I keep repeating myself and would prefer to stop and just post a link. This comes up all the time in business and people needing favors. Try to see it from my perspective. Yes you are allowed to wire and plumb your own single famly residence legally and I support this. This varies by state law. Usually if it's a multifamily you are not allowed to do the work. Some states have no licensing requirements and private companies for permits and inspections. But the question of liability assignment remains. What happens when something bad happens and the cost is too much for you to bear alone. Catastrophic property damage, personal injury, and loss of life, which you could easily do wiring your own boiler controls. Everyone in the business has seen or heard it happen. Buildings burnt to the ground, CO poisoning, damage to capital equipment ... So, don't take my word for it. Consult with and take the word of the party you have a contract with, your homeowner's insurance company. Call them up and tell them you are wiring your own boiler controls and ask them if you are insured for that. The response will range from "you are no longer our customer", "yes but your premium just went from $540 to $1500 (high risk group)", "yes we take your premium, but no, we do not pay if you invalidate the contract by installing work that does not meet code or is illegal". I do not say this, ask your agent and underwriter what they will say. It's accidential or act of God if the structure meets code. Your homeowner's also covers your negligence, if necessary. But do they cover "you" for your own negligence. Can they? They may pay the injured party then counterclaim you, if you caused willfully, or no pay at all. This is why I say ask them. But depending on the company, they may be quick to deny the claim if they find evidence of code violations, even unrelated but evident and nearby code violations. Don't take my word for it. Buy your agent lunch and present him with these questions. I would like to know the answer myself. I see dangeous violations and fraud all the time. I agree with the insurance companies if they say they do not insure this when found. They may take your premium right up to the point someone gets hurt and the cost is huge. Then it is to be expected they will not want to sit at the same side of the table with you, or reach out to other parties to spread the pain around. I will try to keep my word and this will be my only post in this thread. Go ahead and have at it. But to be fair to me, ask your insurer what they will say to these questions. Do they pay if some illegality of any kind is found at or near claim.