Tag Archives: utilities

How close to net-zero are we?

To answer this question, let’s look at the data for the solar year 2020 when our electrical use included space conditioning.

Our annual use totaled 13,428 kWh that year, while our annual production amounted to 11,390 kWh. The solar array produced enough electricity to cover 85% of our annual consumption.

To reach net-zero, we would need to be at 100% or above. So we are around 15% short of net zero and had some more homework ahead of us.

The moving goal post…

When we embarked on the project in 2009, all-electric homes were not a thing yet, heat pumps were hard to find, and solar arrays were uncommon.

At the time my focus was on using a solar hot water system to heat the building and for domestic hot water, and a photovoltaic array to cover our electrical needs. But I always found myself on thin ice when attempting to cover space heating and domestic hot water with a solar hot water system alone. In other words, getting away without a natural gas connection seemed impossible, which made the net zero goal hard to reach.

I pivoted my focus into significantly reducing the overall energy load of our building. If I had to use natural gas as an energy source, I wanted to use as little as possible. That put us on the path of our deep energy retrofit.

And it paid off.

Interim results in 2012 showed that our improvements reduced our electrical consumption by an estimated 57% and preliminary results from 2016 showed that we reduced our heating needs by an estimated 80%.

A lot has happened since 2009. Green building technologies that once were only known from excotic places like Europe or Asia suddenly made an appearance in the U.S. market, such as heat pumps. And with that, my focus on solar hot water fell away, because heat pumps emerged as a more economic option that I still could use, even if the sun was not shining.

Reducing the general electrical load of a building also has become easier since 2009 with increasingly efficient energy star appliances, LED lighting, etc.

What is standing in the way of net zero?

Yet we are not net zero, to my chagrin. What is standing in the way are two key factors:

  1. That we still rely on natural gas for cooking, domestic hot water, and occasional heating. And we still have a gas dryer.
  2. That our solar array is not large enough to cover 100% of our energy needs should we go all electric.

The second point should be reasonably easy to solve. Because we have reduced the energy load of our building significantly, we have enough room to expand our solar array to cover 100% of our energy use. And we plan on doing so – eventually – once technology catches up.

Regarding the first point – our natural gas connection – it helps to know how much natural gas goes towards what source in our building.

Analyzing our utility bills over the past seven years revealed that about 700 therms (70%) went towards space heating, with only 300 therms (30%) going towards domestic hot water, ranges, and the dryer.

The 300 therms seemed to be easy to solve. We can replace our gas dryer with a condensing dryer. The gas ranges can be replaced with induction stoves. And the heat pump water heater technologies have improved to the point where we could say goodbye to a gas fired water heater too.

As for the 700 therms going into space heating, one could argue that we solved that problem already with the addition of our minisplits. We used them to heat our building during the solar year 2020, and it worked.

But there is a problem: we drank the kool aid.

We originally, and occasionally still rely on our hydronic heating system, powered by a high efficiency boiler. The steel baseboard radiators and radiant floors deliver a comfort during the heating season that is unmatched.

The good news is that we potentially could replace our boiler with an air-to-water heat pump that used CO2 (R744) as a refrigerant. These units are slowly making an appearance in the U.S. market and are able to deliver 130F water even at very low exterior temperatures. 130F would be a suitable temperature for our hydronic heating system and domestic hot water.

Not only that, but an air-to–water heat pump would be two to three times more efficient than our high efficiency boiler. In other words, it would only require half or one third of the energy input to produce the equivalent of 700 therms heating output.

I am hopeful to eventually replace our boiler with an air-to-water heat pump and solve the 700 therms that were needed for space heating.  We subsequently could cut our natural gas supply to the building, and yet still enjoy the comfort of our hydronic heating system.

That must be expensive!

In the big picture, what is the cost of doing nothing?

And on a project basis, if it is expensive depends on one’s mindset.

Most of our system decisions, such as the heating system, were not solely based on the economics of the day, or “what is the cheapest system I can get.” We were comfortable investing in systems with a longer payback period as long as they came with:

  1. a high level of energy efficiency,
  2. some level of resiliency and longevity,
  3. improved indoor comfort and health without an energy penalty, and
  4. systems that were somewhat future-proof so that they could adapt to technology upgrades.

This required a lot of research and careful planning at the onset of our project. And it required a lot of luck, as we were gazing into the future trying to predict the path green building technologies would take.

And in practical terms?

It appears that our utility room layout could accommodate the switch from boiler to air-to-water heat pump without revamping the whole hydronic heating or domestic hot water layout.

And because we were mindful when we installed an all new electrical metallic tubing (EMT) based electrical system, providing 240V for the induction stoves and potentially the condensing dryer should just be a matter of simple rewiring.

The one item that wasn’t even remotely on the radar in 2009, and that I still have to wrap my head around, is how best to integrate and accommodate EV charging stations.

In summary: We are not net-zero yet. We are fairly close, and we know the path that will take us there.

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Roof vents

It was nice that our roofing crew took care of the roof tear off. That gave me the space and time to focus on the little side projects, like the roofing vents.

Let’s start with the main roofing vent, or the main drain-waste-vent (DWV) stack, if you want to call it that. It services the laundry room, main bathrooms, and kitchens.

Back in 2011 we decided to slightly rearrange the bathrooms. That meant we had to move the main vent stack over by about four feet in the plumbing wall.

Rather than punching a new hole into the roof to surface the vent stack, I put a kick into the stack right under the roof so that I could surface it through the existing hole of the old vent stack.

That was meant as a temporary solution, and now was the time to discharge the temporary and build the permanent.

With the roof torn off, it was easy to cut out the temporary stack. We abandoned the awkward kick right under the roof and filled it with insulation. We cut a new hole that was centered right over the main DWV stack and reconnected it. This way the stack runs in a straight line from the basement slab to the roof – the way it should be.

And then there was the need for a whole new vent stack, which services the 2nd bathroom on the 1st and 2nd floors. We again cut a hole that was centered right over the stack and connected it.

These are the kind of connections you want to do while you are re-roofing. This way the roof penetrations become part of the waterproofing system, rather than another patch to your roof.

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Cleaning heat exchanger coils

The troubleshooting of our busted boiler (a Trinity LX150 by NTI), led me to the fact that mineral deposits inside the heat exchanger led to partial or complete blockage.

I knew that I had to clean out those mineral deposits, but I wasn’t able to get my hands on the recommended Fernox DS-40 descaler and cleanser – at least not quickly.

My next best option was to use widely available cleaning vinegar. But for this to work I had to isolate the boiler. In other words, I needed to just flush the boiler with the cleaning vinegar, but not the whole hydronic heating system, because that would take gallons upon gallons of cleaning vinegar.

Isolating and flushing the boiler should have been a cake walk, if our boiler had been installed with the drain and isolation valves as shown in the nifty manufacturer-issued plumbing diagram.

The reality of our boiler plumbing required a little creativity, because I only had one isolation valve and did not have drain valves as shown in the diagram.

I isolated the boiler by turning off the isolation valve on the outlet side, and turning off the isolation valves for the boiler pump on the inlet side. Removing the boiler pump was the best substitute available for the missing drain valve.

I then proceeded to remove the pressure relief valve on the outlet side and replace it with a simple ½ inch riser.

By pouring about one gallon of cleaning vinegar into the boiler through the riser, I was able to displace the water in the boiler and heat exchanger.

I added about another gallon or two into the bucket below the boiler pump, set my small sump pump into the bucket, and connected it with a vinyl tube to the riser on the outlet side. With this setup I was able to start flushing the boiler in reverse (outlet to inlet) with almost pure cleaning vinegar.

I also added a small wire tray to monitor the debris discharge. It took me three days of boiler flushing to get the mineral deposits out of the heat exchanger. I actually flushed for four days, but had no more debris discharge on day four.

And don’t be fooled by the rapid flow rate in the video, which I took on day four. On day one, I had a fraction of that flow and the sump pump was cranking pretty hard.

How did we get by without a boiler for three days?

That was thanks to the resilience of our system. We didn’t use any hydronic heating during the three days of boiler maintenance, but instead relied on our minisplits for heating.

And what about domestic hot water?

After each day of flushing, I reconnected the boiler and turned it back on to recharge our buffer tank and domestic hot water storage tank. With both tanks recharged, we had enough domestic hot water for a day.

I sat with the boiler during the flushing process and manually turned it off to let it cool down once there was a hint of hammering. It was time consuming but it worked.

I also noticed during the three days that the boiler operation got increasingly more quiet. Not only did the hammering and banging cease, but so did the hissing of flowing water. With the obstructions in the heat exchanger removed, our boiler ran almost silently and very efficiently once again.

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Busted Boiler

How about a seasonal topic, like a busted boiler?

Our Trinity LX150 by NTI (NY Thermal Inc.) started hammering and banging and eventually shut down. When I checked the boiler display, I found an error message saying: “Lockout 81 – Delta T limit”.

At the time I had no idea what the cause of the problem could be. So I started with the troubleshooting chart in the operation instructions, which was pretty straight forward:

I tested “Fuse A” and it was fine. I checked the pump, and it was running. The plumbing was correct too and I had water pressure of 20 psi. That left me with the dreaded last option: a fouled heat exchanger. Dreaded, because I wasn’t quite clear on what it meant and what the implications were. After some research and scouring through YouTube, I finally was able to put the pieces together.

A boiler doesn’t just break. It usually has a good reason, such as deferred maintenance. And I am embarrassed to admit that I am guilty of such deferral.

Our high efficiency boiler (Trinity LX150) takes care of our domestic hot water and hydronic heating system. I wrote about our mechanical system and how it functions in a previous blog post, which makes for good reading.

The boiler has a modulating capacity from 25,000 to 150,000 BTU and a stainless steel heat exchanger.

It is that heat exchanger that makes these boilers so efficient. In our case, we have small tubing (probably 3/8″) that surrounds the burn chamber. The ratio of the small water volume in the heat exchanger versus the relatively large surface area of the heat exchanger allows for efficient heat transfer.

But this efficiency comes at a price. Because of the small diameter, the tubing can be prone to clogging by lime and other mineral deposits. And once deposits build up inside the heat exchanger tubing, the efficiency of the boiler goes down and the banging and hammering starts.

If the water in the closed loop hydronic system would be treated properly, the risk of mineral deposit formation would be greatly reduced.

When our installer first filled the hydronic system, he added an additive that depletes the oxygen in the water and reduces the risk of corrosion and mineral deposit formation. From that point on, the closed loop system was supposed to run almost maintenance free, as long as no new water (i.e new oxygen and minerals) was added to the system.

Read also: RPA – Chemical Water Treatment

But I did add new water. First when we filled and started up the radiators on the 1st floor, and again later when I partially drained the buffer tank to service a sensor. I did not think about the newly introduced water at the time, and it came around to nip me in the butt!

The first symptoms were the hammering and banging in the boiler. I assume what happened was that the tube diameter was decreased by mineral deposits to the point where the flow volume was so small and slow that the water turned into steam. That’s a very unnerving thought!

The boiler has an amazing array of safety sensors and mechanisms. It recognized the dangerously high temperature in the heat exchanger and automatically shut off.

That is good for safety, but it is not good for maintaining domestic hot water and keeping the radiators running.

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Chiberia 2019 – Choking boiler

This winter, we have being using our minisplit as our primary heating source. It is rated to provide heating down to an outside temperature of -5 degrees Fahrenheit (-20.5 degrees Celsius).

But once we were railroaded by the Siberian express and temperatures dropped below -5 degrees Fahrenheit on January 29th, I turned the minisplit off and fired up the boiler to power our radiant heating system.

Even though everything seemed to be humming along just fine, I heeded the recommendation by the City of Chicago to proactively check on the mechanical systems. It held the promise of soothing my nervousness that arose from the record cold temperatures that remained below (and sometimes far below) 0 degree Fahrenheit (-17 Celcius) for 49 straight hours.

That’s how I discovered that our Trinity LX 150 boiler must have shut down sometime during night #2 of our polar vortex. Because of the insulation, our building takes a long time to cool down, and it may have been another half a day before we noticed that the heat was off.

One of the safety features on our boiler is a combustion sensor, which jumped into action because it detected insufficient airflow into the combustion chamber (see image above).

Outside I found some ice build-up on the exhaust, which is expected because of the water vapor that is in the exhaust. What I did not expect was to find that the air intake pipe had frozen up. It is a little hard to see, but you may be able to make it out in the image below.

That ice build up literally choked our boiler and shut it down.

I whipped the hair dryer out to warm up the pipe and melt the ice, which was a completely futile exercise at -20 degrees Fahrenheit (-29 degrees Celsius). I didn’t even get the ice on the pipe to melt, let alone the ice in the pipe!

Cathy had a better idea and handed me our heating pad, a towel, and a bungee. That did the job within a few minutes, and the relatively thin ice block in the pipe collapsed so I could scrape it out.

Hunting for the cause

With the boiler up and running again, I started to search for the probable cause of the ice blockage, and was handed a “duh” moment.

The wind blew the exhaust loaded with water vapor across the fresh air intake, where it froze up. Cathy pointed out that this installation (having the exhaust blow across the intake) did not make any sense. I checked with the installation manual, and she was right!

The recommendation is a minimum 18 inches vertical separation between exhaust and intake. I used a short piece of PVC pipe and duct tape for a quick fix.

And it makes perfect sense, because the hot exhaust fumes tend to rise up fairly quickly. Having the air intake at least 18 inches lower almost eliminates the risk of exhaust fumes being sucked back into the boiler. I just have to come back and make this fix permanent.

What really bothers me is that I had assumed from the time the boiler was installed that the exhaust and air intake met the manufacturers recommendations. God knows how many times I had the boiler run inefficiently because southerly winds blew the exhaust right across the air intake!

It’s that fine line: Do you micro-manage installations by your contractors, or do you trust that they know how to do things right?

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