5 minute ON, 2 hour OFF oil furnace timer to prevent freezing pipes

[K1JJ]

Hola,

I wonder if anyone has an idea for a commercial device or maybe a ready to go 555 timer circuit design that will give me a 5 min ON every 2 hours or so?

I've had the coal stove running 24/7 and haven't had to turn on the oil-fired furnace for 3 weeks now. However, I realized that the copper baseboard heating pipes are not getting hot water and may freeze. Last night it hit 8 degrees F here and I turned the furnace on for circulation. There was a section of the copper pipes that did not flow right away - evidently had ice inside. So I manually run the furnace circulator every few hours now... whew!

 I think maybe a 555 that does a 5 minute duty cycle pulse with a 2 hour base could drive a relay?  I was hoping there is a circuit out there so I don't have to do R&D.  

I looked at the day/night digital lighting timers and the descriptions are not clear enuff to figure if they can do what I need.   I want to turn it on and see a 5 minute ON every 2 hours or so, continuously.

Ideas and circuits are appreciated.

Thanks.


T

[KL7OF]

Don't you have glycol in your hotwater system?

[K1JJ]

Don't you have glycol in your hotwater system?

Hmmm... don't know. The furnace was recently installed new a year ago. Is this a standard thing?  I shud call the guy and axe him.


BTW, the furnace does come on regularly now to heat the water for washing - but the circulators for the baseboard heat do not come on at the same time beacuse I have the thermostats turned down.. Maybe there is a way to allow this to occur at the same time? There is a digital control box on the furnace...

T

[Todd, KA1KAQ]

I think some of the newer systems use a closed circuit with a coil inside the boiler to heat the baseboards or a slab, most likely filled with some sort of glycol substance. Older systems like the one I had in the VT house simply circulate the boiler water through the radiators and back to the boiler. They auto-fill from the water line to compensate for losses through the over pressure valve and so on.

Your timer/cycling question is an interesting one, Tom. Never had that issue since the old house wasn't terribly tight and even with the wood stove cranking, it would still kick on regularly. There's a control sensor (Aqua-stat?) that allows you to set the high and low cut off temps for the boiler itself kicking on to maintain temp, wonder if that system could be adapted to the circulating system itself? I became quite fluent in the use and setting of that little beasty on my circa 1991 system when fuel oil prices got up around $4/gallon a few years back and I wanted to optimize the settings. Turns out it could've been set down lower long before I did it, since the internal hot water coil had been replaced by an outboard water tank. It was maintaining the boiler at an unnecessarily high temp in case someone used the hot water. 

[K1JJ]

I talked to the installer who said there is no glycol in the heating system. It would cost about $300 to fill, unless I bought it and did it myself.  

He also said that pipes can freeze in 30 minutes when super cold. They had cases where a working system had frozen, never mind my intermittent coal aided system.

So looks like I may have to go with a  5 minute on every 30 minutes when it gets cold.


T

[N8UH]

I've used sprinkler timers for a lot of timing applications. Lots of them have very flexible programming options. With a little trickery, you could even use some kind of N/C thermal switch with the rain sensor input to have it switch on (N/O on input) when it gets below a certain temperature.

And they are relatively cheap. 

[WA1GFZ]

Tom,
Turn off the system power.
It is pretty easy to do. Turn off auto fill and drain out some water. Then go on the second floor and pour some glycol into a register. Take a bleeder off and get a couple fittings to interface to a funnel. I would think the system has about 15 gallons so you just have to decide how much you want to use.
Then close everything up turn the auto fill back on and bleed the system.
Make sure you drain out a bit more than you plan to pour in.

[SM6OID]

Hej!

I would say that running the burner for a short period of time may cause trouble in the long run due to condensation, if you let it run longer then you will not have that problem.
And, it is probably more economical to let it run 15-20 minutes/day?

Condensed water + sulfur (comes froom the oil) is probably not good?  

[WA1GFZ]

Another option is a second thermostat in parallel set to a low temperature located in the basement.

[Mike/W8BAC]

Tom,

Is it possible to circulate the water without running the boiler? If that can be done a few of the radiators could be used in reverse. A fan or two pushing warm room air over a radiator to keep the water above freezing. Just moving the water might be enough. Add a fan if you like.

Mike

[Jeff W9GY]

Had our hot water heating system winterized at our place in Michigan before we left for the winter.  The cost of anti-freeze was in the neighborhood of $300.  But we'll not need to do that again next year and onward.  Plumber told me that my system is in very good condition and adjustment, thus little or no water will be added, so shouldn't need to test the antifreeze for some time down the road. 

[W1AEX]

Tom,

As SM6OID mentioned, condensation is a real issue with the boilers of oil furnaces when they are allowed to cool down enough for it to form. It is a mess to clean up once it starts!

Rob

[WA1GFZ]

furnace makes hot water so cycle isn't an issue. Tom how about some insulation in the basement around the sills. It will make a big difference the basement temp. Usually only a couple inches of wood to the outside in each cavity just above the foundation.

[flintstone mop]

Don't you have glycol in your hotwater system?

Hmmm... don't know. The furnace was recently installed new a year ago. Is this a standard thing?  I shud call the guy and axe him.


BTW, the furnace does come on regularly now to heat the water for washing - but the circulators for the baseboard heat do not come on at the same time beacuse I have the thermostats turned down.. Maybe there is a way to allow this to occur at the same time? There is a digital control box on the furnace...

T

You might be on a good thought to have a timer to give a closure to the thermostats in question to call for heat every two hours just to move the water in your two minute window.
Or a closure right at the circulating pumps. How many zones do you have?
I think it takes much longer for the cold to penetrate and start freezing water. Pipes exposed to the direct cold?. How's about heating tape on any exposed pipes?
Are there unheated areas that are getting into the 30's?
When we heat with the pellets the unheated areas in our house only go down to 55 on our single digit nights.
I realize your cold is more severe than Western Pa.
FRED

TOM I saw your post about 30 minutes to freeze a WORKING system,,,you have serious cold there bro!!

[W2VW]

Lease out space on your towers to a few FMs and vent their tx shack into your place.

[K1JJ]

furnace makes hot water so cycle isn't an issue. Tom how about some insulation in the basement around the sills. It will make a big difference the basement temp. Usually only a couple inches of wood to the outside in each cavity just above the foundation.

Yes, Frank, the hot water cycle comes on often enuff so that the boiler is warm/hot all the time. I don't see condensation an issue because of that.

The problem is there is an exposed 1' long piece of heating copper pipe that runs under the house to a house section that has no basement. It is an inaccessible crawl space, so that pipe must have some hot water or glycol run thru it. Can't get at it for heat tape.  That was the section that I found clogged with ice this morning when I turned on the circulator and found the water hot going in, but cold on the output for a minute. It then cleaned out and is normal now.

It's a two zone system and there are thermostat terminals I can key closed right on the furnace controller. So if I can find a good timer circuit I will put a pair of contacts there to activate the circulator. The boiler appears warm most of the time and many times the circulator pushes hot water without the boiler coming on - at least enuff to keep the pipes hot.

Frank, maybe I'll pay you to come over and add some glycol..   There's no fillers upstairs - all work must be done at the furnace valves, etc. Can I use standard car antifreeze and do a 50-50 mix? Maybe with that and the timer it will cheaper and be OK. lt might  work in conjnuction with the timer circuit to be effective against freezing.

T

[n2bc]

Auto antifreeze is likely a bad idea.  The stuff you use should be safe for human consumption - not the correct terminology but that gets the point across.   

Why?   Your domestic hot water coil is sitting in the middle of the heating water. 

Typically a failure (leak in the domestic heating coil) will cause the heating system a problem because the pressure in the heating side is only 10 or 12 PSI (there's a pressure reducer on the heating water feed) vs the domestic water side at 40 or 50 or more psi.   

However, if you get a leak and Murphy is really lurking, you don't want to be sipping auto antifreeze.

Good Luck!    73, Bill  N2BC

[K1JJ]

Good thinking on the antifreeze risks, Bill.   Yes, if the dog got some, it doesn't take much.

I decided to buy one of these digital light timers. Not bad for $16. It will take detailed programming up to 120 entries, so this should handle a long list of on/off commands to keep the circulator going every hour or so, depending on outside temperature.

It will key a 120V relay and then key the two circulator zones for 5 minutes each cycle.

I'll hold off on the glycol for now. I think running the circulator at least every hour will keep the pipes safe. I mean, WTF.


T

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[W1ATR]

Wow. There's a lot to sort out here. First off, do yourself a favor and try to keep the antifreeze out of the system. Propylene glycol (pink stuff) should only be used where there is no other choice to avoid pipe freeze up. It'll harden up any seals it comes in contact with like flo-checks, domestic coil gaskets, circ shaft seals, etc... To get the proper mix into a system, the preferred method is two hoses, a pump, and a bucket. The reason they want 3 bills to do it is because it takes about 2 hours to do it right, and a 5gal bucket of NoFreeze is about $75.

I think jogging the circulator is a bad idea. Hot water freezes faster than cold water. I had a call a while back in which I was bleeding out a system that had one leg of copper in an attic. I knew about it, so in the time it took me to go out to the truck and grab a bucket of the crap and come back in, that pipe froze. We're talking not even 10 minutes and the returns were coming back hot before I went outside. It was down around 5° when this happened. The fix was to put a 500w halogen on it, rebleed the zone and get some NoFreeze into the system. In your case, jogging the circ would just heat the pipe momentarily and not provide any heat to the surrounding area to keep things warm during the off cycle.   

The better idea would be to determine exactly where the freeze up happened and address the problem at the cause. Is the frozen pipe in the basement? The most common freeze up point in basement piping is where the pipe's run near the rim joist and stub up for each radiator. Make sure the pockets above the sill plate are all filled in with insulation. In other words, if it's a cold air infiltration problem causing the pipe to freeze, then I would address it there.

All that said, it's impossible for me to know what you have going on out there. Installations vary widely and it has nothing at all to do with the house itself. I've seen the nicest most expensive houses have the most embarrassing hack job installs, and I've seen regular every day homes have the cleanest nicest installs ever. Every system is different, and it totally depends on how your system is set up and planned out if crutches like antifreeze and heat tape are needed. I say try to figure out where it froze and see if there's a way to correct it. Once those options are exhausted, then put the pink bile of death into the system.

J     

[flintstone mop]

hey Jared,
I think I read that Tom has one(?) inaccessible area that is prone to freezing.
And right on to hot water freezing faster......it was a school homework assignment I did with a high schooler. Unbelievable!
I was thinking for Tom to keep both systems on and they assist each other.
sorry if this is hijacking the thread::::::::
I have tri-level house. And I need to heat the upper floors with pellet stove. 73 is much nicer than  68 degrees,,,,,,,,,ya I'm spoilt.
In the past I would shut the entire heating plant off and only heat with pellets. The family room would be 55 degrees. And turning on expensive space heaters to make it comfortable doesn't work. The furniture and walls are still cold and we are never comfortable. By keeping the main heat on, hopefully keeps the lower levels comfy and will "assist" the pellets.
I ordered a wireless thermostat. ( A good Honewell unit) I'll install it in this "family Room" and will keep the main heat system on at 66 degrees,,,,,close all the supply vents UPSTAIRS except my son's room,,,coz it gets a little cool in his room, when we heat with pellets, and see what happens this season. I'm afraid to see the gas bill for the last month.
I have been hanging those digital thermometers all over the place the last two weeks and I think I have it figgered out
FRED

[W1ATR]

Hi Fred. What is your system exactly. Is it a straight air furnace, or hydroair fed with a boiler? Reason I'm asking is because if it's a straight air furnace, then closing off supplies (more than one or two anyway) will cause the furnace to cycle on the high limit. The lack of airflow overheats the heat exchanger and causes the high limit to cycle the burner off. This will usually crack the heat exch in a very short time ruining the furnace and introducing a not so nice helping of CO into the living area. Not a good thing. 

[W3SLK]

Jared, you jumped in here right on cue. I was going to ask where our "Forum Resident HV/AC guy" was hiding........I mean operating. 

[W1ATR]

Hiya. I try to help out anyway I can. I know that there are some of the best minds on this board and I can pop a radio related question out there and they jump right on it and straighten me out. So my contribution to the hive is my 20+ years experience dealing with hvac/r system design and failure analysis/repair.   

[K1JJ]

Thanks for the info, Jared.

Yes, as Fred mentioned, I have a 1' length of copper pipe that goes under an inaccessible crawl space outside (in cold air) before it enters the house addition. No way to get at it for insulation. It has been that way for 25 years with no problems when the furnace ran itself without the coal stove.

But now, the coal stove heats the whole house quite well and except for hotwater, the furnace has no need to come on.  

I'm surprised that the hot water can freeze so quickly. (10 minutes)

I will stay away from the glycol.

The problem is that it is difficult to set the furnace thermostat to any workable back-up level because the coal stove does not have a stable temp range as you know. The coal stove would have to be watched too closely as it goes thru its burn cycle.

Maybe I can drill some holes and snake some insulation around the exposed copper pipe. But I want to try the jog circulator idea too - even if I have to auto-turn it on every 15 minutes during the real cold days.  

T

[KL7OF]

Jared,  We have to put a glycol based fluid in all boiler systems in Alaska......You made mention of the glycol being tough on some of the components and seals.....Doesn't seem to be a problem for us...The boiler runs year round in most areas....just not as often in the summer month......Steve