Indirect water heater replacement

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ekd4176

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I currently have a Burnham AL53A indirect water heater that is leaking and I would like to replace it. I am considering a Burnham AL50SL but as I look at the wiring, the TPI calls for 24v power but I don't know where to get that from. The current setup has a single thermostat wire from the water tank Aquastat that goes to a Honeywell YHR845A switching relay that runs the Taco circulator.

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ekd4176

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I have located a 24v transformer in the mechanical room. Tested with a meter. Would the Burnham TPI simply need a wire ran from the transformer to the unit to keep it powered?

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ekd4176

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I have reviewed that several times and my take away from it is that I would no longer need the Honeywell YHR845A and just run the 24v line from the transformer and then hook the circulator up to the TPI? Forgive my ignorance but does the Honeywell YHR845A do what the TPI will now do by itself?

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Bannerman

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It appears you are referring to the upper wiring diagram on page 14. How is the boiler controlled?

If planning to eliminate the YHR845A, you will need to ensure the TPI's 120-volt pump circuit current rating will be sufficient for your pump's current draw. If you continue to use the TPI to control the YHR845A, then the TPI will only need to switch 24-volts to control power to the switching relay's low current magnetic coil and the relay's higher current rated switch contacts will control the load of the pump.
 
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ekd4176

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Boiler is controlled with a Honeywell L8124A. The circulator is a Taco 007 which I believe is rated for 115v. Boiler runs 3 zones of heat as well as the domestic hot water. It appears that it is setup to treat the domestic water as its own zone.

I wasn't necessarily looking to eliminate the YHR845A in fact, I would rather keep it because of some issues with the TPI I have read. If it fails, I would like to put a Honeywell Aquastat on the tank and run it similar to how its currently configured.

In that situation, connect the TT on 845A to the TT on the TPI and run a new line from the transformer to the 24v in on the TPI?

Thanks
 

Bannerman

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my take away from it is that I would no longer need the Honeywell YHR845A
From this I took it that you were planning to eliminate the YHR845A.

Since the YHR845A appears to be equipped with its own 24-volt transformer, there should be no need for the separate 24-volt transformer you mention.

See wiring diagram for YHR845A on page 4. The T-T thermostat terminals are the 24-volt output.
https://www.google.com/url?sa=t&sou...FjAAegQIARAB&usg=AOvVaw2lB9teh_WncbqvJ5zNP1Xz

While you said your Taco pump is rated for 115 volts, that is not current draw (power consumed) which will be rated in watts or amps.
 
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ekd4176

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The pump is stamped with .70 Amp.

Not sure if I am reading this correctly but the diagrams in the link specially say to use a separate transformer if trying to supply low voltage as a second load.

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Bannerman

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The T-T connections are intended to feed a thermostat which is a temperature-controlled switch used to activate the relay coil on the YHR845A. When the thermostat contacts are closed, the YHR845A relay coil will be powered, then the relay contacts for the pump circuit will close causing the pump to become powered. From your description, it seems the TPI is the thermostat to control the circulator pump using the YHR845A.

Because the YHR845A is capable of controlling 2 circuits at the same time using contacts 3-4 & 6-7, 3-4 will be utilized for controlling (switching ON/OFF) line power (120 volts) for the pump, and 6-7 could be utilized to control power for another 120-volt device OR for a 24-volt device such as a humidifier or low voltage gas valve. Because terminals 6-7 are not powered by the YHR845A, the alternate device is required to utilize its own dedicated transformer.

This link provides various wiring configurations for the Honeywell L8124A: https://images.homedepot-static.com/catalog/pdfImages/71/71b8fcd9-eb3a-476a-8aac-6153ba78e6e7.pdf
 
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