Low pressure.....

[Pssst]

It seems that there is a fair bit of it about and its on the increase as the colder weather creeps on.

Typically,we would like to see a WP of around 19-22mb at the meter outlet but what happens when we dont get it?

TOO HIGH ? Well this is likely to be due to a faulty or maladjusted regulator. There are "replace on find" instructions on certain types of domestic regulator,most commonly,the Donkin 225/2 regulator. The reason? It has been found that the plastic valve can sometimes shear off due to fatigue and allow service pressure through to the installation.

TOO LOW ? Again it could be caused by a faulty or maladjusted regulator.
It may well be that the regulator is working ok but that the network can simply not deliver the pressure that we would aspire to.

It is now becoming accepted practice for distribution networks to manage the network pressures toward the lower end of the spectrum.

This can lead to lower pressures at the extremities of the network and in higher demand areas especially at peak demand times.


This is exacerbated by increased demand on existing networks due to upgrading of appliances. For example, a typical road will have a gas main of a particular size. A couple of decades ago it may have serviced a street full of domestic boilers of maybe 75,000 Btu input. Fast forward to today and everyone has 30Kw plus combis and you can see that during peak time demand,there may be reduced pressured and a certain amount of sharing of available gas.

Most domestic PE services that have been renewed will have been replaced with smooth bore 20mm PE. Many will also have been replaced using an insertion technique in which corrugated PE service is inserted inside the old steel SP.

So the issue becomes..is the low pressure consistently low or is it a peak demand issue?

Also..how do we measure it? I would suggest that the WP should be measured at the meter outlet with a combi boiler delivering hot water at the point where it is run from cold..i.e not modulating.

If it is found that it is simply a network issue,and that pressures are not excessively low...then the ESP will be likely to leave as found.

District regulators respond to demand and a measured low pressure on one day may well be found to be acceptable the next day.


Of course as far as the ESP is concerned,they only want to know about meter OL dynamic pressures.

Are you seeing increased low pressure reports?

 

[SimonJohns]

I thought it was just because the network turn down the service pressur in sunmer and back up in winter. Perhaps they havent turned it up enough in your area just yet

 

[diamondgas]

pssst .. something that has taken a lot of thought with such a long post ... My first thoughts are "aren't the suppliers suposed to guarantee a minimum suply pressure?" I'd have thought that to be 21 mbar? Maybe there are some tofo engineers that can enlighten me/us further?

Good thoughts, thanks 🙂

 

[AWheating]

the min is 19mb but in peak demand periods they used to be able to allow 16mb i think. Basically because the mains are not adequate instead of huge costly improvements they found it easier to just re write the regs and allow for less pressures. Money makes the world go round as they say.

The problems they have around my area is the gas is dirty and mains are old, and full of carbon/corrosion. The years spent not improving the supply pipework means major problems. same with water, trains etc.....

if you look at the water boards, they are self regulating and will only take you to court if you waste or contaminate water yet they lose 20-30 percent of there own water. Will they take themself to court for wasting water? its a joke really.

 

[CMairiD]

Never experience low pressure due to supply in our area. I understand that London can be an issue.

One of our areas is in a valley and we suffer with water in the supply which makes the pressure bounce like mad.

 

[Pssst]

Its true that in many areas,the usual schedule was to reduce pressures in Summer then ramp them up in Winter. Now though,it is often the case that they try to run the Winter period on lower pressures also. In addition,if people are putting in 30Kw plus combis wholesale,well the mains are not being upsized in big numbers so clearly there may be issues. OFGEM,the industry regulator, has for a long time tightly controlled expenditure on mains renewals. t is only in recent years that they have finally agreed to a long period of expenditure,hence the mass digging thats going on all around the country.

Of course as CMair says..water ingress can be a big problem especially in Winter. Reduced pressures means that even more water can leak in and increased use of new PE mains means that it cant leak out again !

I know that ESPs will live with working pressures as low as 15mb as long as it isnt for a sustained period.

The difficulty is of course that for eg ,on routine service visits,engineers dont see what they deem an acceptable wp at their boiler and so turn it off and phone ESP. ESP comes,says all ok and turns it on again..and so it goes,round in a loop..

I know Worcester put out a bulletin about low pressures but did Vaillant put out similar?? also i seem to remember a Potterton boiler that seems touchy about this..is it the promax with the E119 code or is it EA?? cant recall..