Suddenly need to turn faucets to 9/10 hot to get hot water out of them

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BC Canada
I live in a low rise condo. We have gas-fired boilers in the basement and no individual hot water tanks. So a week or so ago they replaced the aging boiler.

A couple of days ago in the evening I noticed the water would only get lukewarm. Odd, never happened before in all the time I was there. So I waited a couple of hours and then it got hot again so I thought nothing of it.

Yesterday I went to shower, and I put the faucet handle at the 75% to hot point, where I always do, and it was lukewarm. I had to crank it all the way to hot to get it hot, which it was scalding, and I backed it up a couple of millimeters and it was somewhat hot but not super hot. I do know I need a new cartridge for that shower, so I ordered one.

Last night I decided I'd try the other bathroom shower. Same deal - 3/4 would normally get pretty damn hot, now it's lukewarm. So I eventually kept turning the handle to hotter and hotter until I couldn't turn it anymore. It was pretty hot, not as hot as it normally is. But if I turn the handle back to cold a little bit and then all the way to hot, it gets scalding hot...for a few seconds, and then go back down to decently hot but not anything like before. Sounds like a mixing valve issue? But two showers at the same time to have this issue?

So I notice if I try my kitchen sink, and my bathroom faucets, they will only get lukewarm water unless I turn them ALL the way to hot and then the kitchen gets scalding hot, and the other bathrooms get pretty hot but barely enough to burn my hand, whereas before if I did it by accident I'd be in serious pain.

So...some hot water is getting through; the kitchen is scalding hot when turned up all the way, and the other ones get decently hot (though not as much as before), and the upstairs shower will get scalding hot for a few seconds and then revert back to a much lesser temperature.

I could contact my condo board, as they control the hot water boiler and I have no access to it, but I'd like to see if there's some insight to this random problem I can resolve. I have my own unit shut offs but no hot water tank.

Thank you


The wife is still training me.
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Orlando, Florida
It is not possible to determine the cause but for one thing, it never should be scalding hot for any amount of time.

Few things may be going on, the new boiler has the temperature set different than the old unit, there may be a tempering valve for the entire building that is set for the old temperature mix, when you get the scalding hot (that should not happen) the shower may have its own anti scalding valve.

For large use buildings such as condo's and apartments with one water heater, a thermostatic mixing valve is used. It allows the water heater to be set to a high temperature like 140º F. After the mix it should be no hotter than 120º. Depending on the cold water inlet it can about double the size of the water heater. That is a 50 gallon tank may provide an equivalent of 100 gallon tank. CASH ACME calls it a tank booster.

Read here so you have some idea what needs to be addressed if the problem is not resolved.

From a google search:
How does an anti-scald shower valve work?
These devices have a chamber in which they mix hot and cold water before it flows out through the faucet. A thermostatic element inside the chamber expands and contracts with changes in the water temperature. As the temperature rises, the element expands to limit the hot water entering the mixing chamber.Sep 3, 2020
Hey, wait a minute.

This is awkward, but...

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