small boiler - greenhouse application - questions

mrwoo

Hello.



I do a lot of plumbing, mainly using pvc for chemical injectors in a greenhouse setting. I do some copper work as needed. Lately I have been working more with our boilers (radiant floor heat) to get rid of some air lock situations.



A few years ago we purchased a kit that was designed to heat the bottom side of plants for propagation. The kit came with a small 90k Raypak boiler and manifolds with rubber tubing for 10 tables. Installation was easy, as the kit was "plug and play" as they say.



Anyway, after many small issues, I have decided to rip apart the loop and all plumbing and start new, primarily because the design and installation "trapped" the boiler to the point you could not even light the pilot without some circus grade contortionism going on.



From examining the boiler and other boilers plumbing, there seems to be a few methods of plumbing. I will describe how it came and how I plan on creating it.



AS IT CAME

fill valve > expansion tank > air scoop > check/screen > boiler pump > inlet of boiler

outlet of boiler > flow switch > high thermal cutoff (state mandated) > zone pump

a connection or loop "between" inlet and outlet side of boiler exists



when a remote thermistor calls for heat on bench, zone pump and boiler pump actuate (flow switch and pressure switch for safety). Boiler fires. Zone pump moves hot water along pex piping to tables. If zone pump shuts off, boiler pump still moves water because of the "loop" between the inlet and outlet. Obviously return line brings cooler water back from tables.



Boiler is 2 stage burner (low & hi).



AS I PLAN

flow switch > inlet of boiler

outlet of boiler > fill valve > expansion tank > air scoop > check/screen > taco cartridge >

(boiler pump still in same position right at inlet, with inlet/outlet "looped" together)



I have seen two systems that fill and air purge before the zone pump. This would be advantageous for space / installation. Is this acceptible?





Question 2



I have learned about adjusting the pH and calcium carbonate levels. I do this for water quality on plants already, so that is easy once you know the proper range. This system develops an algae/bacteria problem, as do all my pipes. On 2-4" pvc, not a problem. On 1/8 id tubing for the bench heat, it becomes a problem. I have found a product that is supposed to kill the algae/bacteria. The issue comes that I must put X ppm into X gallons of water of the boiler plumbing and let it sit overnight.



My boiler has a pot or chemical bypass feeder. What I want to also know is if there is a method calculate the dilution ratio of a chemical bypass feeder. I doubt there is. What would be the correct procedure to optimum dilution? I assume to create a slight pressure differential, and over time of circulation, the contents of the bypass feeder will be fed into the lines. I cannot inject the solution into the lines because none of my injectors will dilute at 10:1 (can do 100:1 to 2000:1). I can make the chemical more concentrated, but it becomes more of a health hazard as levels go up.



My thought was to fill the 1 gallon bypass feeder with the correct concentration for the amount of water in the boiler circuit, then allow it to be fed into the system. It should not be dumped into the system at once, as too great of concentration and it can attack the copper/metal parts of the boiler. It is not super critical that it be at exactly 50ppm initially, but I need to ensure it isn't at 350ppm etc. So I need to find the method to use the bypass feeder which will introduce the chemical slowly.



As well, since I am replumbing the entire system, where would the best location be for the bypass feeder? I assume since the chemical can attack metal, it would be best just before the pex pipe portions. I was also thinking of installing a second bypass feeder just after the pex pipe portions, before the boiler. This second bypass feeder would be wide open, allowing a larger area for incoming liquid to "mix" in, even if the mixing is minimal.



Thanks for any advice.

LarryC

What is the alge feeding on?

DISCLAIMER: I am not a plumber or heating professional.

 

If I understand you description correctly, you have a primary secondary setup.  The boiler loop is your primary loop and each table is a secondary loop. 



1)  Is the primary loop all metal? 

 

2)  Are the secondary loops all PEX? 

 

3)  What is the algea feeding on?

4)  Do you have an on going water make up issue?

5)  Is the PEX tubing an oxygen barrier type?

6)  What is the system static pressure (no pumps running) ?

7)  What is the water supply like?  Well or city water, hardness, pH, etc.

8)  What are the loop pumps?

mrwoo

providing more data

1) Is the primary loop all metal?

yes, all copper 1" with only a few non-copper (like air scoop)



2) Are the secondary loops all PEX?

the majority is. There are 10 tables with each table having 2 copper manifolds. Each manifold has 20 3/8" female adapters for the tubing to mate with. The total length from boiler to end point is 80 feet. There are 3 pex lines used. One is a return line, 160 feet long. The return line starts near the boiler, picking up the hot water fed to the table, and continues, to the end (80 feet), picking up each tables hot water as it goes. At the end (80 feet) it turns around and goes back to the boiler.



The outlet of the boiler goes to the middle (40 feet) and tees off. Each tee then feeds 5 tables. This was done to try to get the heat evenly dispersed. The kit design had the outlet of the boiler feeding directly into the first table, then second, etc. That caused the first few tables to be much higher in temps than the end tables, so we ran the water to the middle. This works good, achieving a good balance throughout all tables.



3) What is the algea feeding on?

Not sure exactly. My ph ranges from 7.8 to 8.2 depending on time of year (aquifer level/ mountain runoff). The CaCO3 levels are 130-160 ppm. The water is very pure but high in ph/alkalinity for plants. Not much in way of any element that I can find to cause algae growth. However, the real problem stems from some clear pex that was used that introduced algae into the system. As well, it used to be plumbed in sch80 pvc, which I changed out to pex and copper. All of my pvc pipes develop what is coined a "bio slime", even fresh water lines. I have read that this bio slime can have a symbiotic realtionship with with algae, allowing algae to grow in absence of light. Cutting my pvc lines for repairs/upgrades over the years allows me to belieive this, especially in lines that have been fertigated. I don't normally see that though in fresh water lines, that is no algae only the bio slime.



4) Do you have an on going water make up issue?

There was. The kit called for sch80, and being new to boilers I assumed the aquastat would be set by the makers of the kit. Wrong. It was set to standard 180 I guess. It ruined my very straight and exactly measured piping, warped it like a big dog. It had a few drips at that point, but not too bad. The situation became worse when the state mandated an external high limit sensor. The guy who installed that set the boiler back to 180 again and I had to scab in many new male adapters for the manifolds for ball valves. It leaked a lot after that, but I could not replace it during it use. After that season, I replaced the sch80 with pex and copper. Now it is leak free AFAIK.



5) Is the PEX tubing an oxygen barrier type?

I don't think so, it is a standard 180 deg. in floor 1" pex.



6) What is the system static pressure (no pumps running) ?

I believe it is about 15-18.



7) What is the water supply like? Well or city water, hardness, pH, etc.

It is well water. I don't test for hardness, only CaCO3, which is typically 130-160ppm and ph fluxes seasonally between 7.8 and 8.2 or so.



8) What are the loop pumps?

Both are Taco cartridge model 007



Thank you for the time.

LarryC

More questions

DISCLAIMER:  I AM NOT A HEATING OR PLUMBING PROFESSIONAL.

 

If I understand your descriptions correctly, you have Primary Secondary setup.  The boiler and boiler pump is your primary loop.  The secondary loop is the loop pump feeding two sets of 5 tables that were plumbed in a ten table reverse return setup.

 

I believe the boiler maintains a constant temperature and when any table calls for heat, the loop pump turns on and also starts the boiler pump. 

 

1)  Is this a correct description of system layout and system operation?

 

You have a problem with algea in all of the heating plant plumbing.  The algeacide in high concentrations could be corrosive to metals.

 

WATER CHEMISTRY GURU QUESTION

 

2)  Could Mr. Woo use a 10 % solution of household bleach to safely clean out and flush his system piping? 

 

 I'm thinking empty system, refill with bleach solution, heat and circulate for 24 hours, drain system, refilling with clean water, heat, circulate, and drain two more times.  Refill with suitable solution for extended operation.

 

3)  What would be a suitable  solution for extended operation?  Copper Sulphate or dilute bleach (2% ?)

 

4)  Would this system be a good candidate for a water heater tank to be used as a hydraulic separator and run the boiler independently of the table temperatures?

mrwoo

more data

If I understand your descriptions correctly, you have Primary Secondary setup. The boiler and boiler pump is your primary loop. The secondary loop is the loop pump feeding two sets of 5 tables that were plumbed in a ten table reverse return setup.



I believe the boiler maintains a constant temperature and when any table calls for heat, the loop pump turns on and also starts the boiler pump.

>

It is good to know the terminology. Primary Secondary sounds correct. The primary and secondary loops also sound correct. The boiler is only used for this table heating application. I will describe it at the end.



1) Is this a correct description of system layout and system operation?



You have a problem with algea in all of the heating plant plumbing. The algeacide in high concentrations could be corrosive to metals.

>

True.



2) Could Mr. Woo use a 10 % solution of household bleach to safely clean out and flush his system piping?

>

Possibly.



I'm thinking empty system, refill with bleach solution, heat and circulate for 24 hours, drain system, refilling with clean water, heat, circulate, and drain two more times. Refill with suitable solution for extended operation.

>

Very similar to my thoughts.



3) What would be a suitable solution for extended operation? Copper Sulphate or dilute bleach (2% ?)

>

See end for answer.



4) Would this system be a good candidate for a water heater tank to be used as a hydraulic separator and run the boiler independently of the table temperatures?

>

I think I understand what you mean. I think when you read below this will most likely be answered.

>

>



This was a kit specifically designed for bench heat propagation. The boiler Primary loop is quite literally 2 feet of 1" copper on the outlet, with a tee at the top, which runs about 8 inches to the inlet, which enters the boiler pump and then the inlet of the boiler. The Primary loop is a loop I suppose, albeit a very small one.



The system has a control module which reads a thermistor placed on one of the tables. As the control module senses a 3 deg drop, it in turn actuates 2 relays, which open vent louvers, starts the secondary pump, initiates the boiler firing sequence. The boiler, once initiated, checks for flame and water movement, then fires. As the water is heated, some obviously could return via the Primary loop, but I think most of it heads to the Secondary loop. About 2 feet after the outlet is the Secondary loop pump. This, as you say, heads out to the tables in a reverse return setup.



As the boiler finds the incoming water to be at the aquastat temp, it drops to its low setting. The Secondary pump continues to run, and eventually the return water has cooled enough that the boiler goes to the high flame range, and the cycle repeats itself, until the control module senses the set point has been reached. Once the control module set point is reached, everything shuts down.



I had a problem where, once everything shut off at once, the water in the heat exchange was still very hot, and the pilot light would actually drive the water in the boiler up to almost 180 deg. The external high temp cutoff was strapped to the outlet of the boiler, and it would sense this and trip its relay. I solved this problem by installing a time delay relay using a "delay on release" which keeps the Secondary pump running after the control module shuts everything else down. This circulated the water out of the heat exchange I believe, and is enough that the pilot no longer heats the water over 160 deg, which is the thermal cutoff temp.



Question # 1 is a design/layout question. Is it acceptible to put the makup/pressure regulater/expansion tank/air scoop/vent AFTER the outlet, then the secondary pump. The inlet is obviously the return from the Secondary loop, with the boiler pump being right at the boiler inlet. The ORIGINAL design called for the makeup/regulator/expansion/air scoop/vent to be BEFORE the inlet (at the end of the secondary loop return). In changing this design, obviously I don't want to invest labor that is wasted, and I want to fix it and not have to visit it again because of design shortcomings except routine maintainance.



Question # 2 is, how can I get the solution into the system to kill the algae using a bypass feeder?



The algae does propogate in the tubing. The use of chlorine I have explored already. There is however a better product, chlorine dioxide. This chlorine gas, suspended in water, will permeate to the pipe wall. Research shows it will be much more effective than chlorine. Research also indicates it will be less of harmful to the metal (oxidizer?).



My plan was to fill the system with the chlorine dioxide at 50ppm and let it sit for 12 hours, which should be an effective kill time. The problem is that I have no means to dilute 500ppm into a 50ppm solution and also fill the lines. If I double the concentration by only creating 3.5 gallons of chlorine dioxide instead of the 7 gallons called for, I calculate that only 1 gallon is needed (@ 1000 ppm) for the entire system. My chemical bypass feeder is a 1 gallon model. It stands to make sense then to fill the bypass feeder and introduce the solution into the system. However, I don't know what the approach would be to make the bypass feeder "slowly" let the 1000ppm concentrate "leak" into the system so that it is not at high levels (like 200ppm + ). I assume the answer lies in the valving of the bypass feeder. So for example, the 1" loop valve has a 3/4" valve above and below it that each go into the bypass feeder. It stands to make sense that slightly closing the loop valve and slightly opening the incoming bypass valve (with the bypass outlet open fully) would create a pressure drop that would induce a slight flow (regulated by the bypass incoming valve) through the bypass feeder and into the system plumbing. As I said though, I don't know this is the case nor have I found a source which tells me even remotely what to expect for diluton rates, even a rough idea would be nice.



The simplest solution would be to make the chlorine dioxide very strong, like 3000ppm or more.Then I could use one of my chemical injectors and simply fill the lines. But after talking to someone who knows about it, it is not advisable to do, as at that concentration, one would most certainly need to use extreme caution when handling the solution.



Again, thank you for your time to mull this over. The plumbing/design question is probably an easy answer, but the dilution question is likely not. I don't recall the information now, but when reviewing the efficacy of chlorine vs. chlorine dioxide, it is a hands down choise to use chlorine dioxide, especially since I found a product that doesn't require me to have the generator on-site anymore, simply drop the product in water, wait 12 hours, then use.



MrWoo.

LarryC

Why mess with the feeder at all?

Why mess with the feeder at all?  Drain the system and then fill it with the proper concentration of the solution.  Circulate for the 12 hour period, drain system, and refill system.  Done.

I assume you have access to a suitable pump to charge the system.

mrwoo

more data

Why mess with the feeder at all? Drain the system and then fill it with the proper concentration of the solution. Circulate for the 12 hour period, drain system, and refill system. Done.

I assume you have access to a suitable pump to charge the system.

>

I have considered this as my only alternative, which is to buy a pump to fill the system. This is something, if it works, that I will be performing periodically, so I was seeking to find a solution that did not involve draining the entire system when I need to do so. Thus the use of the chemical bypass, which already exists, would be a good option to use. It simply might not be feasible, and I will have to drain/pump/drain/fill/use. Time is money as they say, and I am busy enough that anytime I can cut time I make money



Thanks again.



MrWoo.

Mark Eatherton

Observations...

You may have a primary/secondary piping system, but unless you have a thermal mixing valve on the outlet of the secondary system, you are running a much higher water temperature than would typically be associated with a soil conditioning system. You originally stated you had rubber tubing in the planting beds, then later said it was 3/8" PEX. If it is rubber, it may not be an oxygen barrier tube, which is part of the reason you have algae blooms growing in the pipes. Without oxygen, the algae should die off.



The use of strong oxidants in a PEX based system will cause the tubing to become brittle and fail. PEX is manufactured with antioxidant packages when it is extruded, and if exposed to high concentrations of oxidizer, it will get hard, crack and fail due to its inherent high expansion rates. I would not exceed 2 to 5 ppm of the chlorine based product.



There are proven methods of piping which should be employed to avoid air elimination issues, pump cavitation issues and oxygen difusion issues. Done right, the system should be fairly maintenance free. Done wrong, it will be a nightmare and a continual headache.



All tubing MUST be oxygen barrier tube, or the steel tube sheet on the boiler, and possibly the cast iron headers, and any other ferrous components will dissolve due to oxygen impingement.



Got pictures?



Is the tubing in the soil, or stapled up to the bottom of the plant beds?



If you go to Laars.com you can down load the I&O manual for your boiler, and the drawings depicting the use of a 3 way tempering valve are shown.



ME

mrwoo

more data

You may have a primary/secondary piping system, but unless you have a thermal mixing valve on the outlet of the secondary system, you are running a much higher water temperature than would typically be associated with a soil conditioning system. You originally stated you had rubber tubing in the planting beds, then later said it was 3/8" PEX. If it is rubber, it may not be an oxygen barrier tube, which is part of the reason you have algae blooms growing in the pipes. Without oxygen, the algae should die off.

>

I was refering to the manifold having 3/8" ports for the rubber tubing. Each table has 2 copper manifolds. One manifold (inlet) recieves the hot water, which is mated via 3/8" fipt to insert fittings for the tubing. Each tubing then routes the heat on top of the table (with 2" beadboard foam under tubing) back to the other manifold (outlet), which in turn returns to the boiler via the 1" pex pipe return line. The tubing is I believe EPDM. I have expanded metal on top of the tubing held up with spacers. So the effect is the table is lined with 2" insulation, the rubber tubing sits on this, spaced at approx 2" apart, and perhaps 1/2" above the rubber tubing is the expanded metal table top. The flats in this case sit on the expanded metal. I have constructed frames on the table and covered them with removable poly-carbonate twinwall panels. A mist system run off a hot water heater supplies the moister, the rubber tubing provides the heat, and the poly-carbonate provides a chamber that can be used to build humidity. This provides a means to regulate the heat on each table by adding/removing panels to allow more/less heat to escape. The setup works extremely well, we have cut the losses from cuttings to only 1%, which is really good.



The use of strong oxidants in a PEX based system will cause the tubing to become brittle and fail. PEX is manufactured with antioxidant packages when it is extruded, and if exposed to high concentrations of oxidizer, it will get hard, crack and fail due to its inherent high expansion rates. I would not exceed 2 to 5 ppm of the chlorine based product.

>

Hmm. I did not know that. I will have to check and see if the chlorine dioxide has been tested with regular pex pipe before I fill my system with it. I will also find out if it is oxygen barrier from the parts house where I get it from. I have tests that show how it effects copper and pvc, etc, but did not see pex. Isn't pex "cross linked polyethylene", or something else?



There are proven methods of piping which should be employed to avoid air elimination issues, pump cavitation issues and oxygen difusion issues. Done right, the system should be fairly maintenance free. Done wrong, it will be a nightmare and a continual headache.

>

This is my first question, when I replumb it (which I am in the process of doing), is the changes I intend to make correct. In looking at our other boilers, which provide radiant floor heat (concrete) and general hot water use, both of them have the water supply/psi/expansion tank prior to the highest point, and at the highest point, the air scoop/air vent, then a pump, then returning to the boiler. I am proposing doing just that, realizing that the air handling needs to be the highest point, just changing it to be on the outlet side of the boiler instead of on the inlet side.



All tubing MUST be oxygen barrier tube, or the steel tube sheet on the boiler, and possibly the cast iron headers, and any other ferrous components will dissolve due to oxygen impingement.



Got pictures?

>

I certainly do/can. Specifically, what would you like to see?



Is the tubing in the soil, or stapled up to the bottom of the plant beds?

>

As described above.



If you go to Laars.com you can down load the I&O manual for your boiler, and the drawings depicting the use of a 3 way tempering valve are shown.

>

I don't understand this, but will learn about it. This is a mixing valve to keep the water at a certain temp? Are you eluding to the boiler providing water that is too hot for the use? The kit, as I can tell, has no option for a mixing valve. I have no idea what thier optimum temperature would be, but to safeguard my sch80 I had it set to 130degrees (aquastat) and the high temp cutoff (external thermostat with trip) to 160degrees. I have left it there even though I have copper and pex which could both withstand higher temperatures.



I contacted the manufacturer of the boiler on a few issues, and when asking questions of this nature, they referred me to who they said was the "authority" in bench heat, which ended up being the people I bought the kit from. I have no idea if the design is good, bad or indifferent, all I know is I have had to babysit it and fix it many times, and need to stop investing money into it like that. It is true I have learned a lot about boilers because of it, enough that I don't need to call the plumber in as much, but I am going to fix it so there are no more "oh crap, the boiler stopped" moments when it is the most inconvenient.



Thanks for the reply, greatly appreciated.



MrWoo.

Mark Eatherton

Problems...

EPDM in and of itself is NOT an oxygen barrier product. There is one (1) rubber product on the market that purportedly has a mylar oxygen barrier built into the tubing walls, and it is suspect as of lately due to sludging occurring in the field. It is called Onix. Anything else is just rubber hose and it will not stop oxygen migration, and oxygen is our enemy in closed loop systems.



The problem with not having a mixing station to lower the fluid temperatures is two fold. One is protecting the growing beds from too hot a fluid which may upset the roots. THe other is that the boiler must be protected from long term condensation production at the heat exchanger, which in a copper fin tube boiler will plug the heat exchanger, and cause a whole host of other fire side problems. The normal method of protection is to allow the boiler to run at a temperature of around 150 to 180 degrees F, then mix the water going to the grow beds to the lowest temperature needed, and that wold be YOUR call.



Simply turning the boilers operating stat down is guaranteed to cause the heat exchanger to condense, and eventually cause the flames to roll out of the lower combustion chamber, burning up wiring, discharging carbon monoxide and more.



THe 2" centers of the tubing should allow you to operate at a much lower water temperature. There are other methods of delivering good heat transfer without having to have the tubing at 2" O.C. There are extruded aluminum heat transmission plates



http://www.radiantengineering.com/ThermoFin.html



You could also build the base with a product called WarmBoard and place the tubing at 12" O.C. and still deliver excellent thermal performance. WarmBooard can be seen at http://www.warmboard.com/



There are numerous other aftermarket radiant panel heat emitters available on the market, but these two are what I would consider the most durable for your wet application. you will want to seriously douse the WarmBoard in sealants to keep the plywood from seeing any moisture, otherwise it may delaminate. Both of these products will accept a 1/2" o2 barrier PEX.



Regarding PEX compatibility and the chemical oxidizer, I would suggest you run it by the tubing manufacturer for their approval. And yes, PEX is cross linked poly ethylene tubing, but there are three different methods of cross linking, including the Engle (thermal ) method, Silane method and irradiation methods.



Before we dive into the piping methodology, does the boiler have a tendency to short cycle when it is running, or does it lock into the load and stay on for longer periods of time? If it short cycles (BAD for the equipment) then you should consider incorporation of a buffer tank into the piping picture.



Speaking of pictures, near boiler piping, distribution piping, manifold piping and anything else you think might be relevant would be helpful.



Also, the "kit" manufacturers web site would be helpful. Some times, people come up with really great ideas, but have no idea what they are doing when it comes to hydronics. Is there a web site that we can review?



Properly configured, the system should be able to give you many years of trouble free service. Nothing is "maintenance free", but yours can be scheduled during the warmer months when rot zone heating is not necessary.



Improper;y configured, well you've already experienced that...



ME

mrwoo

more data

Here is a link for the pictures

http://www.hoopersgardencenter.com/woo/house9_boiler.zip



Here is a link for the vendors website and product page

http://www.trueleaf.net/heat/hot_water_systems/benchwarmer



Regarding the boiler:



This boiler has a low and high flame stage. When boiler first comes online (after flow/psi checks, etc) flame is on HIGH. With the aquastat set at 130 degrees, the returning water is (obviously) initially at something like 80 degrees, depending on the time of year. The flow rate through the EPDM tubing I don't know.



The way the system is designed, all of the outgoing hot water MUST pass through the EPDM tubing before it can enter the PEX return line and head back to the boiler. It would take roughly 10 minutes for the returning water to reach it average maximum temperature of 110 degrees. The time of year also effects this, so I am giving what I would call an average.



When the boiler first fires, on HIGH flame range. I don't know the timing, but at some point the boiler switches to LOW flame range. Eventually the gas valve cuts the flame, and the water continues to circulate to the tables for maybe 5 minutes before the gas valve applies flame again. From my watching this, it appears that the boiler does not stay in HIGH flame range for long, but switches to LOW flame range fairly quickly.



On an average day then, the boiler will come one for 20 minutes, then about 1 hour between another heat cycle. I would say roughly half of that time the flames are present, the other half they are not. I would say the HIGH flame range is operational for the first 3-5 minutes, then LOW flame range for maybe 5 minutes. Then the flame is off for 5 minutes but the pump is still circulating. When incoming water has cooled, flame is applied at HIGH for a minute or two at most, then LOW flame is applied for maybe the duration of run time. It seems that the LOW flame is currently running about 1/2 the time that the set point is achieved, so when the boiler shuts off, sometimes the external high limit temp cutoff would pop the reset. One never knew when that was going to happen, so I made sure the secondary pump stayed running for 2 minutes.



These times will vary greatly depending on whether the panels are on or off the tables, or how many panels are on or off. The panels are used to control the heat to each table, as there is only one zone and one thermistor. We use one table as the average, then the other tables will have panels on/off depending on the need.



So what is short in short cycling? I do know that for this boiler, there is a certain amount of degree separation you don't want to exceed to stop condesing. I thought it was like 10 -15 degrees, but cannot recall. It matters little because the incoming water just barely makes it to where it needs to be by the time it shuts off anyway.



We have both a bacteria and algae problem. The bacteria is a rust bacteria (I forget the name of it right now). We normally see a very light coating of it in all our piping (copper, galv and pvc). It is more prolific in areas exposed to sunlight of course (like spin down filters). We don't have a lot of algae in most fresh water lines, generally only in lines that have fertilizer injected into them. This boiler system had a lot of the rust bacteria and some algae. The clear PEX that was used in part of the water makup line had a LOT of algae in it. This was introducing it into they lines.



Having worked on this a few times, the algae nor bacteria was present until the lines were melted/warped from the guy who installed the state mandated external high temp cutoff. I could not tear the system down at that time as we were in full production, so it ran with many small drips/leaks for about 4 months. I assume because of the clear PEX actively growing algae at the incoming source of water and the leaks in the system provided a nice entry point for it to occur.



With the small EPDM tubing, I want to avoid plugging them, thus the desire to disinfect with an algaecide before this occurs.



You will note in those photos that the boiler kit and where it had to be installed created quite the obstruction to actually reaching the boiler. This affair started because we had a flame rollout sensor that needed to be reset, and it was hard to see where it was. So I decided the plumbing needed to be moved. Space contraints lead me to move the piping but leave the boiler where it currently sits. We hired a competent plumber to install it originally, but all they did was to assemble/mount the kit as per instructions.



Now I am looking to change it a bit by moving the location of the exiting components to better fit the room I have to work with. While I understand the basics of how it operates and why, and I think my logic is sound, I certainly don't want to have to do this more than once. In my rework of the plumbing, the basic principles of what components are needed is kept, it is only that I wish to place them on the outlet side instead of the inlet side of the boiler, and I will be placing them about a 1-2 feet further away and 1-2 feet higher.



I hope that is enough info to give you what you need.



MrWoo.

Mark Eatherton

The pictures didn't come through...

If you can, post them here as JPEG's. The web site wouldn't allow me access to the files.



At the bottom of this page, there is an ADD FILES button. Use that to post the JPEG format photos here.



Your boiler is a 2 stage boiler, and if it is spending most of its time on the low burn capacity, its thermal efficiency is terrible. No way of adjusting secondary air when the burner turns down, consequently, poor combustion efficiency and thermal efficiency. Doesn't sound like it is short cycling too bad (5 on, 5 off would be a bad thing), but if it is spending a lot of time on the low burn capacity, it is wasting fuel. You might want to consider upgrading to a condensing boiler. It will reduce your energy consumption by a minimum of 30 percent.



The factory actually sells a time delay relay kit for this boiler to avoid the hi limit manual reset button from popping out, but it sounds as tho you already have it covered. Ingenious!



Constant return water temperatures below 140 degrees F will cause condensation production at the heat exchanger, which may or may not be evaporated as it occurs. If it doesn't evaporate, there is usually a trail of rust coming from below the boiler. The temperature differential should not exceed 30 degrees F, and is typically more like 10 to 20 degrees F. Your milage may vary...



The bacteria is a hydrophylic bacteria that can survive with little to no oxygen. It is referred to as an iron reducing bacteria. It will consume any ferrous components in the system. I have seen it survive temperatures as high as 205 degrees F,so it can't be scald sanitized. You are going to have to induce an oxidizer in order to erradicate it. Best suggestion I can make would be to contact a professional boiler water treatment company and have them give you guidance as to what products to use, in what quantities.



The rubber tubing that your supplier is selling is not an oxygen barrier tube, and that it going to be an ongoing problem. With non oxygen tubing, there are three prescriptive methods. The first is to make certain that all materials that come into contact with the working fluid are non ferreous. Must use bronze or stainless steel pumps, bronze of stainless steel air separators/eliminators and phenolic lined expansion tanks. NO steel or cast iron allowed.



The second method is isolation of the heat source and its components with a heat exchanger, ferrous components on the heat source side, and non ferrous components on the load side of the exchanger. An expensive route for sure.



The third method is chemical treatment of the fluid, maintaining oxygen scavengers and a pH of 7.6 to 8.5. Works OK, but requires continuous monitoring and maintenance.





Bear in mind that the oxygen problems are due to the use of non oxygen mini tubes. If you went to an oxygen barrier tube through out, most all of your O2 problems will subside, including the algae problem. It can't survive without oxygen. In my 30 years of working on these systems, I've never seen algae in the systems.



THe hydrophylic bacteria is a naturally occurring bacteria, that is typically inadvertently spread by the well drillers. If they don't follow protocal for sanitizing their drilling equipment when moving from job to job, the bacteria gets spread. All the flushing in the world will not cure it, because you are re-introducing it in the make up water.



I have successfully used clorox on smaller residential systems, but you must be careful not to put too much in or it will cause other problems, including erosion of the copper heat exchanger, and oxidation of plastic tubing and eventual embrittlement of same.



The fact that you had to reset the rollout switch is an indication of the previously stated possibility, that being the heat exchanger is becoming plugged on the flue gas passage side. The clinkers buildup on the heat exchanger, and cause the radiant energy from the flame to be reflected downward, and it then bounces up to the switch location causing it to trip out.



If there are physical scorching signs at the combustion chamber inlet, then that is an indication of actual rollout occurring, which is an indication of CO escaping into the surrounding environment. Probably not a big deal in a wide open green house area, but could be dangerous in a smaller confined space. In any case, it indicates the need to pull the heat exchanger out and service it with a high pressure washer to remove the byproducts of corrosion.



Send pictures...



ME

mrwoo

very nice

That was a very informative and easily understood piece you wrote there. Very nice, thank you very much. All of that is helpful to know and does answer many questions I had.



I will pick the best pictures and attach them here in the next post. I will also (crudely) draw what I propose to do in the plumbing, which is most likely going to be needed to "see" what I am saying.



Thanks again.



MrWoo.

LarryC

You have one of the best hydronic people helping you

Mr. Woo,

You have one of the best hydronic people helping you. I would follow what he says very carefully.  Good luck and happy growing.

 

LarryC

Mark Eatherton

Aw jeez Larry.... (blushing...)

Thanks for the kind words. I'm just doing my part to Help out here at Heating Help. I owe our host a lot for his teaching me and getting me involved in hydronics. Just trying to pay it forward.



This is the BEST community on the web, bar none. Powered by the people who are, The Wall.



Thanks for participating. That's what MAKES it work.



ME