Category Archives: heating

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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2016 heating savings

It is friggin cold outside, and I can’t shake the urge to keep talking about heating related matters, so here we go again:

One goal of our deep energy retrofit was to save energy, and along with it, some Benjamin Franklins. The money we invested in tightening and insulating the building was meant to save us dollars on our heating bill, for instance.

But how would we measure how much we save? Our problem was that we had no starting point. We bought our building as a foreclosure in 2009 and thus had no data – no access to utility bills – that would tell us what it took to keep the building heated and comfortable.

That said, there are plenty of buildings in our neighborhood that could serve as a comparable (comp). Not only are they the same construction type, but also in the same energy deficient shape as our building was before we started with our deep energy retrofit.

I found a building that was a good match, and the owner that was happy to share their utility data with us.

To compare apples to apples – or in this case, therms to therms – I calculated the amount of therms used per square foot per month for both buildings. Our building’s natural gas consumption is reflected in the blue bars, while the comp, or pre-retrofit state, is reflected in the red bars.

Data reflections

Why is there natural gas used during the summer months (off heating season)? Because in both cases natural gas is used to produce domestic hot water, i.e. washing the dishes, running the washing machine on warm or hot cycle, taking a shower, etc.

You may have seen me bragging about turning our heat on as late as mid November. If you look at the consumption for November 2016, you see that we mostly used domestic hot water while our neighbor in the comp building had the boiler already buzzing away.

Looking at the big picture, our building consumed 0.200 therms/square foot over the course of one year, while the comp usage was at 0.976. Our deep energy retrofit improvements appear to have reduced our natural gas consumption by 0.776 therms/square foot/year. That equals a reduction in our heating needs from November 2015 through December 2016 by a whopping 80%!

For our metric friends (i.e. the world with the exception of the U.S.): Our natural gas consumption equated 63.04 kWh (or 226.95 MJ) per square meter, while the comp came in at 307.89 kWh (or 1108.39 MJ) per square meter.

I typically don’t like to measure the improvements in cost savings, as supply cost and taxes may vary between jurisdictions or energy companies. In addition, the fixed costs on the gas bill, although often small, prevent accurate scaling to a square foot basis.

Yet getting an approximation of the monetary savings would give us a sense of the potential return on investment. We paid $0.27 for natural gas per square foot over the course of a year. The cost of the comp were $0.98. The estimated total cost savings for the 2,900 square foot of conditioned space in our building from November 2015 through December 2016 would be in the range of $2,000.

Yes – I am beaming right now! Yet, this somehow seems too good to be true. I think the flaw with my analysis is that I have based it on one comp only. I plan to find another couple of buildings that I could include in the analysis. That should give me a number that would be easier to defend.

Stay tuned, because I will keep you posted!

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Welcome waste (energy)

Today, we are not pinching nickels, but degrees.

I mentioned in the last post that it took us until November 17 before we turned the heat on, whereas other Chicagoans fired up their furnaces in early October. Why were we still comfortable several weeks into the cold weather?

Waste heat!

Boiling the kettle, cooking dinner, baking banana bread … Then add in all the electrical appliances that produce waste heat: running the fridge, TV, laptop and desktop computers, having the lights on … all this and more produce some level of waste heat which is welcome during this season. Not so much during the dog days of summer, though.

But wait! There’s more. Let’s not ignore the four critters occupying the space. Two of them two legged, and the other two four legged. Believe me, they all have a healthy metabolism going, based on the heat they throw off! Seriously, body heat from building occupants is not to be ignored – not in the context of a deep energy retrofit.

Let’s think of these heat sources as miniature radiators. Individually, they don’t do much. But cumulatively they begin to matter, if – and this is a big IF – the building is well insulated  and as good as airtight. Because now this waste heat doesn’t escape. It lingers around and keeps the building interior at a comfortable temperature when others have long reached for their thermostats.

In this context, your furnishing and the actual interior of your building begins to act as a heat sink – it becomes thermal mass. Your oak dresser, your hardwood floors, your drywall, your bathroom tiles, you name it – they all store heat to some degree, which adds to the comfort.

Another gadget that helps us to delay the start of the heating season in the Energy Recovery Ventilator (ERV). It delivers fresh air into our airtight building envelope, but does so with the help of a heat exchanger. This allow us to recover most of the precious waste heat and yet still get fresh air.

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