Gledhill Boilermate 2000 & The ever increasing cost of gas/electricity

hdsn555

Thanks for the feedback everyone. So good points to consider.

I've already got a Hive thermostat, and there are TRV valves on all radiators in the house (except the bathroom and ensuite)

When we moved in 6 years ago, I upgraded the loft insulation from 150mm by adding 170mm on top giving us 320mm with loft legs and boarding over the top. We can certainly tell we've got that up there during the heatwaves we're having!

I'd already read about making sure boiler is set to max, a previous service on the boiler had the engineer reduce the temp, but he had no knowledge about the thermal store, so it was promptly returned to max.

I've checked the header tank and it has water in it, we've drained the system before to change.a rad valve, and it took an age to refill!

I really think cavity wall insulation would make a massive difference to heat retention, and certainly cheaper than replacing the ageing double glazing. But I'm really not sure where to find a reputable company to do the job, and that won't rip me off. A few years ago back when there were grants available I'd signed up to have it done, then read horror stories about some of the workmanship, so promptly backtracked. Isn't hindsight a wonderful thing...

Bendy_House

Thanks RedFraggle - so it is a vented tank as S62 thought.

Hdsn, I haven't a clue how best to operate the Gledhill, given that it is a Thermal Store and not a conventional hot cylinder.

A normal hot cylinder stores the actual hot water that's about to come out your hot tap, so you can normally turn its thermostat down a bit - say to around 60oC - in order to save a bit of energy, and now have it wasted. 60oC coming out of your taps is fine.

Thermal Stores are quite different, tho'. The stored water does NOT come out your tap, but just circulates between the TS, the boiler, and the radiators. To get hot water, there is a 'heat-exchanger' inside the tank, sitting in the hot stored water. This is often just a coil of pipe. Cold mains water feeds one end, and the other goes to your taps. Turn on a tap, and the water flows - driven by the mains pressure - and it gets 'instantly' heated as it passes through this coil, immersed, as it is, in hot water.

You will see, then, that for this to work successfully - for the cold mains water to be so quickly heated up enough for 'hot' use - the water in the TS will need to be very hot, a LOT more than 60oC.

And that strikes me as being the biggest drawback of a TS - if it isn't kept piping hot, then you won't get adequate hot water out your taps. Of course, if you are not requiring hot water during the day, for example, then there's no need to keep it hot for that time. But, although well insulated, the simple fact is that the hotter you keep the temp of stored water, the more that will be lost to the surrounding air.

Hdsn, I think in your position I'd contact Gledhill by chat or email, and explain your setup, and the make of boiler. Also describe your home use - when you most need DHW, and at what times you are out. Ask them the best - most efficient - way to run it.

FreeBear

hdsn555 said: I really think cavity wall insulation would make a massive difference to heat retention, and certainly cheaper than replacing the ageing double glazing. But I'm really not sure where to find a reputable company to do the job, and that won't rip me off. A few years ago back when there were grants available I'd signed up to have it done, then read horror stories about some of the workmanship, so promptly backtracked. Isn't hindsight a wonderful thing...

Have cavity wall insulation here (just on the bottom half, as the upper half is solid brick). To be honest, I have noticed very little, if any improvement. Slowly going round insulating the walls internally upstairs, and that has made a huge difference. That said, some of the improvement is down to having modern DG windows fitted, and all potential sources of draughts plugged.

Contemplating insulating the walls internally on the ground floor. Just 50mm of Celotex/Kingspan will get me up to minimum Building Regs standards, but it would mean ripping out half the kitchen and redecorating the lounge (again). The hallway is not practical to insulate due to the staircase running up against the external wall.

Bendy_House

It makes simple sense to me that fitting INTERNAL insulation will be FAR more effective than either 'cavity' or (especially) external.

Bendo

Not sure about the BM 2000 but the A Class you can put the hot water on a timer. In the summer I set ours to come on between 7 and 9 AM which reduces gas consumption down from about 7KW to less than 3 most days whilst still providing hot enough water for the morning showers and washing etc for the rest of the day.

Obviously not possible in winter when you want to use the heating as it needs to be hot for that.

Lots of people don't like the boilermate but I love ours. Radiators hot instantly, no shortage of hot water.  A combi might be cheaper to run but running a tap for minutes to get limited hot flow doesn't appeal to me.

BUFF

Bendo said:

A combi might be cheaper to run but running a tap for minutes to get limited hot flow doesn't appeal to me.

Modern combis have largely overcome that delay by holding a small amount of stored hot water. This is what "eco" function normally switches off as it obviously takes some gas to keep that hot 24/7.
Properly sized for a smaller house a combi will give adequate flow but obviously not as much as a pressurised, stored dhw tank.

Bendo

Yes a storage combi will work around some of the deficiencies of a combi, but it won't deliver the sustainable flow or a thermal store or unvented cylinder.

For me I'm considering replacing the boiler with a condensing one,  just trying to research the return temp from a boiler mate to figure out if it's worthwhile (I believe the water at the bottom is a lower temp and it's taken from here so will be lower overall but it's hard to get actual figures).

Then again many people rip out their stores and replace with a condensing combi that will rarely condense anyway as you really need oversized rads to enable a lower flow temp but people just swap the boiler and not the rads.

The other issue with ripping out a store and replacing with a combi is that the combi will need a lot more gas and the pipework that was fitted for the stores system boiler probably won't be a big enough. Depending on where the boiler is, it may not be trivial to run new pipework.

RonRamsgate

We had a BM2000 in a previous house and a suprima boiler, new build estate cicra 1999.
That was the days of cheap gas and electric, we decided to change the BM when it reached 17 years old  as a precaution as many others neighbours had bad water leaks (sludgy water through ceilings) from their BM's cylinder itself.
Something to do with corrosion from sludge sitting in the bottom of the BM, due to insufficient inhibitor. our BM needed 2.5 liters of inhibitor.
Anyway due to having 2 baths,2 showers with body jets which were often in simultaneous use and many other hot water outlets we opted for an unvented cylinder as a combi would not supply sufficient water flow.
Our installer mentioned high output gas combination gas boilers but they said they are expensive to heat up hot water and there will still be hot water flow restrictions.
Since fitting the unvented cylinder our gas consumption reduced 35%  No constant boiler cycling on/off. No noise from the three grundfoss pumps.
Yes the unvented cylinder needs an annual service but our BM needed constant expensive repairs. So happy seeing the BM being carted away 

BUFF

RonRamsgate said:

Anyway due to having 2 baths,2 showers with body jets which were often in simultaneous use and many other hot water outlets we opted for an unvented cylinder as a combi would not supply sufficient water flow.
Our installer mentioned high output gas combination gas boilers but they said they are expensive to heat up hot water and there will still be hot water flow restrictions.
Since fitting the unvented cylinder our gas consumption reduced 35%  No constant boiler cycling on/off. No noise from the three grundfoss pumps.

Yes, for 2 bathrooms & 2 showers with body jets you are going to need stored dhw. Even the largest storage combi wouldn't cope with that simultaneous demand. iirc a WB 550CDi is 25l/min.

Did you upgrade the boiler at the same time or do you still have the Suprima? 

RonRamsgate

BUFF said:

Did you upgrade the boiler at the same time or do you still have the Suprima? 

Kept the potterton suprima, it was not working so hard anymore and could now turn down the thermostat from max to mid. With the new zone controls and programmer it could be independently timed for when we wanted heating or hot water.