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The Irish Times - Thursday - Property - - Advice -

QI have a gas-fired cen­tral heat­ing sys­tem with 16 ra­di­a­tors. On the ground floor are eight ra­di­a­tors (in­clud­ing one in the con­ser­va­tory); on the first floor there are seven; and one in the at­tic room.

The new ra­di­a­tor in the sit­ting room has been un­der­per­form­ing (warm at the top, cool at bot­tom).

Its pre­de­ces­sor wasn’t great ei­ther. We got the new one be­cause it was larger.

Re­cently I turned on the heat­ing in all 16 ra­di­a­tors si­mul­ta­ne­ously and mon­i­tored the per­for­mance. The at­tic and first-floor ra­di­a­tors worked well. The ground floor per­for­mance was patchy. Of the eight ra­di­a­tors, only four were hot at the top, two oth­ers were warm, an­other two were luke­warm.

It has been sug­gested that the prob­lem is residue in the sys­tem and that power-flush­ing is the so­lu­tion.

How­ever, all the ad­vo­cates of this are com­pa­nies or in­di­vid­u­als sell­ing that ser­vice. I have failed to find any ob­jec- tive sci­en­tific eval­u­a­tions of the process. And it is not cheap. I am look­ing at ¤700 or more to get it done, tak­ing one day. Can you ad­vise?

AThere are many vari­ables with heat­ing sys­tems. Any di­ag­no­sis in the first in­stance deals with the iden­ti­fi­ca­tion of the sys­tem in use. You have not set out the type of sys­tem in your house, and I will there­fore deal with the an­swer in broad terms.

There are two prin­ci­pal pipe arrangements: one-pipe and two-pipe. The one-pipe sys­tem is the sim­plest and cheap­est and most com­monly used in spec­u­la­tive devel­op­ment. Ra­di­a­tors be­come pro­gres­sively cooler from first to last as you move away from the boiler. Reg­u­la­tion or con­trol of heat to in­di­vid­ual ra­di­a­tors is chal­leng­ing.

The two-pipe sys­tem is a su­pe­rior sys­tem where one pipe de­liv­ers hot water to the ra­di­a­tors and a sec­ond pipe car­ries cold water from the ra­di­a­tors back to the boiler. In­di­vid­ual con­trol of the heat to each ra­di­a­tor is more ef­fec­tive.

Tra­di­tion­ally, heat­ing sys­tems were fed from a small water tank in the at­tic. This pro­duced a “head” of pres­sure in the sys­tem, usu­ally aided by a cir­cu­la­tion pump. This type of sys­tem was prone to loss of water through evap­o­ra­tion, with new water added by way of a ball cock feed­ing the header tank.

The prob­lem with this was that the in­tro­duc­tion of fresh water pro­moted cor­ro­sion, with sludge and rust build­ing up within the sys­tem as a re­sult. The ex­pan­sion of water when heated and con­trac­tion when cool can also in­tro­duce air into the sys­tem. Both of these prob­lems can cause ra­di­a­tors to be cool at the top yet warm at the bot­tom. All ra­di­a­tors have an air re­lease valve (square headed nut at the top of the PHO­TO­GRAPH: GETTY IMAGES ra­di­a­tor), which al­lows this air to be man­u­ally re­leased by open­ing the nut slightly.

More mod­ern sys­tems will be pres­surised. The tank in the at­tic is no longer re­quired and an ex­pan­sion ves­sel will be pro­vided close to the boiler. The sealed sys­tem elim­i­nates evap­o­ra­tion and re­duces rust, and will also im­prove cir­cu­la­tion.

Other fac­tors, apart from sludge and air, that in­hibit cir­cu­la­tion can in­clude the poor oper­a­tion of valves or in­cor­rect bal­anc­ing of the heat­ing sys­tem. Each ra­di­a­tor has a wheel valve at the entry point and lock shield valve at the out­flow.

The wheel valve can be ther­mo­stat­i­cally con­trolled, mean­ing that the tem­per­a­ture of the ra­di­a­tor can be set at a de­sired heat. The lock shield is used to con­trol flow of water, forc­ing hot water past the early ra­di­a­tors to re­mote ra­di­a­tors fur­ther away from the heat source.

Most mod­ern sys­tems will op­er­ate with zones. This means that, for ex­am­ple, the ground and first floors are plumbed sep­a­rately, al­low­ing them to be used in­de­pen­dently of each other. The zones are typ­i­cally con­trolled by ther­mostats and timers and these ac­ti­vate a mo­torised valve, al­low­ing hot water to flow in the sys­tem at par­tic­u­lar times or when the tem­per­a­ture drops be­low a de­sired set­ting.

These must be mon­i­tored to en­sure they op­er­ate prop­erly. I have seen cases where the ther­mostats were con­nected to the wrong mo­torised valves.

The ad­just­ment of the ther­mostats is also an is­sue. In my own house, the ther­mostats al­ways ap­pear to mys­te­ri­ously move up­wards in my ab­sence. The place­ment of the ther­mostats in im­proper lo­ca­tions, such as in an area af­fected by heat from down­stairs, will mean that the up­per floor zone may not op­er­ate as it should.

You have 16 ra­di­a­tors. A typ­i­cal four-bed­room house will have 11 or 12. I note that you have an at­tic room and con­ser­va­tory and that the new ra­di­a­tor is big­ger than the orig­i­nal. Your is­sue may be an un­der­sized boiler. If you have added the con­ser­va­tory and con­verted the at­tic with­out con­sid­er­ing the re­quire­ment to im-

Send your queries to prop­er­tyques­tions@irish­

or to Prop­erty Clinic, The Ir­ish Times, 24-28 Tara Street, Dublin 2. This col­umn is a read­ers’ ser­vice. The con­tent of the Prop­erty Clinic is pro­vided for gen­eral in­for­ma­tion only. It is not in­tended as ad­vice on which read­ers should rely. Pro­fes­sional or spe­cial­ist ad­vice should be ob­tained be­fore per­sons take or re­frain from any ac­tion on the ba­sis of the con­tent. The Ir­ish Times and its con­trib­u­tors will not be li­able for any loss or dam­age arising from reliance on any con­tent. prove or in­crease the out­put from your boiler, this is prob­a­bly the is­sue in your house. In your case, as ra­di­a­tors are hot at the bot­tom, it is un­likely that you have an is­sue with sludge. The cost as­so­ci­ated with cleaning the sys­tem may be better di­rected towards an im­proved boiler.

The iden­ti­fi­ca­tion of any de­fect will in­volve a full anal­y­sis of the sys­tem in a prop­erty. Is the sys­tem one-pipe or two-pipe? Open or pres­surised? Ther­mo­stat­i­cally con­trolled ra­di­a­tors? Zoned or not? Are ra­di­a­tors heat­ing at top or bot­tom? What maintenance regime had been in place be­fore now? What al­ter­ations or ad­di­tions have taken place?

To jump to a con­clu­sion could bring you in the wrong di­rec­tion in terms of rem­e­dy­ing your par­tic­u­lar is­sue.

It would be more pru­dent to spend your money iden­ti­fy­ing the is­sue to be ad­dressed rather than treat­ing this prob­lem on a trial-and-er­ror ba­sis. Your lo­cal char­tered build­ing sur­veyor will be able to as­sist in di­ag­no­sis of the prob­lem and de­vel­op­ing a so­lu­tion.


are two prin­ci­pal pipe arrangements: one-pipe and two-pipe. The one-pipe sys­tem is the sim­plest and cheap­est and most com­monly used in spec­u­la­tive devel­op­ment

Noel Larkin is a char­tered build­ing sur­veyor and mem­ber of the So­ci­ety of Char­tered Sur­vey­ors Ire­land,

Di­ag­nose the prob­lem for a rad so­lu­tion.:

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