DHW boiler help

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Old 12-07-07, 05:45 AM
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DHW boiler help

I have a Thermo dynamics boiler model S-135 http://www.thermodynamicsboiler.com/....htm#EQUIPMENT . My question is can I preheat my DHW before it goes into my HW heater (electric) to save some money. There is an in and out fittings right behind the Honeywell controller. Are these the DHW hook ups. Do I need a mixing valve? Is there anything else needed to do this?
 
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Old 12-07-07, 06:54 AM
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According to the spec sheet that is a domestic coil, so yes you could use it to preheat water going to your electric. The other thing you could do is just use it to supply your hot water instead of the electric WH or you could also add an aquastat to the WH and a bronze or stainless steel pump and keep the water in the tank heated directly by the boiler instead of using electric but still be able to switch back to electric in the summer if you wanted. Lots of options sir... but for any of them you really should put a mixing valve on top. A Taco 5000 is $100 - cheap anti-scald prevention. It also allows your tank a bit more flexibility. Run a bit lower tank temp through the week (120) when maybe the demand is lower and save a bit and then evict the nasties each weekend at (135), or crank it up (145) to extend the available hot water if you are having tons of company in.
 
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Old 12-07-07, 06:44 PM
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Yeah that was kind of my main thought of offsetting the electric bill and use a mixing valve.
Is that Taco programmable?
 
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Old 12-07-07, 06:58 PM
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Yup... you uncap the green cover and the little triangle on the top of the cap fits into a triangle impression and then give it a turn to the right output.

I'm not sure if it's marked... I managed to get the right temp on the first try and never bothered looking at it with the ol reading glasses.
 
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Old 12-07-07, 08:37 PM
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Do they sell a valve that is able to be actuated and controlled remotely? (Low voltage wired I mean)
 
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Old 12-07-07, 08:58 PM
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I would say not really... there are 3 way motorized mixing valves but they are for heating and are controlled by expensive hydronic controllers.

What you want is something that keeps the temperatures to a given max... regardless of tank temperatures or sudden pressure changes like a toilet flush.

What are you thinking?
 
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Old 12-07-07, 09:16 PM
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Pre-heat

If you want to use the domestic coil as a pre-heater to feed the electric tank & don't intend to supply the faucets directly off the coil, omit the mixing valve. No sense in heating the water then adding cold to it.
 
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