EFM 520 Aquastat

northernmainecoal · Post by **northernmainecoal** » Wed. Jan. 22, 2014 8:39 am

I finished the install of our new EFM520 yesterday. I have programmed the aquastat at the following:
High limit- 195
Low limit- 177
Low limit differential- 12
The boiler is coming on at 195 and shutting off at 185, any idea why this would be? Am I programming it incorrectly? Is it possible there is an issue with the aquastat itself?
Thanks
Rob

GoodProphets · Post by **GoodProphets** » Wed. Jan. 22, 2014 1:56 pm

Are you taking those readings posted from the aquastat or the gauge from the boiler?

Sounds like wiring is not correct.

I am not a wiring genius, so hold tight until pros come to help out.

Fill in your profile with location, etc, it could help in the future

franpipeman · Post by **franpipeman** » Wed. Jan. 22, 2014 2:06 pm

there are many different types of aqua stats what is the manufacture and model number?

northernmainecoal · Post by **northernmainecoal** » Wed. Jan. 22, 2014 2:08 pm

My plumber just called with what he hopes is the answer. The 520 is piped in with my existing oil boiler because of this we are constantly circulating water between the two boilers. In order to do that the TT has to be jumped on the aquastat which is also the reason it is acting funny (that's my understanding of what he had to say at least) Without looking at the aquastat I believe is an L7224A, but I'll double check when I get home

Post by **stoker-man** » Wed. Jan. 22, 2014 3:19 pm

You should move the high and low limit settings apart by 40 degrees or you may have trouble with your fire going out. 20 degrees doesn't work with coal when the temperature is more moderate.

Post by **Rob R.** » Wed. Jan. 22, 2014 4:57 pm

If you short the TT terminals the aquastat will try to keep the boiler temperature at the high limit setting...which is what you are observing. At 195 it will shut down the stoker, when it gets to 185 (high limit differential is fixed at 10 degrees) the stoker will resume operation.

The way your plumber has it setup will work, but I prefer to connect the TT terminals to the end switch of the zone relay(s).

McGiever · Post by **McGiever** » Wed. Jan. 22, 2014 5:02 pm

Is it a typo? He says On @ 195...and Off @185 ???

Post by **Rob R.** » Wed. Jan. 22, 2014 5:11 pm

McGiever wrote:Is it a typo? He says On @ 195...and Off @185 ???

I assumed it was a typo. if not, I have no explanation.

northernmainecoal · Post by **northernmainecoal** » Thu. Jan. 23, 2014 1:17 pm

Yes it was a typo, sorry
To fix the issue we removed C1 and C2 connections and put them on L1 and L2 so if the boiler has power the circ will run. removed the jump from the TT terminals and all is well
thank you

Post by **Rob R.** » Fri. Jan. 24, 2014 4:34 pm

That is fine...as long as the heating load doesn't drag the boiler down to a temperature less than desired.

northernmainecoal · Post by **northernmainecoal** » Fri. Jan. 24, 2014 4:53 pm

Its been working beautifully. The temps here have been 20-30 below with the wind chill this week. Even with constant call from the t stats its been maintaining the LL seemingly effortlessly. I'm considering dropping from 4 teeth to 3