Radiant Open Direct Sysytems

hot_rod

Try driving around, or should I say sitting in the passenger seat, with a brand spanking new driver! Makes open systems look pretty tame(G).

Besides which, you guys are doing an excellent job without my input. Anybody advocating open system construction needs a check up from the neck up IMHO.

You can't miss me though - I'm the guy screaming "help me" in the wildly careening car going through your neighborhoods!

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mike14

Radiant Floor Open Direct systems

From reading previous posts, it has become clear you guys don't think much of "that Vermont outfit." Setting aside that for a moment, I'm intrigued by their "Open Direct" design set forth in their schematic attached. It can also be viewed at:

http://www.radiantec.com/opendirect04.htm

It seems that this system is very efficient and would provide for almost unlimited hot water because of the over-ride feature. I plan to intall a 5 loop 1/2" Wirsbo system in my basement using my existing 40 gal gas water heater. Are there any inherent problems with the Open Direct design that you guys have experienced? Thanks for any input.

Mark Hunt

What will


happen in the summer with all that nice cold water running through your slab?

Looks like a great way to condense water and grow mold.

If you are going to use your water heater, use a plate heat exchanger and keep the two liquids separate.

Mark H

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Earthfire

Wirsbo's fault????

Will it be Wirsbo's and RadiantHeatings fault if somebody gets sick or mold takes over the house???? Spend the couple extra dollars to do it right (SAFE). Get another waterheater or a heatexchanger and install a dedicated control, circulator,and expansion tank for the floor heat. Besides in most areas of the US interconnected systems are not code legal.By the way the hot tub room that I build for my wife is radiant heated using a 50 gal. electric waterheater.She loves that warm floor after getting out of the tub, to the point that she would rather hangout out there, then her family Rm. which is scorched air (like the rest of her house)

John Felciano

Open systems

I wouldn't want my family drinking or bathing in water from an open system.There is just too much chance for someone getting sick from what may be growing in the water all summer long.

Put it on it's own source or isolate it.It's just not worth what little you may save.

Everyone thought asbestous and lead were safe too once????

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Art

open system

Mike,
I have done 2 of these systems for myself. The first one is a staple up with the plates with a polaris. It works good and have not had any real problems after 1 year and 3 months of running. There are pros and cons to it though. The biggest thing that I don't like is that when you run the hot water the cold must go through the all the tubing before it gets to the water heater, this makes ALOT of noise becuase of the plates and tubing expanding and contracting. This happens everytime you run the hot water for awhile. In Alaska our water comes out of the ground at 40 degrees, this system does warm the water up to 60 before it goes into the water heater. This does give you almost unlimited hot water, you realy have to try to run it out of hot water to start depleating it. The polaris seems to be running fine so far but I have heard about alot of problems with it. It is a little senative on the gas adjustment though. You have to compromise a quiet start for quiet running though, you end up with a little noise on both. If you could optimize the start and running the thing is silent. I also don't like the fact that it has a fixed differantal of 5 degrees as it makes it run in short cycles. On, off, on, alot when it is heating.
My other system is a 40 gallon regular gas water heater that heats tubing that is in a slab. This works much better in the noise catagory. It still preheats the water before it gets to the water heater but does not put out near as much hot water (100,000btu for the polaris vs 40,000btu for the regular water heater) as the polaris.
I have noticed that just about eveyone in the heating profession does not like an open type system. I have had my water tested several times with no problems. It does make me nervous in the back of my mind that the posibility exists that something could grow in the system. I do think that this system setup probably is the safest setup for a open system though. One thing that I don't understand is why the water sitting in your presure tank, hot water heater, and hot water recirculation lines are not subject to the same potentual problems of something growing say when you are gone on vacation for a week or two? I think that being gone for a week or two would be your biggest concern with an open type system, this might give something some time to grow.
I probably will end up changing these systems to a closed type in the future though to give myself a pieace of mind.
Good luck!
Art

hot_rod

fickle Polaris

I have 6 installed so far in radiant applications. Very efficient, and a good match for radiant. I dislike the tight differential also, more like 2 degrees! The factory tells me this is to keep the efficiencies high?

No reason you couldn't add another controlling stat, however. Use the factory control as the high limit. I am going to try adding a setpoint controller into the circuit. You could just break? the 120 volt circuit. or cut into the orange wire from the exisiting stat. Thought I'd try a 10 degree setting.

Ignitors are the biggest "weak link" I have a three year old system that has completely trouble free, another has eaten 4 ignitors in a years time?? Incoming voltage is important at 120 V the ignitor runs at 2600 F, at 120 3600 F, above 120 Volt the disappear quickly, the factory tells me. Time to data log the voltage on my problem one!

hot rod

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mike14

Combi-cor unit?

Alright, so maybe I'm convinced to go with a closed system, but should I use an extenal heat transfer plate or buy a new combination hot water heater like the Bradford White Combi-cor. The Combi-cor eliminates the extra circulator and heat transfer plate, but is it a good unit that will last for a long time? Anyone instaled one of these in a RFH slab system?

PJO

Dangerous Places...

for your water sitting include these areas you mentioned, but the key is two things IMHO; 1) The temperature has to be in the ambient range (say 60 to 130F), and 2) It has to sit for a while with no disinfection...I assume you don't have much chlorine at your tap if you have "city" water, and none (or UV) if you are fed by a well. Chlorine in water is a seperate issue, and won't be covered here.

In a typical HWH, you will have the water sitting in there when you are away on vacation, but hopefully it is kept at a high enough temperature...although I seriously doubt the entire contents of the tank is above 130F unless you have a recirc. system and you purposely turn up the temperature. Most situations are probably not this way.

My own hot water is as follows; I have a well and UV disinfection. My water is heated through a tankless coil, and comes out of my boiler at about 150 to 160F depending on what I set my high limit (tempering valve wide "open" if it feeds the next tank)...never below this. It then goes to a 50 gallon tank that is an electric HWH with the t-stats set high. In the case of being away, my HWH would also probably be a little cooler (the electric elements alone have kept it warm), but as soon as my hot water demand starts I have 150/160F water coming into the bottom of the tank and the element down there assures me it will stay this way (give or take a few degrees I suppose). The only downside is that it is a bit hot at the taps and we have to be careful...I would like to get mixing valves at the sinks someday - I'll add it to the "HoneyDo" list :-)

If everyone is so into the open systems for efficiency, instead of running (cool) potable water through tubing...with the possibility of floor condensation and L.D. coming into the mix...why don't more people simply get tankless heaters (probably the most efficient means) or simply crank up the HWH high (above 135F) with recirc. and then mix it back down? I believe the reason is money...tankless heaters are more expensive up front, and it costs a bit more to turn up the temperature on your HWH and to have a recirc system and mixing...although this saves in fuel costs as well by not dumping anything while you wait.

Where's PAH? I figured he be into this discussion by now :-) He's the resident expert 'round theses parts. I am in the majority of Wallies against the open systems as well...and my background is in water and wastewater treatment. I think it's one of those things that looks good on paper, but simply shouldn't be done as it is in some places...why take the chance?

Jump in Dave...I'm sure I missed some stuff here.


Take Care, PJO

Bill Clinton

combi-cor? Yikes!

Take it from someone who installed about 20 Combi-Cor and watched them all fail in less than five years: don't! My experience is substantiated by numerous people who have installed/sold them.

The question as to why water sitting stagnant in the supply system during vacations isn't a problem: Likely it is! A formidable percentage of water systems out there are already contaminated with noxious bacteria such as the legionella dude. We seem to be just beginning to realize the extent of the problem. You see, we are accustomed to the fact that weak and old and feeble people die. That's a law of nature. Underlying infirmity is the root cause, but a huge part of the time the immediate cause is pneumonia. We have long accepted this, even at times referring to pneumonia as "the old man's friend" because it gently puts people out of their misery.

Surprise! A significant portion of these pneumonia cases it is turning out, are contracted from inhaling tiny water droplets from the potable water system. A lot of folks not quite ready to be put out of their misery could hang around a while longer if our water were clean.

I'm not quite sure whether an open direct system increases the risk, let alone by how much. Still, I'll sleep better at night not doing it.

By the way, Hot Rod, that bit on ignitor temperature vs. voltage is enlightening info. Two questions for you:

1. Have you tried the new Polaris and if so, what's your experience?

2. Do you have a model number for that buffer tank?

Thanks,

Bill