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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Hz311 and nest how to reset fuse on hz311
, I have an

Customer Question

Customer: hz311 and nest how to reset fuse on hz311
JA: Thanks. Can you give me any more details about your issue?
Customer: I have an hz311 just for heat with two thermostats I rpelaced on thermostat with nest - works great the first thermostat had two wires white and red - no common bc the thermostat had its own battery - so I connected the common which was not connected to the hz on both sides this worked great (and is still working) I then hooked up second thermostat - but it had a green wire also - supposedly for fan call the second thermostat also did not have common much online says hz311 and nest needs common
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Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
want to fix - quick question is where is resettable fuse on hz311
Expert:  Phil replied 1 year ago.

There is no resettable fuse (or breaker) on the Hz311 zone controller.

If you would like some electrical systems engineering help, that will take me about an hour and cost you $60 additional I will submit an additional service offer for that, you acceptance is optional.

Customer: replied 1 year ago.
If you google resettable fuse and hz311 all the vendors say there is a resettable fuse - are you sure?
Customer: replied 1 year ago.
I checked power at the HZ311 Rh and common and get 24V - so, I will disconnect wire to thermostat plate (thermostat is removed) and see if there is a short - if so, I will splice wire.
Expert:  Phil replied 1 year ago.

Hello again,

these systems are best diagnosed with your particular wiring diagram in hand.

Next please attach a well focused, close up photo of the wiring diagram glued inside the service panel of the zone controller, and also a picture of how you have the zone controller wired, the picture needs to be taken from straight on, in very good light.

You can use the paper clip- icon at the right end of the tool bar at the top of this dialog box to attach it here.

If there is no paper clip-icon, look for the '+attach files' link at left of your send button.

I can mark it up with trouble shooting instructions.

We can go from there.

We can go from there.

Customer: replied 1 year ago.
pretty simple wiring - 5 wires from each thermostat to HZ311 transformer wires (2) to HZ311 DATS wires to each damper - and two damper control wires - Hcall line to furnace - have been through all HZ311 manuals I can find online to know where the fuse reset is - system has been workgin fine for 2 years - NEST requires common - prev thermostat was bettery operated with no common - hook up common and no workie workie
Expert:  Phil replied 1 year ago.

Hello again, I have been at this for 51 years so far, 21 years consulting nationally for fortune 500 companies, now I am retired and have been here for 6 years. (98.8% success record, not 100% however.)

A wiring diagram tells all. I have never seen a reset on the HZ311, but I only see 4 or 5 a year these days, I will take a look for you.

Use the paper clip icon to attach the diagram, or the attach files link to the left of your send button, and tell me which NEST model you have, we can go from there.

Expert:  Phil replied 1 year ago.

Those references regarding a fuse reset etc appear to be from laymen referring to their breaker box or in the case of oil burners the reset button on the oil burner.

Get me the diagram and wiring photo's I need, we can sort this out in no time.

Customer: replied 1 year ago.
No, if you google resettable fuse and HZ311 the product docs from Honeywell and others point out a feature of a resettable fuse. I appreciate your experience, but if you really don't have any experience with this device and have not taken the time to google as I mentioned and look at the prdjuct literature online as I have - I am not sure that it gives me confidence to pay $60 to let me know where the fuse or resettable fuse is in the panel.
Expert:  Phil replied 1 year ago.

Hello again, I see that none of our other several dozen HVAC experts here have picked up your question.

I notice that Honeywell does mention a resettable fuse, but does not show it anywhere, and I myself have never had an occasion to use the feature.

It is most probably that you simply made a wiring error when connecting the C wire... thats common an issue I deal with and solve all the time.

My situation is that after 51 years in the business and consulting nationally, most of the last 20 years on large scale projects for IBM, Texas Instruments, the US dept of Energy etc (nuclear safety controls issues) and a few of the major manufacturers such as Trane and Carrier...

....that, unfortunately of all the virtually hundreds of thousands if not millions of pieces of equipment ever built, I have only seen maybe 1% of them in person, and even at that, considering the array of defects that can develop I might have seen and corrected way less than 0.0001% of those defects.

I rely on my basic understanding of the various disciplines involved, that has worked out well for myself and others over the years.

Let me know if you if you want to continue, in that case attach a photo of how you wired the thermostats to the hz311 and where you picked up the 24v common.

we can go from there if you like, I will need you to accept the additional service offer in that case however.

Customer: replied 1 year ago.
I fixed it - the AC contractor neglected to splice all of the wires at a splice joint under the house - just the ones the needed red and white. I spliced the blue common and everything is working fine. Thanks - Jeff
Expert:  Phil replied 1 year ago.

Good work Jeff!