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 regularly attend. Most Gulfstream 2000 breakdowns fall into one of the following categories:

1) 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. 

2) 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.

3) Overheating.

Another expensive thing to fix. The 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 it allowing 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, and a new heat exchanger has to be fitted. The system needs to be powerflushed at the same time and the correct corrosion inhibitors added to prevent recurrence. This adds up to an extremely expensive repair. Many owners decide to fit a new boiler rather than repair a Gulfstream with this problem.

4) 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.

5) 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). 

6) 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.

7) Central heating failing intermittently.

Usually caused by triac failure on the main control board. A new board will be needed. 

8) 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.

9) 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. 

If you'd rather I came and fixed your Gulfstream 2000, give me a call but beware, many repairs on these turn out to be expensive. Given the catalogue of faults to which this model is prone it may make sense to  consider replacing it instead. That's just my personal opinion.

Mike Bryant, AKA Mike the Boilerman. 
0118 966 0166 office
07866 766364 mobile

This page last updated 23rd May 2008.