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Ronin33 04-03-2007 10:16 PM

Tankless hot water sporatic until........
I have furnace with tankless hot water. Getting hot water has been difficult consistantly. My bathroom and kitchen water can be hot and then after turning the shower on that water would be luke warm then turn to cold. I then walk to the kitchen and turn the faucet on and get luke warm. I can wait awhile and try again and get hot water out of the faucets again but when the tub water is turned on it happens again. Recently after observing this for weeks (not a very good DIY'r yet) I tried something. Before I needed to shower I would up the temp on my thermostat by 2 degrees. This would turn on the furnace and I get HOT water for as long as I want. Each of the five times in a row I have done this I got hot water.

There must be something simple that is causing this? At first people told me it would be the coil but it is brand new as is the furnace. The people that installed this were the same people that I bought the home from. After watching them work on other issues that I had them fix I decided to go at this one on my own. The furnace is a Smith.
Any help on this would be great. Thanks,

hvactech 04-04-2007 05:43 PM

you best bet is to junk the tankless and go back to a regular 40 gallons water heaters or be ready to waste some $$$$$

harleyrider 04-05-2007 09:47 AM

Thats a foolish response......Tankless units are 70% + more effecient then a tank hvactech, do not fear the unknown, educate yourself.

Ronin33, it sounds to me like your unit may have a flow control issue or it may be under sized. The best thing to do is find a local contractor who is autorized by the factory to service your unit.

Brik 04-05-2007 10:41 AM

Don't be so quick with responses. I don't think the OP has tankless like the bosch aquastar or something. His hot water is generated via his furnace. I'm no pro but I think this is called a summer/winter hookup w/o a storage tank. Clue is he sets his furnace thermostat higher and has hot water. A band aid solution may be to add a storage tank. Downside of this system is he needs to run furnace all summer to provide hot water for showers. I think we need more info.

hvactech 04-05-2007 05:46 PM


Originally Posted by harleyrider (Post 39691)
Thats a foolish response......Tankless units are 70% + more effecient then a tank hvactech, do not fear the unknown, educate yourself.

Ronin33, it sounds to me like your unit may have a flow control issue or it may be under sized. The best thing to do is find a local contractor who is autorized by the factory to service your unit.

I disagree, tankless water heaters work well under specific conditions not met by most homes in this county, the savings if any are lost to maintenance cost, they are junk period!

harleyrider 04-05-2007 07:36 PM

Thank you slick!

Clutchcargo 04-05-2007 07:57 PM

63 Attachment(s)
Is it a furnace (air) or boiler (water) system?
I went through the hot-cold-hot-cold effects of tankless HW from a boiler. I'm going to make a blanket statement here... tankless HW fired off boilers just don't work that well.
If you do have a boiler consider junking the tankless coil and adding an indirect water heater. If you are a DIY'r then it is not that difficult to do, just set aside a weekend for the switch.

ewils91 04-05-2007 09:40 PM

Hi there,

Ronin33 is a friend of mine whom just happens to be on vacation as of this post. :mad: So I'll see if I can help, the system is a boiler type, forced hot water, I know this has been driving him batty for a while now and I know he will be checking this thread as soon as he QUITS vacationing. Hope I shed a little light on the problem.

Ronin33 04-22-2007 01:02 AM

More Info
Well I have returned from vacation. I was happy to see the replies so far. Thanks Harley.
So I am using a Smith Boiler series 8.
The house is steam heat with base board style radiators vs. the old cast iron style. And the condition is still consistant. If I turn the furnace on I get hot water all of the time. Now, even If I do not turn it on I still get hot water at the taps. But if I then turn on the shower it seems to hinder the faucets hot water to the point were it goes cold or luke warm.

Is there some a gadget that tells my furnace to turn on when the shower water is turned on? Could it be as simple as that? Maybe not cheap but simple.

Here is the link to the exact boiler.

troubleseeker 04-24-2007 09:24 PM

Sounds like the bathroom water, kitchen, and shower is just plain exceeding the capacity of the unit. This is easily done if dealing with older plumbing fixtures that do not have flow restricters in them, and/or an older tankless heater, as they did not have as high a capacity as modern units.

Ronin33 04-28-2007 08:11 PM

But I am not running them at the same time. I run the sink and get hot water, then I turn it off and walk to the bathroom to turn on the shower. After turning the shower on I get luke warm then cold water. Then I shut that off and walk to the kitchen and turn that water on again. Now, the water that was hot only seconds ago runs cold. Seems that something in the shower effects the other water supply.

If I turn the boiler on by notching up the thermostat I get HOT water in all taps at the same time. Maybe it's just time to call someone eh?

moneymgmt 04-30-2007 03:18 PM

Although I do not understand why someone would go tankless with a boiler, what is the physical connection/flow between the two? I'm guessing the tankless system was installed where an indirect hot water heater used to be. Meaning, water flows through into the boiler then into the tankless, then into your pipes. You get hot water when the boiler is on because its hot before it even gets to the hot water heater. I would make sure the tankless even works if it gives no hot water. If they're not connected I'm completely speechless.

Clutchcargo 04-30-2007 06:01 PM

63 Attachment(s)
There's a coil that sits inside the boiler that is submerged in boiler water. As cold water flows through the coil it cools the boiler water down until it hits the boiler's set point. When the boiler water cools off enough the boiler will fire and heat the boiler water again and in turn heat the coil. If you let the water run it will eventually get hot again. The coils are always too small and they don't sufficiently perform the heat exchange very well. You would be throwing your money away trying to get the tankless hot water to work any better. If you want to run hot water off your boiler than an indirect hot water heater is the way to go. It's a separate tank that gets plumbed into your boiler as a separate zone.

Ronin33 05-01-2007 11:51 PM

Well that gives me a few more things to check on. Thanks a lot for your insite. May ask a few questions for you folks in the future.

#CARRIERMAN 05-11-2007 08:03 PM

Hi Ronin33

Your post basically confused the he** out of me as to what you have. If you have a tankless water heater (very good purchase) all that it needs is the water regulator rebuilt and it will work like new again. If you are using a potable water heater off of the boiler, than the only way you will have hot water is to run the boiler. This is the best that I could make out of what I saw. The water regulator kit for most tankless water heaters range from $50.00 to $150.00, depending on the make and model.

Good luck

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