Windhager People: Boiler Temp Question

[velvetfoot]

Rather than a 0-10Vdc control, you'd be farther ahead letting a Tekmar outdoor rest control manage the water temp in your storage.
Simply connect the output leads from it to the xx connections on your Windhager board and watch what happens. Set minimum water temp at 125 - 130 on the Tekmar.

I took a picture. The 10 v. external heating demand terminals are intriguing:

 

[heaterman]

Intriguing possibly but they are not going to help you get what you're after, which is longer run time if I'm not mistaken?

I would get rid of your "latched relay" and use a normal aquastat with adjustable differential in your buffer tank. run the set point on that at 180 and the boiler at maximum (176*) You'll get longest possible run time from that configuration.

 

[velvetfoot]

Intriguing possibly but they are not going to help you get what you're after, which is longer run time if I'm not mistaken?

It's intriguing, and I have a 0-10 v. controller laying around, but I'm not sure it's worth the risk, for as you say, possibly dubious rewards.

I would get rid of your "latched relay" and use a normal aquastat with adjustable differential in your buffer tank. run the set point on that at 180 and the boiler at maximum (176*) You'll get longest possible run time from that configuration.

I might, but I'm pretty sure I'm getting the most run time this way. Besides, there's no guarantee that the tank would hit 180 each time. If the boiler aquastat shuts things down at 181, or whatever, and the tank is still calling for heat, the boiler will start again after it cools to 160 or so. Then if it makes it to 180 on the tank, it will shut off the boiler again after a short while.

 

[bdud]

It's intriguing, and I have a 0-10 v. controller laying around, but I'm not sure it's worth the risk, for as you say, possibly dubious rewards.

I might, but I'm pretty sure I'm getting the most run time this way. Besides, there's no guarantee that the tank would hit 180 each time. If the boiler aquastat shuts things down at 181, or whatever, and the tank is still calling for heat, the boiler will start again after it cools to 160 or so. Then if it makes it to 180 on the tank, it will shut off the boiler again after a short while.

You could lower the boiler output temp and have the boiler controlled by the tank aquastat set at a higher temp as heaterman said. I have boiler water temp at 167F and the tank aquastat at 170F. I get ~3hr average run times when it is real cold, ~2hrs back in November. If any one heat zone is calling for heat, the boiler will not turn off. You just have to find your own sweet spot.

 

[velvetfoot]

I forget, where is your tank aquastat located? The Ranco has a 30 degree differential, which is also a factor. 170 at the top isn't awesome, in my opinion.

 

[bdud]

I think it is about 1/4 - 1/3 way down the tank. I have a 25 degree swing, I replaced the mechanical aquastat with the electronic one. As long as your home is heated adequately with whatever you set your boiler to, it does not matter what that temp is. I personally think, maybe rightly or wrongly, with a lower tank temp I have a less heat loss from my tank / boiler / piping. European - English boilers do not run as hot as ones in the US. My house is nice and warm at 66 - 72F with the way it is set.
YMMV

 

[heaterman]

It's intriguing, and I have a 0-10 v. controller laying around, but I'm not sure it's worth the risk, for as you say, possibly dubious rewards.


I might, but I'm pretty sure I'm getting the most run time this way. Besides, there's no g and idle as long guarantee that the tank would hit 180 each time. If the boiler aquastat shuts things down at 181, or whatever, and the tank is still calling for heat, the boiler will start again after it cools to 160 or so. Then if it makes it to 180 on the tank, it will shut off the boiler again after a short while.

The boiler will not shut down if there is still external demand present. It will reduce firing rate but stay on while that demand is there along with a differential temp on its supply/return.

Mine has a constant external demand because of the type of heating system I have. When it reaches my internal set point (whatever I have that set at) it will just ramp down the firing rate. About the only start/stop cycle is the 6 hour cool down & self clean period. Right now it has 7336 hours run time and 1659 starts. 4.42 hours per cycle average since start up.

 

[velvetfoot]

About the only start/stop cycle is the 6 hour cool down & self clean period.

So, a majority of that time it's more than 30%?

 

[heaterman]

The firing rate will typically be 30-50% depending on weather. The only time I see output around 60-70% is at outdoor temps <10*.
Outdoor temp today is 25* and the boiler is running between 30-40%. Boiler and system temp are sitting at 162* with a 165 internal set point.
My boiler is a 210 or, 72,000btu max.
I have no heat storage other than the water capacity of the system which is around 75 gallons.
System flow and boiler flow are constant but variable rate depending on the TRV's, zone valves, DHW etc etc.

 

[velvetfoot]

More or less constant flow.load is probably the way these things like to operate, vs. setback recovery, varyable building aux supply (wood stove), etc. As I said here or somewhere else, with both zones on recovering from setback and the tank manually turned off, it came up to temp quickly and modulated very nicely at its set temperature at 70% or so, as I recall. I'd like to emulate that with my fabulous tank bypass concept, detailed elsewhere.