Vented Thermal Heat Store Replacement

[NorthEast]

My son's flat has a vented indirect twin coil 120ltr thermal heat store tank with in built make up cold water section for the domestic hot water heated by a sealed system boiler.
Anyway the DHW coil has started to leak causing continual overflow from the cylinder cold water section.
Tried to source another tank, the original tank is no longer available, replacement cost for a new tank seems to be around £800-1,000 plus fitting.
Options seem to be to fit an unvented H.W tank or fit a combi, although space is limited for fitting a combi to replace the exisiting Potterton system boiler.
Concerned that only a small combi may be only option and hw flow rate will not be great.
Anyone had any experiance of replacing a Gledhill Systemate sp thermal store? if so what did you do, or any heating engineers views welcome.

[Rickyy]

Providing the flow rate from your cold main is adequate, I'd opt for an Unvented Hot Water Cylinder. It will need converting to an S-Plan set up, which is basically a fully pumped set-up with 2 x 2 port valves.

I'd imagine that in a flat the hot water flow rate is pretty poor with an open-vented hot water system?

Bear in mind that with an unvented set-up you will need to run a pressure relief pipe to atmosphere, at least 22mm copper pipe, potentially 28mm if the distance is excessive.

In my experience, Gledhill Thermal Stores are bad news, especially ones with any sort of electronic controls.

[NorthEast]

Rickyy said:

Providing the flow rate from your cold main is adequate, I'd opt for an Unvented Hot Water Cylinder. It will need converting to an S-Plan set up, which is basically a fully pumped set-up with 2 x 2 port valves.

I'd imagine that in a flat the hot water flow rate is pretty poor with an open-vented hot water system?

Bear in mind that with an unvented set-up you will need to run a pressure relief pipe to atmosphere, at least 22mm copper pipe, potentially 28mm if the distance is excessive.

In my experience, Gledhill Thermal Stores are bad news, especially ones with any sort of electronic controls.

The Systemate uses the vented cylinder as a heat store and runs the mains cold water through it in the second coil to heat the water from the cylinder water, so pressure is/has been ok until the coil started to leak and cause the cylinder to overflow.
Fortunately no electronics on the systemate, just a thermostat and a 3 way valve for the heating on the indirect coil from the boiler.
The cylinder is in an inside cupboard and has a 22mm o/flow leading to the outside. Hopefully this would be sufficient for the pressure relief valve escape.
From what I read an unvented cylinder needs to be fitted by a qualified engineer and serviced annually, is there a list of engineers anywhere who can do this work?.

Edited by NorthEast on Tuesday 30th August 22:15

[Arthur Jackson]

Rickyy said:

Bear in mind that with an unvented set-up you will need to run a pressure relief pipe to atmosphere, at least 22mm copper pipe, potentially 28mm if the distance is excessive.

Or a soil stack.

[NorthEast]

NorthEast said:

My son's flat has a vented indirect twin coil 120ltr thermal heat store tank with in built make up cold water section for the domestic hot water heated by a sealed system boiler.
Anyway the DHW coil has started to leak causing continual overflow from the cylinder cold water section.
Tried to source another tank, the original tank is no longer available, replacement cost for a new tank seems to be around £800-1,000 plus fitting.
Options seem to be to fit an unvented H.W tank or fit a combi, although space is limited for fitting a combi to replace the exisiting Potterton system boiler.
Concerned that only a small combi may be only option and hw flow rate will not be great.
Anyone had any experiance of replacing a Gledhill Systemate sp thermal store? if so what did you do, or any heating engineers views welcome.

A Combi boiler seems a non runner due to lack of space in the kitchen unless I rip out a nice kitchen and plan new kitchen units around a new combi, looks like an unvented cylinder is the way i will have to go, best price for a vented combined heat store cylinder i have found is around £680, although I have not actually seen a drawing yet of the cylinder to see if suitable. Other cylinders are all around £900-1000 plus fitting etc.