there's an oil line - a cold water line and then 2 recirculating lines - plus at least one hot water out....
to further complicate the matter - this morning i got hot water (constant) out of the sink in the problem bathroom....
maybe i could probe some minds by asking - how does a tankless boiler work? how does it keep pumping out hot water? perhaps the problem is the boiler is older then dirt and needs to be replaced?
Lets keep this simple, it sounds like you may have a brass cartridge in your shower valve that may be providing a cross over. Due to the nature of our conversations i think you should have a plumber come by to look at this. There is nothing quite like a frozen cartridge without an insert removing tool.
could the crossover prob in the cartridge be making the problem for the sink in the same bathroom?
would it mean that a cartridge replacement would fix the whole bathroom? (that being said - i understand the moen old cartridges are quite a pain - to say the least)
only reason i say that is perhaps this morning's hot water availability in the sink faucet was my wife and i's fiddling around with it yesterday....?
thanks again for all the replies
You don't have a faucet or piping problem. Your issue is most likely the tankless coil on the boiler. It should have a mixing valve. Have your plumber check it for scaling. Have you had the boiler serviced this year? You might also have a problem with the limit switch.
i appreciate the quick replies - but people need to read the whole thread... the rest of the house is working fine - i'm pretty sure we've isolated this to a cartridge problem in an old Moen shower control - just wondering if that could have an effect on a sink in the same bathroom... from what i've researched online, seems it can...
next problem - in a shut off valve (main) that doesn't seem to close all the way (after it's cranked - water still slips by) - can that be adjusted, or does that need to be replaced entirely... in order for me to tackle the cartridge problem, i need to shut the main - but after trying to do so, i'm still getting water to flow by the valve...
it sounds like your having some erratic behaver with your plumbing system.
sometimes it's not that easy to figure these things out without being there. i understand and apprectiate your enthusiasm, and with all do respect i think you need to call in a plumber.:)
i would call an electrician if i was having electrical problems.:D