Freeze Protection

[Lurch16th]

I have seen some scattered information about this, so I thought i'd try a thread topic that is easier to find .

After thinkin bout it, it is one of the biggest concerns to an OWB system, although only in cold months.

So i'll start with questions comments;

Seems like bottom line/worst case scenario is power goes out for a day or more in freezing temps and owner is away for whatever reason and nobody available to tend to owb.

with that in mind, only defenses are

1. use anti-freeze


Short of worst case;(available power)


If i have to be away for a week, i've considered;

1. shut blowers off, leave pump run, set up light inside back of furnace, wired to s imple thermo-stat to go on at 50 deg.

2. shut blowers off, leave pump run, leave Dom Hot Water tank give heat through side-arm and back to furnace.

3. shut blowers off, leave pump run, shut off all exchangers


Is there a new anti-freeze that has good heat transfer?

If i used anti-freeze, and knowing i'd be away for more than a few days i considered, shutting of supply and return lines so, very cold fluid can't get into house.

 

[sorethumbs]

consider this.....

I'm not sure how many gals of PE you'd need for your OWB, but lets say you need 200. Figure about, what, 2-3,000 bucks for the PE. I'd be willing to bet that you could purchace and install a propane fired generator with automatic transfer switching capibilities for that. Then you could run all your heating equipment including you back-up system.

If I did it that would be my first choice.

 

[Lurch16th]

There's supposedly a new anti-Freeze, which heatmor recommends, called Dow Frost HD in 5 gal buckets.

Haven't got any data on it yet.

Anybody ever use ant-freeze or Dow frost?

 

[applefarmer]

It seems funny that every time this type of post comes up, nobody has a straight 100% answer. I have read alot of "theories" but have not been satisfied with any answers. I to would like to know how to leave my boiler for a week in the middle of winter. I have propane backup so I don't have to worry about the house. Until I find a good way for freeze protection I plan on draining it before I leave. What a pain in the butt! Hopefully an experienced owner will have an answer for us.

 

[Lurch16th]

Yes, indeed. My Dealer said ant-freeze in general doesn't have "As Good" a heat transfer capability. But what does that mean? 1% less, 50% less?
Dow has some technical data on the website, but a little above my head. Guess i'll just have to call them.

Looks like i may have to try some for next winter and try to test it.

meantime, since i don't see any other solutions, i'm building a thermo-light(my new name for it) at least for spring and fall.

 

[John D]

A relative went on vacation for 2 weeks in late feb here,and he just left the circs on on his 340 Shaver(it is feeding 2 large houses).He turned off the indoor loop pumps,and just let the circs run,his theory was with 310 gallons of water it would take a long time to freeze,and just running the water into the house thru the hx and back,it would pick enough heat in the boiler room to keep from freezing.He is aplumber by trade,and he was right,gone 2 weeks,and nothing froze,it worked perfectly.It was down in the single digits several times when he was gone.

 

[Lurch16th]

Yeah, that was my other option and may be testing it soon.Although we are a little further south and only gonna be low 30's over night.

 

[Scootermsp]

I've got Cryotech

I've got 15 gal of Cryotech in mine. It will only buy me a few degrees. If you really want to lower your FP get it in 55 Gal drums...much cheaper that way.

 

[Steveguy]

John D. in the post above is correct. If you have an HX in your forced air furnace and leave circulator pumps running, when you come home, if your gas furnace is set at 62 degrees, the water temp in the boiler will be very close to 62 degrees as well. Some people have alot of concern as to how much gas you would burn heating the boiler, but they are well insulated, mine usully won't even melt the snow off the top when the water temp is at 170, let alone when it is only at 62. Another concern is what happens if the pumps quit? Well, I don't know about you, but I don't spend the whole winter worrying about my pumps. It would have to be off quite awhile before it would freeze anyway. If you were going to be gone a long time you could have someone check on the temp. occasionally. I just run water in my system, with the boiler treatment recommended by central boiler.

 

[Steveguy]

If you don't have a heat exchanger in a forced air furnace, leaving the heat exchanger on your water heater active should also provide enough heat to keep the boiler protected. Like I said in my last post, they are well insulated and don't take much to hold temp.

 

[Lurch16th]

Scooter, looks like you have some experience with this stuff.

What's the capacity of your CB?

Was there any way to tell what the heat transfer loss was if any?

What was the cost per gal.?


My Heatmor 200 hold 114 gals and i'll add 10 gals for lines etc.

Dow pec sheets say roughly 48% concentration for -25 degrees, So i would need 50 to 57 gals.

 

[Lurch16th]

My system has a HX in a forced air plenum, but i can easily isolate it with the installed valves.

so yes, heat from the sidearm on the hot water tank, should easily protect it.
A day or 2 should be no big deal.

The only thing i wondered about, is if you are away for a week or 2, will the hot water tank be running constantly, racking up some ridiculous electric bill.

The Dom hot water tank will try to make the furnace water stay at whatever the hot water tank is set at.

Everything is well insulated and you could set the hot water tank to it's lowest, which i think is 120 deg, so maybe it wouldn't be too bad. It may only be no different than running one giant 350 gal hot water tank.

 

[sorethumbs]

My system has a HX in a forced air plenum, but i can easily isolate it with the installed valves.

Why would you do that if your wanting freeze protection? Leave the OWB circ pumping and let the gas FA furnace run. The furnace will heat the air-water HX and give you excellant freeze protection.

If your going to leave for a few days don't sweat it. First get the house as hot as you can, even burn some gas and get 'er up to 80. Then load the OWB to the MAX. Turn the OWB t-stat to 65 and the back-up gas furnace to 60. You'll be just fine, you'll probibly have enough hot coals to start a fire when you get back. I do, even after 3 days.

I also think your over estimating you side-arms ability to heat the OWB. The thermosphyon process probibly will work in reverse, but there's no way its going keep the OWB at 120, if that whats your thinking. In fact I'd bet it would still cycle, albeit faster than usual.

PS - I'll also add that if your really wanting insurace, and your good at circutry, then you'll want to re-wire your OWB to shut down the damper (or blower) if your boiler water drops below a setpoint, say 100*F. There is a member here, I think his name is Aviator, who has posted on how to accomplish this. I havn't done it, but it is an excellant idea, and I'd like too.

 

[Steveguy]

I usually have my waterheater shut off during the heating season so I would rely on the forced air HX to keep boiler temp safe. People really over estimate what it takes to keep the boiler warm for a week or so. You could turn off the water heater while you were gone, many people do that when they vacation anyway to save energy. If you did that, everything would equalize at the thermostsat setting you have on the gas furnace. I agree about the sidearm thermosiphoning in reverse, it probably wouldn't be as effective as normal operation. That is a good idea to rig up a shutoff for the damper/combustion blower when boiler temp drops down to keep from blowing cold air through your woodboiler and cooling it from the inside of the firebox. If that isn't possible then I would at least put a switch in to turn them off manually for a longer absence. For a two or three day deal I would pack it full and let it go and accept the heat loss after the boiler ran out of wood.

 

[Lurch16th]

I don't have any gas furnace. My forced air plenum is what used to be mounted on top of my Harmon wood furnace. My back up heat is baseboard electric.

Now the Plenum is extended and just sits on the floor.

But i do wonder (inSpring or Fall only)if leaving the circ pump on,
hot water tank off and sidearm isolated,

Plenum HX open

and circulating the 55deg water, which is picked up from a cold Heatx and ambient ground temp, is enough to keep it from freezing.


I'd want to test that first and be there to monitor it, but might have to wait until next winter.


yeah, i also doubt a hot water tank/sidearm will keep the owb at 120 deg




Gonna check out the wiring shut-off by Aviator

 

[Steveguy]

Just having the water circulating will provide some protection, and it should pick up a little from the air in the plenum. For mild conditions you should be ok, and using the sidearm/waterheater in cold weather to protect the boiler should work. It won't keep the boiler 120, but its a long way down from 120 to freezing. I haven't tested the theory, but you should be fine.

 

[beagledog]

I know a family that has 3 homemade systems between them. They said just go around to gas stations and get their old antifreeze. They have to pay to get rid of it, so they gladly hand it over. As far as the heat transfer situation, their burners are a little over built so I don't think it is an issue.

 

[mtfallsmikey]

Glycol is not as efficient as straight water...do some research on heatinghelp.com for exact numbers....Expect to pay around $10/gal. for hydronic-rated antfreeze, mix is usually 1/1, so depending on the size of your system, and the capacity of the boiler, you can wrap $1K or much more in anti-freeze easily. Standby generators look like the better investmant to me. Auto type antifreeze is a no-no.