Vented System - No Hot Water

[zom247]

Looking for some advice from the plumbers in here please

We currently have no hot water even though the hot water is switched on. The heating is switched off but the radiators are red hot so not sure what's happening there. I've managed to get someone to come tomorrow afternoon but is there anything I can check myself now? The boiler seems to be up and running ok and the pressure is fine.

It's ironic really as me and the Mrs were only talking about boilers a couple of days ago. Ours is 15 years old now and we were talking about whether it was worth changing to a combi so the decision might be taken out of our hands!

 

[Countcussy]

Not a plumber, but had similar experiences over the years. Could be the Motorised valve.
Vented systems are really quite simple. Motorised valve would be my first check. You may know this but its a brass valve with a silver box on top and a cable coming out. Also has a manual override lever.
Depending on the system, you may have more than one. Its possible one is stuck open/closed. (You may also have solenoids if its a newer system, but they do the same job)
The hot water in your cylinder may now be heating the radiators. If the boiler is off, the heat has to come from somewhere.

 

[-Ad-]

I wouldn't get a combi. If you want the best gas condensing boiler then get a viessmann W200 with the outdoor weather comp sensor.

Sounds like the motorised valve for the hot water is the issue. Either the valve is stuck closed or the motorised head is broken/has an electrical issue.

You should be able to take the motorised head off, turn on your hot water and see if it is working. It'll help you troubleshoot which part is the issue.

Countcussy has given some good advice also, you should be able to use the manual override lever, if it's the motorised head with the issue. At least you'll be able to get hot water then, take a look online at a few youtube videos on how to do it. If you can't get it to work then you should be able to use the immersion within the water tank to heat up the water, there should be a switch to turn it on.

Not a huge job to replace it if access is decent around it.

 

[Mysterae_]

Looking for some advice from the plumbers in here please

We currently have no hot water even though the hot water is switched on. The heating is switched off but the radiators are red hot so not sure what's happening there.

Sounds very much like the mid-position valve is stuck in the central heating position and the hot water flow is being diverted to the radiators rather than the storage tank. You can override the valve to have heating, hot water or both (mid position).

Either the motor in the valve has failed or the hardware of the valve has seized.

 

[DXP55]

Do not buy a combi - keep your hot water tank and just buy a boiler to run it and heating - thats if your plumbing is in good condition.
At my last house my boiler came on if hot water needed topping up or heating came on - No complicated boiler control's - just on or off and diverter valve.
I do miss it.

 

[FlyingFish]

Take the advice given here with a pinch of salt m8

If you're thinking of a new system then get a professional to assess your system, listen to your requirements, and weigh up the options.

Do you really need to heat 150-200 litres of water daily and keep it at 60C? Gas isn't cheap any more, and most people don't need that volume of water. 60C is how you don't grow legionella in the cylinder, whether you use it or not!

A combi only heats the water you use, so bare that in mind.

I fitted a combi boiler for my mum (and a couple of friends) last year, it came with 18 years warranty & lifetime on the heat exchanger. Weather comp is included, and both cold and ch filters, the inbuilt controls can time the ch and the dhw preheat.

One single appliance can replace your existing: Boiler, cylinder, header tanks, pump, motorised valve(s), controls, etc. Great if they are old and tired.

To your current problem:

You've most likely got a Y plan, that has a motorised valve stuck in the heating position, this can either be from a stuck spindle or a stuck synchron motor. Using the manual lever will generally not fix this, as all 3ports are spring return to dhw, therfore the lever is only to open the ch. Removing the head will also not fix the problem of a stuck spindle or motor, because like I mentioned above you need the spring mechanism in the head acting against the motor to move the spindle into a dhw position.

Have fun

 

[mattyg]

Take the advice given here with a pinch of salt m8



A combi only heats the water you use, so bare that in mind.

Sorry what....
What about the unused hot water thats left in pipes going cold after you turn the tap off. What about the hot water thats now cold that you've had to run off to get the new hot water.
Yes Combi's have their place but its going to struggle to supply hot water to more than one tap at a time.

It's not quite as straight forward as you are suggesting

Most modern Cylinders only lose between 1.2-2.4 KWH in a 24 hr period.

 

[FlyingFish]

Sorry what....
What about the unused hot water thats left in pipes going cold after you turn the tap off. What about the hot water thats now cold that you've had to run off to get the new hot water.

And how is that any different to a cylinder setup, apart from heat loss into the pipework?
Once you've cleared the volume held in the pipes then you're only burning gas for the time you're drawing water. A cylinder will lose heat constantly, especially the older open vented types. Apologies if I didn't make that clearer.

You can also get combi boilers powerful enough to manage two taps at the same time, if the pressure, plumbing and outlets allow (as with anything). I don't know if many standard domestic properties that have two baths! But like I said at the start of my last post, this will depend on the home owners requirements and current setup, hence getting a professional round for a chat.

 

[mattyg]

And how is that any different to a cylinder setup, apart from heat loss into the pipework?
Once you've cleared the volume held in the pipes then you're only burning gas for the time you're drawing water. A cylinder will lose heat constantly, especially the older open vented types. Apologies if I didn't make that clearer.

You can also get combi boilers powerful enough to manage two taps at the same time, if the pressure, plumbing and outlets allow (as with anything). I don't know if many standard domestic properties that have two baths! But like I said at the start of my last post, this will depend on the home owners requirements and current setup, hence getting a professional round for a chat.

Secondary circulation!
Combi's are great for that really long shower. Or for a family of really long showerers, But i dont think i'd ever go back to combi again

 

[-Ad-]

Take the advice given here with a pinch of salt m8

The same applies to your post then

If you're thinking of a new system then get a professional to assess your system, listen to your requirements, and weigh up the options.

From my experience, professionals "plumbing fitters" can diagnose a dead circulation pump as "Need a new boiler m8" or can't do a simple heat loss calc and just want to slap in a 35kW boiler "Cos bigger is better m8, years of experience"

Do you really need to heat 150-200 litres of water daily and keep it at 60C? Gas isn't cheap any more, and most people don't need that volume of water. 60C is how you don't grow legionella in the cylinder, whether you use it or not!

Water doesn't need to be kept at 60C all the time, that's just legionella paranoia. The bacteria dies after a few hours at 50C so you can keep water at a lower temperature between 50-60 degrees to reduce standing loss. If the water has been turned off (say away on holiday) then it can be heated to a higher temp upon return if there's any worry. I'd be more worried about water sitting in the pipes for a long period in a hot house over a summer heatwave if it's left for a long period. All taps should be run through with hot water after a long period away.

Gas also isn't expensice, it's circa 4p/kWh on a tracker tariff currently, and hasn't been over 6p/kWh in the last year plus.

 

[FlyingFish]

From my experience, professionals "plumbing fitters" can diagnose a dead circulation pump as "Need a new boiler m8" or can't do a simple heat loss calc and just want to slap in a 35kW boiler "Cos bigger is better m8, years of experience"

And sadly that's the state of our trade. But like everything, there is always going to be good advice and bad advice. There's not much I can do about that.

All I was doing here was offering a bit more balance against those people saying don't get a combi. Whether a combi is right or not for the OP, is something I wouldn't say without a proper site visit. And they can't be that bad, as combi's are the UK's most popular type of boiler

Water doesn't need to be kept at 60C all the time, that's just legionella paranoia. The bacteria dies after a few hours at 50C so you can keep water at a lower temperature between 50-60 degrees to reduce standing loss. If the water has been turned off (say away on holiday) then it can be heated to a higher temp upon return if there's any worry. I'd be more worried about water sitting in the pipes for a long period in a hot house over a summer heatwave if it's left for a long period. All taps should be run through with hot water after a long period away.

I'm not disputing any of that, but your average home owner is going to have a simpler life where legionella isn't a concern and they can turn the dhw temp up or down to meet there needs at the boiler.

The same applies to your post then

Totally

Secondary circulation!

Which will remove heat from the cylinder faster, great for convenience and if you're on a water meter. You only really find this in larger properties, not your average domestic size house. Don't the majority of families also prefer to have a shower for work/school/convenience etc. Without having to think about whether there is enough hot water? They are still free to have a bath when they want... And then turn it into a death trap with the super slippy bath bomb residue

 

[Mercenary Keyboard Warrior]

The considerations are more now about the future than just now.
Pressurised (system)* > combi > old vented
Especially when you add in being able to use off peak tariffs for heating water etc.

Have a think about the future before you make a decision.

Personally having had a system boiler I would never, ever, get a combi again.

*the issues with changing to this can be that pipework is not up to scratch and the higher pressure of the hot water in the system leads to leaks that neither of the other options would show up.

People will make comments in regards losses on the tank of hot water. Modern tanks are uber efficient compared to the old unlagged ones people compare to.
The boilers themselves are basically equal now in efficiency, so you need to consider if a tiny amount of energy loss from the stored water is worth the better overall that a system brings (assuming you can have one).

Another VERY real world consideration is are you within an Octopus powerups area. I regularly, like 1-2 times per week on average get free electric sessions which means I turn off the gas water heating in advance and heat my water for free when those sessions are on.

 

[dlockers]

Yeah you've gotta really think through removing an existing cylinder setup when the future is distinctly in solar inverters etc

Combis generally oversized for water use which makes them inefficient for heating use.

 

[-Ad-]

And sadly that's the state of our trade. But like everything, there is always going to be good advice and bad advice. There's not much I can do about that.

All I was doing here was offering a bit more balance against those people saying don't get a combi. Whether a combi is right or not for the OP, is something I wouldn't say without a proper site visit. And they can't be that bad, as combi's are the UK's most popular type of boiler

Yeah, you get the good and the bad. Too many bad ones have meant I've learned a lot more myself and take a lot less BS if I do require someone else to come in. At least I can vet them in advance.

A combi has it's place in a small place, or something like a Viesseman 111 or 222 could be a great option.

Legionella isn't a joke, but I think the "worry" is a bit excessive. Especially when the blanket advice is "keep your water temp high", when other unused taps where water has remained warm are a far higher risk area.

I'm still running an open vented system with a heat only boiler and there really isn't a point of changing anything. I have a wireless weather comp sensor and the boiler is tweaked as much as it can be with pump overrun etc (just wish it would modulate lower). Gas usage has dropped and it's always in the highest part of the condensing zone it can be. The smallish water tank is lagged heavily and I've insulated all the pipework I can. I'm even about to put some temp sensors (via a Shelly uni) on 3 points of the water tank, so I can effectively monitor the temperature of it, to tweak the DHW timings further.

The cost to change to a high gain unvented cylinder with larger area coil, a Viesseman 200W, remove associated pipework and tank, plus pipe for the 4 pipe PDHW would probably be about £6k. A Vaillant 12kW Heat Pump and associated tank would probably cost similar or maybe a bit more (after taking into account the BUS grant), so either option would really just end up setting money on fire.

That £6k can be used for many other better things, such as; installing a water softener system, upsizing a few of the older/rusty rads , plus putting in my UFH pipe under the suspended floor and hooking it up to the second zone on the wiring centre (so the whole gnd floor is one big emmiter running almost open loop). Then I can reduce the flow temp further, and as an added effect, will prepare the house for a Heat Pump in the future....... 12-13kW heat loss can't be reduced that much more without spending a silly amount with no ROI in this lifetime.

All fun and games

 

[Countcussy]

Combis generally oversized for water use which makes them inefficient for heating use.

Agree. People tend to put massively oversized combi`s in, to maximize hot water flow/pressure.
To counter that though, its down to the individual to decide, as its nice to have choices.
Each system has its place. There is not a "one size fits all".

Our first home had the most simple boiler/heating & hot water system. We also had an electric shower.
in 15 years I replaced a thermocouple, and a small section of pipework on the hot water side where all the magnetite had congealed in a low flow area, blocking the pipe.
Also removed various things from the loft tanks occasionally.
Think I had it serviced.........once.

Our current property has a 250l unvented cylinder, with 2 coils. One from the boiler, and one lower down fed by a solar collector on the roof. From late spring to late autumn, we use NO gas, unless we have the heating on.
Also has Immersion option, in case of no gas supply. Luckily, we have decent water flow and pressure, meaning showers are a joy.
We have 11 rads and the System boiler is only 18kw
It is more complicated however, and needs servicing every year. It takes up a LOT more space & expansion vessel(s) will fail and need replacing at some point.

It's no doubt far more expensive to own and maintain an unvented system. It's whether you value the benefits that come with that. Including having more than one shower at the same time.
(Maybe the simple answer is to not have children )

 

[dlockers]

It's no doubt far more expensive to own and maintain an unvented system. It's whether you value the benefits that come with that. Including having more than one shower at the same time.
(Maybe the simple answer is to not have children )

Also lovely to basically shed your skin the flow and pressure is so high

 

[Countcussy]

Also lovely to basically shed your skin the flow and pressure is so high

Absolutely.
I`m on a water meter. Something I seem to forget when I`m in the shower

 

[FlyingFish]

Absolutely.
I`m on a water meter. Something I seem to forget when I`m in the shower

Don't we all!

I put a new fancy bathroom in a few years ago, with a fancy digital shower etc... It wasn't long before the daughter was complaining that the new shower was faulty and kept turning off....

Turns out the shower turns itself off after 20mins!

Teenagers

And I thought I was the one who took ages in the shower

 

[gingergundog]

...

 

[mickyflinn]

It sounds like the diverter valve (3 port vale) is stick in the heating position , there's a little slider that can be moved , Google it.

It should be next to the cylinder.