Side Arm Heater on supply or return

[psdaigle]

I am hooking up a side arm heater to my DHW. Everything that I have read says to hook this to the side arm heater first before going into the heat exchanger in the plenum. I would like the hottest water going to the furnace and then to the side arm heater. Are there any problems with this?

Also I have purchased a mixing valve. My concern however is that the mixing valve will not adjust to temperature fluctuations in the boiler temp, and that I will constantly be playing with the water mix. Any advice would be greatly appreciated.

Thanks

 

[superwd6]

Always go to the water heater first. If you have just a side arm (copper pipe inside another) it will rob very little heat out of the boiler water anyway. They operate on thermosyphon action.
Your mixing valve is for lowering DHW levels to 120*f instead of the water tank temperature. When your boiler runs 180*f the water heater will be about 20* cooler -160*f. Good reason for lowering temp with mixing valve!
Check out Central Boilers website for instructions if you need em.

 

[psdaigle]

Will the mixing valve adjust to the different incoming water temperatures? For example the incoming water temp might be 170*F after filling the stove and 140*F when I get home from work. I believe that this will vary the water heater tank temp, and affect the mixing valve outlet temp.

 

[superwd6]

http://www.centralboiler.com/otherExamples.html Check out the plumbing diagrams here. Your boiler water doesn't touch the domestic side. The mixing valve is there to limit hot water temp @ your sink, tub etc.It does this by mixing water heater hot with cold to what ever you set your mixing valve at (120*f max in Ontario). Mixing valve can only lower temp so if your tank is 110 than thats all you get
Make sure you have the proper "Thermostactic mixing valve" as they automatically set temp outlet regardless of hot temp inlet

 

[blackdogon57]

Good post - rep sent !!

 

[Medman23]

Also, don't forget to put a horizontal swing-check valve on the domestic side at the top of the sidearm, so that when the boiler side is colder than the tank, you don't have reverse-thermosyphoning and lose stored heat from the tank. You can really eat a lot of fuel/elec. if the sidearm is trying to heat the boiler side, even with no flow in the boiler loop.

Insulation on the sidearm is a must to keep the heat in the tank, as well as raising your tank 3"-4" off the floor and insulating underneath. This made a huge difference for me.

 

[oneoldbanjo]

Also, don't forget to put a horizontal swing-check valve on the domestic side at the top of the sidearm, so that when the boiler side is colder than the tank, you don't have reverse-thermosyphoning and lose stored heat from the tank. You can really eat a lot of fuel/elec. if the sidearm is trying to heat the boiler side, even with no flow in the boiler loop.

I have never heard of putting a check valve in the sidearm.....the thermosiphon induced by the the water becoming hotter in the vertical pipe is not a very powerful process and I would suspect the check valve could greatly reduce the amount of flow and reduce the efficency of the sidearm as a result of the resistance caused by a check valve.

When I have the OWB burning I just shut the water heater elements off completely to prevent my electric water heater elements from doing any heating. When the OWB is not running I turn the heating elements back on and I have a ball valve in my sidearm that I close to shut the sidearm loop off to prevent the backwards thermosiphon from occurring.

And yes.....Insulation is very important as my basement and house would occasionally get too warm from the heat coming off the sidearm. Without insulation it acts just like a vertical baseboard heater!

 

[psdaigle]

Thermostatic mixing valve I am assuming this is the difference form the one that I purchased.

My side arm is in and I have insulated all of the piping. I have not installed the mixing valve yet because of the concerns mentioned. I will send some pics tonight for evaluation.

 

[psdaigle]

I have finished the installation on the side arm heater. Attached are some photos. Please be easy on me. I am not a plumber, but I do not like to pay plumber wages. Everybody on this thread has been very helpful. I have not installed the mixing valve yet. I am still concerned that I have the wrong one. The one that I purchased is not a thermostatic mixing valve. It is an Amtrol 421-1 mixing valve with adjustable dial.

Thanks again for all of the replies

 

[oneoldbanjo]

Looks like it will work fine.

The next thing to do is get some plumbing installed on the T&P valve so that if it does work - it doesn't blow scalding hot water across the room at face level.

 

[psdaigle]

This was the plan however I ran out of 3/4 inch male connectors