Raising pump launch temperature?

[vtwoodheater]

Does anyone see a problem with raising the pump launch to 175-180? The factory controls only allow for 170 as the highest temp. It seems my boiler really just kind of hangs out between 165-174 with the pump set there. Way too much cycling for me, not enough heat distribution.

Once the boiler hits 180 finally, I can put the grundfos 15-58 on speed 3 and the boiler just keeps chugging up to 190+, if the wood is there.

Also by raising the temp to 180, the pump wouldn't continue to circulate the water back to the boiler from storage, cooling it all back down to 170. (that kind of pisses me off)

BTW, I didn't get that Viridian pump installed like I wanted to.

 

[foamit up]

I have the same problem with my boilers. On the Vigas firewood fired i lowered the temp probe to bottom 1/3 of storage tank instead of top of tank and that solved that now it will not cycle till 2/3 tank is at 185. On the BioWin pellet boiler i have tried a couple things but have not got it to work. It cycles at 170 which is not enough hot water. Not sure if it is the probe that defines this or something in the electronic board. Like to have it adjustable so could push to top without boiling water. But usually by the time it is done with burnout it is down to 165 and ready to start relight.

 

[velvetfoot]

What are your BioWin settings? I got mine up to 180 top/ 177 the other day. The boiler shut down at 183. The max temp on my BioWin is 176. I have mine set right now at 172, with the external control setting 'on'. I like to have it run a little longer each cycle. What happens for me is that the boiler temp gets to near 172 or whatever, and then it starts modulating down, percentage wise, but it doesn't shut itself down until 183. If you want it more vigorous, you could set the temps, both internal and external, to 176, then it would only cut its output nearing that and again off at 183. That's how it works for me anyway. Just curious, where on the tank are you measuring the 165? You have 4 apartments depending on heat and hot water, so it's a little different from my setup, for sure.

 

[Nofossil]

I have an old EKO where you couldn't set the launch temperature at all. I ended up taking over control of the circulator since I had the control capacity to do it. I'll actually change the outlet temp target depending on what heat loads I'm supplying, ramping iyt up as high as 190 to 'top off' storage, or as low as 165 if I'm heating the hot tub or DHW.

Failing that, the Viridian looks like a very elegant solution. It will vary its speed to maintain the outlet temp that you want. Launch at a really low temp and let the Viridian do its thing.

 

[velvetfoot]

Additionally, for me, I see no sense in heating storage any more than I have to. Why have the potentially pretty darn cold water in the tank come back to the boiler. Even with the temp controlled auto feed pump, or boiler protection valve, you'd lose potential hot water flow due to the slowdown of the auto pump, or the recirc through the protection valve.

I put in a bypass around my buffer tank and control return temperature (set at 155 now) through an electric three way mixing valve. My idea is that I'll get more and hotter water out of the boiler for the zones when it's running, like for coming back from setback. It's only a 120 gallon buffer tank, so maybe ultimately not worth it, but I can see it helpful for a wood boiler if the zones are calling while the boiler is on.

 

[Nofossil]

Additionally, for me, I see no sense in heating storage any more than I have to. Why have the potentially pretty darn cold water in the tank come back to the boiler. Even with the temp controlled auto feed pump, or boiler protection valve, you'd lose potential hot water flow due to the slowdown of the auto pump, or the recirc through the protection valve.
.

True, but system-dependent. Depending on how the system is plumbed this may or may not be an issue.

On mine, storage is another zone that I don't turn on until more critical zones are satisfied OR if the boiler outlet is getting hotter than in needs to be.

In primary-secondary systems you presumably wouldn't divert heat to storage until similar criteria have been met.

In hydraulic separator type storage systems (like in the 'Simplest Pressurized Storage' sticky above) there would be no flow to the boiler through storage unless the boiler was producing more hot water than the active zones required. With a Viridian or similar variable flow from the boiler, this will change automatically as the boiler ramps up. Even without variable speed circ, net flow from the boiler will change due to recirculation/inlet protection as the cold return temperature changes. If the zones want more than the boiler can provide, the difference is made up by supplying the zones from storage.

I don't know how the OP's system is plumbed so I can't comment on whether any of this applies....

 

[vtwoodheater]

My system is plumbed just like the "simplest pressurized storage" design. It seems to work very well. Just the 170 launch and no shutdown with the boiler controller leaves something to be desired. It doesn't take long to cool down the tank storage through a non running boiler.

I just throw wood in the morning, and whenever I remember too. Any extra heat goes to the tanks. If the fire is lacking, it draws from the tanks. Works very well. In fact, I disconnected the oil boiler again.

I might be installing the Viridian pump sooner than later.

 

[maple1]

Does anyone see a problem with raising the pump launch to 175-180? The factory controls only allow for 170 as the highest temp. It seems my boiler really just kind of hangs out between 165-174 with the pump set there. Way too much cycling for me, not enough heat distribution.

Once the boiler hits 180 finally, I can put the grundfos 15-58 on speed 3 and the boiler just keeps chugging up to 190+, if the wood is there.

Also by raising the temp to 180, the pump wouldn't continue to circulate the water back to the boiler from storage, cooling it all back down to 170. (that kind of pisses me off)

BTW, I didn't get that Viridian pump installed like I wanted to.

Even if you raised your launch temp - wouldn't the boiler just cool back down to your current levels shortly thereafter anyway due to the cool return water from storage being the same temp as before? The dT through the boiler would assumedly be the same, and the return temp would assumedly be the same - until you get that first lap through storage done.

Mine sort of self-balances when my house is cooled & I am trying to recover its temp - i.e., house heat load is high. That means most of the boiler flow goes to zones (sometimes all 4 open at once for a period of time) and not storage, which means warmer boiler return water & the boiler temp smoothly rising, usually to the 180 or so area on supply. As opposed to normal 160 supply (for first storage lap) when charging storage. Then as the loads get satisfied, more return comes from storage, and the boiler supply drops back to 160 again - until that first lap gets done.

I think lower boiler temps =somewhat increased efficiency, the lower temps pull more heat out of the HXs. Just that, depending on your distribution system, the zones may have to run longer to satisfy the thermostats.