How to dump heat with df 520

I have DF 520 settings at 3 teeth and 3and ¼ air 200 high 160 low (2min per half hour)
I have radiant tubing in concrete floor in basement. With 3 teeth the boiler works long
I then go to 4 teeth 4 air and its works much better. The problem is the concrete holds heat for 9 hours ,and cause there is no call for heat ,with 4 teeth the boiler temp climbs to 200 limit and shuts down the timer . I have baseboard heat in garage with its own thermostat and circulator that I don’t use. The question is how can I run the circulator in garage to dump heat when boiler goes to 200 without using the thermostat . Could the aquastat be wired to start the pump on high temp and shut off at lower temp ?
Auquastat # L7224a,c

Either install an R832A to work with your L7224, or install an L6006 on your boiler to turn on the garage circulator when the temp gets to 200. The efm manual shows how to do this. www.efmheating.com manuals.

Thanks stoker-man I appreciate all you guys do on this forum Happy Holidays

When you say the boiler ran a long time on 3 teeth...can you be more specific?

What temperature is the water you are circulating through the radiant slab? Too warm will cause temperature swings and infrequent heat calls...a cooler temperature in the radiant system may help.

If you prefer the way the boiler runs on 4 teeth, have you tried reducing the timer duration? Perhaps 1 minute (or 1.5) every 30 minutes is enough to maintain the fire without overheating the boiler. Lastly, do you have a bypass installed between the supply and return header?

Just trying to think of some possible remedies before you start dumping btu's to the garage.

Rob R. wrote:When you say the boiler ran a long time on 3 teeth...can you be more specific?

What temperature is the water you are circulating through the radiant slab? Too warm will cause temperature swings and infrequent heat calls...a cooler temperature in the radiant system may help.

If you prefer the way the boiler runs on 4 teeth, have you tried reducing the timer duration? Perhaps 1 minute (or 1.5) every 30 minutes is enough to maintain the fire without overheating the boiler. Lastly, do you have a bypass installed between the supply and return header?

Just trying to think of some possible remedies before you start dumping btu's to the garage.

Read up on yanche and robs threads regarding having an oversized extrol tank and banking the heat.

Why not dump to one of the homes other zones instead of the garage? That would be better than throwing heat away.

I thought that with the efms you can really turn down the teeth and get the black magic spot and really throttle it down. No?

You can cut the coal feed back, but the article below shows what can happen if you cut back the feed and don't keep an eye on the pot.

Pictures of a burned pipe and worm due to improper feed/air

stoker-man wrote:You can cut the coal feed back, but the article below shows what can happen if you cut back the feed and don't keep an eye on the pot.

Pictures of a burned pipe and worm due to improper feed/air

Could you add a sensor that would bump up the feed rate to 4 if tube fire was detected?

Could you turn your aquastat down a bit? Say 140 - 180? (that is what I run mine on 3 and 3)

Also (not trying to tell you what to do but if you have PEX radiant type tubing in that floor I was thinking 130 was as much as it liked (preferring 100 - 120).

Do you have a mixing valve for that zone? Thinking that with boiler temps that high even a mixing valve might have trouble after awhile if you are needing to dump heat.

ValterBorges wrote:I thought that with the efms you can really turn down the teeth and get the black magic spot and really throttle it down. No?

Works good for me.

Mark (PA) wrote:Do you have a mixing valve for that zone?

He should, otherwise the floor would be pretty "toasty".

Yea that is what I was thinking Rob!

wouldn't have to run that zone very long to get it up to temp. I'm not sure why else they would need to dump heat.

I've never had that problem using the lower boiler temps (dumping heat somewhere). Just seems like if you don't need that heat pull it back a little, save some coal possibly... Dumps zones are necessary evils of hand fed boilers mostly (until you get to be a really excellent firemen!) . but a stoker you should be able to get it a little closer i think.

I'll second that question from Rob.

How long does it run on 3 teeth if that is your concern maybe?

Valter
The feed rate on the EFM is a manually controlled item. wouldn't be able to have a sensor do that task in this case, nice thought though.

I have no dump zone at all, but I will admit that I have a lot of mass in the system. Between the EFM and my oil boiler there is about 2000 lbs of steel and 60 gallons of water...no doubt that smooths out my temperatures.

I still think the easiest place to start is with timer cycle. If 1 minute every 30 provides a good burn, he probably won't need to do anything else.

You can go to 210 on the high limit, I was having outfires in the warm weather due to poor draft, I increased my timer run time and the boiler hit the high limit of 200 and the aquastat prevented the stoker from running and caused more outfires. Once I increased the high limit to 210 everything worked smoothly, the boiler just couldn't heat the water to 210 on the timer.

Also, why are you running the timer every 1/2 hour in the cold weather? Go to once an hour, you'll have to monitor the boiler to get the correct run time, try starting with 2 to 3 minutes, depending on how your chimney drafts.

I learned (from Coal Berner) that when you run the boiler on the timer for 4 minutes every hour as opposed to 2 minutes every 1/2 hour the boiler will build up more heat on the 1/2 hour cycle, there's less time for the boiler to cool down between cycles.