Can anyone help with my query?

There are a couple of commercial tenants in a small building; who are probably lone workers. Each tenant uses a domestic combi boiler. Would these fall outside the scope of the Pressure System Safety Regs?

If we have no requirement for a written scheme I assume an annual service will be all that's required.

Grateful for any advice.

Forget the 110*C bit

You need to check if you have a relevant fluid. Don't think you do, so PSSR doesn'r apply.

Check the flow chart in the ACOP, to help you decide

Relevant fluid
26 The following conditions have to be fulfilled for a fluid to be a relevant fluid within the scope of the Regulations:
(a) the pressure has to be greater than 0.5 bar above atmospheric (except for
steam). Where the pressure varies with time, then the maximum pressure that is normally reached should be the determining factor;
(b) either the fluid should be a gas or mixture of gases under the actual
conditions in that part of the system or a liquid which would turn into a gas if system failure occurred. Therefore the Regulations will cover compressed air (a mixture of gases) as well as other compressed gases such as nitrogen, acetylene and oxygen. The definition will include also hot water contained above its boiling point at atmospheric pressure (pressurised hot water) or aqueous solutions where a vapour pressure above 0.5 bar (gauge) is generated. Classifications of gases are given in BS EN 720-1:1999 Transportable gas cylinders. Gases and gas mixtures. Properties of pure gases.