Increasing the Efficiency of an Old Boiler

<...upgrade...burner...>

Good point. If the thing is 20+ years old there may be a viable project concept to replace it with a modern recuperative boiler on dual "stay in business" and "investment to reduce operating costs" justification, particularly in light of the original poster's expenditure levels...

At 20+ years old it might be a high efficiency design, since the first big oil price spikes were in 1979-1980, which would be an impetus to make high efficiency furnaces which have now reached a relative peak with condensing furnaces now above 95% efficient, discharging room temperature exhaust. This is a conservative industry. In any event, if you have some nameplate data the efficiency can be looked up.

It is not likely that a burner change will upgrade an inefficient boiler. That might make a 55% efficient unit 60% or a little more efficient. The entire boiler needs to be replaced. Fortunately, the design procedure to make high efficiency condensing furnaces attracted many new players into the field and they improved the cost structure of the boiler as well as the efficiency. From the sound of it, this does not boil water, thus it has no high pressure vessel to create high costs, it would seem to be a water heater, and it may well have a countercurrent waste water heat exchanger to preheat the incoming water from the used water. That means a high efficiency water heater, of the type used and perfected in laundromats can be had for a modest cost.

Consumer coin Laundries will use the same water heating and recovery machines, and replacing a 20+ year old design can have a payback as low as 2-3 years, especially if you avoid too many high priced contractors and just use a local gas/oil fitter/electricians to install the correct sized high efficiency unit.

Some efficiency may be gained by isolating the slab perimeter with foam insulation, windbreaks, or by closing off one end of a drive-thru during winter months.

Thanks for all the great responses! I just contacted Raypak (boiler mfg.) to see what can be done, if anything to increase the efficiency of my boiler model.

Since I have a fairly large self serve car wash (9 total bays that need heating), I am thinking about possibly closing down four of the bays during the really harsh cold spells (this will be a dual savings since I won't need to heat the floors, turn on my metal halide fixtures at night, or weep water through the lines to prevent freeze ups). The most cost-effective method I have found for closing off the bays will be using 18 mil vinyl tarps to close off each end of the bay.

After 20 years there are more efficient boilers you could replace it with. Question to you is the increase cost due increase fuel usage or increase cost of fuel?

You also talk about shutting down some of the bays during the winter month. You will need to maintain the floor temperature above freezing. In you business I would think the pad stays saturated with water. Concrete will hold water if it freezes in the concrete it may cause damage.

I think the increase is due to both. I run a production boiler that constantly makes/produces heated water to wash the cars with and that boiler runs quite a bit more, while only using a fraction of the cfm's (they are comparable btu's by the way).

When I reference shutting down a few bays, I don't intend to shut the floor heat off. I will place tarps at each end of the bay and then lay some foam insulation down on the concrete so that I don't dissapate so much heat through the concrete. Make sense?

You might want to look at individual units for each bay that will heat the water on demand. A smaller boiler to heat the floor.

A boiler that is 20 years old, is probably down to 45% to 55% efficient.

A modern condensing boiler can be 95% efficient. This 40-50% saving in fuel goes right to the bottom line to buy a new boiler or your pocket.

Installation should be less than $5000 to $8000, since most things stay the same, just the boiler changes.

So it will pay off quickly.

Insulation of the floor with foam and tight end tarps = very low air exchange, will also help.

So this looks like a summer project, and you co-ordinate with the boiler people to rent a steam jenny for the few days you are changing over the boiler = hot water all the time

Talk to Lynn Mueller at Free Energy Solutions in Vancouver, BC (West Coast Canada). Tell him what you've described right here and he'll tell you about these thermal super-conductor rods that FES sells. Here's the web address for info:

www.freeenergysolutions.ca

He'll show you a way to use them to keep your concrete floor warm enough year-round by drawing heat from the ground underneath (or maybe around .. but most likely underneath) your floor.

And the kicker: once installed, these things run on their own forever. There are no moving parts ... ground heat will be conducted through the rods, which will be set in the concrete, with no moving parts anywhere and no power provided to the rods. Purely passive!

Free Energy and my firm (SPP Consultants) will soon start marketing this thermal technology in North America. E-mail me or Lynn (see addresses below) for pictures of something similar the FES did in Vancouver ... thermal rods to prevent ice and snow from piling up on a truck-docking bay. No more shoveling snow and ice, ever!

Tell Lynn that Stratos sent you. ;-)

Lynn Mueller, Free Energy Solutions (Vancouver, BC (Canada)) ... Lynn@freeenergysolutions.ca

Stratos Psarianos, SPP Consultants (Montreal, Quebec (Canada)) ... stratos@spp-consultants.com

Cheers!
DZ

Look also at some good old boiler maintenance issues. In an older boiler like this, there may be build-up of scale (precipitated minerals) on the water side, or build-up of soot on the fire side. Either of these will reduce the heat transfer in the boiler, which will show up as higher than usual exhaust stack temperatures. (In other words, energy going up the chimney.) Perhaps some chemical cleaning on the water side and brush cleaning on the fire side can restore your boiler to decent efficiency. Newer designs will be even more efficient, but will require substantial capital outlay. Another thing to check would be the fuel nozzle for oil fouling, drippage, etc. A boiler tech can also inspect the flame shape and color to see if they are correct. With luck, a fairly simple tune-up may solve your problem. Best of success with this.

If the pipes are buried too deep, the poor thermal conductivity of the concrete may lead to poor efficiency. The conductivity of concrete (and its hardness) can be increased by adding stabilized iron powder to the cement. The pipes can be brought nearer the top surface as well.

Bioramani

It may be very economical to install a 'convection/economizer section' heat recovery system on your present heater. This is simple in concept, with the devil in the details. It is basically a 'radiator' in the hot exhaust circulating cool glycol solution to the cold concrete. 20 years ago, economic heater design was exhaust gas temperatures of 600F or even higher. Today, recovering heat down to 100F or so is economical in some situations. The convection/economizer section would likely be much lower cost than a new heater since the new one must have the equivalent hardware to achieve the higher efficiency. Higher efficiency requires more heat exchange area.

New burner technology has greatly improved combustion efficiency and lowered excess air requirements. Retrofit of improved combustors and excess air control should be investigated during the investigations.

When it reaches 30 degress here cash washes shut down and only reopen when the temp is above 32 degrees the added cost is just not worth it to them.

The cars are lined up too when the places reopen. So they save and they still make the profit just not as much outlay. The workers take the days off with pay but they worked 12 hours when the places reopened with no overtime per aggrement.

If you're looking at a replacement boiler, look into wood/woodchips rather than natural gas. If you have a good local source, that should save you significant money. And wood doesn't have to pollute: http://www.alternateheatingsystems.com/woodboilers.htm

Gentlemen:

The suggestions above are ok. However, the suggestions from "Tornado" is the most viable/practical. Furthermore, it is also worth taking into consideration or "bench-mark" what the conditions on a seasonal basis (i.e.: outside temperature, etc.) since these could add or decrease your fuel consumption.

Likewise, a "20 year old" boiler does not have a dramatic efficiency drop (at least structurally) unlike cars. It is more likely that the insulation have deteriorated plus the "internal factors" as mentioned by "Tornado".

Thanks for all the great responses! Before last year's winter season, we went through and cleaned all the boiler fins using a soft bristle brush, compressed air and a mild detergent and water. Suprisingly, they weren't bad and cleaned up even better. We adjusted the flame properly and went on our merry way. It wasn't until we got into the real harsh winter months that we found our hard work was only marginal at best.

I have called Raypak to see about what a new high efficiency boiler would run me. I probably have until mid-November before the boiler will need to be on constantly, so I need to get my ducks in a row.

-As far as that car wash in Tenn. goes, if I shut down when it was below 32 degrees, I would have November to April off! LOL!

Great idea! I will check into that with my Raypak distributor and see what he has to say. That makes sense that over 2 decades, there would be some type of buildup that would inhibit proper flow.

Does your stack have a thermometer, a simple way to keep track on heat transfer.

Are you shure your setpoints are were they need to be. you might be a little too generous with the setpoints. Carefully calibrate test and monitor system set-up. A guess work set-up will always loose-out to auto detect and respond systems that is and only when it is properly understood and cared for. Are your slabstats giving you a true reading and the list goes on. Just a few quick thoughts from a Stationary Power Plant Operators perspective.

That's what I am going to do is replace my thermostat from an old dial mechanical to a new digital one and I'm going to replace the the slabstat too. Those are at a bare minimum the two things that I will do before it gets too cold.

sounds to me that the glychol/antifreeze solution is passed through the boiler(what kind and how big?), using circulator(s) what kind and how big?). Water is your best transfer fluid, so why not use a heat exchanger large enough for the snow melt system, and run water from the boiler to the H X and back with 1 circulator, then circulate the snow melt side with another pump. Then optimize the burners in the boiler and make sure the intake air and flue piping are right. Some control systems for snow melt are on standby during the season, then ramp up 3 to 4 degrees to melt snow. (tekmar systems). H T H

After speaking with some old school car wash guys. They recommend that I use an aquastat to control the boiler cycling by the return line temperature of the solution coming back from the car wash bays. Is anyone familiar with an aquastat and what type of accuracy they have? Here is one website I found, but I haven't done too much digging.

look at post #10 again (Tornado). Add to that, completely clean the burners (no dust) and keep them clean, Proper antifreeze (anti foaming ) and up to date, use a primary/secondary piping arrangement (and tecmar controls) to keep boiler return water above 135. If you can't keep the return water above 135, re pipe system and use heat exchangers. (below 135 degrades boiler badly) Also , if you run your boiler on a return water temp. aqua stat, it will run more. HTH