BOILERS & WATER HEATERS


Combatting T/PRV drips


Since the launch of his first product the managing director of RA Tech, Russell Armstrong (the inventor of the hotun dry trap tundish) has been investigating the reasons why many temperature and pressure relief valves are left unnoticed, untouched with the home owner simply allowing water to constantly drip out of the relief valve and down the tundish


R


ussell says: “When I first started to think about the concept of a dry trap tundish, I started to get involved with the many factors that go along with issues to do with the subject of dripping T/PRVs. What causes them to drip/ flow or run and why don’t people react to the situation to get the problem fixed?”


System degradation - boilers


Example of boiler PRV constantly dripping and causing stains on wall of building


We assume they should, but do they? It is my belief that the current generation of homeowners have lost touch with the association of a dripping PRV and remedial action needing to be taken However, their solution may be to simply top up the system. They won’t realise that this loss of water is letting out the system water that has, hopefully, been treated to prevent corrosion, the fresh water being introduced brings in fresh oxygen that increases the risk of system corrosion. Once topped up they don’t realise that the discharge cycle will start all over again, and again until they finally get fed up of topping up and call out an engineer to finally look into the problem (probably the expansion vessel needing a re-charge – a simple enough fix)


However, in the meantime, due to a loss of system water and fresh water being introduced, it could possibly mean that corrosion has started to set in to the system, leading to more expensive repairs rather than just the re-inflation of the pressure vessel.


Landlord costs


How about if you are a landlord? Would a tenant necessarily report to you or the agent, that the boiler is loosing pressure or would they just keep topping it up and the first time the landlord gets to know about it is when the tenant tells them that the boiler has catastrophically failed, who then gets to pick up the bill?


Loss of precious resources – unvented cylinders


So for boilers, it’s an issue of corrosion, but for unvented water heaters the issues become more about wastage.


The consequences for the system vary depending on the application, for instance, with a boiler, the PRV will only drip until the pressure is relieved but, once enough water has dripped out of the system, the boiler will lock out due to low pressure. This then draws the attention of the homeowner and they do something about it. But what do they do? For most of the UK’s boiler market the PRV point of discharge is located outside the house and water dripping out of the PRV is left to simply drip down the wall. Does the homeowner/building user actually associate this drip with the discharge coming from the boiler, do they even notice it? Even if they do, are they fully aware that they need to take remedial action on the boiler system because something is wrong to cause the pressure that is then dumped to outside?


We all know that unvented cylinders have, by and large, two ways of accommodating water expansion caused due by temperature. If we don’t allow water to have somewhere to go to when it warms up, pressures within the system increase quite quickly.


Air bubbles and expansion vessels


Over time, air bubbles get absorbed into the water and for expansion vessels, the Schrader valves can weep or bladders within the expansion vessel fail.


Water dripping out of the T/PRV on an unvented cylinder with excessive limescale


www.heatingandventilating.net Russell


Armstrong, MD of


RA Tech


 January 2021


www.heatingandventilating.net


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