D:\standards downloads\NHS\HTM\HTM 03 check on the control functions, how to R1.docx 1 of 10 Guidance note: on how to, check the control functions of ventilation systems DRAFT 1. Introduction Why check "control functions"? poorly set-up or operating or non operational control functions, are very common resulting in poor environmental conditions in many healthcare buildings adversely affecting productivity and increasing errors and mistakes by healthcare staff, these are well known and supported by research, some on healthcare workers. (Wyon, Fanger, Lidwell & Wyon, Bordass and Leaman et al). Leaman A, Bordass B. Productivity in Buildings: the ‘killer’ variables. Creating the productive workplace. Workplace Comfort Forum. London. 29-30 October 1997. The availability of plant and therefore ventilation systems is also adversely affected by needless failures of ventilation systems due to controls either not being installed or correctly commissioned, resulting in theatre closure, department partial closure or closure and in the case of PFIs substantial fines for unavailability. The positive side of checking "control functions" is the checks and tests are cheap, very quick and reliable, when carried out by people with appropriate basic knowledge and training. This also reduces corrosion and water logging in the ventilation system, because water and wet surfaces are effectively eliminated to just the cooling coil and the AHU after the cooling coil, before the heater battery; this being the area made from stainless steel and therefore largely immune from corrosion. Thereby significantly minimising (periodic) bacterial colonisation and conditions leading to colonisation of Legionella.
Transcript
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Guidance note: on how to, check the control functions of ventilation systems
DRAFT
1. Introduction Why check "control functions"? poorly set-up or operating or non operational control functions, are very common resulting in poor environmental conditions in many healthcare buildings adversely affecting productivity and increasing errors and mistakes by healthcare staff, these are well known and supported by research, some on healthcare workers. (Wyon, Fanger, Lidwell & Wyon, Bordass and Leaman et al).
Leaman A, Bordass B. Productivity in Buildings: the ‘killer’ variables. Creating the productive workplace. Workplace Comfort Forum. London. 29-30 October 1997.
The availability of plant and therefore ventilation systems is also adversely affected by needless failures of ventilation systems due to controls either not being installed or correctly commissioned, resulting in theatre closure, department partial closure or closure and in the case of PFIs substantial fines for unavailability. The positive side of checking "control functions" is the checks and tests are cheap, very quick and reliable, when carried out by people with appropri ate basic knowledge and training. This also reduces corrosion and water logging in the ventilation system , because water and wet surfaces are effectively eliminated to just the cooling coil and the AHU after the cooling coil, before the heater battery; th is being the area made from stainless steel and therefore largely immune from corrosion. Thereby significantly minimising (periodic) bacterial colonisation and conditions leading to colonisation of Legionella.
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2. What are control functions What are control functions? These split into three categories, these are: Control functions, to allow the ventilation system to operate safely and to prevent damage to the plant and components in ventilation systems, these include interlocks to prevent the operation of the fans until the control dampers are open, to prevent the fans from operating when the supply of hot water is interrupted or lost to the frost and secondary heater batteries, these interlocks for example prevent damage to the dampers, filters, freezing heater batteries etc. Control functions, to control the temperature and humidity in medical locations where the ventilation system performs a vital part of the infection control strategy for the patients. When these controls are not working correctly; the result is often increased energy costs, more importantly poor environmental conditions in t he medical location and poor conditions in the air handling unit. These include increased water carry over onto the filters from air inlets and cooling coils, resulting in moulds and bacterial colonisation of cooling coils, filters and ductwork. Control functions, to allow the user controls perform the correct function, both with respect to the controls in the department or theatre and the ventilation control panel.
3. Requirements All ventilation systems should be inspected annually to ensure conformity with minimum requirements, whilst there are many who offer these services, many do not inspect , or report on all the areas of ventilation systems defined and required in HTM 03-01. The following details how the control functions of a ventilation system can be carried out, so that the Verifier, Validator, AP, CP, maintenance technician etc. Can conclude in the quarterly and annual verification of a critical ventilation system, the annual inspection of all other ventilation systems and the commissioning and validation of refurbished and new systems, that the "control functions" are working correctly.
4. Competence All people carrying out works (including testing) on ventilation systems, in this case "control functions" should be competent and have the appropriate knowledge to carry out the works safely. This document concentrates on providing additional information on how to carry out a check of the "control functions" without needing to refer or normally even to look at the control system set-up or building management system head end. It is assumed those undertaking these works have acquired the appropriate knowledge about healthcare ventilation systems by for example attending and having successfully passed appropriate training courses on this subject and others for example on say electrical installations, permitting systems etc.
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The subject of ventilation for all non domestic installations is covered by the workplace (health safety and welfare) regulations 1992; in regulation 5 and 6 of the workplace regulations ACOP 2013, this deals with the maintenance of the workplace including ventilation and in regulation 6 the provision and suitability of ventilation in the workplace, there are other relevant sections to the suitability of the environment. These requirements have not substantially changed from the 1992 requirements. This makes it very clear that suitable ventilation must be provided at all material times (as detailed in the HTM for healthcare estate) and for the systems delivering this to be maintained such that they deliver appropriate ventilation (this demonstrated, by carrying out tests and checks and recording them).
HTM 03-01 Specialised ventilation for healthcare premises Part A design and installation and part B Operational Management: November 2007 This covers the design and installation of ventilation systems in the Healthcare Estate in part A, part B covers the quarterly inspections and annual verifications of for example AHUs (there is no maintenance requirements for AHUs). in Part B 4.9 vi requires a check on the control functions, as a part of the" annual Verification" see earlier discussion. also in Part B item clause 4.15 "Table 1 provides a model for the verification of critical ventilation systems." table 1 Operational management and routine verification process model in item 5 asks Does the control system function correctly? • Desired environmental conditions • Control sequence logic • Run; set-back; off philosophy requiring the verifier to Establish the design requirement Inspect/test to verify performance.
5.2. CIBSE Guide H Building Control Systems:2000 & 2009
for example requires, annual maintenance
5.3. BSRIA BG 4/2003 BMS Maintenance guide:2003 for example requires, sensors every six months and interlocks every year
5.4. HVCA SFG 20 Standard maintenance specification for services in buildings
for example requires, sensors and interlocks every year
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6. Control function AHU Schematic The following diagrams show the AHU components that must operate for a variety of outside conditions, for the plant to operate correctly and result in the correct temperatures and humidities as required by HTM 03 and other European and UK standards.
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There is no objection to the free reproduction of these diagrams providing is source and author Richard Knight is acknowledged
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The same can be illustrated for ease of use on site , by the following controls flow diagrams:
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There is no objection to the free reproduction of these diagrams providing is source and author Richard Knight is acknowledged
7. Operation of the plant safety devices The following diagram shows the correct operation of these main devices
There is no objection to the free reproduction of these diagrams providing is source and author Richard Knight is acknowledged
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Note there are others, these include: The correct operation of the frost capillary, this is achieved, by ensuring the coil is installed correctly and a loop is provided so it can be immersed in a plastic cup of water at say 4 deg c with crushed ice. The testing of the low air flow alarms these are required to trigger and change over to the spare fan motor (if installed) and, when the second fan is failed send a low flow alarm to the departmen t served (typically at surgeons control panel or nurse base in a HDU etc. the alarm is to be triggered at 80% of design flow, in pressure terms this would be in the region of 600pa to 800pa ). The filter alarms are tested in a similar way, typically 150 pa for a panel filter and 250 pa for other filters (excluding HEPA filters).
8. Test order These should be carried out in the following suggested order:
Carry out the environmental controls test i.e. check which plant is on or off e.g. cooling coils
Synthesize the plant failure modes e.g. fail the first fan motor (fit lock and "caution" sign), see that the second motor starts (if fitted) then, fail that motor by isolating it (fit lock and "caution" sign), see the motorised dampers close promptly, and the frost coil valve opens promptly, and then the other control valves close.
Carry out the internal physical inspections of the plant as normal
Restart the plant/ventilation system
Carry out other physical tests
Air flow failure pressure switch/sensor
The final test being the proving of the frost coil capillary as the ventilation system will be operating, the frost coil control valve will often have closed, therefore when the capillary test loop is immersed in a cup of crushed icy water, the fan(s) wi ll fail and dampers close, etc. and the frost coil will get hot again, making the outcome of the test easy to see and clear.
Note: it is often easier and better if the environmental conditions in the area are checked first by recording
the temperature and humidity in the space and the temperature and humidity has been set to in the space. This would be done at the same time as the area to be tested is checked to confirm that the area is not in use (i.e. when the safety documentation is signed and issued).
Note: suggest some of these test are NOT carried out when the air temperature is close or below freezing .
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9. Cost impact statement
Costs these are split into, capital, equipment, labour, maintenance, energy as follows: Capital Clearly Nil. Equipment Less than £100, life 3+ years, also see next item, equipment should already be held by technician. Labour Additional 5 mins maximum, verifications and quarterly inspections are commonly carried out a high number of people carrying these works out claim this is their main work, so efficient working would be the norm. Cost based on £50 (€65) per hour, therefore £5 (€6.5) per ventilation system. Maintenance Significant savings with respect to cost of needles repair and replacement of ventilation plant components, most reasonable sized hospitals will replace one or more frost coils etc. per year. Also significant reduction in corrosion and reduction in opportunities for bacterial/mo uld colonisation. Energy These savings are significant with respect to cost for test, common for components operation to clash e.g. energy recovery device not working e.g. run around coil, energy recovery recuperator in bypass, when the plant needs heating......
10. Additional Resource or Equipment requirements Temperature probe and humidity detector. This already required to measure and record room environmental conditions e.g. theatre, ICU temperature and humidity, in this case equipment cost would be NIL . The instruments are only required to measure the energy recovery device as the temperatures are low and the supply air condition by inserting the probe in a convenient supply diffuser. In practice this equipment would commonly used by any technician, verifier, etc.
11. Current situation Well over 90% of current ventilation systems fail these tests, plainly these tests will reduce revenue expenditure, business and reputation risk, through un planned failure. The current position is the environmental controls, control panel operation are rarely carried out or recorded, the user controls in the department are often also not recorded or reported on.
