Different boiler controller needed when eliminating a tankless water coil?

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Old 10-30-13, 10:34 PM
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Different boiler controller needed when eliminating a tankless water coil?

I have a Utica Starfire 3 that was in my house when I bought it. It's one of two furnaces in the house (2 family house). It has a tankless coil built into it for hot water for one tenant. I just recently installed a new water heater because the tankless just wasn't able to deliver the necessary hot water and I don't like firing up the boiler all summer to provide hot water.

I want to keep the changes to the boiler minimal, so I would prefer to leave the tankless coil in. It will be bone dry inside because it isn't hooked up to the water system. I'm a little nervous to do it because I know that the Starfire 3 has a different temperature controller for units with a tankless water heater installed and ones without.

I have 3 options:
1. Install the new controller, remove the tankless coil
2. Plumb the tankless coil back into the plumbing system, just shut off the feedwater to it.
3. Stop worrying about it and trust that the temperature controller won't be negatively effected by the lack of water in the tankless heater.

Any input on this would be helpful.
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Old 10-31-13, 07:18 AM
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1. Install the new controller, remove the tankless coil
Some models of aquastat (controller) are easily modified to operate as 'cold start'.

In any case there is no reason to 'remove' the tankless coil, simply disconnect the piping to the tankless coil. Do NOT solder caps to the pipes coming out of the abandoned coil, but rather just slip fit them on.

2. Plumb the tankless coil back into the plumbing system, just shut off the feedwater to it.
There is no reason to do this. Potable water systems should not have 'dead ends' in the plumbing where 'creepy crawlies' can breed.

3. Stop worrying about it and trust that the temperature controller won't be negatively effected by the lack of water in the tankless heater.
If the aquastat (controller) is not modified, the boiler will continue to cycle on it's own in order to keep itself warm and use fuel needlessly.
 
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Old 10-31-13, 07:19 AM
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What is the model number of the aquastat controller that is installed on the boiler now?
 
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Old 10-31-13, 01:55 PM
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The one currently installed is a Honeywell L8124A. Here is the spec sheet on the two different controllers:

https://customer.honeywell.com/resou...0s/63-9419.pdf

Good point on not plumbing the water back into the system. I hadn't factored in things growing in the lines.
 
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Old 10-31-13, 04:11 PM
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I hadn't factored in things growing in the lines.
Legionella is one thing... waterborne 'cysts' are another...

Legionella - Let me google that for you

Water-borne cysts - Let me google that for you

Here's how to modify an L8124 to operate 'cold start':

 
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