Floor Heat-Timer or return line thermostat or both?

[Turbo]

Should I put a timer on my boiler or regulate using a return line thermostat or BOTH?

I have read a variety of posts and it seems that to more accurately regulate floor heat I should put a thermostat on the return line of floor heat system (vs the slabstat I have now). This makes sense to me.

I have also read that I should cycle boiler on and off via a timer (30 minutes on/off at night and 15 minutes on/off during day. Modify as necessary to eliminate ice. This I dont understand as I think that if boiler needs to run based on return line temp then it should be running or ice will form. I am willing to take on faith as I think quite a few are doing this.

Questions:

1) what type of thermostat on return line? Something from Honeywell where the sensing unit is held on to the 2"copper line?

2) Should I do one of these, neither or both? I am inclined to do both.

Thanks

Turbo

Chicago, 3bay ss, 1 auto, 3 oil change

 

[Turbo]

I did both and I kept the slab stat. So now the slabstat has to say its cold, the return line has to say its cold and the timer has to allow boiler to fire in order for it to fire. The pump control is operated by an airstat completely seperate from other controls and runs from nov 1 to march 31 continuously.

The slab stat was difficult to access so we left it there. If it says slab is warm then it should have veto power.

I am looking forward to results. If this reduces bill be 20% its spectacular. I will probably but doors on both sides too. If doors are 14k and a boiler is 11k then I think I am better off with doors that will reduce load AND enable more revenue via detailing.

 

[mjwalsh]

I did both and I kept the slab stat. So now the slabstat has to say its cold, the return line has to say its cold and the timer has to allow boiler to fire in order for it to fire. The pump control is operated by an airstat completely seperate from other controls and runs from nov 1 to march 31 continuously.

The slab stat was difficult to access so we left it there. If it says slab is warm then it should have veto power.

I am looking forward to results. If this reduces bill be 20% its spectacular. I will probably but doors on both sides too. If doors are 14k and a boiler is 11k then I think I am better off with doors that will reduce load AND enable more revenue via detailing.

Turbo,

We are using all three stats for the deicer return, slabstat, & outdoor air --- it has definitely been helpful now for about 20 years. Our main deicer pump does not run continuously by calendar days. It only runs when needed. One factor to consider on the overhead doors ---- the outer skirts & aprons will still need to be deiced so I am thinking that your load will not actually be reduced but the floor temp inside will be slightly higher. We like the fact that our hot water Trane unit heaters in the bays keep the fog in the bay down with their blowers --- which is another approach if you go with doors.

You must have a different format than us --- if the customer is detailing & other people are waiting --- it is a problem --- that we need to address.

What brand & model # of stats did you finally settle with? Mine are Goldline thermistors & 2 stage + alarm controllers from Independent Energy of Rhode Island.

MJ

 

[Turbo]

Turbo,

We are using all three stats for the deicer return, slabstat, & outdoor air --- it has definitely been helpful now for about 20 years. Our main deicer pump does not run continuously by calendar days. It only runs when needed. One factor to consider on the overhead doors ---- the outer skirts & aprons will still need to be deiced so I am thinking that your load will not actually be reduced but the floor temp inside will be slightly higher. We like the fact that our hot water Trane unit heaters in the bays keep the fog in the bay down with their blowers --- which is another approach if you go with doors.

You must have a different format than us --- if the customer is detailing & other people are waiting --- it is a problem --- that we need to address.

What brand & model # of stats did you finally settle with? Mine are Goldline thermistors & 2 stage + alarm controllers from Independent Energy of Rhode Island.

MJ

MJ

-my pump runs off temp as well. it just seems to be on for majority of OCtober through March
-I am hoping that I lose less heat due to doors (no air flow). return line stat will tell boiler to run so I am guessing that the aprons will be deiced as well. I might have to adjust return line stat and disconnect slabstat (it has veto power and is placed inside where the doors will be. It could tell boiler not to run due to warm temp due to doors).
-format is 3 self serv bays next to each other. We will be detailing customers cars during the week using 1 or 2 bays when we are usually slow. If it gets to point where I have to close self serv due to too many details then I will be making more money. Not couting on that though.
-thermostats are Honeywell basic ones. just on/off based on a temp (normally off)
-I am hoping the timer helps as well

Thanks

 

[Sequoia]

Equipment

Back when I had a boiler that was FAR oversized, I put a cycle timer on the thermostat which called for heat. At 30 minutes on, then 30 minutes off, then repeat-- this effectively cut the operation and the bill in half. A crude method, but it worked.

However, unless your boiler is oversized, I don't understand why you would have a different setting at night vs day? It seems you want to config the thing to just barely keep the slabs ice free- any time of the day?

I just finished installing a new Knight/Lochinvar boiler; however, I do not have a slab stat to work with. At 35 degrees, I have my Weepmizer activate "output 2", and this is what tells the boiler that heat is needed.

The system has a return water sensor (system sensor), and this is the primary means it uses to control heat and firing rate. The instructions make it clear that using a return water sensor is the most efficient way to run your boiler. However, it also has an outdoor sensor which modulates how "hard" it fires. (Burner is running at a higher range the colder it gets outside.)

My system, to handle my size slab and local temps, is set to push out hot liquid until the return water hits 70 degrees. The boiler then "turns itself down" but the liquid is still circulated by the pump, slowly decaying the temperature. Once the return water liquid hits 60 degrees, the boiler increases heat and repeats the same cycle.

btw, a little off topic, but I bought the optional PC interface kit for the knight unit so my PC can connect to the boiler. This morning, while at home 90 miles away and sipping a cup of coffee, I was on my laptop, connected to the boiler, making fine tuning tweaks. A nice feature if you buy a new boiler, but probably not backward-compatible with older systems.

Hope any of that helps.

 

[Keith Baker]

I've been told that a boiler or instant water heater runs more efficiently with a longer burn cycle. The more it starts and stops, the more heat goes up the chimney without being transferred to the fluid you are trying to heat. I don't know if that's true, but it makes sense.

So if you add a timer when you already have a thermostat, you could be shutting the boiler down just when it is getting to run the most efficiently.

Just my .02

Keith

 

[Turbo]

I've been told that a boiler or instant water heater runs more efficiently with a longer burn cycle. The more it starts and stops, the more heat goes up the chimney without being transferred to the fluid you are trying to heat. I don't know if that's true, but it makes sense.

So if you add a timer when you already have a thermostat, you could be shutting the boiler down just when it is getting to run the most efficiently.

Just my .02

Keith

I understand your point and think it might be true. But since a number of people are doing it I and saving money I thought I would try it.

 

[Turbo]

Back when I had a boiler that was FAR oversized, I put a cycle timer on the thermostat which called for heat. At 30 minutes on, then 30 minutes off, then repeat-- this effectively cut the operation and the bill in half. A crude method, but it worked.

However, unless your boiler is oversized, I don't understand why you would have a different setting at night vs day? It seems you want to config the thing to just barely keep the slabs ice free- any time of the day?

I just finished installing a new Knight/Lochinvar boiler; however, I do not have a slab stat to work with. At 35 degrees, I have my Weepmizer activate "output 2", and this is what tells the boiler that heat is needed.

The system has a return water sensor (system sensor), and this is the primary means it uses to control heat and firing rate. The instructions make it clear that using a return water sensor is the most efficient way to run your boiler. However, it also has an outdoor sensor which modulates how "hard" it fires. (Burner is running at a higher range the colder it gets outside.)

My system, to handle my size slab and local temps, is set to push out hot liquid until the return water hits 70 degrees. The boiler then "turns itself down" but the liquid is still circulated by the pump, slowly decaying the temperature. Once the return water liquid hits 60 degrees, the boiler increases heat and repeats the same cycle.

btw, a little off topic, but I bought the optional PC interface kit for the knight unit so my PC can connect to the boiler. This morning, while at home 90 miles away and sipping a cup of coffee, I was on my laptop, connected to the boiler, making fine tuning tweaks. A nice feature if you buy a new boiler, but probably not backward-compatible with older systems.

Hope any of that helps.

A modulating boiler seems like a great idea. I am trying to use tested, reasonable ways to reduce the load and then see what size boiler I need or if I even need a new one (depending on load reductions).

The 30 on/off at night and the 15 on/off during the day idea is from my local supplier. That is what he did and he saves quite a bit. I will tweak my system until I get no ice at near minimum setting. It seems that whatever the interval it should be the same all day/night.

Thanks for comments