Mesys pellet boiler and radiant floor

[tythib]

looking to find someone who has this set up and what they have their settings at. Currently the boiler is set to shut off at 180degrees and I dont see any reason to be heating water that much. I have a tekmar control for an outdoor sensor. any thoughts and input would be appreciated

 

[velvetfoot]

You should've posted this in the boiler section, where you might get an answer. Maybe ask a moderator to move it.
I don't know if I can help since I don't have radiant and don't know the capabilties of you boiler, but it will be an interesting discussion. I'm thinking maybe a little more background on the system and its capabilities.

Welcome to the forum.

 

[heaterman]

Your Tekmar control........is it an outdoor rest control that adjusts boiler temp based on outdoor temperature?
Don't see any reason you couldn't use it be aware about maintaining a minimum return temp to your boiler.

 

[__dan]

Boiler hot water supply setpoint has to be maintained above the flue gas condensing temp ~ 140 deg F. You could try lowering the HWS setpoint to ~ 160 F from 180 but I probably wouldn't go lower than that. If you have a DHW indirect tank, it may be slightly slower making DHW from a cold tank or have slightly less GPM production at constant load, but you may never notice the difference except in lower fuel consumption.

If the Mesys has a modulating firing rate to match demand, make sure that's working. Make sure the OAT reset to mix down the radiant floor HW temp is working and the boiler dials down the firing rate to match the low demand. That would be key.

Sounds like a sweet system. It's pretty much what I would recommend as a standard replacement for oil.

 

[tythib]

its a brand new house. heating the garage and house. 1750sq ft house. and 1250 sq ft garage. I have a 1000lb hopper on the system. im thinking if I drop the high temp on the boiler to 160 degrees I will save in pellet. any thoughts

 

[CaptainK]

Yes that is what we have. Have set the following values..
P202 170
P163 160
P281 140

I have been playing with the settings since April. For the summer this worked quite well, I set the Summer/Winter switch to Summmer and it would fire once or twice a day for DHW. Run times where longer with the lower settings but with our tank we never had a DHW shortage (two adults).

Turned on the system to Winter two weeks ago, thinking that extra heat would be good turned up the run temp to 170. No good. Noticed extra cycling in the boiler and set the run temp back down to 160. Waiting on a weeks worth of data to filter through... hopefully it helps. As for if Im saving pellets its hard to say. I have 3 ton hopper and its hard to gauge usage. I do know that boilers are most efficient when they run over time, and since these settings accomplish that I would like to think its helping.

Should be noted I do not have an external temp monitor installed.
Standard disclaimer here.. I'm not a HVAC specialist.. just a home owner.. yada, yada, yada.

 

[tythib]

Yes that is what we have. Have set the following values..
P202 170
P163 160
P281 140

I have been playing with the settings since April. For the summer this worked quite well, I set the Summer/Winter switch to Summmer and it would fire once or twice a day for DHW. Run times where longer with the lower settings but with our tank we never had a DHW shortage (two adults).

Turned on the system to Winter two weeks ago, thinking that extra heat would be good turned up the run temp to 170. No good. Noticed extra cycling in the boiler and set the run temp back down to 160. Waiting on a weeks worth of data to filter through... hopefully it helps. As for if Im saving pellets its hard to say. I have 3 ton hopper and its hard to gauge usage. I do know that boilers are most efficient when they run over time, and since these settings accomplish that I would like to think its helping.

Should be noted I do not have an external temp monitor installed.
Standard disclaimer here.. I'm not a HVAC specialist.. just a home owner.. yada, yada, yada.

How are you collecting all this data? I was thinking off turning it down as muh as possible because the hottest water you want going through a slab is 120. I have a boiler mate also. I just think it would take more pellets to keep a water temp of 185 vs 150

 

[velvetfoot]

I've been thinking along the same lines with mine (I have a buffer tank). A slab would be awesome-no need for a tank, I imagine), and lower temps required than for my baseboard. I think I would turn it down to 150, but I'm just a homeowner with a new boiler and a different setup. I wonder if it could run continuously then, if the boiler modulates down to the heat required by the slab? Would running it continuously be good for the boiler? I've been charging my tank to about 177 with a 176 boiler setting. When I set the boiler down and keep the tank's temp the same, it modulated down to 30% for a long time before it reached the boiler setpoint-it didn't get to the tank temp in that experiment; I think the basement got warmer than before.

Isn't your usage on your control panel somewhere? You would still have to correct for the weather (degree days?) somehow.

What does "extra" cyclling mean?

 

[__dan]

How are you collecting all this data? I was thinking off turning it down as muh as possible because the hottest water you want going through a slab is 120. I have a boiler mate also. I just think it would take more pellets to keep a water temp of 185 vs 150

As you turn down the HW supply setpoint, the biggest problem will be when you get flue gas condensation from running the boiler supplty temp too low. These type boilers are not condensate rated and it makes a mess.

If you have a primary secondary plumbed loops, only the primary boiler loop is running at the higher water temp, which is a lot less water and less loss compared to running the distribution loop at the boiler supply temp. Taking only the boiler primary loop up or down ten degrees is peanuts, a miniscule load, compared to the other factors of what is supposed to be happening in a state of the art system.

If you turn the HW supply setpoint down to the point where you get condensate in the wrong place, in the boiler or in the flue, your operating costs are going to go up a lot with higher maintenance and less efficiency because it will need to be cleaned. The condensate is mostly H2O.

Tweaking the HW supply setpoint is not going to get you the kind of gains you should be getting by tweaking the secondary distribution (radiant) temp, which should be done for you in auto by the OAT reset controller, and by tweaking (modulating) the firing rate of the boiler to match demand, which should be done for you in auto by the modulating burner controller.

This is where the big gains are and where I would suggest people look to make sure that is working, or especially if they are building buying new, what they should be buying.

 

[CaptainK]

Would not turn down as low as possible, for many reasons. Dan makes good points, but for me lowering the max temp along with the set temp works. I am collecting the data with the CF card port that is in inside the main cover. You have to add a card, then turn it on and set the recording interval, P236 and P237 respectively.

Velvetfoot, in my case "extra cycling" is when there is call for heat/DHW the boiler fires to meet demand hits the high temp and goes to shutdown but there is still a call.. after 5-10 min re-fires to meet demand again, and then shuts down. It happens if I have the high temp shut off to close to the operating temp best I can tell. Its easy to see in the data you get a two spikes of output next to each other. I'm sure there must be a better name for it.

 

[CaptainK]

A current graph of 30OCT2014 Note the long runs at night when its colder... durring the day I get lots of stops starts.. depends how sunny it is. Im curious to see how this works out when is actually cold out...