1. Is Being Gas Safe
Registered guarantee of carrying out competent repairs?
The answer is no! Being Gas Safe
registered is only proved to certain safety standards,
and it is nothing to do with boiler repair skills.
Before I registered with Gas Safe
in 2009, nobody in my training centres or none of my gas
safe inspectors had taught me any on boiler repairs.
One of my fellow boiler repair
men said this in a closed forum: "To be able to repair modern
boilers a heating engineer should be accomplished in
the following area:
A degree in electronic engineering.
An understanding of how the boiler
is actually doing what it does normally.
Years of doing my own car
Then ring manufacture technical
support if stuck. They are supposed to know their
own boilers best and most likely better than we
2. British Gas Fixed Price
Repairs - Are they real?
Fixed fee repairs have some
interesting details in the small print as I found out
recently when I didn't fancy repairing a boiler myself.
Not surprisingly, BG came up
first at a search offering to sort the problem for £69.
Or FROM 69 quid rather. Typing in the requested
postcode, raised it to £89. Still a good price, so rang
After giving name and address,
the girl immediately asked for credit card details. A
bit reluctant, but she did give some further info. Yes,
£89 was the all in price to sort the boiler out. Yes,
parts labour and vat.
“So, £89 will get the boiler
repaired, no matter what the problem is?”
After a slight pause, I was
informed that if it took more than 30 minutes, the price
would go up to £269. Not exactly a huge surprise to me,
apart from the 30 minutes. If we reserve a modest 10
minutes for showing the chap the boiler, unpacking and
repacking tools and doing the paperwork, that leaves not
much more than 20 minutes actual working time before the
extra £180 is due. Ouch.
Still, £269 as a maximum to get a
bad problem sorted, didn't seem to be too bad. Let's
ask, just to be sure: “Right, so £269 will get the
boiler back working perfectly, no matter what the
Another slight pause. Well, no,
if the job took more than 2 hours, the price went up to
Fook me sideways, that is more
than the price of a new budget boiler complete with
flue, clock and vat. Still, it is significantly less
than a new Bosch or Vaillant, not to mention the install
So I asked the same question
again: “Will £529 give me a perfectly working boiler, no
matter what the problem is?”
It turns out that there was no
guarantee it would.
529 squid would only guarantee to
bring the boiler back to work if there was only ONE
fault. If after 121 minutes of work it turns out there
is a second fault, the clock is reset and the bill jumps
up again, presumably to £618 provided the second fault
takes less than about 20 minutes to find and resolve.
Admittedly I didn't actually
double check that after 31 minutes into the second fault
the bill would reach £788, but as she didn't mention
anything about second faults being cheaper than first
faults, it seems fair to conclude there is no such
discount, and it would be indeed 788 notes.
I can't wait for the next time
somebody tells me I'm too expensive because BG will do
it for £69.
(Copied from bengasman at the
Combustion Chamber, Last edited on 28/11/2012)
3. What is reverse
In summer when you turn off
central heating but you still get radiators hot when the
boiler is heating the hot water. This is some times
caused by "Reverse circulation".
Here is the explanation of
Reverse Circulation and remedial methods:
A reverse circulation can only happen in the following
1. It is not going to happen on a combi system, ie, a
reverse circulation can only happen in a system which
has a cylinders for hot water.
2. It has likely happened when adding some new radiators
to an existing system, eg, new radiators added after new
loft conversation, so the T-off points are not correct.
Radiator Balancing - Balancing a Central Heating System
Radiator balancing or balancing
radiators goes by several titles. You'll also hear it
called balancing the central heating system. Unless it's
referring to a warm air central heating system or
underfloor heating it all means the same thing, ensuring
that all the radiators get equally hot. Ideally they
will all get hot together, in about the same time. If
all your radiators get hot pretty evenly you don't need
to balance the heating system. Adjusting radiator valves
can sometimes make them leak so don't turn them if you
don't need to.
Before you try balancing it's
important to make sure that the radiators have been bled
(that is, all the air trapped at the top of radiators
has been released). If some of your radiators are hot at
the bottom but cold at the top (even the very top) you
need to bleed the radiators before balancing the heating
system. If you bleed a lot of air out of a radiator with
the system warm, the water entering the radiator to
replace the air may make the radiator hot. You'll only
really know whether the radiators need balancing if you
start from cold.
Also, before attempting to
balance radiators, make sure the pump is not set to too
low a speed. Try turning it up; it shouldn't pose
problems. If it causes your system to pump water over
into the feed and expansion tank (known as the F+E tank
or the header tank) or causes air to be pulled down the
open vent pipe into the system you may have to slow the
pump down again. This usually indicates a system design
fault or a blockage somewhere.
Balancing radiators is simple, it
just takes a little time. There are more complicated
methods but the following method works fine for us. We
don't use thermometers and we judge radiator temperature
There are some basic things you
need to know to balance radiators but they're simple
too. If you're not sure of any of the terms, follow the
blue links for an explanation then come back here.
Almost all radiators have 2
radiator valves, generally at the bottom on opposite
ends. (Some very old systems may have one at the top and
one at the bottom on opposite ends; some newer systems
have both valves at the bottom in the middle of the
Water enters the radiator through
one valve (the flow end or flow valve) and leaves the
radiator through the other valve (the return end or
Usually we are restricting a
lockshield valve. Different manufacturers' valves turn a
different number of times from fully open to fully
closed. Some turn only 2½ turns and some as much as 5 or
6 turns. If your valve turns 2½ turns from open to
closed, closing it by 80% means 2 full turns closed (or
only ½ a turn open). If it turns 5 turns open to closed
80% closed means 4 full turns closed (or only 1 turn
If you close a valve on the flow
end by 80% or more, the gap left open in the valve is so
small that even a small air bubble coming in with the
flow can become trapped in the valve and stop the flow.
It may sound daft but it happens. If the flow valve is
fully open and you restrict on the return valve, any air
bubbles come through the flow valve and rise to the top
of the radiator, safely out of the way. They don't enter
the return valve which is substantially closed so they
don't block it and stop the water flowing through the
The type of valve fitted is not a
guarantee of which is the flow and which the return end.
To be sure, start with the heating system cold and go
round checking which end of the radiator (which pipe or
valve on each radiator) gets hot first. Mark the end in
some temporary way; a bit of tape will be fine.
Sometimes slightly colder water coming along the flow
pipe from a different part of the house can deceive you,
making the flow end temporarily cooler than the return
end. Check again as they warm up to be sure.
You may need to be quick moving
round the radiators because a very small radiator
connected to a powerful boiler like a combi may get hot
too quickly to be sure which end is which. If necessary,
check the smaller radiators first. You can check them in
any order and if you've marked with tape you'll know
you've checked them all.
If a central heating system needs
balancing we start by opening all radiator valves fully,
both flow and return. Adjusting radiator valves is not
without its consequences, it can make the valves leak.
If you're not sure how to deal with leaking valves, read
that section first.
Different parts of the central
heating circuit have different resistance to water flow.
Generally, the nearer a radiator is to the boiler, the
quicker it will get hot. In a well designed and
installed heating system little balancing is needed.
With all the radiator valves now
fully open, if all the radiators become similarly hot in
a similar time there is not much more to do and your
radiator balancing is completed. If not, and "not" is
usually the case, we go to the radiators which get
hottest quickest and restrict the flow through them. We
set no fixed order in which to restrict radiator valves
except to do the hotter radiators first. This pushes
more flow through the remaining, slower, radiators.
Where possible we always restrict the flow on the valve
on the return end (the cooler end) and there's a good
reason for this. To balance a poorly designed system it
may be necessary to close a valve more than 80%, perhaps
even 90%. Let me explain what I mean.
Having restricted the return
valves on the hottest radiators by 50% or 60% to start
with, we wait to see what happens. Cooler radiators will
start to get hotter. Some previously cool radiators may
get fully hot. If some are still cool we go round again,
restricting all the hotter radiators, some which we
restricted before get closed down even more (always, if
possible, on the return end) and some which weren't
restricted first time round are restricted this time
because they are now hot. Again we wait to see what
effect we've had and again, if necessary, we restrict
the hotter radiators. We'll do it yet again if
Hopefully this process brings the
radiator system into balance; you'll only know for sure
when you heat the system up again from cold. If you
close a valve down too far, that radiator will cool down
and may go cold. Just open the restricted valve a little
(10% of its total travel between closed and open) and
see if that sorts it. Open it progressively more if you
If balancing radiators doesn't
resolve the problems, and no matter how you try you
still have some cold or very slow radiators, there are
two likely causes. First is a failing pump (but make
sure someone hasn't partially closed one of the pump
isolation valves). Check to see whether you can turn up
the pump speed. Second likely cause is sludge build up
and partial blockage of pipework or of an air separator.
We would always opt to try changing the pump before
trying a process like power flushing to clear possibly
should I do if a single radiator is not hot?
If all other radiator are hot but
only one is not, it is probably a problem only related
to this particular radiator. You need to do the
Set boiler out put between 80% to
100% of full scale.
Open both valves on each side
of the radiator. For lockshied valves, use a spanner if
For TRV valves, often TRV pins
are sticking at closed poistion, you need to free its pin,
following YouTube clips (TRV pin stuck).
Here is one.
Bleed air out from the inside of
radiator. After bleeding please don't forget to top up
some pressure if it is a sealed system.
Balancing the whole system. See above.
Above procedures are for general
house holders to complete, otherwise you are expecting
to pay min one hour labour to call a plumber.
pressure drops over a period, is this a problem?
In a system with good quality
radiator valves and no microscopic leaks it is possible
for the system pressure to hold up adequately between
annual services. Most people seem to find that they have
to top up a few times a year, and some people more
often. If you find that you are needing to top up more
than once a week it might be worth trying to find the
problem or see if the relief valve is leaking and
expansion vessel is flat. If topping up annoys you (or it’s awkward) then
you might be able to get the system to hold pressure
better by adding an internal leak sealer such as Fernox
F4. This seals very small leaks but it is worth
checking that the boiler manufacturer allows its use
especially if the boiler is still under guarantee.
7. Can a modern
condensing boiler deliver an over 100% efficiency?
It is impossible! As flue gas
temperatures are still higher than ambient air
temperatures, some energy is lost through flue gases.
You can’t beat law of physics, conservation of energy.
On average, a modern boiler has
around 90% overall energy efficiency.
But why do we sometimes get
figures saying a boiler’s efficiency is over 100%? That
is from a misleading calculation by some boiler
In St Albans, we have another
good gas engineer,
Braithwaite. He is not only good on boiler repairs,
also good on boiler theory. Here is
one of his writings about boiler efficiency calculation,
which explains the way how an over 100% energy
efficiency calculation is achieved.
are the pros and cons of a boiler manufacturer fixed
Most of boiler manufacturers are
offering boiler repair service for their own boilers, by
around £300, so we called it as Fixed Price Repair.
The advantages are: 1. They own
engineers are competent on their own boilers, they are
much better than most of our independent gas operatives.
2. These engineers have most of parts or spares in their
vans, so more likely they will fix the boiler by first
visit. 3. The price from a manufacturer is capped. Even
a part plus labour are exceed £300, they still carry out
the repairs agreed.
And the disadvantages are: 1. If
you have a simple problem, they will still charge you
£300. 2. In winter times it will take days for them to
come out. 3. They only repair boilers but not for
heating which is outside the boiler.
Mobile: 07944 168888 / Email:
Telephone: 01727 537688 /
Fax: 01727 537689
Address: 77 Batchwood
Drive, St Albans, Herts, AL3 5UF