Convert radiant floor heat source to domestic hot water

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ClarkB

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Our gas boiler died and we will replace this summer. We have four zones—three for baseboards upstairs, one for ground-floor in-concrete radiant floor heat. I would like to convert the radiant floor heat zone to its own system with a heat exchanger from domestic hot water source. What’s the simplest way to do this? Obviously will need a circulator pump. Water refill? Air release? Glycol? Expansion tank? Would a heat pump regulate it to a consistent temp (say 68 F) without needing a thermostat? Thanks in advance.
 

Fitter30

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Have any idea how many feet of tubing the floor heat has and size of pipe By using a water heater for both dhw and heat there's two problems. One is your robbing btu's from dhw second is the only way for work around the relay to turn both pumps on. Flow switch makes on flow powers a relay contact opens in heating pumps circuit pumps turn off till dhw flow stops. Timer is used to stop short cycling. Heat exchanger and pump has to be for potable water
 
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Peter Varieur

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Our gas boiler died and we will replace this summer. We have four zones—three for baseboards upstairs, one for ground-floor in-concrete radiant floor heat. I would like to convert the radiant floor heat zone to its own system with a heat exchanger from domestic hot water source. What’s the simplest way to do this? Obviously will need a circulator pump. Water refill? Air release? Glycol? Expansion tank? Would a heat pump regulate it to a consistent temp (say 68 F) without needing a thermostat? Thanks in advance.
I have a 5 loop radiant system around 1500 feet of 1/2" pex. I have an 80 NG hot water heater with a heat exchanger, it's plumbed pretty much like a boiled. It's been running for 2 seasons. I live in NH so it gets cold. I did pour light weight cement over the pex and ceramic tile for flooring. It works great. I have a circulator for the heat exchanger set with a thermal switch so it doesn't run all the time. I have another circulator for the 5 loops. my highest bill for gas which includes heating, domestic hot water, gas dryer and gas stove was $267. I keep the house at 70. I'm 75 and have tried water to air, hot water baseboard in other houses I've owned and this is by far the most comfortable and efficient.
 

Fitter30

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1500 ' pex x 32= 48k btu's approximately. Pump ,expansion tank, fill , relief valve and you have multiple zones. Their heat loads can't be all the same. Might need three pumps one for w heater, one for primary loop and one for secondary loop and zone valves. How were you controlling it with the boiler? What water temp were you running?
 
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