Home Radiant Floor Heating- issue with getting hot water


Old 03-27-18, 07:26 AM
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Home Radiant Floor Heating- issue with getting hot water

We live in a home where the previous owner installed raidant floor heating throughout the entire house. It worked fine for the first year we were in the home, but for the last few weeks we have had problems with getting our domestic water (shower, sinks) to heat up. I've found that if I increase the thermostat for our upstairs then I'll have hot water for my shower (shower is located upstairs). This seems to be the only way to get our water to be hot. The problem is that we don't plan on having our heat on all year (just when it is cold out) and this wasn't a problem before. All of the plumbers we contact do not understand the heating system. Has anyone experienced this before and know how we can resolve?
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Old 03-27-18, 08:38 AM
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Is this a tankless hot water heater?
Old 03-27-18, 09:31 AM
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Welcome to the forums.

Your thread has been moved to the boiler forum.

You have a boiler with a tankless coil in it for hot water. That coil is heated by the same hot water that heats the house. The hot water inside the boiler is much hotter when the boiler is supplying heating water for the house. This is one of the most common system around. Any plumber that works on boilers should recognize it.

If the boiler had been supplying enough hot water then the tankless coil may need to be cleaned.
Old 03-27-18, 11:53 AM
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With the limited info provided I agree with PJ. Tankless coils get limed up and it acts as insulation inside the coil so it stops the boiler water from heating up the cold water going through it and must cleaned or replaced.

What you can do is raise your temp control settings on your boiler to raise the hot water temp in the boiler as it is when the heat is on and then you don't have to run your heat.

You should have a high and a low setting on you control. Try raising the low up 10 deg and start from there until you get your hot water back. Whatever you do to your low you must also do to your high limit. If you raise your low 10, then you must raise your high the same amount keeping them 20 deg apart.

This is only a band aid until a permanent solution is made.

Just my thoughts. Hope this helps a little.
Old 03-28-18, 07:36 AM
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Don't they usually install thermostatically controlled heat exchangers on systems like that, so that the floors don't overheat when you want the water to be hot enough for a shower?
Old 03-28-18, 08:43 AM
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Basically the water temp to the radiant heat is controlled with a mixing valve since the water temp is cooler to the radiant than it is with conventional baseboard heating.

All this does not effect the temp of the boiler water. Everything is separated after it leaves the boiler if need be.

Hope this helps a little.
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