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[morfem]

This topic has probably already been beaten to death over the years but I have looked in some older posts but have not found what I am specifically looking for.

The question is regarding heat x-changers for Domestic hot water heaters

From what I have been seeing there are 2 types.
Side arm and Plate.

Below are a few assumptions I am following........ Correct me where I am wrong.

Side arm :
Pros-Good for keeping hot water inside tank hot.
Cons- Any new water added to the tank will be cold. Not good for large amounts of hot water.

Flat plate:
Pros - Heats water when adding it to tank.  Good for large amounts of hot water
Cons - If hot water is not used frequently water in tank will cool off.

Is there a way to hook up a heat x-changer to be some sort of hybrid? I would like to be able to use large amounts of hot water and keep the tank hot when not in use?

Use a flat plate to dump hot water in but also use it to keep it hot?

Does it make sense to have both a side arm and flat plate?

[mlappin]

I did a Hybrid system much like you described basically just out of curiosity. My flat plate is after the water heater.

A sidearm doesn’t pull hard at all, never seen any more than a 5 degree drop in boiler water, a flat plate can pull harder than your furnace HX.

You can install a flat plate ahead of the water heater, then just turn the water heater control most or all the way down, if the temp drops far enough in the tank water heater kicks on to reheat it.

It doesn’t take but a few minutes with a couple of hot taps turned on for a flat plate to bring the temp back up in the tank.

[E Yoder]

We use flat plates exclusively. Never had an issue with cooling off as long as they take about two showers a day.

[stmftr]

I have a side arm and have a 10 plate hx piped into the cold line to the 50 gallon water heater and have a bypass piped to it on the boiler side. In the spring and fall under low heating loads I leave the bypass shut and run 100% of the boiler water through the hx. During the winter I open the bypass about half way. The demostic cold fill to the water heater gets tempered to about 80 to 90 degrees. It seems to work very well.  I have a family of 4 and we all can shower and not run out of hot water.

[morfem]

Has anyone done anything like this? Would it work?

Plumb in the lines to the water heater like normal and dump cold water into the tank.

When the temperature inside the tank gets low enough it would kick on a pump to recirculate the water through a flat plate heat x-changer instead of kicking on the electric element inside the water heater.
Pump would then kick off when tank is up to temp.

[Smokeless]

You need a expansion tank in there or your going to blow that tank apart with all those check valves!!!

[mlappin]

Has anyone done anything like this? Would it work?

Plumb in the lines to the water heater like normal and dump cold water into the tank.

When the temperature inside the tank gets low enough it would kick on a pump to recirculate the water through a flat plate heat x-changer instead of kicking on the electric element inside the water heater.
Pump would then kick off when tank is up to temp.

You could, but if your going to add a pump anyways, just install one of those that always keeps hot water in your lines.

Putting the flat plate ahead of the water heater works well enough and its simple. Remember KISS, the golden rule of engineering which all engineers  seem to have forgotten.  KISS, Keep It Simple Stupid.  The simpler you can keep it, the less chances of something going wrong in the future.

WE got to looking at upgrading corn planters, some of the new ones will have an electric motor on each seed meter, so going around a long corner the outside will run faster while as you go to the inside of the circle they will run slower so each row will in theory have a perfect population. In theory it’s great, out in the field surrounded by dust, vibration and moisture its gonna be a gigantic cluster f*ck when one of the connectors in a VERY expensive wiring harness gets a little corrosion. The old planters as long as everything turned, they planted corn, period.

[shepherd boy]

 Yes, we did a few years ago till I learned better. Just preheat it. If it's done right your water heater shouldn't come on. With Marty. if simple works, why put in more stuff to go wrong.

[juddspaintballs]

A flat plate before the water heater will put hot water in the tank.  The tank holds heat pretty well, so if you leave the heater on, it won't take much, if any, energy to keep the water inside hot.  Get one of the water heater blankets to further improve the efficiency of the tank if you must. 

[Crow]

 I have a 20 plate feeding a 30 gallon water tank. Family of four, generally showers taken in the morning. Oil fired water heater gets shut off when the boiler is fired up and have yet to run out of hot water.

[wreckit87]

Has anyone done anything like this? Would it work?

Plumb in the lines to the water heater like normal and dump cold water into the tank.

When the temperature inside the tank gets low enough it would kick on a pump to recirculate the water through a flat plate heat x-changer instead of kicking on the electric element inside the water heater.
Pump would then kick off when tank is up to temp.

My folks have a setup similar to that, but piped between the relief and drain ports like a sidearm would be. Circ pump draws water from the drain port and pushes it across the plate and back into the relief port. There's an aquastat on the hot line to trigger the pump. It's pretty silly in my opinion, when you can just run all cold water through the plate year-round and if the plate doesn't heat it up, the water heater takes over. That's how I always do it anyway