Fleck 5600SXT for Hydronic Heating

[Tacotime]

My home has a hydronic heating system (Bradford White Combi series combination water heater and two air handlers) and hard water. It's a two occupant home with low water usage, but that may change at some point in the future.

Based off many reviews I read, I ordered an Fleck 5600SXT Softener & Carbon Filter from ABCwaters. I will have a local plumber install it within the next 2 weeks. However, I'm now second guessing this purchase and wondering if I should return it and order a twin tank setup instead. Would twin tanks be better suited for a hydronic system? Something like the Fleck 9100SXT Softener, perhaps?

We only turn on our heating for roughly half the year, but when we do the hydronic system will usually run throughout the night and early morning. Since that is when most people set the softener tank regeneration to occur, I'm concerned that I'll be introducing a decent amount of hard water into the system during regeneration. Is that enough of a concern to warrant a twin tank setup or will a single tank suffice? I'm most concerned with protecting my plumbing and fixtures from hard water.

Appreciate any help!

 

[Tacotime]

I guess another option if I stick with the single tank softener would be to set an automatic schedule on our thermostat to turn off the heat during a small window in the night to coincide with the regeneration process? (i.e. from 2 AM to 3:30 AM or however long it takes to complete)?

 

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[Reach4]

The Combi 1 uses a heat exchanger. https://www.bradfordwhite.com/combi-1-atmospheric-vent-system and Combi 2 uses 2 heat exchangers for redundancy it would seem. https://www.bradfordwhite.com/combi2-atmospheric-vent-system The heating water does not mix with the regular hot water. If the automatic refill turned on during that 1.5 hour window, then some hardness would be taken in. It is my understanding that with a good thermal expansion tank for the heating and with a working valve for topping up the water only when the water pressure drops to a low limit, there would not be any hard water taken in.

Dana has often suggested that you could usually close off the automatic refill valve input to work around a leaky refill valve.

 

[Tacotime]

The Combi 1 uses a heat exchanger. https://www.bradfordwhite.com/combi-1-atmospheric-vent-system and Combi 2 uses 2 heat exchangers for redundancy it would seem. https://www.bradfordwhite.com/combi2-atmospheric-vent-system The heating water does not mix with the regular hot water. If the automatic refill turned on during that 1.5 hour window, then some hardness would be taken in. It is my understanding that with a good thermal expansion tank for the heating and with a working valve for topping up the water only when the water pressure drops to a low limit, there would not be any hard water taken in.

Dana has often suggested that you could usually close off the automatic refill valve input to work around a leaky refill valve.

Thank you for the response! Really appreciate it.

I don't know if it's a Combi 1 or 2, but I know it has an Amtrol Therm-X Span Expansion Tank. Both the Combi and expansion tank were installed new around 1.5 years ago. I'm not sure about the valve for water refill based on pressure, I will have to ask the plumber. I'm assuming that is a standard feature? Sorry, I'm still learning!

 

[Bannerman]

A hydronic heating system normally operates in a closed loop where the 'cooler' water exiting the air handler(s) will be returned to the boiler/heater to be continuously reheated and circulated. Since water exiting the air handler will usually be only a few degrees cooler than when it entered, if that somewhat cooler water was simply discarded, an extreme amount of energy and water would be wasted.

In space heating mode, there normally should be no need for additional fresh water to enter the heater. Since your heater is a combi unit to provide both domestic hot water and space heating, fresh water should only need to enter the heater when hot water is being drawn to your fixtures. Because the unit contains a heat exchanger which will be a separate space heating loop from water for consumption, soft water will be required when the water within the heating loop is to be periodically replaced which will be a manual task for you or someone you hire to perform.

 

[Tacotime]

A hydronic heating system normally operates in a closed loop where the 'cooler' water exiting the air handler(s) will be returned to the boiler/heater to be continuously reheated and circulated. Since water exiting the air handler will usually be only a few degrees cooler than when it entered, if that somewhat cooler water was simply discarded, an extreme amount of energy and water would be wasted.

In space heating mode, there normally should be no need for additional fresh water to enter the heater. Since your heater is a combi unit to provide both domestic hot water and space heating, fresh water should only need to enter the heater when hot water is being drawn to your fixtures. Because the unit contains heater exchangers thereby a separate space heating loop from water for consumption, soft water will be required when the water within the heating loop is to be periodically replaced which will be a manual task for you or someone you hire to perform.

Thank you for reaching out!

That makes sense. It's a relief to know the single tank water softener I ordered should have no issue with my combi heater/hydronic system. On that note, do you think the Fleck 5600SXT Softener & Carbon Filter is a good choice? Any other units I should consider over it?

Really appreciate your time and expertise.