Radiators work great, but the hot water not so much

midiman143

Hello everyone,

Let me start off by saying in advance thank you to anyone who tries to help with our issue . I am a new home owner and I have been doing what ever research I can get my hands onto to solve the following issue. The heater works great in terms of heating up our radiators, but we can't seem to get hot water from it for the rest of the house. It was coldish at first when the aqastat was set for 120 degrees. I have been adding about 15 degrees to the aquastat each night and it is at about 180 degrees and this doesn't seem right to me. I know an electric hot water heater is usually set around 120 and will burn you. We also turned the anti-scald valve to the max hot position. This heater is about 3 years old and I feel lost as to what else to check/adjust. I have attached photos for some of the parts. I am trying to learn more about how the piping schematic works to better understand the situation. Photos show the two items I tried to adjust and the third is the water system as a whole.

Lost. Paige

delta T

When you adjust the aquastat temperature, does the boiler ever fire after you turn it up? You have a pretty basic set up, Best guess is that the aquastat is not working properly. Try turning the heat up all the way (just for a little bit) and once the radiators are getting hot, try running some hot water and see if it gets hot (if it doesn't there is something wrong with the mixing valve, if it does, there is something wrong with the aquastat)

That being said. Your system has a few other things that I would address:

-The flue does not appear to have a liner. This can cause condensation from flue gases to deteriorate the brick of your chimney over time.
-It is not generally good practice to pipe a steam boiler in copper (I am only referring to the main 2" riser feeding the steam out of the boiler.
-I am not great at steam but the whole supply header looks like it is not quite right (I deal primarily with hot water, could be totally wrong, others on here who are steam experts will chip in later I'm sure.) Can you post a picture of the other side of the boiler?
-The system you have in place for DHW (Domestic Hot Water meaning water out of your faucets as distinct from water in your heating system) will require the boiler to run all year (albeit at a lower temperature) if you want hot water. Efficiency wise this is probably not the best set up.

Any one else have thoughts?

midiman143

Delta that is some wonderful suggestions, i will try and let you know how it works out! To answer one of you questions, when we take a shower I do believe the furnace does turns on and stays more or less on the shower.

Is the mixing valve the knob I referred to as a anti burn valve?

delta T

Yes that is the mixing valve. If the boiler does turn on when you run water, then my best guess (without being there) is that the mixing valve is acting up. Hard to say for sure over the interwebs though

Where are you located? we can probably recommend a good pro that is nearby to come take a look, or check the 'find a contractor' link on this site.

EBEBRATT-Ed

120 deg boiler water is no good. (the tankless heaters are rated at 200 deg boiler water) With a tankless heater you need to set the aqustat by doing some experimenting. Set it for 160 to start with. Turn the mixing valve to the hottest setting. Open a hot water faucet and let it rip. Watch or listen to when the burner fires and hold your hand under the faucet (but don't get burnt). If you run out of hot water turn the aqustat up in 5 degree increments. I wouldn't go over 180 regardless. If you don't run out of hot water turn the aqustat down in 5 degree increments until your happy with the way its working.

If you run out of hot water (and the boiler temp is up to 160-180) and the mixing valves is set to max it could be a defective mixing valve element.

Once you get this set you may need to use the mixing valve to to temper or reduce the hot water temp when the boiler is steaming for heat because the boiler water temp will rise to 212 deg which may make your hot water to hot.

as others have mentioned a indirect tank is a better more efficient solution although a tankless heater is usual only adequate for 1-2 people

EBEBRATT-Ed

Forgot to mention the aqustat is only used for summer operation. It keeps the boiler hot when NOT being used for heat.

midiman143

Hello again everyone,

I am still waiting to run some of these test we have talked about. To answer your questions. We are located in Woburn MA Delta. Ebebratt and Hatterasguy, the water is not even close to what I would consider hot. With the setting as 180 degrees now I can leave any body part under the "hot" water and it would slightly warm me. Aka our showers are now at least doable with the water dial on full heat, but we would never come out hot from the shower. So essentially the faucet could be at max hot, the mixing valve at max hot, and the aquastat set to 180 at the moment and the water is not even close to burning anyone. THANK you again guys for the insight. I am going to verify that the heater comes on and stays on for the shower tonight I hope.

midiman143

Are mixing valves prone to being defective in a short amount of time? Assuming that the shiny new copper pipe is as old as the heater, we are only talking 3 years old.

midiman143

Hey guys!

Thank you for the last comment Hattersasguy! So I have definitely observed this hot water pipe from the tankless heater. It gets VERY VERY hot, what i would assume to be 180 or whatever the aquastat is set to. it get drastically colder after the mixing valve and only gets colder the further away from the valve. I talked a fellow handy man and he suggested turning off the cold water heading into the mixing valve and seeing what kind of water we get a sink/shower as a way to diagnose the mixing valve. Would you guys agree that this may be the next test?

-Paige

BobC

Just be careful nobody gets scalded, that water might now be blistering hot.

Bob

EBEBRATT-Ed

I think you have found the problem thanks to Hatterasguy. You can replace the entire mixing valve or just replace the element if you can get it apart

midiman143

Hello everyone again. I wanted to update everyone. So I did try turning off the cold water feed to the mixing valve, only to realize that I need the pressure from the cold intake to get any water anywhere. I did try something new which basically says close to the same thing, I tried tapping the mixing valve a bunch on multiply nights to "loosen" it up. It really made a world of difference, but the other night I tried turning the aqua stat down to about 180 degrees and the water was no longer hot, so I had to turn it back up to 200. I believe at this stage I am going to drain the system, install a valve before the mixing valve (on the hot water side) and clean or replace the old mixing valve and see if that does the trick. To me it still seems odd to have the aquastat still so high. Thank you again for the suggestions and any input is appreciated.