No Hot Domestic Water in FHW Oil Burner System

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Old 03-29-15, 01:22 PM
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No Hot Domestic Water in FHW Oil Burner System

It has been a record-setting cold winter. My hot water has been slowly diminishing as winter progressed. I now only get warm water. My mixing valve is turned all of the way to 160 degrees. Setting it lower provides only cold water. Turning the hot water on does not call the furnace to come on. I have four heating zones in my home that provide adequate heat and all appropriately start the furnace when they call for heat. The furnace temp range is set at 175 for low and 200 for high. If I turn the hot water on after the furnace has been running, I get hot water for about 3 seconds, then I just get warm water. I know that getting hot water directly from my 20 year old oil furnace is inefficient, but what can I do for now to get hot water again?
 
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Old 03-29-15, 03:27 PM
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Could be the thermostat in your mixing valve has gone bad.

Is the pipe coming out of the coil and into the mixing valve HOT?
 
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Old 03-29-15, 04:00 PM
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The pipe directly out of the furnace is hot, but it turns only warm after the bend just before the mixing valve.
 
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Old 03-29-15, 04:08 PM
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There are a couple possibilities...

The coil could be 'limed up' internally and unable to transfer the heat from the boiler, and suffering low flow.

The mixing valve could be kaput. What's the make/model of it?
Are there sufficient valves to isolate the mixing valve in case you need to replace the 'guts'?

Do you know the hardness of your water?
 
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Old 03-29-15, 04:28 PM
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I have sufficient shutoffs on each side of the mixing valve. I'm on a well and have hard water. I have a softener system now, but the furnace ran for 10 years without one. The mixing valve is a TACO 508-4. Can I just unscrew the brass fitting on the top of it or does the whole valve have to be replaced?
 
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Old 03-29-15, 05:27 PM
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I THINK this is the element for your valve, verify before purchase!

507-046RP - Taco 507-046RP - Thermostatic Valve Element

Yes, you take the top off, replace the thermostatic element only...

No guarantee that this is what's wrong, but it's basically a 50-50 gamble, and it's easier to try this first than have your coil 'acid boiled' to get the minerals out. You may still need to do that too, so keep that in mind.

The times I've been up yer way I've found the well water to be pretty soft. Maybe different areas have different water? I was in York County mostly.
 
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Old 03-29-15, 05:43 PM
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That appears to be the right element. I'll give it a shot and post here afterwards. It doesn't look like I'll find one locally, so it may be a few days.
Thanks
 
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Old 04-01-15, 10:48 PM
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I received the part today. It was not an exact match to the existing piece, but it looks like it will work. It was a very easy install. The old one came off very easily. I instantly had more hot water, but it doesn't stay hot for long. Setting the mixer to the lower end of the temperature range seems to keep the water hot a little longer.
 
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Old 04-02-15, 07:13 AM
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It's important to limit flow through the coil. That's why setting the mixer to a cooler temperature is allowing the water to stay hot longer. You are mixing more cold with the output of the coil, and limiting the flow through the coil.

Even under the best of circumstances, with a new clean coil, you can't expect the water to stay hot with gushing unlimited flow simply because those coils aren't rated for that... they have a GPM rating at which the will provide continuous hot water, and that rating is usually around 2 GPM. Many have a flow restrictor built into them.

In addtion, your coil is probably also 'limed up' which adds insult to injury.

Try a flow restricting shower head and see what happens...
 
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Old 04-02-15, 10:28 AM
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Watts #lfp3 is nice for a adj. flow restrictor at the coil when needed.
 
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Old 12-06-15, 06:40 PM
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Is problem solved?

did your problem solve? I have similar situation and I solved mine with coat of silicon on 'O' ring and middle sliding part.
 
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