DIY Doctor

Boiler won't Fire With Second Command on Programmer

Postby Moo84 » Mon Sep 09, 2019 5:06 pm

Hello everyone,
Hoping to get some help on an issue.

Y-Plan system
Programmer: Honeywell ST9400A
Boiler: Ideal Logic Heat 15

If no program is selected, and I, for example, select the extra hour function on either the HTG or HW, the boiler fires up no problem. If I turn it off and then select the other function, the boiler shows the 'c' for calling but doesn't actually fire up.

Any ideas?

Thanks in advance.
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Postby ericmark » Wed Sep 11, 2019 6:13 pm

Water too hot in the boiler? The turning off of boiler should allow boiler to run on until cool with most modern systems, but years ago the supply to boiler was turned off.

Looking at https://idealboilers.com/uploads/docume ... vicing.pdf it seems that boiler is OpenTherm enabled so not sure why fitted with a Honeywell ST9400A, I would have expected EvoHome.

But I am an electrician not plumber, maybe a plumber can explain?
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