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Dual smart ciruclators for redundancy and a good nights sleep

Started by coldfeet, February 24, 2011, 06:37:31 PM

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coldfeet

Here we go again! I am in the process of installing a Vedolux 37 143k BTU with 500 gallons of storage (it's all I can fit). I am alarmed by the fact that if the circ pump fails (and everything fails) just after I loaded it with 24 sticks of nicely split wood and headed for bed the boiler will sit there cooking full blast with no real way to get rid of the heat. Yes, I know all about the pressure relief valve and dump zone, etc. But why not use TWO smart circ pumps in parallel from the boiler to the storage tank? The chances of both pumps failing at the same time are very small. Since they are smart circs, when one fails the check valve will close and the other one will 'sense' a change and try to make up for it.

That way, the water will still be pumped from the boiler to the storage no matter what. By the way- I have a Generac generator so power outages are not a concern- a pump failure is my worry.

Signed,

Sleepless in Montville, OH  :D

Any opionions from all of you pros would really help. I have talked to four 'pros' so far and they all say to do everything a different way. I even bought 'Modern Hydronics-3rd Edition' for $165 bucks so now I'm armed and dangerous.


beenthere

Sounds like you are saying that when the water gets up to temp, the unit doesn't shut down.

Wonder why that would be.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

coldfeet

No it's not that- it's the worst case scenario. Right now the boiler isn't even hooked up.

The worst case scenario would be:

Full of wood
Induction fan on (let's say the thermostat to shut it off doesn't work)
Pump fails

Now you have 325,000 BTU's of fan-induced heat (a freight train) with nowhere to go. A dump zone is supposed to work- and I will make one but that is a last stitch fail-safe which I don't ever want to have to use.

With dual circs, one would keep running and pump the water from the boiler to the thermal storage tank.

Holmes

Coldfeet  In your worst case scenario I would suggest an alarm on the boiler . Something that will wake you up and shut the power off to the fan. It can be tied in to your alarm system. Much better to be woken up by an alarm than a Fire. The boiler should have a high limit switch to shut the fan down. Most name brand circulators do not have a high failure rate.  Holmes  ps you could add a sprinkler head or 2 in the boiler room.
Think like a farmer.

SwampDonkey

I know what I'd do, but you won't want to read about it. :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

Brucer

Operating 2 pumps in parallel can get you into all sorts of problems. You may create a situation where the pumps can maintain one pressure at 2 or 3 different flow rates. The system will then start to switch back and forth between those different flows trying to "find" the "best" condition (and there isn't one). It's called hunting.

When you have pumps with individual flow controls it gets even more complicated. The pumps can start to interact with each other and the controls start to fight each other.

It's safe enough to install 2 pumps in parallel if you only run one at a time (i.e., an installed spare) providing they each have a check valve. If one fails you can switch over to the other one (assuming you have an alarm system to get your attention).

If you do this, it's a good idea to run each one for a while. I can't begin to count the number of times when I've seen a plant fire up an installed spare (in an emergency) only to find it wouldn't run either.
Bruce    LT40HDG28 bandsaw
"Complex problems have simple, easy to understand wrong answers."

coldfeet

Wow, that's some valuable information there. I can see now that you mention it that two variable circs would constantly be causing each other to react to the other circs adjustment.

Oh well it was fun while it lasted! I guess I'm back to trusting (and testing) a dump zone.

thecfarm

I have never heard of a Vedolux before.I googled it.I read it quick,maybe too quick.But I noticed a suction fan.I have no idea about a vedolux,but with my OWB,Heatmor,the fire will just about go out without the blower on.It will smother the fire right out if I last power.Just a thought.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Al_Smith

I'm not all that familiar with outside boilers but I would certainly think they would be designed as a fail safe system .If not the manufacturers would be open to a lot of law suites  should a failure occur and cause damage or injury .

I would also think that any alterations regarding a manufactured system would relieve that  manufacturer of any responsibilty .Something to think about .

thecfarm

My Heatmor is a non-pressured system.The manufactures can fly under the radar this way.I think most OWB are non-pressured.It would just boil over out of the top.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Al_Smith

If a person were mechanically inclined then about any safety device or methods used on a commercial pressurized  system could be incorperated .

A normal old run of the mill boiler has a bunch of redundant safety devices all supposed to be fail safe .Of course a short jumper wire would render most of them ineffective .

I have no doubt with the trend toward lesser costs involved my guess is a majority of them use solid state microprocessors made in some Pacific rim country or relays and control devices made in Mexico . Being somewhat old school and set in my ways I don't subscribe to that theory but I'm fighting an ever increasing loosing battle or so it seems .

Hilltop366

Quote from: Al_Smith on February 25, 2011, 12:47:28 PM

I have no doubt with the trend toward lesser costs involved my guess is a majority of them use solid state microprocessors made in some Pacific rim country or relays and control devices made in Mexico . Being somewhat old school and set in my ways I don't subscribe to that theory but I'm fighting an ever increasing loosing battle or so it seems .

I'm with Mr. Smith on this one. I kept my home system very simple with all mechanical controls and no zone valves. The system has a manifold with ball valves so after a few days I got things balanced out to get the right amount of heat in the right areas of the house by closing the valves some to the areas that require less heat, I even have a high voltage thermostat so the whole system draws power only if the circulator is on which is less than 1 amp.

In my work I look after 3 buildings with hot water heat it adds up to 6 circulator pumps and 32 zone valves, maybe it is because there are more than 5 times as many zone valves as pumps but I rarely have trouble with pumps most problems are with zone valves. One building we use to have had a circulator pump for each zone instead of zone valves it looked odd but worked well. (zone valves and pumps cost about the same)

Will the dump zone have it's own circulator? If not it won't do you much good if your circulator quits. I'd say get a spare circulator and store it in a dry place, and put shut off valves on both sides of every circulator, zone valve, pressure regulator and back flow preventer with threaded unions where required to be able to replace all of the common fail parts. Also be able to shut off any branch of the system (different building or different wings of a building) from the rest is handy at times.

Is it possible to hook up a gravity (thermosyphon) circuit for the dump zone? no pump required.

coldfeet

Thanks for all the input. Since the boiler and storage are going to be in my attached garage and it needs to be heated I plan to have a heat exchanger with a fan on it (up high in the garage pointing down) to keep the garage warm (warm car=happy wife). I was planning for sure to put a dump zone but I wonder if I couldn't somehow use the heat exchanger with the fan for a dump zone.

You must be running your circs constantly?

I do plan on running the circs only when heat is being called for. I only have an 1800 sq./ft house so an exchanger in the plenum of the furnace and a plate exchanger for hot water. But in the summer I'd like to heat my 27' round above-ground pool and hot water. The Vedolux 37 boiler I'm using with storage is made in Sweden and they don't mess around when it comes to heat.

Al_Smith

I've never done it but I suppose you could get as fancy as you wanted to with hydronic valves and zones .I would even imagine using an output board connected to a home computor or a designated cpu you could run about any combination you wanted to .I'm sure there's a program for it or a way to do it .

By the same token depending on the skill level you could hook up a bunch of relays and do about the same thing .

The actual safety fail safe system of the boiler is where I personally would be most concerned about rather than heat distribution .If nothing else you could use throttling valves for that .

That's all I do on my geo thermal is throttle the discharge water rather than use a modulating valve .Works just as well and didn't cost me 200 bucks .The ball valve actually didn't cost me a dime . ;D KISS --keep -it-simple-stupid

bandmiller2

Coldfoot,what if you used an aquastat type control that would sence higher than normal temp. and start the backup circulator. Frank C.
A man armed with common sense is packing a big piece

coldfeet

Well I talked to my guy who sold me the Vedolux and is helping me put it all together and he said 'they' have been doing it for years with a dump loop and no problems. I'm a network engineer and I've seen hard drives fail and data lost so I get all wound up on DR (Disaster Recovery). When I realized that if the main circ failed the boiler would (could) be sitting there with 24 sticks of wood and I just don't like the thought of that water in the boiler boiling out (if it did). But I'll make a dump loop and TEST it thoroughly. I will think about some kind of backup circ you'd think someone would have thought up a way to have one.

I did have a plumber tell me about a boiler that didn't have a dump loop and the power failed and the thing looked like it was going to explode I guess. I have a generac generator but even that could fail so I have to put in the loop and test it by pulling the plug with full of wood. That's the only way I'll sleep soundly at night.

coldfeet

I think I found a solution to dual redundant circs.... you have 2 circs in parallel each with check valves. The 'main' circ runs and has a flow sensing switch after it and as long as the circ is running the flow sensor says 'we're good', the circ fails the flow stops, the sensor detects it and starts the other pump. Since they have check valves it will just be the opposite as before but the same flow through the secondary route.

These are regular circs not smart circs. And as for the idle circ seizing for lack of use I would alternate their use maybe every month so each one would not sit idle and seize.

Please blow holes in this theory.  8)

beenthere

With my boiler, if there is a power failure then the unit shuts down and doesn't get any more air. Without air, it doesn't burn the wood charge.

When the water gets up to the hi set point on the hydrastat, then the air is shut off until hot water is drawn off by the circulator pumps.   

If too hot (closed system), the water is vented through standard relief valves such as found (required) on domestic hot water heaters.

I haven't worried about it in 30 years and hasn't given me a cause to worry.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Hilltop366

Quote from: coldfeet on February 25, 2011, 08:29:40 PM
Thanks for all the input. Since the boiler and storage are going to be in my attached garage and it needs to be heated I plan to have a heat exchanger with a fan on it (up high in the garage pointing down) to keep the garage warm (warm car=happy wife). I was planning for sure to put a dump zone but I wonder if I couldn't somehow use the heat exchanger with the fan for a dump zone.

You must be running your circs constantly?

I do plan on running the circs only when heat is being called for. I only have an 1800 sq./ft house so an exchanger in the plenum of the furnace and a plate exchanger for hot water. But in the summer I'd like to heat my 27' round above-ground pool and hot water. The Vedolux 37 boiler I'm using with storage is made in Sweden and they don't mess around when it comes to heat.

Ok I forgot to mention that I have in-floor with concrete so my circulator only runs when heat is required, it is turned on directly by the thermostat on the wall, I used a electric heat thermostat , no zone valves, and 2 mechanical aquastats (like Bandmiller mentioned) and the furnace has a hydraulic draft control so I could eliminate the step down transformer, the entire system is 110v (ran it off a truck battery and 200 watt inverter for the first year or so before I decided to pay the $$ to get the power line run) and it only draws power if the thermostat is calling for heat and the low limit aquastat is up to temp. It has a second aquastat for the over heat protect (dump zone) that will turn the same circulator on (the circulator has 2 electrical circuits to turn it on) which puts the heat in the floor, my intention was to add a second circulator for garage heat and put the dump zone to there but I haven't made the garage yet.

I took a peek at your boiler info it looks like a very nice set-up it is my understanding that with the large storage type systems that you would run a fire in the boiler to heat the 500 gal. up to temp and then let the boiler go out in order to get the low smoke and high efficiency by burning the wood all at once at optimum fire box temperatures and putting the heat in storage and avoiding the idling fire (the zero mpg times so to speak) which would greatly reduce the chance of over heating and creosote build up ,  with this type of set up I'm guessing there would be 1 circ pump between the boiler and the storage tank and than another between the tank and your heat exchanger, hopefully you can get enough heat through the exchanger to keep the house up to temp. Can't see any reason why a dump zone in the garage would not work you might look in to wiring it so the first option would be to dump in to the storage tank and have a aquastat that would redirect circuit to garage if storage is to capacity.

P.S. looks like a great opportunity to add some hot water solar panels to the storage system.

I'm no heating expert just going by my experiences ,

Holmes

Quote from: coldfeet on February 25, 2011, 10:02:41 PM
Well I talked to my guy who sold me the Vedolux and is helping me put it all together and he said 'they' have been doing it for years with a dump loop and no problems. I'm a network engineer and I've seen hard drives fail and data lost so I get all wound up on DR (Disaster Recovery). When I realized that if the main circ failed the boiler would (could) be sitting there with 24 sticks of wood and I just don't like the thought of that water in the boiler boiling out (if it did). But I'll make a dump loop and TEST it thoroughly. I will think about some kind of backup circ you'd think someone would have thought up a way to have one.

  This is not a bad idea but I like bandmiller2's idea. Your boiler has an alarm build in, you could use that contact to engage a second  circulator to the tank.  The boiler should already have a circuit for your dump zone. Now you have 2 dump zones.  The only times I have seen a boiler run wild with wood in it has been when the door has been left ajar after putting wood in. This usually happens after someone comes home late from partying and is careless {drunk}.  Holmes
Think like a farmer.

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