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Central Heating Question.

gleneagles
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Central Heating Question.

Warning,.....Long Post.

Our system is open vented.

The problem is that the pressure in the central heating system is low as everything is on the same level and the water tank cannot be placed any higher, the low pressure means some radiators take a long time to get warm or do not get warm at all.

Using flushing fluid followed by inhibitor has improved things to a degree but speaking to a plumber who is quite competent he suggested it would be possible to change the central heating system into a pressurised system leaving the other part of the system open vented.

This would mean incorporating a pressure vessel into the CH system and of course closing off the pipes from the CH tank.

In theory I can see no problem with this other than the slight chance the increased pressure on any joints might cause a leak but that would also have applied if I had a combi boiler.

Changing the boiler is a non starter as it’s only a couple of years old.

The thing is I can see nothing about this idea on any of the plumbing sites on the internet so that worries me a bit.

The plan is to get this done next month....

Any thoughts.....and if you do find anything on the internet (uk) sites only please let me know as the US has some weird and wonderful systems.

Thanks.

 

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20 REPLIES 20
Mook
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Re: Central Heating Question.

What about replacing the water pump with a higher rated one to drive the water thought the system.

Minivanman
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Re: Central Heating Question.

Would a larger water tank help with the pressure - assuming your joists could take the weight?

Just a thought off the top of my head as we had a similar problem years back and I changed the small galvanised one for a larger plastic type one which sort of solved the problem. Still had to bleed the rads from time to time though and I take it you've done that. It's the most common cause of cold rads. 

I don't suppose your'e on any sort of benefit and you say your boiler is only two years old so I doubt this will help, but throwing it into the mix so to speak might help others.  

Good luck. 

@Mook 

Interesting idea, but I'd be careful with that one m'self because of existing joints as I think @gleneagles mentioned. Pumps are not cheap either. Same with a larger tank in a way but not so harsh on the system?

 


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HelloDuck
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Re: Central Heating Question.

Good afternoon  

 

Minivanman
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Re: Central Heating Question.

Other than points mentioned, is it worth considering leaving well alone until next spring.

Last thing you need right now is a cold house or leaky pipes over Christmas!  

Brrr. 🙂


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Baldrick1
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Re: Central Heating Question.

@gleneagles 

I'm about to change my boiler next month and have been sorting out the same problem with my plumber.

There is no reason for not changing the primary circuit to a pressurised system apart from, as you say, the risk of leaks. We have a mixture of concrete floors and fairly recently fitted solid oak flooring downsrairs and the thought of the increased pressure and the response of SWMBO to having her new beloved floors ripped up if we have leaks has caused me to chicken out and stick with the present system. I have found that boiler specs are different. Worcester Bosch regular boilers will work with a static head as low as 0.25m, that is about 0.025 bar. Pressurised primaries run arount 1.5 bar. In fact I have come across some boilers that will lock out if the pressure drops below 1.5bar.

My current system works well enough and I have quite a powerful pump. I changed this years ago to help the circulation. As long as the expansion pipe is correctly fitted you should not get any pumping over from the expansion pipe with a bigger pump.

If you have a good insurance policy and don't mind the risk of leaks then the pressurised option might be more efficient, I honestly don't know what the advantages are apart from not needing the second header tank in the loft.

gleneagles
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Re: Central Heating Question.


@Mook wrote:

What about replacing the water pump with a higher rated one to drive the water thought the system.


Whilst trawling through the various plumbing sites the general advice was to use the lowest setting for the pump, one site did mention that if the pump was set too fast steam could come out of the vent pipe causing steam to be circulating around your attic.

The existing pump appears to have 2 setting but I think these settings control the direction of flow rather than speed.

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gleneagles
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Re: Central Heating Question.

@Minivanman 

The existing tank is indeed small but there is very little room in the loft and the tank is not in a easy place to get to.

No doubt the tank was put in place after the rafters but before the roof went on.

I have no problem going along with the plan suggested by the plumber as logically it would work and access to install a small pressure tank is good it’s just unconventional and I normally like to read reviews or problems people might have had doing this but so far I have found nothing on the internet.

We are born into history and history is born into us.
gleneagles
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Re: Central Heating Question.


@HelloDuck wrote:

Good afternoon  

 


Not thought of that, might be a alternative idea but requires a electrical connection plus of course pump so cost may not be all that different, could increasing flow in a vented system introduce air into the system....must admit I do not know but adds to the questions as I have not come across that idea either on the internet.

Thanks for the idea.

We are born into history and history is born into us.
Minivanman
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Re: Central Heating Question.

@gleneagles 

Happy to come round as a 'qualified plumber' and sort it out for you, but I would have to charge £100 a hour, plus parts, plus travel expenses and of course plus VAT.

PS. I would also need safe and secure parking for my new Lamborghini. 😆

 


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gleneagles
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Re: Central Heating Question.

@Baldrick1 

Thanks.

We have the same make of boiler and it has been very efficient but unlike a combi that provides hot water on demand and includes more components in the case ours basically just heats the water so no chance of it locking out due to pressure or at least I assume not.

No regrets in getting this basic boiler as a combi would have been more expensive along with removal of hot water tank.

If the boiler ever failed we would still have hot water due to the immersion heater in the tank.

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gleneagles
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Re: Central Heating Question.

@Minivanman 

Sounds good.

Don’t worry about the car most of our ‘downstairs staff’ are good drivers.

😉

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Baldrick1
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Re: Central Heating Question.


@gleneagles wrote:

@Minivanman 

I have no problem going along with the plan suggested by the plumber as logically it would work and access to install a small pressure tank is good it’s just unconventional and I normally like to read reviews or problems people might have had doing this but so far I have found nothing on the internet.


Pressurising the primary circuit whilst using gravirty for the hot water system is very conventional. If you download this manual you will see it a an option on Page 13 https://www.worcester-bosch.co.uk/professional/support/literature/greenstar-27-30-ri-regular-install....

Two pumps are a bad idea. If your pipework is correct and you have a properly set by pass then there is no pumping over as the pump is just circulating the water. Equally you always need your circulating pump to pressurise the pipework. If you create a negative pressure by using the pump to pull rather than push water around then the very slightest of leak will suck in air or even suck it in the expansion pipe on an open system and you will be bleeding radiators for ever more.

Longliner
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Re: Central Heating Question.

Been there, done that! Our 1970 original oil-fired one-pipe system was fed from roof tank and pipes were accessible under suspended floor. Separate circuit for hot-water tank. Never worked well, downstream rads only tepid, so I removed all lagging and found some genius had re-routed the one-inch pipe with a few feet of half-inch … I kept the one-inch as the feed and installed a half-inch return to each rad. This produced an immediate improvement, and one rad which wasn't heating was replaced – inside was full of gunge despite flushing so it was probably the original.

 

System has two big underfloor sections which contributed to airlocks, so fitted pressure vessel to produce a semi-pressurised system just as your plumber suggests. Success.

 

Your pressure flushing should have revealed poor flow rates and I suggest you check your system for restrictions. If the feed pipe is hot and the rad isn't, it's probably bunged up, prove this by slackening the return fitting (shallow basin and towels of course!) and feeling for the heat spreading up from the feed fitting. If it doesn't the rad is probably bunged up. Good luck.

Minivanman
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Re: Central Heating Question.

One house we bought and moved into, and within a couple of weeks all the rads went cold.

Checked the usual and decided the pump was not working. Changed the pump still no luck so phoned my cousin who was a plumber and he said "y'know what, it sounds like you have no water in the header tank".

"Don't be daft I said" but I'll check anyway. Sure enough it was empty and I noticed that the ball valve had been tied up so that no water was entering. That's funny I thought, so untied it and watched as the tank nearly filled, and watched as the valve started to rise and shut off the water.

Water now flowing, pump pumping and heating now working. Brilliant.

Middle of the night and my son comes into our bedroom. "Dad, there is water running down my wall!"  Cripes, back up into the loft with torch to find tank overflowing because the float on the valve had not risen.... which was why it had been tied up by the previous owner and the beep beep had not told me!  He knew about it obviously, but rather than change it he'd just gone up to the loft from time to time to fill that tank up before shutting it off by tying up the float.

Guess who just happened to call the following evening for his post. Yep, the previous owner and boy did I give him an ear full.

 

 


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