# Prioritizing Pair of Indirects - Advice Needed from an Expert or Two



## Litawyn (May 16, 2011)

Hey folks,

I'm hoping a couple of you experts can offer me a little guidance. I'm soon to begin the process of having a new home built for myself that will be heavily insulated and relying primarily on a solar thermal system and a wood pellet boiler for space heating and for DHW. I'm talking to potential plumbing subs this week. One indulgence I'm allowing myself is a 6-head shower system that will have the capacity to bleed through a lot of hot water--as much as 15 gpm when all of the heads are going full bore. Although I'll probably never be using more than 10 gpm at a time, I still want to size the system to be able to provide a good long shower @ 15 gpm. 

My questions are about indirect water heaters. I've resigned myself to the fact that my best solution is going to be to have 2 - 120 gallons indirects, with one connected to an 80-evacuated-tube solar thermal system and the other to a 32 kW wood pellet boiler. I'm also assuming that I'd go with the solar tank as a pre-heat, and rely on the wood boiler tank as the primary source of DHW. What I don't understand are the following:

1) Do I go with single coil tanks for each indirect, or should the tank for the boiler be a dual coil, using energy from the solar thermal system as well?

2) If I go with a dual coil for the boiler, can the tanks be configured so that If it's a cloudy day that some of the hot water in the boiler tank can be moved in the opposite direction to the solar pre-heat tank, just to maximize the amount of hot water I could store up for a good long shower? My goal with the indirects is to get each tank to 190F before a shower to give me as much hot water as possible.

3) I'll be using a GFX shower drain heat recovery coil to recover some of the energy that would otherwise go right down the drain. Should the water being pre-heated by the GFX go solely into the solar tank? Would this pose any potential problems?

4) The house is going to be heated primarily via a radiant slab in the garage and six hydronic wall-mount radiators throughout the living space above it. Off of which tank would the water for the radiant systems come? I'm looking at heating the radiators with an EWT of 130F. Could water going into the radiant slab in the garage be at the same temp, or would that just cause problems? 

5) Finally, I'm likely to have days where the solar thermal system is producing more energy than either of the indirects is able to absorb. Rather than going with a dump tank and wasting that energy, could I somehow have it transferred to the garage slab or (in the colder months) to the radiators in the living space without causing problems or making the system way too complicated or costly?

A lot of questions. I'd really appreciate it if a couple of you plumbing experts would give me your 2-cents. Much appreciated.


John


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## easttexasplumb (Oct 13, 2010)

Get yourself on of them fancy new Hybrid water heaters, it should run the whole house on those cloudy days.


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## SewerRatz (Apr 25, 2009)

Thanks for posting on PlumbingZone.com.We would prefer if you post Do It Yourself related topics on our sister site www.DIYChatroom.com 

PlumbingZone.com is designed for professional plumbers to discuss issues and topics related to their profession. Many of our plumbers are also members at DIYChatroom.com and are looking forward to assist you with your needs.

Please take a moment to post your question at www.DIYChatroom.com If your not already a member of DIYChatroom.com you can sign up for a free account by going to http://www.diychatroom.com/register.php/


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## ap plumbing (Nov 9, 2010)

go green . u think the packers use those new hybrid water heaters over there in wisconsin .there are alot of cloudy days over there:laughing:


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## Litawyn (May 16, 2011)

SewerRatz said:


> Thanks for posting on PlumbingZone.com.We would prefer if you post Do It Yourself related topics on our sister site www.DIYChatroom.com
> 
> PlumbingZone.com is designed for professional plumbers to discuss issues and topics related to their profession. Many of our plumbers are also members at DIYChatroom.com and are looking forward to assist you with your needs.
> 
> Please take a moment to post your question at www.DIYChatroom.com If your not already a member of DIYChatroom.com you can sign up for a free account by going to http://www.diychatroom.com/register.php/


SewerRatz:

I will post over there too, but I want to be clear here that I'm not a DIY'er. I simply want to better understand the efficiency of a potential system. This is work that will be handled by a professional plumber, not by me.


John


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## Litawyn (May 16, 2011)

easttexasplumb said:


> Get yourself on of them fancy new Hybrid water heaters, it should run the whole house on those cloudy days.



Could you be more specific? What "fancy new Hybrid water heaters" are you referring to? Make? Model?


John


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