Central Heating / Hot Water Issues

[space.dandy]

Hi all,

We've recently moved house and I'm having some issues with hot water. I'd greatly appreciate any input on the subject. Our heating / hot water system is shown in the photo below. The boiler is configured to run central heating only, with the flow directed through two actuators to heat the water tank and/or the heating system as required. The boiler (hot water) is activated by a switched live (controlled by Tado) wired in series with the tank thermostat.

The issue we're having is that sometimes we run out of hot water in the mornings. The tank is 175L capacity, there's only three of us in the house and we don't take overly long showers. We've programmed the hot water to come on between 05:00 and 10:00 every morning and we normally shower somewhere between 07:00 and 08:00. I have no reason at all to suspect problems with the thermostat or Tado (the water is piping hot to start with) and nor do I think there is an issue with tank capacity as the wife can happily run a full bath at the weekend without issue. This is an intermittent issue, but it happened to me this morning: I was the last to shower and it was lukewarm by the end.

The only thing I can think of is that it's ambient temperature related. It was bitterly cold this morning, everything iced up and as you can see from the photo the boiler system is in the uninsulated loft space. Is the tank simply losing too much heat? Does it need better insulation?

Any advice gratefully received.

Chris

 

[minilathe22]

I am not a plumber but if this is the roofspace I would definitely get some pipe cladding on all those pipes, not just to prevent damage if they freeze but may also prevent your hot pipes loosing as much heat when running.

 

[Sandyn]

I don't think the tank is losing too much heat. They have to have to meet a standard for insulation. I think there is another problem, but no idea what it might be, perhaps the tank thermostat or the thermostat control in the in the shower head has failed. An airlock is another possibility. You have an electric heater, have you tried using it to heat the water. That might show if it's central heating related rather than the shower thermostat. There will be heating experts on here who will have seen this type of problem before. I hate heating problems like this. I always manage to fix them, but am never sure what I did to fix it.
The other advice is to get the first shower in the morning!

 

[NormanB]

Your hot water tank is insulated by design and manufacture - although clearly all your exposed copper pipework is not insulated and very vulnerable in a cold loft and does require fairly immediate action.

In the absence of detailed Information, I would suggest you put the boiler on and observe the operation of the control (actuators) valves for heating and hot water in turn, to ensure each and both operate.

If you are unsure the hot water valve is operating during the above test, you can operate the valve (and actuator) manually using the wee silver coloured lever under the motor unit.

If the valve does operate manually, then it is likely the actuator head has failed and these can be changed independently of the valve unit.

One last thing which I am less concerned about is the functionality of the tank thermostat but while you are up there - it may be worth monitoring at the wiring centre. You will be unlucky if this has failed they are normally good for 20+ years.

 

[space.dandy]

Thanks for all the replies so far. I will take action on the pipe lagging as soon as I can.

@NormanB I am confident that the system is working. I have checked that the boiler comes on and that the flow into the tank coil gets hot, and as I say the first person to shower gets a lovely hot one. I'm just baffled as to how we can get a full bath of hot water some mornings and yet only just manage two showers on others.

 

[NormanB]

@NormanB I am confident that the system is working. I have checked that the boiler comes on and that the flow into the tank coil gets hot, and as I say the first person to shower gets a lovely hot one. I'm just baffled as to how we can get a full bath of hot water some mornings and yet only just manage two showers on others.
[/QUOTE]

Are you able to determine the temperatures of the coil both in and out at the end of the heating cycle?

Has your programmer been set with the same duration on/off periods each day and have you checked, that what you programmed is actually happening as intended?

Are all your radiators working OK?

How old is the system and I take it is it is a pressurised system rather than vented?

I am otherwise struggling with this one.

 

[no idea]

What temperature setting is the tank thermostat and boiler set to? I can't tell from the photograph but the thermostat on the tank looks to be quite low so you will use more water from the tank for a hot shower than if the water was hotter in the first place. I know from experience that a boiler on a medium/low setting and the tank on a low setting seems like it will save energy but in practice it either means either the boiler never gets the water hot enough to trip the tank thermostat or there isn't enough hot water available.

 

[TheUnicorn]

I'm just baffled as to how we can get a full bath of hot water some mornings and yet only just manage two showers on others.

no real plumbing knowledge so this may be a red herring, but I'm wondering if when you run a bath you are taking a lot of water all at once (if not you are possibly doing it wrong!) but when you run a shower you are taking a little bit from the tank, and the tank is then refilling with cold water for some reason and not being brought up to temperature, by the third shower this would account for a tepid mix

 

[Sandyn]

Does your shower head have thermostatic control? There is a wax module which can fail and cause intermittent problems with temperature regulation. I had to adjusted mine. It was giving similar problems. This would possibly account for lots of hot water for a bath, but the shower apparently running out of hot water. If the wax module is in line with the temperature control lever/tap, I found that giving the end of the tap a thump would sometimes fix it short term.

 

[nolly47]

Hi
you say there are 3 of you in the house do you all shower between 7 and 8 am ? you say that the hot water comes on at 5 am goes off at 10 am what other times does it come on and off at ? once you have fill the bath with hot water, then 15 minutes later you run a hot water tap is the water still to hot to hold you hand under? what times does the central heating come on a off at? is there a weathercompensator fitted to the system ?

 

[XH558]

What temperature setting is the tank thermostat and boiler set to? I can't tell from the photograph but the thermostat on the tank looks to be quite low so you will use more water from the tank for a hot shower than if the water was hotter in the first place. I know from experience that a boiler on a medium/low setting and the tank on a low setting seems like it will save energy but in practice it either means either the boiler never gets the water hot enough to trip the tank thermostat or there isn't enough hot water available.

Can I add that water should be stored at 60C+ to prevent salmonella. Raising the temp on the cylinder stat is a start. Also check the boiler stat so that it fulfills the demand of the cylinder. This would mean that you will be using less hot and more cold to bring the showering temperature down to about 38-43C. We have a 175 litre Megaflo and it comfortably deals with three adults and a mermaid teenage girl in the morning..................

 

[NormanB]

Measuring the temperature difference at the feed pipe to the coil and the return from the coil at or towards the end of a cycle will tell you what is going on.

However, from what you have described the primary circuit is fouled and will require flushing, cleaning and inhibiting. This would also be a mandatory requirement prior to fitting a new boiler.

Given the age of the system AND if you live in a hard water area, the hot water side of the coil is likely to be heavily scaled. If that is the case the only practical/cost effective remedy is a new cylinder. So, a double whammy mitigating heat transfer on both sides of the coil.

If you know the history of the system - it is most unlikely the circulating pump is still doing the business - most will have given up the ghost at circa 20 years. Given the state of the primary circuit water adds grist to that mill.

However and all that being said. I have just looked at your photo again and there is no way the hot water cylinder is from the 1960s. I doubt judging by the energy label it is very old at all - when did those ‘labelling standards come in 2000+?

So that must shed some doubt on the age of the boiler I really doubt it’s is from the 60s’ - can you get make and model number serial number and do some googling. Likely to be similar age to cylinder methinks.

 

[porker]

However and all that being said. I have just looked at your photo again and there is no way the hot water cylinder is from the 1960s. I doubt judging by the energy label it is very old at all - when did those ‘labelling standards come in 2000+?

So that must shed some doubt on the age of the boiler I really doubt it’s is from the 60s’ - can you get make and model number serial number and do some googling. Likely to be similar age to cylinder methinks.

I think there is a bit of thread mix up. The other thread running is the old system I think

 

[johnny]

I haven't read all the thread but my immediate thought was...are you aware that running 3x showers in quick succession will have put a load of cold water into your hot water tank ! it will be equal to the hot water that every shower takes out of the tank.

I try to explain to my partner this basic principle . If you have a large saucepan of hot water and you remove a small saucepan of it and put back the same small saucepan full of freezing cold water......how hot do you think the remaining hot water is going to be ?
There is insufficient time for the water to be reheated to temperature ....plus the cold water that is replenishing the hot is really cold this time of year

 

[NormanB]

I think there is a bit of thread mix up. The other thread running is the old system I think

You could well be right - I am easily confused.

 

[MikeJhn]

I haven't read all the thread but my immediate thought was...are you aware that running 3x showers in quick succession will have put a load of cold water into your hot water tank ! it will be equal to the hot water that every shower takes out of the tank.

I try to explain to my partner this basic principle . If you have a large saucepan of hot water and you remove a small saucepan of it and put back the same small saucepan full of freezing cold water......how hot do you think the remaining hot water is going to be ?
There is insufficient time for the water to be reheated to temperature ....plus the cold water that is replenishing the hot is really cold this time of year

And when you run a bath it just takes out the hot water all at once and the cold water that replace's it in the tank has little or no effect.

Two hours of heating the hot water before the showering start is probably insufficient time to heat all of the water in the tank, before you go changing things in the system try starting the hot water heating time a couple of hours earlier.

 

[Spectric]

Hi

I hope that you have a frost stat with the system fitted in that location. You need a frost stat that switches in the central heating when the ambient temperature in that area falls to say 5° and in series with this a pipe stat that opens when the return temperature to the boiler reaches say 25°. Also get all the pipes lagged. What system has the priority if any? At this time of year with the heating on, the cylinder may not be getting fully heated, check boiler temperature as often set lower in summer when hot water only and what time controls are fitted.

 

[johnny]

better still by far is to fit an electric shower !.......instantly available continuous hot water infinitely adjustable temperature

 

[Spectric]

Hi

With the OSO cylinders hot water is taken from the top and the cold water feed enters at the bottom in such a way as to avoid overmixing. This way the hot water sits on top of the cold so that the temperature is not overly changed by a small extraction of hot.

 

[Woody Alan]

Hi,

You've got several things happening here (assuming no fault conditions).
1) incoming mains water temperature is many degrees lower (as said)
2) From what I can see you have two 2 port zone valves, so no specific priority given to heating hot water over the heating. A tank of this type can be left on to heat 24/7 at this time of year as heat loss is minimal to zero certainly not significant.
3) we don't know what temperature your starting point i.e. what was the last off time? was it before somebody had a bath the night before?
4) (again as said) you need to get your tank stat up to a temperature where when the hot tap runs you wouldn't want to hold your hand under for long but not so hot it will burn you.

Solution make sure tank temp is as hot as can be by giving tiny tweaks to stat until happy with hot temp and get the timer to give a long run ealier or even the night before so in the morning it's a minor top up, and it is surprising how much time is wasted in the shower along with a lot of water.

Hope that helps if not you may have an actual issue.