Since I completed installation of my EKO 40 in Sept I have been heating as needed with my water temp set to 170. This seems to provide all the heat I need for my 2200 sq/ft ranch & DHW. However we have not yet had really cold weather. I do not have storage so I realize I will have idle fires some of the time. After some tweaking (with lots of help from this site!) I am pretty comfortable with the operation & performance of my EKO. What are the variables to consider when setting the boiler water temp? Am I running my circ pumps longer than necessary by not heating to 180 degrees as suggested in the manual? No doubt I will experiment with the settings this winter but if I can learn from the experience of others, that is a wonderfull thing.
Boiler Temp Settings & Efficiency
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If you can heat the space comfortably with 160 °F then no reason to run 180 °F .
Ideally you would have a mixing device that could change the supply temperature running out to your system. The best control would watch the outdoor temperature and adjust the supply temperature automatically. These are called outdoor reset controls. I think some of the EKOs have a reset function built into the controller on the boiler.
The main thing you want to keep an eye on is the return temperature (return temperature protection) to the boiler. Usually you do not want to let the return fall below 140- 145 °F or the boiler will start to sweat (condense).
Return temperature protection can be a 3 way thermostatic valve, a device like a Laddomat, or a variable speed pump that operates on temperature, or even a strap on thermostat that would break power to the boiler circulator when the temperature drops.
With a buffer or storage tank you could run the tank up to 180-190 °F , then pull the supply to the heating system via a ODR control. That way you store the most amount of energy in the tank at the high temperature, and just pull off the temperature required to do the job.
hr
Ideally you would have a mixing device that could change the supply temperature running out to your system. The best control would watch the outdoor temperature and adjust the supply temperature automatically. These are called outdoor reset controls. I think some of the EKOs have a reset function built into the controller on the boiler.
The main thing you want to keep an eye on is the return temperature (return temperature protection) to the boiler. Usually you do not want to let the return fall below 140- 145 °F or the boiler will start to sweat (condense).
Return temperature protection can be a 3 way thermostatic valve, a device like a Laddomat, or a variable speed pump that operates on temperature, or even a strap on thermostat that would break power to the boiler circulator when the temperature drops.
With a buffer or storage tank you could run the tank up to 180-190 °F , then pull the supply to the heating system via a ODR control. That way you store the most amount of energy in the tank at the high temperature, and just pull off the temperature required to do the job.
hr
I don't see why you wouldn't crank it to 195 and leave it? Are you using a water-to-air HX? If so, the hotter water will heat your house faster, thus saving electricity for the furnace fan....
I keep mine set at 78C instead of max of 81C it seems like the boiler runs extra hard / long to make the last few degrees and uses wood a little faster. Since I am without storage that extra is just a waste. The furnace fan does run a tad longer so in the end it's pretty much even except I get a little longer run time between fills and sometimes that allows me to heat with wood and not go to the backup gas to keep the heat up.
stee6043 said:
While you could do that, it's a bit of a waste... A boiler will run most efficiently - i.e. get the best transfer of heat from the fire into the water - at the lowest operating temperature it can run without getting condensation... Given that the OP is running w/o storage, he will also waste more fuel both trying to get the furnace up to the higher temps, and spending more time idling because the house gets up to its set temp and shuts down the demand from that end - not to mention possibly seeing more uncomfortable temp swings as he turns the blasting hot air on and off...
While you are right about cutting back on the furnace fan draw, you will go up on other things, so you really don't save - this is a balancing game, what you gain in one place you will often lose in another.
IMHO the OP would get the best overall performance and comfort level by keeping the boiler temps low but non-condensing, and having longer furnace fan run times to keep him out of idle mode.
Gooserider
I think I'm operationally spoiled with storage! You guys make much sense. I learn something every day even without trying!
Thanks for the replies. I failed to mention that I am heating my house with base board heat, so I do not have a heat exchanger. I have noticed that when the boiler is at 170 and the house calls for heat, the temp will drop 8-10 degrees and then the fan will kick on and the cycle starts again. I have also noticed that when my boiler is working to get back to temp and then my second heating zone calls for heat (I have two heating zones, each with its own circ pump), my temp sometime drops to 150. I have a Danfoss mixing valve so that should protect me from condensation. I have not yet, but plan to install an aquastat on my return so I can gauge the temp drop. Are these temp swings normal? I am still learning my boilers moods with the colder weather.
Nothing scientific from me . . .
I run through a 20-plate HX. No storage. So far this fall I have been running the aquastat on the GW at 168*. Last year during cold snaps (negative F numbers) I bumped the aquastat to 190*
The downside of the lower setting is that the oilboiler runs lower, which means that it takes longer to heat the DHW (reheat triggers at 135* and stops at 145*). If a couple of zones call for heat while the DHW is laboring, the operation may be further prolonged. DHW priority helps.
The downside of the higher setting is more fuel usage.
Jimbo
I run through a 20-plate HX. No storage. So far this fall I have been running the aquastat on the GW at 168*. Last year during cold snaps (negative F numbers) I bumped the aquastat to 190*
The downside of the lower setting is that the oilboiler runs lower, which means that it takes longer to heat the DHW (reheat triggers at 135* and stops at 145*). If a couple of zones call for heat while the DHW is laboring, the operation may be further prolonged. DHW priority helps.
The downside of the higher setting is more fuel usage.
Jimbo
Gooserider is right on when he advises against running high boiler temps when they are not needed for efficiency purposes. My EKO40 still does not have storage and I heat for dhw (siedarm) all year long. My system uses an air/water HX. Lower boiler settings in the shoulder season (160f) does save wood because the house is not calling for heat all the time and the boiler does not cool down that fast as a result of the purging process of the EKO. Trying to maintain higher boiler settings increases the "delta" for atmospheric loss (boiler is outside in unheated building) and the EKO will respond by trying to heat the boiler to the set temperature more frequently even if there is no call for heat. That's just burning wood for the sake of burning wood. Except for periodic cleaning/maintenance and a 3 month period this year my boiler has been supplying dhw and or heat for the home since Thanksgiving of 06. My EKO has the older controller and max's out at around 178f and handled the worst 08/09 winter negative temps and the house (1700 sq. ft. w/poor ins. late 1800's const.) at 71-72f with about 2.5 loads per day with wood rated at 20 million btu per cord. Less wood was used when the higher btu woods were used.
I personally am forced to turn down my boiler temp especially in the shoulder season as the gasification will overheat my eko 25. for instance in the shoulder season I turn it down to 172 or so to prevent E2 from showing up on my screen of the eko (overheat notification) granted if your running storage you probably do not run into this issue too much.
I'm in the same situation, 180 gave me excellent temps in the house but the damper is staying open longer and burning more wood. I've been having trouble getting a overnight burn, and the boiler stops producing good heat after 5-6 hours. Lately I've been turning it down to 170 at night and I still have enough heat in the morning.
How can I check the return temp of the water? Will measuring the temp of the return copper pipe be accurate, or do I somehow need a probe in the water?
How can I check the return temp of the water? Will measuring the temp of the return copper pipe be accurate, or do I somehow need a probe in the water?
ashless said:
OK, I misunderstood what fan you were talking about, I thought you were doing the forced hot air w/ a water/air HX, and were talking about your air handler fan - I take it you were talking about the boiler fan instead... My comments still apply, though the timing shifts a bit...
Yes, it is quite normal to see the temp drop - it's the way the system should cycle... W/ no heat call, the boiler will not have any water circulating through it, and will heat up until it goes into idle mode, at which time the still smoldering fire is usually enough to keep the boiler temps OK. When the heat call from the first zone comes, you turn on the circ and start pulling the hot water out and replacing it with the colder return water - which should signal the boiler to come out of idle mode and start heating again. If the second zone comes on, you have the same thing happening, only more so, as you have more water getting moved. 150* return water is OK, sounds like the Danfoss is doing its job properly, though it wouldn't be a bad idea to get some kind of temperature probe on the return pipe to make certain...
You don't really need / want an aquastat at that point just to monitor temps - an aquastat is intended to turn things on and off in response to temperature, as it's the same idea as a thermostat, just measuring water temps. All you need is a thermometer of some sort - there are LOTS of choices! While a well type thermometer will give the most accurate readings, and fastest response, any sort of sensor strapped to the surface of the pipe and wrapped with enough pipe insulation to keep the air from cooling it will be within a degree or so, which is fine for monitoring purposes. (This will also answer Paddock's question)
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