Side arm vs plate heat exchanger for domestic hot water?

[Mister Twister]

Yep..the plate exchangers will plug pretty quick with hard water and should be cleaned yearly. The sidearms are'nt really effected by the hard water nearly at all. Plates do make faster heat but require a pump to circulate the water, where the sidearm works on convection and no pump is needed.
I have a 40gal hotwater tank with a sidearm and have never ran out of hot water either.

Do you have any pics of your setup? I have a fin enhanced sidearm and after 2-3 showers we have luke warm water. Takes a long time to recover after that I also have a 40 gal hot water heater. I am wondering if the way mine is setup the top of the sidearm is about 3 -4 inches above the entrance of the TP valve. That maybe slowing down the convection heating effect? Maybe I can find time to post a picture tonight and you guys can tell me what you think.

 

[Butch(OH)]

Do you have any pics of your setup? I have a fin enhanced sidearm and after 2-3 showers we have luke warm water. Takes a long time to recover after that I also have a 40 gal hot water heater. I am wondering if the way mine is setup the top of the sidearm is about 3 -4 inches above the entrance of the TP valve. That maybe slowing down the convection heating effect? Maybe I can find time to post a picture tonight and you guys can tell me what you think.

You probably read my earlier post but I too had that problem. we have 4-5 in the house. I added a plate type and now have the best of both types, tank stays hot and plenty of capacity.

 

[Jkebxjunke]

I have also heard that if you use a circ pump on the side arm you will get much faster recovery

 

[Mister Twister]

You probably read my earlier post but I too had that problem. we have 4-5 in the house. I added a plate type and now have the best of both types, tank stays hot and plenty of capacity.

Yes I have read your post and I was considering adding a 10 plate exchanger coming into my hot water tank. I just don't want to add a pump to solve my problem because that means more energy.(That was another idea to speed up recovery time which I think would work.)

I still question my install with the pipe 3 -4 inches over the T&P valve then back down into the tank. I have wondered about that since the install in fall maybe if I am working against the thermo-siphon effect.

Seems there are others that have a simple homemade sidearm and are happy with it. My fin enhanced side arm is supposed to transfer more heat 11,500 btus is the claim.

 

[Slick]

Not to try and put the work on your shoulders, but there has been alot of talk around here about if the thermo-siphion is effected by the side arm entering above the tank and having to work it's way down....I think we'd all be curious to see what happens with a before/after test if your was adjusted to not enter to high I know I went with the short e-bay one to not have to come back down into my tank..my sidearm is only about 18" long, it looked so small compared to what I see others having I was worried but my water is really hot and I don't seem to be making a dent in the hot water by doing laundry and showering at the same time.

 

[Mister Twister]

Not to try and put the work on your shoulders, but there has been alot of talk around here about if the thermo-siphion is effected by the side arm entering above the tank and having to work it's way down....I think we'd all be curious to see what happens with a before/after test if your was adjusted to not enter to high I know I went with the short e-bay one to not have to come back down into my tank..my sidearm is only about 18" long, it looked so small compared to what I see others having I was worried but my water is really hot and I don't seem to be making a dent in the hot water by doing laundry and showering at the same time.

I guess the only way to know is lower it. That means it will be lower than the spigot coming out of the bottom where I have a Tee now. I don't think that would have any effect though. The cooler water should be able to drop lower with ease it is going over the top and back in the tank is the issue. Sounds like a weekend project to me maybe Saturday morning.....

 

[oneoldbanjo]

Mr. Twister:

I think that lowering the sidearm below the water heater drain is fine. This is how I did mine:

I also believe that entering the water heater at the T&P valve on the side of the water heater is fine, just move the T&P valve as little as possible. Some claim that the water heater manufacturers will not approve this - and I agree that for liability reasons they should not agree to "messin around" with their stuff. I will post a picture of my revised T&P valve after I install a shorter one tonight.

I also agree that any distance you go above the water heater will cancel out an equal amount of the thermosiphon in your sidearm. If you go 6 inches above then you will be canceling the energy that 6 inches of your sidearm provided. It will still heat up the water - it just won't flow through as quickly and return as hot water to the tank. I also believe that you must have a way to vent any trapped air out of the portion of the system higher than the tank or the flow rate will be affected.

I also believe that tapping the top of the sidearm into the outflow line from the water heater has the effect of pulling cold water off the bottom of the water heater, running it quickly through the sidearm, and then discharging it into the domestic hot water line before it can be properly heated. If you have your system plumbed this way I suggest you check the temperature at the top of the sidearm before running any water.....and then turn the hot water on and check the temperature at the top while the hot water is flowing....I bet you will feel the water temperature drop considerably as the colder water runs through the sidearm.

 

[Mister Twister]

Mr. Twister:

I think that lowering the sidearm below the water heater drain is fine. This is how I did mine:

I also believe that entering the water heater at the T&P valve on the side of the water heater is fine, just move the T&P valve as little as possible. Some claim that the water heater manufacturers will not approve this - and I agree that for liability reasons they should not agree to "messin around" with their stuff. I will post a picture of my revised T&P valve after I install a shorter one tonight.

I also agree that any distance you go above the water heater will cancel out an equal amount of the thermosiphon in your sidearm. If you go 6 inches above then you will be canceling the energy that 6 inches of your sidearm provided. It will still heat up the water - it just won't flow through as quickly and return as hot water to the tank. I also believe that you must have a way to vent any trapped air out of the portion of the system higher than the tank or the flow rate will be affected.

I also believe that tapping the top of the sidearm into the outflow line from the water heater has the effect of pulling cold water off the bottom of the water heater, running it quickly through the sidearm, and then discharging it into the domestic hot water line before it can be properly heated. If you have your system plumbed this way I suggest you check the temperature at the top of the sidearm before running any water.....and then turn the hot water on and check the temperature at the top while the hot water is flowing....I bet you will feel the water temperature drop considerably as the colder water runs through the sidearm.

Wow thanks for the picture that is how I plan on re-arranging mine because my sidearm is to long. I opted to go a couple of inches above the T&P valve instead of going below the hot water tank. In hind sight I knew it was a bad idea and yes I have hot water just bad recovery time. And you are also absolutely correct on purging the air I had to crack my fittings and take an unexpected hot shower to get the thermo-siphon going because of trapped air. I love communicating with individuals on this site because it is very constructive.

By the way how many gallon tank is yours and do you ever run out of hot water?

 

[oneoldbanjo]

Mr. Twister:

I have a 40 gallon water tank, and it is just my wife and I and we never run out of hot water. I have to tell you though.....that we also have a plate exchanger on the inlet to the water heater and it makes all the hot water we need. I added the sidearm to keep the water hot after it was inside the water heater - but the plate exchanger works so well that we can shut the sidearm off and the water takes a couple of days to cool down.

The really weird part of my sidearm is that I added a 90 elbow in the internal 1 inch pipe and external 2" pipe so that I could use all the pipe that came with my sidearm kit. You would have to build your sidearm this way from the start as you have to solder the 1 inch elbow to the 2 straight sections while it is inside the 2 inch elbow - I don't know how you could retrofit this bend.

 

[Butch(OH)]

Yes I have read your post and I was considering adding a 10 plate exchanger coming into my hot water tank. I just don't want to add a pump to solve my problem because that means more energy.(That was another idea to speed up recovery time which I think would work.)

I still question my install with the pipe 3 -4 inches over the T&P valve then back down into the tank. I have wondered about that since the install in fall maybe if I am working against the thermo-siphon effect.

Seems there are others that have a simple homemade sidearm and are happy with it. My fin enhanced side arm is supposed to transfer more heat 11,500 btus is the claim.

Sorry if I am getting the wrong idea from that responce but I did not add a pump when I added the plate exchanger. My well pump pushes the domestic side and I put the plate exchanger in series with the sidearm on the boilerside. I could take some pics but they would be pretty meaningless as I have insulated averything and wrapped it to keep temps down in the basement.

 

[Mister Twister]

Mr. Twister:

I have a 40 gallon water tank, and it is just my wife and I and we never run out of hot water. I have to tell you though.....that we also have a plate exchanger on the inlet to the water heater and it makes all the hot water we need. I added the sidearm to keep the water hot after it was inside the water heater - but the plate exchanger works so well that we can shut the sidearm off and the water takes a couple of days to cool down.

The really weird part of my sidearm is that I added a 90 elbow in the internal 1 inch pipe and external 2" pipe so that I could use all the pipe that came with my sidearm kit. You would have to build your sidearm this way from the start as you have to solder the 1 inch elbow to the 2 straight sections while it is inside the 2 inch elbow - I don't know how you could retrofit this bend.

How many plate exchanger did you use? I was looking at possibly adding a 10 plate to preheat my water and leave the sidearm to keep it warm.

 

[oneoldbanjo]

Butch:

My system works the same as yours....without any additional pumps. My domestic water flows through the heat exchager plate and into the water heater. The sidearm flows domestic water by thermosiphon. The flow from my OWB starts with the Taco pump at the boiler, flows through the underground pipe and into the plate exchanger for the water heater, then through the sidearm, then to the furnace exchanger. Only one pump is requred and it is at the OWB.

 

[Mister Twister]

Sorry if I am getting the wrong idea from that responce but I did not add a pump when I added the plate exchanger. My well pump pushes the domestic side and I put the plate exchanger in series with the sidearm on the boilerside. I could take some pics but they would be pretty meaningless as I have insulated averything and wrapped it to keep temps down in the basement.

I understand completely thanks for your input.

 

[Mister Twister]

Pictures of my Sidearm

Picture of my Fin Enhanced Sidearm installed on my water heater. I am thinking of lowering it so the thermo-siphon effect works better do you think that will help recovery time?

 

[blakey]

I was initially surprised to see it is stainless, would it be as good as copper for heat transfer?

 

[oneoldbanjo]

Mr. Twister:

Looking at your installation.....it would not surprise me if you have air pockets at the top of the loop. When I bought my sidearm it had an automatic air release valve that would install in a setup like yours, and it would automatically let out any air in the system.

Last night I revised my T&P valve. I had initially used the one from the water heater that had a long stem to reach through the insulation. Last night I removed that one and installed one that had a very short stem. I believe the probe now reaches back into the water heater as far as the original did, and it would be even better if I had been able to find a little shorter piece of pipe to fit between the water heater and the Tee.....but this was the shortest one that Home Depot had that would work.

This is the long stem T&P valve from the water heater:

This is the long stem T&P and the short stem replacement:

This is the short stem T&P installed:

 

[gravelracing]

How big of plate exchanger to use

I believe this is an old thread but I am currently hooking up my hot water and believe I need to use a plate exchanger versus a side arm exchanger but dont know how big of plate exchanger to use, what have some of you used and had luck with?

 

[coostv]

This is an old thread.

I have six people in my house and have a 5"x12" 10 plate exchanger. It does all we need so far. I have not seen 4 back to back showers with it yet, but it seems to be handling the demand just fine. It has only been a week so far, so time will tell. As long as I am not the fourth to need the shower I will be happy. LOL.

 

[gravelracing]

Plate exchanger

Thanks for the info, how did you plumb it up? We very rarely take 4 showers back to back but when and if the time comes I want to have hot water enough to do it!

 

[coostv]

This is how mine is plumbed in. On the right you see the copper lines for my DHW, inlet (cold) from the house on top and outlet on bottom into my water heater. On the left are the lines from the boiler, in from boiler on top and out to the heat exchanger in my furnace on bottom.

I put unions in on the copper lines for easy removal later.

If you can sweat a fitting it is no problem.