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Author Topic: furnace then water heater or water heater then furnace?  (Read 615 times)

Gunpowder

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furnace then water heater or water heater then furnace?
« on: December 18, 2016, 09:40:38 AM »

Stupid question probably but Central boiler shows running lines first to water heater and then to furnace and then back to OWB. I am actually wanting to run it to the furnace and then through a bypass valve and on back to the OWB. The water heater may be added at a later date via the bypass valve.

Does it matter whic gets the heat first?
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mlappin

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Re: furnace then water heater or water heater then furnace?
« Reply #1 on: December 18, 2016, 10:54:13 AM »

Youíll want the water heater first, Iíve heated the house with 120 degree water before but 120 degree water makes for a cold shower as no heat exchanger is 100% efficient.

Water first, even if it pulls twenty degrees out of the water, youíll still get sufficient heat for the house.
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BIG AL

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Re: furnace then water heater or water heater then furnace?
« Reply #2 on: December 18, 2016, 04:27:23 PM »

Agreed! my boiler has gone out and heated the house with 110 degrees supply temp , but it would take a lot more to heat up your dhw. Doesn't take much to keep a radiator warm but when you are relying on a heat exchange to heat up water that is say 55 degrees coming in , that takes a lot more to make it happen in a short time.
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Gunpowder

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Re: furnace then water heater or water heater then furnace?
« Reply #3 on: December 18, 2016, 04:32:43 PM »

actually it is for the office/nature center here at work. House comes next summer as a second loop. The gas water heater burner is shot so it hasn't ran for several years (original to the '95 restroom addition). Was thinking tankless replacement to free up room for a water softener but a tank would be much easier to exchange heat with.

I only will be heating (4) sinks and the water from the water closets we use to hose down restrooms. So the hot water demand is minimal. almost not worth running if it werent for free heat being 3 feet from future water heater. frankly I have been running cold for so long that only reason I am considering it is because of the plumbing I am doing in there for the OWB.
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slimjim

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Re: furnace then water heater or water heater then furnace?
« Reply #4 on: December 19, 2016, 01:31:54 AM »

You will be happier with the gas wall hung and they are not at all difficult to plumb in.
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Gunpowder

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Re: furnace then water heater or water heater then furnace?
« Reply #5 on: December 19, 2016, 10:01:46 AM »

I have a takagi LP in the house. I also have 2 electrics for showers in a different public restroom facility. I was actually thinking of going with electric. Since it is on demand and not used often it would be cheaper overall to install, easier to install,  and use is minimal. electric is about as cheap (or expensive) as LP around here.
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RSI

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Re: furnace then water heater or water heater then furnace?
« Reply #6 on: December 19, 2016, 10:52:28 AM »

If you only need / want hot water when the boiler is running then you could just skip having a water heater completely. You can use a plate heat exchanger to supply all the hot water you want while the boiler is running.
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patvetzal

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Re: furnace then water heater or water heater then furnace?
« Reply #7 on: April 17, 2017, 02:55:17 PM »

We have two houses fed off the same P&M boiler. In both cases I used a three way valve to split the flow between house heat and domestic hot water. As long as the boiler was above 150F, it didn't much matter but this spring the temp started dropping to 120 for most of the day (wet wood) and we had to watch water usage. The boiler would get up to 170 towards the end of the burn (5am and 4pm) and the water tanks would get hot but when they refilled the boiler with wet wood and the boiler temp dropped to 110-120 we were not producing hot water so what was in the 40 gallon tanks was all we had for that cycle.
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