I've considered adding a system like this one to heat my domestic hot water. The system requires the removal of the anode rod from the hot water heater. Does anyone know the purpose of the anode rod, what exactly does it do?

anode-removal

The anode rod is made of sacraficial metal.It alows the agresive water to attack it rather than the water heater.It's there to protect the water heater.Your warrantee on the water heater will be void without it.

We did a setup like this (central boiler)not long ago and if memory serves we added a tee under the relief valve and piped it in there.DO NOT just remove the relief valve.

This setup relies on gravity convection of hot water and at the time we questioned the effectivness of it without a pump.the customer hasn't complained so I guess hes getting enough hot water.

The relief valve port should not be utilized for any other purpose. Adding a Tee moves the probe out of, or almost out of, the tank where it is supposed to be "seeing" the hottest zone of storage. Installing a T&P with a longer probe is not a remedy if flow has the potential to enter the tank at this point - bathing the probe in lower temperature water. Like most things in the trades, hot water safety was learned the hard way.

Perhaps the thing to do is replace the ordinary anode rod with a combination rod, i.e. one of those rods that serves as both the hot water outlet port and anode rod below that. Then you wouldn't need to alter the relief valve set-up in any way.

Check waterheaterrescue.com. They can probably tell you which manufacturers use the combination rods.

I just checked. The folks at waterheaterrescue sell the combination rods.

I am not affiliated with them in any way. They just seem to know what they're talking about. Good luck with your project.

[This message has been edited by JamieR (edited 02-09-2005).]

how old is the tank. If it is 5 years or more....

Most of the high recovery tanks have 2 additional side taps for hydronic use. You might consider one of these if you want to replace or upgrade now.

Extended shank T&P are an option as Dave mentioned under the correct conditions.

Triangle Tube, and Viessmann indirects come with a tee and long stem T&P as do many others.

hr

Dave,
I repect your knowlage of water heaters but like HR said many tanks are equiped like that from the factory.We do Viessmann's and Triangle tube that way all the time,with extended prode relief valves.

The water comming from the flat plate will most likely be hotter than the water in the tank.

No problem John. But the potential is there none the less for someone to inadvertantly connect the cooler return side and a gravity flow could keep bathing the probe in cooler water. If the factory provides it that way, the liability issues are theirs to bear. If I alter the connection, the liability issues would seem to be mine to bear. I should add I'm less than thrilled by the factory-provided short-cut for that application and we've installed several. In each case, they were virtually guaranteed to be in the hot water outlet, but a creative piping arrangement could easily compromise safety.

Thank you all for your replies. I think the answer I like the best is using a "combo" anode rod. I would just simply replace the factory anode with the combo and be able to have an open port and anode all-in-one. I then won't have to mess with the pressure relief valve. My thanks to the person who suggested that, your link was a big help. I also may be adding a pump to the system for faster recovery.

Can anyone advise the best way to plumb the ports on a plate heat HX? One pic I saw used 4 unions, one on each port.

I'm not sure it would work properly with a dip tube anode rod.The setup realies on the property that hot water is lighter than cold and causes a gravity flow through the exchanger.The dip tube may hinder that convection.

That does seem like an inefficient way to use a plate exchanger. I'm not sure what kind of transfer you will get with a thermosiphon through a plate type exchanger. I need to talk to the plate exchanger manufactures to get an opinion on that

I highly recommend you install some valves that allow you to delime the DHW side of that plate exchangers. I use the Watts RPV ball valve with a garden hose side tap and valve for this.

Hard water takes a toll on those small passage exchangers. You may need a small bronze or stainless pump on that "B" side. The pump moves the water through faster to help eliminate scale ups.

Heat exchangers perform best with two pumped flows. May as well use it efficiently since you paid for it.

hr

Funny thing is I called Central boiler and talked with a tech about the piping configuration and asked him how much hot water I could expect from this setup.He told me "an unlimited supply" so I asked him how many GPM that was and he said he didn't know.But no one ever runs out of hot water.

I recomended a pump to the homeowner,but,I ended up piping it exactly the way they wanted it as the homeoner believes these guys are Gods or something.I'm not sure how well it works as the water heater is electric,so it will turn on and pick up any slack.

I would say it heats the water, but very slowly.If there isn't going to be a pump or backup source I would put in a very large heater and rely on volume.

Thanks again for the responses. I too am a bit skeptical about the recovery speed of the thermosyphon system.

How about a circulator with a aquastat: Place the aquastat prior to the "in" port on the domestic side of the HX and have it shut the pump off at 130 degrees. Now, I have never used an aquastat before so I'm not sure about cost or even if this is an acceptable use of an aquastat. What do ya think?

Of course I could just let the pump run all the time and have PLENTY of 160-170 degree water at my disposal, but I'm not sure thats the best way to go either (I'd use a tempering valve on the supply in either case, safety first!).

There is nothing wrong with maintaining a higher temp in the domestic water heater as long as the water reaching the faucets is tempered to a safe level.A tempering valve on the storage tank is a MUST!

There is talk in the industry of rasing storge tank temperatures for a variety of reasons,but the important think is to protect the occupants from scalding.

I sat in on a very interesting seminar at ISH on this very topic.The speaker did a great job of presenting some very valid reasons.Now if I could just remember his name

I thought I would get this post going again. I have been researching radiant heat so I am very new to all this. I am looking at a closed loop system in my home for various reasons. My question is - would it be possible to setup an independent zone on your radiant heating system that would somehow kick on the pump sending hot water through the heat exchanger at the same time the hot water heater was calling for cold water? I would like to just keep my current HW heater rather than buy a indirect at this time. The plumbing of this would not involve removal of the anode rod but perhaps running the inbound cold water through the heat exchanger and then into the water heater. Do you guys think this makes sense? What would be the best way to plumb this? For example, how would you turn the radiant pump on when the HW heater is calling for cold water?

Background: I have a NG hot water heater that is set only to 70 degrees, which then enters a tankless unit. The system is redundant in that if one device fails I have the other to fall back on (I travel a lot). Also, the tankless unit can be set at a lower setting and effectively delivers hotter water running more devices in the home as the inbound water enting the tankless unit is warm rather than 45 degrees. The HW heater simply serves as a storage device to bring a bit warmer water to the tankless unit. The HW heater does not run much because the water is only heated to 70 degrees. The tankless uses less gas and then only runs when HW is running.....

Well I SUPPOSE you could put on a low watt circulator and circ the tank, with a strap-on aquastat on the pipe to kick the boiler on/off.