 85% relative humidity for either the relay module or the alarms."

109A_5 · February 9

" "Do not exceed the temperature or humidity limits of +40°F (4.4°C) to 100°F (37.8°C) (such as garages and unfinished attics) and 85% relative humidity for either the relay module or the alarms." "

Well if your basement pipes are freezing it is below +40°F in the basement.

ALSO with 85% relative humidity limit, I use a hot water heater all Summer long and the humidity is commonly over 85% all Summer long here, I don't care for electronics that are intermittent by nature and can fail with no notice, I'd rather have the natural draft.

Martial_7erran · February 9

NYC Boiler Room - Smoke Alarm that will cut off boiler

"Had to do a whole new Boiler room filing for a property in NYC and 1 of the requirements is to have the carbon / smoke alarm tied into the boiler so that it cuts the power to the boiler if the alarm is triggered"

https://forum.heatinghelp.com/discussion/193832/nyc-boiler-room-smoke-alarm-that-will-cut-off-boiler#latest

Here is a CO-Detector with Relay wired to Cut-Off "POWER" to the boiler installed on a new boiler in 2018:

"Installed a CO detector with a relay that will kill the boiler if the CO detector alarm goes off"

The photos show the actual CO-Detector is installed on a junction box at the ceiling above the boiler. It seems to be wired to cut-off the whole 120VAC mains wires into the emergency-off manual switch. This configuration would not require a manual reset, as it would only simulate a power outage. To trigger a need for a manual reset, you would probably need to relay-interrupt the wired connection at a TCO ("rollout" switch or "spill switch")

109A_5 · February 9

To be clear, I'm not against satisfying the code for what ever additional safety related equipment needs to be installed, what ever it may be in any given jurisdiction.

What I am against is time sharing the combustion air between multiple appliances, which is where this thread basically started (I believe), and time sharing the combustion air may actually be a code violation.

Martial_7erran · February 11

Generally, when improving the basement as a living space, and boiler and DHW are in basement,, consideration must be given about adding a dedicated fresh air intake to supply these gas appliances. Fresh Air supply (especially without a Damper) can bring in more cold air directly into the basement. The temptation is to add partition walls around the boiler//DHW to contain the cold fresh air.

Service providers complain that putting walls close around the boiler makes harder to clean and harder to maintain.
https://youtube.com/shorts/sCQpNmRgafM?si=G3Qabd0NVb2Ql5du

Air from elsewhere, needed for combustion, can be obstructed by added walls and doors when furnace is enclosed. Changes often requires added "FieldControl" fresh air vent. The additional (fresh air intake) hole in wall necessitates a (24VAC powered) damper.

https://youtu.be/WVJSRd3aEeQ?t=75

I Want to ADD a 4-wire GVD Vent Damper to Thermopile-powered DHW Hot Water Heater

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