Indirect water heater install questions


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Old 12-16-09, 06:59 PM
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Question Indirect water heater install questions

I currently have an oil fired hot water baseboard heating system with two zones. Domestic hot water is provided by a tankless coil in the boiler. I want to change this to an indirect water heater (Buderus S 120). I know I will need an additional zone valve but how do I disable the current aquastat in the boiler and connect the new aquastat from the new indirect water heater. The domestic coil will be capped off and bypassed. My current system uses two zone valves (Honeywell V8043E) and a Honeywell Triple Aquastat Relay (Type L8124A,C L8151A) mounted on the boiler. Both zone valves are connected to their own thermostats and share a common transformer. Any help would be appreciated.

I was also wondering if it makes sense to install the new tank near the bathrooms (on the other side of the basement from the boiler). Would this allow for quicker supply of hot water to the faucets?

Thanks,
-Adam
 
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Old 12-17-09, 02:51 PM
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Hi Adam... welcome to the forums!

The domestic coil will be capped off
No, don't do that. You don't want to seal the coil closed... either leave the pipes from the coil open, or if you want a neater look, drill a small hole in the cap for pressure relief.

how do I disable the current aquastat in the boiler and connect the new aquastat from the new indirect water heater.
You don't disable the boiler aquastat. That needs to stay right where it is, and working.

The aquastat from the indirect should have two wires, just like your thermostats. Those two wires will go to the new zone valve the same way your thermostats do. The red wires from the new zone valve wire in parallel with the other red wires.

wondering if it makes sense to install the new tank near the bathrooms
If you have room, put it there... makes sense to me! Pay attention to piping a 'heat trap' on the hot outlet of the tank. The hot water outlet pipe should come off the top of the tank, and elbow DOWNWARD for about a foot, then elbow over and up to the domestic piping. This will prevent the hot water from the top of the tank from 'floating' up the pipe and increasing 'standby' losses. Maybe rbeck will stop by with a link to a drawing example.
 
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Old 12-17-09, 03:02 PM
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Here's a basic diagram of how your existing valves are wired:



'Extend' this drawing by one more valve, and think of the aquastat on the indirect as the thermostat.

I'm still debating with myself about the location of the water heater... if the heater is next to the boiler, there will be less standby losses in the piping from the boiler to the heater... but long runs to the point of use... so you will have to run the taps for a while before you get hot water... on the other hand, moving it closer to the point of use, you get shorter time before the hot makes it to the taps... reducing wasted energy in the domestic piping... but slightly higher loss in the pipe to the heater from the boiler... so, insulate those pipes. I think it's definitely less wasteful to move the heater closer to the point of use. Don't skimp on the pipe size from the boiler to the water heater! Follow manf instructions! Recovery time of the water heater will suffer if the pipe is too small... ONE INCH pipe is probably the right size. If you use 3/4", you will be limiting your flow, and that means less BTUs into the water heater.
 
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Old 12-18-09, 01:54 PM
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Thank you! The explanation and wiring diagram are a huge help, I have one more question now that I have a better understanding of how everything will work. Would it be ok to lower the LO temp setting on the triple aquastat? A pseudo cold-start setting? The ultimate goal here is to provide more hot water but reducing oil usage would be a good benefit if its possible. I've decided not to install the tank near the facuets, maybe in the future I'll move it but it will add to the cost and time of install.

Thanks for all the help!
-Adam
 
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Old 12-18-09, 02:49 PM
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Would it be ok to lower the LO temp setting on the triple aquastat?
Yes, definitely... turn it all the way down, but keep the DIFF setting at like 20 or so... keep the HIGH setting where it is (180 usually).

In the future you could opt to replace the boiler aquastat with a cold start unit, but be aware that some boilers have a tendency to 'weep' when they have spent long lives as warm start and then allowed to go cold. If the replacement boiler aquastat were an L7224U, you have the option of turning on or off the LOW limit circuit.
 
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Old 12-18-09, 02:56 PM
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Aaron, I'd like not to see the OP's thread 'hijacked', in spite of the relevance... so, I'm going to move your post into the thread that you started with some other questions... check in there for replies...
 
 

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