Looking for help with efm 520 timer not turning on boiler.

[Walt Drake]

Replacd timer hooked back up to rz and not starting. I've had this boiler running for over 15 years and never had a problem. Even changed the Honeywell aquastat out. Any help would be greatly appreciated.

[Rob R.]

Get a voltage meter and verify that everything is wired correctly.

When your timer is ON there should be power at the ZR terminal. If there isn’t, your timer is likely wired wrong.

[davidmcbeth3]

Get a voltage meter and verify that everything is wired correctly.

When your timer is ON there should be power at the ZR terminal. If there isn’t, your timer is likely wired wrong.

Wires get loose as well. Might as well check the tightness of the connections.

[Walt Drake]

I unhooked wire from zr and getting voltage from zr,the wire coming from timer is turning on and off fine with power.

[Rob R.]

What is the aquastat high limit setting and the current boiler temperature?

[Walt Drake]

It is shut down couldn't keep it running with the warm temperatures. I have the high set at 190 and when it was running it would shut off at 190 and creap up to around 195-200. My question is should the aquastat be hot at the zr with the timer sending power to it?

[Walt Drake]

What I'm trying to say is that there's power coming from both the zr and the switch at the same time and when I separated them, both sides are reading 115 volts.

[Rob R.]

It is shut down couldn't keep it running with the warm temperatures. I have the high set at 190 and when it was running it would shut off at 190 and creap up to around 195-200. My question is should the aquastat be hot at the zr with the timer sending power to it?

Yes. The NO terminal in the timer is connected to the ZR terminal in the aquastat, so if you have power at one you will have it at the other.

It sounds like your issue is the boiler runs hot and skips timer cycles. EFM recommends running the high limit at 200. You may need to tweak the feed and air a bit also to keep the fire alive without overheating the boiler.

[Walt Drake]

I will try setting it at 200 but if I'm running at 190 for 15 years and never had an issue you're saying it's running to hot then why would I set it even higher? I just don't understand why I have power coming from zr and also from the timer when it turns on.

[Walt Drake]

When the timer and the zr are separated there's power at both terminals.

[Walt Drake]

There was a jumper on the t t so undid them and now it is running on the low limit on the aquastat with the timer working.

[nepacoal]

That would do it... Just an FYI. ZR is in the burner circuit and would have voltage on it if the burner relay was closed (jumper on TT would activate burner relay) or if the low limit tripped and the normally open side closed and put voltage on ZR. See diagram below:

[Walt Drake]

Thank you so much I've been going crazy its worked with no problem ever.so should I leave the t t undone and run it on the low limit set at 190?

[nepacoal]

I'd run it with no jumper and set LL at 160 and the HL at 200. Timer would work up to HL.

Can you use a thermostat or is it a remote setup with constant circulation?

[Walt Drake]

I have the timer set for 2 minutes every 1/2 hour. The high limit is 200 and the low is 180 with the dif at 10. So it's been running up to 180 and shutting off and firing back up at170. Should I change the dif to 15 or 20?