Reducing costs w/my horribly inefficient floor heat boiler

[Sequoia]

I have a 3-bay SS with a BIG boiler assigned to the floor heat. It's an old boiler, pretty stupid, waaay oversized for the job so it burns way too much propane, and it comes on below 35 degrees F and run all ^@$^$ night when no one is at the wash. It only turns off the next day after the temp rises above 35 degrees F.

I have purchased a 110V "cycle timer" from my local agricultural store. (These are used in greenhouses.) This unit allows variable settings such as 15 mins ON, then 15 mins OFF. Or maybe 15 mins ON, then 5 or 10 mins OFF. You can control the cycling.

Combined with a 110v relay, I am going to cycle the oversized and inefficient boiler this year instead of letting the stupid thing run full blast all night. I hope to save 50% on the propane bill this year; however, I need to tweak the system to make sure I don't get any freezing on the slabs. Even if I only manage 30% or so it will be a huge savings.

The cycle timer was under $100. The relay, base, and housing was under $50.

 

[Keith Baker]

Duane:
Put a thermostat into the return fluid line to cycle the burner off when the water temp rises. I did this several years ago and my boiler is only on 20% to 30% when the outside temp is in the 20's.
I"ve also added a thermostat into the slab that shuts everything down when the slab is above a certain temp.
Floor heat is a necessary evil, but I try not to spend any more on it than I have to.

 

[Waxman]

Is there any disadvantage to cycling a boiler on and off like mentioned above?

Seems like a super idea!

I also installed a timer on my production water boiler so it turns off at night when the wash is dead and I run off whatever is left in my storage tank during overnite hours. I wrapped the storage tank like crazy with fiberglass insulation this Summer. The boiler kicks back on via the timer in the morning and by the time I get to the wash, the water storage is at normal temp for washing cars!

 

[lag]

If you have not cleaned the boiler in the last couple of years ,you may want to consider removing the burners ,and removing the soot from the coils.

We turn off the floor heat boilers during the day. When it gets bitterly cold we do need to run them during the day.We use a timer to shut down at 8:00 am. All of our locations are attended so we can monitor if we get some icing during the day.

We also have installed temp sensors in the concrete to shut down the boiler when the slab temp is warm enough.

All return lines have thermostats set to 80 to shut down the boilers also.

For our newer locations we have zoned the heated concrete , all zones have there own pump ,with a slab sensor to shut done only that zone. Basically we can direct the heat to where it is needed. an example is our exit from the auto faces south ,and the entrances to the north. The north receives less sunshine so it will ice up more ,than the south exit.


One other consideration when micro manging your floor heat boilers is the cost to heat up the anti-freeze ,after the boiler has been shut down . We used to have a system that the boiler was staged ,so it would run on the highest stage after we had shut it down, because the returning fluid was so cold. I am not sure it was a money saver on colder days.

We always run them at night when below air temp is below 28 ,but we run them with floor sensors ,and return thermostats.

 

[Parker]

We have been rehabbing a car wash for a couple years now and have been working on cutting fuel costs. First we used a laser thermometer to find out what loops heated what part of the floor (nothing was labeled). Then we used these electric thermal actuators that screw on to your radiant manifold to help break up the loops. Basically the manifold only has one circulator that runs and the actuators open and close the valves on the manifold based on which thermostat calls for what. For instance we have a seasonal ice cream shop attached to our car wash with radiant heat in the slab. On the same slab is a bathroom that is used year round. With these actuators our bathroom remains 65 while the ice cream room remains at 55.

heres the ones we used http://www.pexsupply.com/categories.asp?cID=220&brandid=

 

[Ric]

I have a 3-bay SS with a BIG boiler assigned to the floor heat. It's an old boiler, pretty stupid, waaay oversized for the job so it burns way too much propane, and it comes on below 35 degrees F and run all ^@$^$ night when no one is at the wash. It only turns off the next day after the temp rises above 35 degrees F.

I have purchased a 110V "cycle timer" from my local agricultural store. (These are used in greenhouses.) This unit allows variable settings such as 15 mins ON, then 15 mins OFF. Or maybe 15 mins ON, then 5 or 10 mins OFF. You can control the cycling.

Combined with a 110v relay, I am going to cycle the oversized and inefficient boiler this year instead of letting the stupid thing run full blast all night. I hope to save 50% on the propane bill this year; however, I need to tweak the system to make sure I don't get any freezing on the slabs. Even if I only manage 30% or so it will be a huge savings.

The cycle timer was under $100. The relay, base, and housing was under $50.

I cycle the burners on the boiler but put a separate thermostat on the pump so that the fluid is constantly being run. I set it for 37 degrees or so. If you don't have one you can add a thermometer to the fluid line being circulated and watch to see if you get a significant amount of temp. drop while the burners cycle. I've been doing this for 20 years in conjunction with a motorized vent damper that closes when the burners shut down. That helps hold the heat in the boiler. In my case the burners run 10 min on, 5 min off until the outside temp reaches 15 degrees or lower. Then the timer is overridden by a thermostat and the burners run constant since the boiler can no longer maintain the fluid temp.

 

[Earl Weiss]

Is there any disadvantage to cycling a boiler on and off like mentioned above?

Seems like a super idea!

I also installed a timer on my production water boiler so it turns off at night when the wash is dead and I run off whatever is left in my storage tank during overnite hours. I wrapped the storage tank like crazy with fiberglass insulation this Summer. The boiler kicks back on via the timer in the morning and by the time I get to the wash, the water storage is at normal temp for washing cars!

If you jsut cycle it on and off you are just guessing if that tis efficient. If you regulate it with a thermostat on the return line the boiler will only run when the fluid drops below a certain temp. Some days it may run 15 minutes on and a half hour off if it's warmer outside and if it's colder it may run 15 minutes on and 5 minuts off. In either event the temp is seting the cycle, not some arbitrary number.

 

[Waxman]

Should I run both my slab stat thermostat as well as a return line thermostat?

Got a guy coming to look at this this afternoon.

 

[Ric]

Should I run both my slab stat thermostat as well as a return line thermostat?

Got a guy coming to look at this this afternoon.

I quit using my slabstat and hooked it up to the return line. Keep in mind that it's only effective if the pump is running and circulating fluid throughout the floors. I have a separate thermostat controlling the pump. It simply senses outside temp and comes on around 36 degrees. The return line thermostat then senses the fluid temp and turns on the burners as needed.

 

[Waxman]

great info; thanks. have you noticed a savings using this setup vs. slabstat? what made you switch from slabstat?

Thanks!

 

[Waxman]

My distributor questions whether the cycle timer idea would actually save me money. Am I missing something?

 

[pitzerwm]

If you are measuring the return line temp, and killing the boiler when its say 50F or whatever you think is safe can't help but save money, as for killing it at nite, is determined in how long the next day it would take to regain the temp. If it freezes you are screwed.

As far as any advice your distr. (or anyone else) gives you, I'd ask for "proof" as to why he thinks that, a lot of the time a person hasn't tried anything, he just forms an opinion and because he is lazy, he just hopes that he is right.

The people here have actually tried stuff, screwed up and figured it out.

 

[Waxman]

I wouldn't kill the boiler at nite during cold weather; no way.

My glitch is determining which to use for max floor heat boiler efficiency: slab stat, return line temp control, cycle timer or a combination of any 2 or 3.

This had one burner tech stumped, so I am definitely beyond my understanding already.

 

[Earl Weiss]

Save money? Perhaps. But the efficacy of the system is compromised. A cycle timer cycles irrespective of the fluid and outside temp. During colder periods this will allow the fluid temp to cool more than it should in order for it to rise to the needed level during the next cycle.

Per Bill's comments, the floor heat tube should have enough antifreeze to never freeze. If it doesn't, make sure it does. Cheap solution and the risk is too great if you have a power failure.

 

[Waxman]

Just checked the antifreeze. It's at 50% strength.

 

[acbruno]

My floor heat boiler runs when the outside temp is at 32 degrees F. It has a inlet temp gauge set at 80 F and a outlet temp gauge set at 110 F. This was the settings when I bought the place. I think the inlet/outlet temp settings are way too high but I am not an expert. Any way to find out what settings would be optimal? I do not have a slab temp sensor but I don't think you need one.

 

[PaulLovesJamie]

Any way to find out what settings would be optimal? I do not have a slab temp sensor but I don't think you need one.

I dont think there's a magic number we can tell you, for a bunch of reasons. But ultimately its really not that hard to find the optimum temp for your wash -- Test it.

Simply turn down the heat a few degrees, and see if ice forms. Keep turning it down every couple days until you see ice - then turn it back a few degrees.

Now, be careful about this - you dont want to experiment on your customers and have somebody get hurt - turn it down late at night, then check it early in the morning (for example).
Also, I find that when its either really windy or theres a lot of moisture in the air (or its a really busy wash day) I need to turn the heat up a couple degrees. Also, if it gets down to about 15 degrees, I need to turn it up another 5 degrees or so.

I admit that this is my somewhat uninformed empirical method of optimizing - it's quite possible that a heating/cooling expert could do better, but that's how I set mine.

 

[Ric]

I do about the same thing as Paul. My return line temp ends up running in the low to mid 50's.

 

[washnvac]

I recently bought a wash that had no return stat or slab stat. So when the outside temp got to 32, the heater just came on and ran and ran. The high limit was set to 165, so needless to say the temp never touched that. The previous owner cound not understand why his gas bills were $3000+ in the winter. So he stopped using the floor heat. At least it was a simple fix. I can not imagine the installing company did not install it.

 

[Rudy]

I converted from a "slabstat" to a two stat system several years back, and it works amazingly well.

The circulating pump comes on at 33-34 degrees (outside air temperature). A return line stat is set to control the ignition lead on the boiler. For my system, a 76 degree return line temperature keeps everything deiced....just barely. On ultra windy days, we have to warm it up a degree or two.

I think that's as close as someone can cut it........

If it's warmer than 34 degrees outside...you don't need floor heat. If it colder than that....and for whatever reason (such as sun warming the aprons, and circulating the warmer fluid) the slabs are warm...the boiler will not come on...saving you gas.