my wife was complaining the last two days that the hot water in the shower goes from hot to cold (for about "two minutes" and back to hot again. My shower (after hers today) did not give me the same problem, but the dishwasher was running this morning at the same time as her shower (not sure if it was done when I went in), as was the call for heat. She said even while turning the shower up there was no change in the temperature while it was running cold. Once it went back to hot she had no issues with temperature, and neither did i.

I only have one bathroom so I cannot isolate it to just this shower. I do not seem to have the problem at the bathroom sink or kitchen sink.

I am not sure what is causing this at the moment. I am not sure if it is the Boiler or the valve on the shower. or too much going on at once on a cold morning……how can I narrow this down to the source of the problem?

here are some of the information that may be helpful.

I use a Weil McLain WTGO-3 oil fired boiler that supplies the domestic hot water through the coil. It was recently replaced 3 months ago under a warranty issue of the previous unit (old unit cracked after 7 years). My aquastat (dual with no differential) is set at 190 Hi and 160 Low. The mixing valve off the boiler was also replaced 3 months ago (Watts Model LF70A). the temperature at the sink reads between 114-118 Fahrenheit.

The mixing valve on the shower is a single handle model. The Kohler mixing valve Model is GP77759 (was replaced in June of 2014).

thanks for any insight.
brian

brian, while your wife is showering turn on a hot faucet. when her shower water temperature drops see what the hot faucet you have open does.
it might be the tankless coil but it should do the same thing when you are showering.
also, when she is showering, feel the hot coming out of the tempering valve at the boiler. see if there is any change going on there.
WGO-3 doesn't have a lot of water volume so it is possible it is cooling down below 160 when the heat is also calling.
anyway, you need to do some detective work..

Thank you Packy i will try those out tomorrow, and report back.

i didnt think of actually checking the hot from the valve off the boiler when the shower runs cold. im guessing if it is still hot while the shower is cold it could be the shower valve. the distance from the boiler to the shower is less than 20 feet.

what should i expect (or not expect) when i open the hot water on another faucet? and should i open it at the same time shower goes on , or when the temperature drops.

I hope it is not the coil this unit is only 3 months old.

thank you again!
brian

it is not the coil. it doesn't act like that if it is bad.
open a faucet slowly when your wife is showering. when her water gets cold the faucet should also get cold if the problem is with the hot water supply.
if it doesn't get cold while the shower does then it is in the shower control. probably a cartridge or balancing spindle.
one other thing it could be is the water temperature in the boiler drops below 160 and the coil will not produce hot water. this can happen when there is a call for heat. the boiler control should shut down the heating circulator at 160 to allow the boiler to 'catch up' so it can produce hot water. as you can see there are a few possibilities and you need to put on your sherlock holmes hat and start investigating.

Try bumping the low limit up to 170*. What model aquastat do you have?

Ok, I am just gonna throw this out there.. don't turn on the hot while your wife is in the shower. Turn it on and let it run with nobody in there and YOU check the temperature. If you douse your wife with cold water while she is showering on purpose, and use the excuse that Packy told you to do it, she won't care who Packy is, why he told you, or what it accomplished. She will only understand that you intentionally ruined her shower for fun.

thank you all for your help. I appreciate it.


M&M. I don’t have the specific model number I am sorry. I tried looking and found this unit here that looks just like mine. It says Royal “Dual” Aquastat Honewell (Part Number Royal AQ 6200-6490) [www.freeheat4u.com]


I took another look and my unit is set at 180 High and 145 Low. I am guessing the installers changed the settings a little bit when my boiler was installed. I checked the temp and the burner fires at about 180-190 range and it runs till the temperature hits 195-200. after the burner stops the temperature rises to between 205-210. I'm afraid that if i rise the high anymore it well start to leak out the relief valve. I know to keep the high and low at a minimum of 20* apart. should I keep that 20* difference between the two based on the boiler temperature or the actual setting, since there seems to be a little bit of a difference.


KCROTO I could not help but laugh when I read this. To keep it nice my wife told me to go scratch when I turned the faucet on…..she said I can experiment with it when it isn’t 10* degrees out. She had no problem this morning and I checked the temp of the boiler and the felt the Hot water feeding the tempering valve, and the water leaving it while she was showering. All was hot. I left the faucet open while I was in the shower. there was about a minute where the temperature dropped slightly, but never got cold like she said the other day.

The thing that was different this morning is that the dishwasher was not running and there was no call for heat this morning (at least my first floor zone).

So I wonder If it is a volume issue. Maybe if both zones are calling for heat, and the dishwasher or washing machine are running all at the same time. Im going to keep checking on it.

thanks
brian



Edited 2 times.

raise the low limit to 160 and have the oil man downfire the burner by 10%.
reduce the nozzle size to eliminate the thermal overide..
a hi setting of 180 deg should not go to 205..

Raising the low limit up to 160* as per packy's recommendation will not affect the high end temperatures; that should stay the same. The aquastat you show does not have a differential setting for the low limit as most do. Odd. I would attribute most of your hot water fluctuation to hot water use while a heat zone is operating and the burner unable to keep pace with demand. During the extreme cold, you may find that you need to back off the thermostats until showering is done.

m & m, if the electrician fed the zone control from the C1-C2 terminals in the honeywell control as he should have then the zones will not function when the boiler water drops below the LO setting. the hot water making takes precidence.