We have a viessmann atola gas boiler and our renters are stating that the water isn't hot. help!

Hey here is a LINK TO A "PDF MANUAL" FOR SERVICE AND INSULATION, PAGE 53 HAS CONTROLS, NOT SURE IF THIS IS WHAT YOU NEED
http://www.viessmann-us.com/content/dam/vi-brands/CA/pdfs/doc/cpk/vitodens_100-wb1bc_is.pdf/_jcr_content/renditions/original.media_file.inline.file/file.pdf

Turn off heating on the programmer select water only

you did not state which model, therefore detailed instruction or remedy is not possible, telepathy do not work that hot as they show in the movies... these two are most "popular " choices in most of boilers, regardless of brand or heating element.

your release valve is blocked by calcium build-up, lift it few times and it should clean and close correctly, if it is not - need removal and cleaning or replacement, cleaning is cheaper...

another reason can be location of the boiler, if it is much lower than lowest radiator - it can constantly overflow and drip hot water from overflow valve as well.

if these two do not apply - unfortunately - with available information, need to call technician or at least relative with plumbing skills...

odd noise like popping or singeing fire....clicking noises.....sounds like you have a water leak putting out the pilot.......or your thermo coupling is bad....or the noise is the tank full of calcium buildup and that will make noises when the burner is on

Boiler compartment ventilation will not stop you getting hot water . Its sounds like you have problems with a sensor or the water section on the boiler .

check the pcb.

Hi - hope someone can help. I have a VOKERA EXCEL 80SP combi boiler and been without hot water/central heating for two days. The pilot light is on, the fan is on, but boiler not triggering once the hot water tap is turned on.
Hopefully someone come to look at it today but hoping for some advice. Anyone else had this problem?
Thank you.

if cold supply to boiler and shower are off the same feed this could be your problem as the boiler governs flow of hot water best of luck

Check all your limit switches on this unit. One of them is either tripped or bad.

what size of gas line is going into boiler and water heater? is it black iron ? natural gas or propane? have you checked gas pressure at water heater and furnace ? if they work fine individually then you have a problem with incoming gas pressure. Call gas company and ask them if they would come out and check gas pressure.