how to test honeywell 8148e aquastat

Old 09-20-10, 09:22 AM
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how to test honeywell 8148e aquastat

Hello everone, I went to fire up my boiler this weekend and it would not fire up. I removed the cover from the aquastat pulled in the relay contact and it fired right up, zones opened, dampner opened, and circ pump turned on. When I let go of the relay it all shut off again. I was thinking it was the aquastat, but now im not so sure!

I removed the aquastat and am in the process of bench testing it. But I do not know where to begin. I have 120 volts at the line in(L1 and L2), and 24 volts to the secondary leads of the transformer(T2 and T1).
I read on here about jumpering TT, I do not have a terminal named TT.

The terminals for the thermosta is TV, W, T, and W??? thanks for any help, Aaron
Old 09-20-10, 02:55 PM
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Hi Aaron, a good number of aquastats have thermostat terminals that are designated T T , but your's doesn't. On your model the thermostat connections are labeled T and TV .

I hope you made notes or took pictures of where the wires go!

Let's start by giving you a link to the book for your aquastat:

You really didn't need to remove the aquastat to test it...

With 120 VAC applied to L1 and L2, if you jumper T and TV the relay should pull in. That's about all you can do with it on the bench.

When you manually pushed the relay, you said "zones opened"... how do you know that? Because if you have zone valves, they would not have opened when you pushed the relay.

My advice: after you determine that the relay does pull in on the bench, re-install the aquastat.

What make/model are the zone valves? How many ?

When you tried starting the boiler up, did you try EACH of the thermostats? If not, do that next. It is possible that only ONE of the zone valves is malfunctioning.

Each thermostat operates one zone valve. When the thermostat calls for heat, the associated zone valve should open. The thermostat only 'talks to' the zone valve, and the zone valve passes the message along to the boiler via it's 'endswitch'.

Each zone valve has what is called an 'endswitch' that signals the boiler system that a zone valve has opened, and is calling for heat. These endswitches are wired in parallel, such that if any ONE or MORE calls for heat, the boiler will get the hint and fire up. If you have one bad endswitch, and that was the only one you tried, the others will probably be OK...

Time for the obligatory silly question: Did you change the batteries in the thermostats?

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