EFM 520 issue

Hello again fellow coal enthusiasts. A friend of mine is having an issue with his boiler. He has a hydronic 520. He states that when its warm out his fire is going out. Also told me he has his aquastat set at 180/160 but when its running the boiler climbs to 220.
To me it seems like he need to replace his aquastat but I'm not sure about why the fire is going out. Said his timer is running (old honeywell timer) but doesn't kick on the boiler. The only thing that keeps it going is the thermo when its cold out or HW demand

Don't replace the aquastat, it's doing exactly what it should be doing. If the boiler temp is over the HI Limit on the aquastat, the timer cannot run the stoker. This is a safety feature.

You friend needs to turn the HI Limit up to 200 degrees like the manual shows. This will allow the stoker to catch more timer cycles to preserve the fire. The timer should be set for about 2 minutes every half hour.

-Don

Wouldn't that make is domestic water ridiculously hot?

He just told me he had it set at 200 before and the temp went all the way up to 250!!

If he is heating the domestic water with the DHW coil in the boiler, it runs on the LO Limit of the aquastat, 160. If he is using an indirect water heater, it is a zone off the boiler and when it calls for heat it will run on the HI Limit of the aquastat. Running up to the HI Limit for a DHW call on warm days can cause some nasty over shoots due to the light load of a DHW call.

Does it pop the pressure relief valve? Does the boiler sound really hot when this happens? If not, the gauge might be off a bit.

-Don

hardcoalhardcore wrote: ↑

Tue. Oct. 23, 2018 8:24 pm

Wouldn't that make is domestic water ridiculously hot?

That's why everyone on a tankless coil needs to have a thermostatic control valve...mixing valve to temper the water to an always safe temperature.

StokerDon wrote: ↑

Tue. Oct. 23, 2018 7:58 pm

Don't replace the aquastat, it's doing exactly what it should be doing. If the boiler temp is over the HI Limit on the aquastat, the timer cannot run the stoker. This is a safety feature.

You friend needs to turn the HI Limit up to 200 degrees like the manual shows. This will allow the stoker to catch more timer cycles to preserve the fire. The timer should be set for about 2 minutes every half hour.

-Don

Don, you are assuming that the aquastat and temperature gauge are working correctly, and that the timer is wired properly. I had an old aquastat that was off by 25 degrees, so I never assume they are perfect.

Turn up the thermostat until the stoker starts running, let it run for a few minutes, and then turn down the high limit setting until the stoker shuts off. Then compare the high limit setting to the boiler temperature gauge. The temperatures should be within 5-10 degrees. If there is a large difference, either the gauge or the aquastat (or both) are not reading accurately.

Checking the wiring is self explanatory, just compare it to the diagram in the EFM manual. During a timer cycle, if the boiler is at the high limit setting the stoker will not run.

I would check the chimney draft if it is dying in warm weather. Not an uncommon problem, especially with a tight house. Try cracking a window open where the boiler is?

Here are a few threads on outfires:

EFM 520 Outfire Problems
Fire Went Out Twice in 2 Weeks