Just Moved In -- Hot Water Is A Mess!

Hi Guys,

I hear there are some experts on this board so I thought I would see if someone can point me in the right direction with my problem, or at least who I should direct my question to -- a furance expert or a plumber?

I have a Slant Fin Liberty LD-30 furnace with a tankless coil. The unit is 12 years old. The coil was replaced 3 years ago in 2003, it has a 4.5GPM flow rate. The original apparently broke according to the previous homeowner.

The issue is this -- when taking a shower, initially I get hot water for about 45 seconds, but then it jumps to luke warm. It stays luke warm for about 30 seconds, then it gradually kicks back in and can get really really hot! Then after a minute or two it goes luke warm again and gets really cold. It's driving me nuts as you can imagine.

The Aquastat was originally at 160 low, 180 high. I adjusted it down to 145 low, 165 high because I was getting scalded in the shower when the temperature was changing. It didn't help the problem at all, but at least now I'm not getting burned.

I think part of my issue is that my valve in the shower is 40 years old and does not have any temperature control features built in, but this is happening on ALL of my plumbing fixtures (faucets, other showers, etc.)

Any thoughts on what the scoop is with this? Bad mixing valve? Bad coil? I just bought the house, and the lady was good about having a tune up every year. I am the only person living in the house, so I'd like to try and stay away from getting a hot water tank.

Any advice is welcome. I had a 2 year old Weil-McLain furance that was tankless at my previous house and it never gave me any problems at all. I don't sit in the shower for an hour -- I'm in an out in about 5 minutes.

Here are some pictures to give you an idea of my setup. I have a feeling it's a hackjob. If you need bigger pictures let me know and I will be happy to oblige.





Before I call someone, I wanted to get some ideas. Any advice is appreciated!

Thanks for your time,

Chris

Check the Mixing Valve

I had the same problem and it was a mixing valve problem that showed up in the winter when the supply water was about 34F.

I took the temperature control stem out of the mixing valve.

I also found that keeping water hot in the summer was burning a lot of oil just to keep the boiler hot for hot water. I put in a 40 gallon electric water heater and piped it in series with the tankless coil, with the tankless coil outlet feeding the hot water heater.

In the summer, the boiler is off and electricity heats the water. In the winter, the boiler temperature is hot enough that the electric heater never comes on. The saving in oil cost at current $2.00+ per gallon is twice the electric cost. Since you are only one in the house, your saving would be even more.

It paid for itself in one summer for a do-it-myself installation where I was only paying the cost of the heater and a circuit. It would be more if you had to pay someone to do it.

I think I see evidence of hard water scale on the front of the coil. If the coil is loaded up with scale, then the ID of the col is reduced and water flowing through it has higher velocity than it was designed for. That mans the water moves through the coil lots faster than it takes to heat it up and... the scale has to be heated first, so you raise the temp, and create more scale....

I also see a mixing valve, that cross over pipe from the cold to hot water lines above the coil with the valve on the right side. That will be mixing cold water with the hot and probably more if there is a restriction in the coil due to hard water scale build up.

A water test for hardness will tell you the probability of scale in the coil. A water softener will prevent scale build up and then dissolve the scale in the coil opening it for full flow and even water heating. That will decrease fuel cost and electric use if you did as Bob suggests while protecting the life of the coil and any electric water heater.

Gentlemen, many thanks for your responses. I will be sure to check out the mixing valve and will probably get it replaced. I used to have a water softener and miss it, so that will most likely be on my list of things to do as well.

Thanks a lot for the advice, and if anyone has any other thoughts please chime in!

Chris

Gary, You Know Your Craft

I'm impressed, great call

Thanks, not too bad for a water guy huh.