How much do you spend on gas each day?

[Bobby Dazzler]

That's an astonishing amount of energy for what is essentially losses on a hot water system with no hot water being used.
I too had a circulating system for hot water although mine worked on thermo syphon that I designed myself rather than being pumped. It still managed to lose approx. 6 kw per day so I've turned it off. We now run taps close to the cylinder without circulation and heat water locally at the furthest tap which is 68ft of pipe work away from the cylinder.

Professionally I have worked with large pumped hot water systems with many dozens of outlets in large laboratory buildings and the losses are colossal. I came to the conclusion that heating water locally with under sink electric heaters was far more cost effective and this was 25 years ago when energy was cheap. That it also resolved concerns about legionella sealed the deal particularly for showers. There will still be losses if you heat locally but nothing like 81kWh a day for a domestic property.

That’s very useful, thank you for sharing.

I have no idea how much pipe is between the cylinder and the tap, but the cylinder is close to the centre of the house, so the furthest taps are probably 40ft away horizontally and 20ft vertically so I suspect it will be similar to yours as I doubt the pipes take a direct route. However there are 5 hot water taps at that distance from the cylinder, which may not help.

I will turn the pump off and see if it makes a difference. Bizarrely I’ve only just paid “too much” to have that circulation pump replaced as the originally was very noisy. Perhaps the last people who lived here didn’t use it because it was so expensive to use, and a few years of not being used didn’t do it much good.

 

[Bobby Dazzler]

No wonder Rob came home to a cosy house. The circulating hot water was just enough to keep the CH stat from kicking in.

You’re not far off the Mark Ant. The floor in our bathroom was warm when we got back this evening! Guessing the hot water pipe runs through the middle of it!

 

[GeeJayW]

At present rates, through the winter we’ve been using about £7/day gas, that‘s for heating (19 degC) and hot water (60 degC). Electricity usage is about £2.50/day and is quite steady through the year. That’s for a 70’s 4-bed detached with double glazing, cavity wall insulation and upgraded loft insulation.

 

[Bobby Dazzler]

Intriguing reading Rob.

A long shot but I wonder if your hot water tank is twin coil? The spare coil can be used to throw a couple of solar panels up there to aid the heating of the water.

If it’s not a twin coil tank it maybe well worth investing in a replacement.

Thanks Ant/ I’ll have a look at the label and ask Google how many coils it has. I suspect one as there is no solar for electricity or water.

 

[Bobby Dazzler]

Just a side note Rob. On a circulating hot water system it’s paramount that the pipes are maxed out with lagging to reduce heat loss.

Maybe check this out and if possible up the spec of the lagging.

Edit: Sorry @Will didn’t see your post making the same point.

Haven’t read all the pages of this thread, but that seems like an astonishing amount of wasted gas energy to maintain the hot water when not in use and with reasonable ambient temperatures too?

I wonder if the pipework for the hot water is well insulated?

My other thoughts were would it perhaps be cheaper to invest in multiple combi type boilers or even a different source of heating the hot water? Long pipe runs must be the cause of the heat loss, so if you can avoid that you can reduce the losses.

Would definitely look at solar options, and consider if you can drop the HW temp a few degrees without getting too cool to grow bugs or reduce the performance?

Thanks Ant and Will. The house was built in the late 19th century and was never intended to be a house but was converted into a house 4-5 years ago. Some aspects of the conversion are very highly specified, and other aspects feel like corners have been cut.

I would like to think that the hot water pipes are well insulated but I wouldn’t be surprised if they weren’t. The pipes I can see in the boiler room are all neatly lagged, so I assume the rest of the house is to a similar spec. I posted a photo in this thread, I’ll see if I can find and repost it.

I would like to install solar tiles on the new garages I’m planning to build, but perhaps I need to consider solar heating for water and/or a ground source heat pump whatsit thingymagig too.

 

[Bobby Dazzler]

I guess in another thought though, whilst the house has been occupied over the winter months with the heating set at 22c (24 hours a day), any losses from the HW will just be heating the house with gas anyway via the HW system - so gas consumption relatively similar either way?

I had exactly the same thought Will. Some of the pipes may run below the floor downstairs though, and so may loose a fair amount of heat as it’s almost certainly colder down there.

The heat lost through pipes that run through the house will have helped keep the house warm though. There are several parts of the floor which are warm to the touch but do not have UFH as far as I’m aware, so maybe not we’ll insulated!

 

[ALFAitalia]

22 degrees?....really?....I think most would fund that uncomfortably warm.....my family certainly would (that's an old folks home sort of temp!). We have it at 18 all year round....very occasionally 19 if it's really cold out. I thought us southern folks were supposed to be the softies!

 

[Bobby Dazzler]

22 degrees?....really?....I think most would fund that uncomfortably warm.....my family certainly would (that's an old folks home sort of temp!). We have it at 18 all year round....very occasionally 19 if it's really cold out. I thought us southern folks were supposed to be the softies!

It didn’t feel uncomfortably warm. Last night when it was down to 16.8 degrees in the main part of the house it didn’t feel cold, but when the weather was much colder outside, anything below 20 degrees in that room felt uncomfortably cold. Must be because it’s a drought old place with unusually proportioned rooms.

 

[Will]

22c sounds on the comfortable/warmer side but not exactly uncomfortably hot - how do you cope in the summer!

18c is pretty cool, I guess if you’re wearing warm clothes it’s okay.

Personal preference at the end of the day, and no two homes are the same. Also depends on thermostat type and position etc too

 

[BTB 500]

Also depends on thermostat type and position etc too

Assuming you have one, of course!

 

[Bobby Dazzler]

Taking the “used this week” figure on the smart meter, and pro-rating it to allow for the remaining few hours of the week, it looks like we’ve used £9.35 (81 kWh) of gas per day whilst we were away. As there was no heating on, then I can only assume that is the cost of heating the water 24/7.

So last night I switched off the hot water recirculation pump (before midnight) and looking at the gas consumption so far today, and prorating it through to midnight, it looks like we’ve used £7.50 (65 kWh).

That’s a reduction of 20% with everything else the same (ie thermostats set to 11 degrees C), so based on this initial check, it seems that reheating the circulated water is taking an additional 16 kWh per day.

Before changing anything else I’ll see what the consumption is tomorrow (and maybe Wednesday) in case today’s consumption is anomalous. Heating the cylinder twice each day might be the next test.

I have been unable to work out how to check what temperature the hot water cylinder is set to.

 

[Bobby Dazzler]

A long shot but I wonder if your hot water tank is twin coil? The spare coil can be used to throw a couple of solar panels up there to aid the heating of the water.

Any, this is the hot water cylinder we have:

CenterStore Indirect unvented cylinder 250ltr | Wolseley

Looking for a CenterStore Indirect Cylinder 94050220? Order from Wolseley today - free delivery or click and collect available nationwide.

www.wolseley.co.uk

The product description mentions “Purpose-designed solar coil provides maximum efficiency”, is that what you had in mind Ant?

 

[HappytalkAgain]

Any, this is the hot water cylinder we have:

CenterStore Indirect unvented cylinder 250ltr | Wolseley

Looking for a CenterStore Indirect Cylinder 94050220? Order from Wolseley today - free delivery or click and collect available nationwide.

www.wolseley.co.uk

The product description mentions “Purpose-designed solar coil provides maximum efficiency”, is that what you had in mind Ant?

So just a single coil Rob. (Primary flow and return).

A twin coil cylinder has 2 flows & 2 returns. One set for the boiler and another for the solar.

Might be worth considering Rob. It’ll certainly reduce the gas usage on the Hot water side of things.

 

[Bobby Dazzler]

So just a single coil Rob. (Primary flow and return).

A twin coil cylinder has 2 flows & 2 returns. One set for the boiler and another for the solar.

Might be worth considering Rob. It’ll certainly reduce the gas usage on the Hot water side of things.

Thanks Ant. Appreciated.

 

[190]

o last night I switched off the hot water recirculation pump (before midnight) and looking at the gas consumption so far today, and prorating it through to midnight, it looks like we’ve used £7.50 (65 kWh).

That’s a reduction of 20% with everything else the same (ie thermostats set to 11 degrees C), so based on this initial check, it seems that reheating the circulated water is taking an additional 16 kWh per day.

If I'm understanding this correctly you are still using 65kW per day with the pump off and no heating consumption ? If that's the case you may still have hot water circulation due to the temperature gradient. If the outlet from the hot water tank is higher than the return. It will still circulate even with the pump off. Unless there is a physical isolation valve a stationary pump will not stop it, just slow it down.

 

[Bobby Dazzler]

If I'm understanding this correctly you are still using 65kW per day with the pump off and no heating consumption ? If that's the case you may still have hot water circulation due to the temperature gradient. If the outlet from the hot water tank is higher than the return. It will still circulate even with the pump off. Unless there is a physical isolation valve a stationary pump will not stop it, just slow it down.

That’s right, I’m still using 65 kWh. Tomorrow night I will turn the heating off tomorrow night (rather than just turn the thermostat down to 11 degrees C), and see if that makes a difference. Then on Thursday night I’ll switch to heating water twice per day, and see if that makes a difference. Then I might turn if the water heating altogether to see if consumption drops to zero.,

 

[HappytalkAgain]

That’s right, I’m still using 65 kWh. Tomorrow night I will turn the heating off tomorrow night (rather than just turn the thermostat down to 11 degrees C), and see if that makes a difference. Then on Thursday night I’ll switch to heating water twice per day, and see if that makes a difference. Then I might turn if the water heating altogether to see if consumption drops to zero.,

As Will Mentioned Rob. Is it feasible to turn temp down on water stat. Just a degree or 2 would make a fair difference and probably wouldn’t be even noticed.

 

[Bobby Dazzler]

As Will Mentioned Rob. Is it feasible to turn temp down on water stat. Just a degree or 2 would make a fair difference and probably wouldn’t be even noticed.

Right I’ve just found the manual to the boiler and the hot water temperature is set to 65 deg C and the heating flow temperature is set to 80 deg C.

Based upon a little internet research it seems that the hot water temperature is as low as it can safely be, but the heating flow temperature may be relatively high.

However some websites warn against reducing the flow temperature (on system boilers with a water cylinder) without professional advice.

Other websites suggest that it’s fine to adjust the flow temperature down to 65 deg C, but no lower as it won’t be able to heat the water in the cylinder.

 

[190]

Right I’ve just found the manual to the boiler and the hot water temperature is set to 65 deg C and the heating flow temperature is set to 80 deg C.

Based upon a little internet research it seems that the hot water temperature is as low as it can safely be, but the heating flow temperature may be relatively high.

However some websites warn against reducing the flow temperature (on system boilers with a water cylinder) without professional advice.

Other websites suggest that it’s fine to adjust the flow temperature down to 65 deg C, but no lower as it won’t be able to heat the water in the cylinder.

The 65 Deg C water temperature will have been set with a view to controlling legionella. I think the risk was overplayed because the known cases were mostly from open evaporative cooling towers and to a lessor extent showers particularly infrequently used showers. Frankly more harm has been caused by dangerously high hot water temperatures because in the legionella panic they didn't get the balance right between controlling legionella and scalding. 65 Deg C will scald. 60 Deg C is high enough and still safe for Legionella. Legionella won't grow above 50 Deg C and 60 Deg C is high enough to kill it, therefore the usual guidance is store at 60 Deg C and ensure a minimum of 50 deg C at the outlets.

The boiler is presumably not a condensing boiler otherwise it would be operating inefficiently at 80 Deg C. If it will meet the heating load at a lower temperature, I would reduce it to the same temperature you choose for the hot water or perhaps a few degrees above. A lower temperature will reduce distribution losses depending where the pipe work runs are and the level of insulation.

 

[Will]

I would also think with that constant circulation on the HW the risk of low temperatures and stagnant water at outlets would be even lower, it’s definitely worth looking into a slight reduction on the set temp if efficiency is being considered, along with the heating flow temp too.