Hi first time user on this sight I hope this question makes sense.
Can anyone tell me what is happening with my hot water boiler? Recently it seems that our thermostat has no control over the amount of heat that goes through our hot water heating pipes. I replaced the thermostat, but does not seem to change the situation at all. When we need hot water for showering etc. we turn the furnace switch on for about fifteen minutes or so, well the water the water gets hot OK but the temperature in the house also gets way up too. I guess what I'm asking is if there is a secondary thermostat on the furnace that controls the water for showering etc?

(Question moved from Introductions to more appropriate topic area in order to get the most exposure to those best able to answer the question. The Introductions topic area is for introducing yourself and we try not to ask questions in that area. Thank you!)

Even if you have a combination boiler, the Heating thermostat should have nothing to do with the domestic hot water. The sanitary water you drink and shower with, should not be the same water you heat with.