What do you mean by loading unit, (boiler circ.) ? If that's what you are referring to, my boiler circ does modulate also.
FHG 40/50 .. boiler set point temperature
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What do you mean by loading unit, (boiler circ.) ? If that's what you are referring to, my boiler circ does modulate also.
The Froling typically is equipped with a LK810 loading unit which operates at a fixed speed, based on info in the manual for the LK810 that I have. By modulate I mean variable speed (more or less gpm) in response to available boiler output to minimize the likelihood that the boiler slumbers. The loading unit is intended to move boiler output to storage. The loading unit is not intended to be and typically is not the circ that moves hot water between storage and loads. Yours may be plumbed differently.
Mine is a 240v grundfos circ .. which does modulate.. I think your loading unit prolly has a 120v circ in it. I think you guys down there get your froling with some sort of step down transformer to 120v . Which nullifies the modulation capabilities.
You can increase the gap between boiler setpoint and the slumber setpoint. One of the earlier poster indicated slumber is an adjustable offset, I forget exactly how I did it but it's adjustable.
The Froling is slow to modulate the firing rate turndown, 20 minutes at least, so it needs this bigger gap, at least on my system. I'm set to achieve setpoint, enter turndown, just immediately above the temp where the loading unit is fully open, ~ 72 C. Boiler will not get to 72 C from a cold start in less than 1 hour when the slabs and DHW tank are cold.
When the boiler is 72 C the slabs are returning warm water and the loading unit is fully open.
When the boiler is hot and the slabs are up to temp, it is limiting the fuel loading and timing that works. If I'm loading and see the boiler is in the 70's C, I will throw two or three pieces on a coal bed (or just poke the existing fuel load). If I'm loading (boiler off and hot) and I see the boiler is at 87 C, I will wait 1 - 3 hours until the boiler is back in the 70's C and then load it half or less.
I never load the firebox full unless the boiler has been off for 24 hours and it's cold outside. Mostly never burn overnight.
Of course during the time the boiler is 87 C and off, the boiler circ, injection mixing circ, and slab circ are all on and scavenging heat from the boiler out to the slab. Boiler actually burns slowly some remaining charcoal while off.
Equipment matching, boiler to demand full load and low load, slab storage to the load, slab temp to space temp, space temp to 70 F, is all very good.
The Froling is slow to modulate the firing rate turndown, 20 minutes at least, so it needs this bigger gap, at least on my system. I'm set to achieve setpoint, enter turndown, just immediately above the temp where the loading unit is fully open, ~ 72 C. Boiler will not get to 72 C from a cold start in less than 1 hour when the slabs and DHW tank are cold.
When the boiler is 72 C the slabs are returning warm water and the loading unit is fully open.
When the boiler is hot and the slabs are up to temp, it is limiting the fuel loading and timing that works. If I'm loading and see the boiler is in the 70's C, I will throw two or three pieces on a coal bed (or just poke the existing fuel load). If I'm loading (boiler off and hot) and I see the boiler is at 87 C, I will wait 1 - 3 hours until the boiler is back in the 70's C and then load it half or less.
I never load the firebox full unless the boiler has been off for 24 hours and it's cold outside. Mostly never burn overnight.
Of course during the time the boiler is 87 C and off, the boiler circ, injection mixing circ, and slab circ are all on and scavenging heat from the boiler out to the slab. Boiler actually burns slowly some remaining charcoal while off.
Equipment matching, boiler to demand full load and low load, slab storage to the load, slab temp to space temp, space temp to 70 F, is all very good.
I can't remember off hand ,I'll check when I get home. The VFD is a function of the froling though. I think 25-60 rings a bell though.
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Very good. Interesting and helpful discussion.
From your description, it appears you do not have storage, and load matching and other settings then become very importance to prevent slumber. Storage is just another load, but if the goal is to load storage to the maximum, then the matching strategy remains very important. If the goal is to use storage to something less than the maximum, then storage is the place where the btus can go and prevent slumber, if the other loads are not matched.
In the conventional sense of a 400 to 1000 gallon HW storage tank, no nothing. The system is planned, piped, and tapped for the tank but no tank.
The house has thermal mass used as storage or buffer. The radiant basement slab has 2" blue EPS board under it and the same wraps the exterior of the foundation wall. When I do it again it will be a contiguous 4" EPS wrap.
If the house space temp is below 70 F I put wood in and if it's over 70 I stop. Basement slab usually runs between ~ 82 and 92 F. Basement slab circ is slaved to the boiler cir so there's always constant load on the boiler when its over the boiler circ launch temp. Primary Secondary piping with the radiant loops always mixed down with an OAT reset injection pump controller.
With no heat but the slabs are charged, house drops pretty quickly from 70 to 62 - 65 F, one to two days. However with no heat in January weather and the slabs are charged, it will take another three weeks for the house to drop from 62 to 52 F. Not possible to freeze it in the winter IMO.
This morning with no overnight fire, boiler off for 12 or so hours, outside temp climbed to 52 and inside temp climbed to 71.5 from ~ 70.0 F. That's the passive heat slab storage responding to the load, no fire no fuel no electricity no controls (the system off condition). That's typical for many of the heating days of the year.
For the rare atypical day I can fire the boiler and crack a lower and upper window for a fresh air change on nice days over 40 F OAT.
When to load fuel and how much is the only manual intervention. System runs perfectly in auto the heat is awesome.
Four necessary conditions to make this work: modulating firing rate boiler, well insulated modern home construction with more than usual thermal mass, radiant in slab distribution with OAT reset of the loop water temps, minimum constant load always on the boiler when firing. The house construction is matched to the heating system design type.
Omit any of those four and I do not see this system working.
. working great now , no slumbering to get there.
Excellent. I'm getting 188 top/182 bot on my tank too. Of course it's a 120 gal tank fired by oil. 
Excellent. I'm getting 188 top/182 bot on my tank too. Of course it's a 120 gal tank fired by oil.
must get to those temps fairly quickly then
oaksplitter
Member
I am just learning my Froling 20/30, but have found that a boiler set point of 86C gets my tank (820gallon unpressurized) to 84 top and 80 bottom. I was of the understanding that slumber was a fixed point (93C) that cannot be re-programmed. The froling works to stay within 4 or 5 C of setpoint. One trick I use relates to the overtemp zone which runs off an aquastat on boiler. Usually this is set above the slumber point and in case of a run away boiler (term used in manual) it opens a zone in your house and begins to dump heat to that zone. I adjusted the aquastat just below the slumber temp and above boiler set point, to avoid slumber and put a little extra heat to a couple of cast radiators in the basement.
W
Have you checked the hrs that your boiler has been in slumber? I checked mine last year and it said around 200. What happens if your fhg or s3 slumbers occasionally anyway? My fire tubes had no creosote whats so ever?
Have you checked the hrs that your boiler has been in slumber? I checked mine last year and it said around 200. What happens if your fhg or s3 slumbers occasionally anyway? My fire tubes had no creosote whats so ever?
oaksplitter
Member
I had 25 hours of slumber in the first 250 hours or so and very few after I made the adjustment to the over-temp aquastat. The 25 hours I blame on pushing the system toward higher tank temps which my old baseboard convectors need. I speculate that any creosote that may come during slumber disperses once fan comes back on
maple1
Minister of Fire
oaksplitter
Member
That is the next phase. Add more and replace existing with units that have better performance at lower temps, so I can use more of storage tank energy. Currently my baseboard convectors cannot keep up with winter temps once storage tank drops below 69C/156F. Any suggestions for new baseboards/rads?
maple1
Minister of Fire
Not really. I have ordinary Slant Fin stuff. I'm usually good down to 130 or so before my house starts losing temp. Quite sure they over installed it when my house was built but I'm not complaining.
The smith’s HE2 dual element work well, with multiple piping options and are easy to install. I’ve installed close to 100 ft between 3 houses, two of them use outdoor reset with max temps below 150 degf.
Froling S3 50 here this year.
290 hrs
1 hour of slumber ( I think it may have been on the controller. It had 1 hr from the near beginning)
290 hrs
1 hour of slumber ( I think it may have been on the controller. It had 1 hr from the near beginning)
I anticipate the same issue in my home. I'm interested in what you come up with.
Beagle Dad
Member
Usually when your boiler goes into slumber it happens at then end of the burn when the load drops off more than the boiler can modulated down (about 50% of output). At this point the wood is usually charred when the fan shuts off leaving clean fuel which tends to prevent dirt from accumulating in the boiler. Loading just a bit less wood will eliminate slumber.
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