What IS a Gulfstream 2000?
The Gulfstream 2000 is a another example of the thermal stores that
Gledhill specialise in making. Unlike their other thermal stores though,
the Gulfstream is self-powered by gas. It incorporates a high efficiency
condensing gas boiler inside the casing which heats the store water.
Other than having a gas boiler built in, it is pretty similar to all
the other 2000 series Gledhill thermal stores.
Like
conventional hot water cylinders, a thermal store is a container filled
with hot water but here the similarity ends. Once filled, the water in a
thermal store never changes. Instead, the hot water stored in it is used to
heat the tap water using a heat exchanger. This allows the hot tap water
to be delivered at full mains pressure, and is one of the primary
benefits of installing a thermal store instead of a conventional hot
water cylinder. For central heating, the hot store water is pumped
directly around the radiators.
The Gledhill Gulfstream transfers heat into the tap water using a pump
and an external 'plate heat exchanger'. A plate heat exchanger is a
block of very thin stainless steel plates arranged so that cold mains
water can flow through one set of spaces between the plates, and hot
water from the thermal store core can flow through an alternate spaces.
Heat transfers through the plates and heats the cold mains water on it's
way to the hot tap.
How does the Gulfstream 2000 work?
The integrated condensing gas boiler heats the water inside the thermal store. A
thermistor (heat sensor) is attached to the domestic hot water outlet
from the plate heat exchanger. When the thermistor records a fall in
temperature it knows a hot tap has been turned on and the circuit board runs the pump. The pump circulates stored
hot water through the plate heat exchanger, heating it, and the circuit
board turns it off again when the thermistor reports a temperature rise.
This system is proportional. The bigger the temperature fall seen by the
thermistor, the faster the circuit board runs the pump. This way the
designed flow temperature (of 52 degrees Celsius, I think) can be
maintained at almost any flow rate when a hot tap is turned on. Central
heating is very simple in that the CH pump starts and circulates water
around the radiator circuits whenever the CH timer and room thermostat
are both calling for heat.
Common problems:
I'm afraid I don't hold the Gulfstream 2000 in very high regard due
to the common and expensive breakdowns call-outs I used to regularly attend.
I no longer repair them now I'm afraid. Most Gulfstream 2000 breakdowns fall into one of the following categories:
1) The red "Store Overheat Lockout light" keeps coming ON.
This is usually a terminal fault as a new
gas-to-water heat exchanger will be required. Gas-to-water heat
exchangers seem to be intermittently available but even when available
the cost is prohibitive, generally being about the same price as a whole
new boiler. The gas-to-water heat exchanger in the integrated
gas boiler becomes contaminated with products of corrosion if the
correct corrosion inhibitors are not added to the circulating water by
the original installer. This restricts the water flow though the boiler
causing the top of the heat exchanger to overheat. One, or both, of the overheat
protection thermostats trips and the unit stops working until the user
re-sets them. Then the cycle repeats. The unusual cylindrical design of
the heat exchanger means that the corrosion deposits cannot be
effectively removed by chemical or powerflushing treatment, so a new
heat exchanger has to be fitted. Or better, a new boiler.
2) The "Boiler Overheat Manual Reset" button popping out.
Same comments as 1) above. It's usually caused by poor water flow
though the gas-to-water heat exchanger as a result of contamination by
system corrosion deposits.
3) Red "Ignition lockout" light coming ON.
Pressing the "Reset" button makes the light go out, but
fails to start and the light comes back ON again after a short wait.
This is failure of the flame to light. I've seen this twice now caused
by pre-mix fan failure. The impeller disintegrates and the debris simply
jams the fan and stops it from rotating. A new pre-mix fan fixes the
problem. The "Ignition Lockout" light coming ON can also be
caused by an absence of gas, failure of the ignition module on the gas
valve, or the condensate trap (or drain line) being blocked.
4) Leaking pump isolation valve leading to pump failure.
The pumps fitted to Gledhill appliances (sensibly) have isolation
valves fitted, so failed pumps can be replaced without draining the
whole system. Not so sensibly, the type of valve used is the 'ball' type
which tends to leak after a few years. On a 'ball' type valve there is
no packing gland to tighten so as the leaks can't be fixed except by
draining the system and replacing the whole valve, so as the leaks are
small they tends to be ignored. Unfortunately though, the water drips
onto the pump and eventually finds its way into the pump motor windings,
causing the pump to fail. Of all the Gledhill range of appliances the
Gulfstream 2000 seems especially prone to this problem.
5) Pump failure leading to control board failure.
When any of the three pumps in a Gulfstream fails it tends to damage
the electronic control board. This is an expensive board to replace and
I've seen dozens of these failures (sometimes initiated by the leaking
valve problem explained above). The repair bill to fix it runs into
several hundred pounds.
6) Thermistor failure.
The heat sensors (there are actually two) can become unreliable with
age. This usually presents as unpredictable hot water performance or
unstable hot water temperature. The thermal store will be hot, but the
pump will not run fast enough (or at all) when the hot tap is open
leading to warm water from the hot taps degrading to cool and staying
cool, or simply running hot/cool/hot/cool/hot/cool and driving users to
distraction.
7) Central heating timer clock failure.
The clock appears to work correctly but the switch inside fails to
operate. The CH remains permanently ON (or OFF).
8) Water scale-contaminated plate heat exchanger.
The plate heat exchanger is prone in some areas to water scaling.
This presents as maximum water temperature becoming progressively lower,
and in the final stages of scaling, the flow rate from the taps reducing
too. The fix is to either fit a new plate heat exchanger, or to de-scale
the existing heat exchanger using conventional descaling
techniques.
9) Central heating failing intermittently.
Usually caused by triac failure on the main control board. A new
board will be needed.
10) Central heating failing to turn OFF.
Once timer clock failure has been ruled out this is usually caused,
once again, by control board failure. A new board is probably required.
11) Water dribbling from the overflow.
Usually caused by the automatic filling device (RPZ valve, or 'CA
device') failing to close properly and discharging through the safety
discharge pipe. A new CA device will be needed. They cannot be
successfully repaired in my experience.
12) Concealed flue duct not accessible for safety-checking
In addition to the long list of problems above, many Gulfstreams have
potentially defective flue installations. To be more precise, many
Gulfstreams have long concealed flues that cannot be visually inspected
and therefore cannot be verified as safely/correctly assembled/installed
and safe to use. Anyone working on a gas appliance is required by law to
examine "The effectiveness of any flue". Not being able
to visually inspect the flue presents quite a problem as the technician,
according to Gas Safe Register, needs to satisfy him or herself that the flue is
both continuous throughout its length, and properly jointed &
supported.
Gas Safe Register have issued a Technical Bulletin (TB008) giving details of how
to install and safety-check these long flue ducts. TB008 requires
builders to install inspection panels along the length of a concealed
flue duct. Absence of acess to inspect a concealed flue duct means the
gas technician must issue a Warning Notice must be issued classifying
the installation as "At Risk".
Finally, due to the
persistent unreliability of the Gulfstream 2000 and the Gulfstream
A-Class I am no longer prepared to repair them, sorry! Given the
catalogue of faults to which this model is prone I recommend you consider replacing
the Gulfstream instead of repairing it. The comments on this page are
all my personal opinion.
Mike Bryant, AKA Mike the
Boilerman.
This page last updated 2nd January 2018.
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