Pressure in Boiler affect by cold weather/water restrictions?

Annie76

I have Gas central heating (switched over from oil 2 years ago) & a glowworm boiler that seems to be loosing pressure. A few months ago the pressure started to rise very high in it followed by water coming out the discharge pipe at the side of our house, the original installer who I have to say was very thorough & obliging all along came out, the pressure valve which is in our attic had started leaking & he put in a new one, which I think is an automatic refill valve & pressurised our boiler to 1.2 bar. This was at the start of October, since then however, the pressure (when radiators completely cold - think its called resting pressure?) has slowly but surely started started to drop & has for the last four weeks gone to .9 when the system is completely cold, this would only be first thing in the morning before the heating comes on. I called our heating man up when the pressure was at 1 bar & he insisted that this wasn't a problem & there was no evidence of leaks in our house & it wasnt something to be concerned about. When it dropped to .9 my husband rang him again as we were unable to top up the pressure as we had previously done by opening the filling loop. Again, we were told this wasnt a problem, he agreed to come out though & have a look. When he did he was quite short with me & said the heating was working fine, that the pressure in the boiler at the time (1 bar as heat had been on an hour previously) & that .9 was 'in the valley' of what it was set at. I asked him was there a possibility of it eventually dropping below .5 as this would cause out boiler to not come on & he laughed & said no, the valve was attached & working properly & there was nothing blocking it.. Basically making me feel silly as though I was wasting his time. Now today after being out for a few hours, the pressure was at .8 & is dropping back to .9 after the heating being off for around 45 mins. Would this be because of the water restrictions ( I am in Dublin..) or is it because of something else?
With this weather being so cold & christmas approaching I dont want to find myself in a situation where my heating wont start & noone is available to come out.

heinbloed

It is absolutly normal that the pressure varies. The water will expand when heated up and shrink when cooling down, the pressure changed accordingly.
The expansion barrel will make up for increasing/decreasing pressure so there is no or very little risk that pipe(s)-joints will be stressed.
Keep an eye on the pressure anyhow, the 0.5 bar min. pressure is important.

Demand the user AND the installer manual, you propably get it from the manufacturer for free (download).

Annie76

Thanks for coming back, I had a look at the manual & it says pressure should be between .7-1.0 bar (preferably 1 bar..) My concern is it will slowly reduce until it gets below .5 bar & so the boiler wont fire up on a day like this! As it seems to be slowly but surely reducing. I preferred it when I coulld manually refill it myself other than it having an auto valve do it.. My heating installer after looking up in our attic at the vale is adamant that wont happen, its fed in correctly to our water tank but its just niggling me that the pressure is slowly reducing & I have no way to replenish the water in the system.

Buford T Justice

Auto filling loops are a bad idea anyway.. They disguise a leak in the system as it keeps topping it up, although you're one doesn't seem to be doing that.

If you want to be able to top it up, then ask the plumber to change it back to a manual filling valve.

heinbloed

Get a real plumber in, Annie 76.

Yours isn't competent to explain to you how your system works, he has over-run a vital safety function ( auto-filling of pressurised systems connected to drinking water supplies is illegal).

Your boiler came with a manual, study it.

It is very simple to top-up the pressure, but you must stick to the boiler manual.


EITHER you have a closed loop pressurised central heating system OR you have an open vented central heating system with a tank in the attic, in the tree or wherever....

The system's configuration you have described in your last post makes no sense to me.

Having 1 bar pressure on an open system demands a height difference of 10 meters between the tank's water surface and the pressure reading, apply logic. You can't have both systems running paralel within the same system in a two storey house.
But you might live in a 5 storey house ....

And you should certainly never have central heating system loop connected to the drinking water (" auto - filling " ) due to the high risk of pollution !

A drinking water suply should be save AT ALL TIMES.

Buford T Justice

heinbloed wrote: »

And you should certainly never have central heating system loop connected to the drinking water (" auto - filling " ) due to the high risk of pollution !

A drinking water suply should be save AT ALL TIMES.

Will an NRV before the loop not fix that bit?

EosEnergy

Fingers McGee wrote: »

Will an NRV before the loop not fix that bit?

NRV should be fitted too, but must not be left connected, as the NRV might fail, exposing the drinking water to contamination.

heinbloed

Fingers McGee asks:

Will an NRV before the loop not fix that bit?

Yes and no. In principle the non-return valve would stop a flush back. But valves can fail, therefore a permanent conection between the pressurised closed central heating system and a drinking water pipe is illegal.

The filling loop should be disconnected after every filling. So if the heating system looses pressure the drinking water system is not effected.
Again: this is what ALL boiler manufacturers trading legally in Europe have to recommend in their manuals. And what every plumber with a bit of responsibility should stress when commisioning a central heating system. Filling loop connected - no comissioning !

Anything else is professional misconduct.

See also the post of EosEnergy.

Buford T Justice

Thanks for that. Maybe I misunderstood the difference between a filling loop and a filling valve.

I understood that a filling loop was to constantly keep topping up the pressure in a system automatically when it dipped, thus the ability to disguise a leak.

As opposed to a filling valve which is turned on and off as needed to manually top up a system?

heinbloed

Fingers McGee asks:

I understood that a filling loop was to constantly keep topping up the pressure in a system automatically when it dipped, thus the ability to disguise a leak.

As opposed to a filling valve which is turned on and off as needed to manually top up a system?

The filling valve is connected permanently to the boiler, it comes usually with the boiler and is an integrated part of the system.

It usually is designed as a non-return valve, draining of the boiler is done via another valve, the drain valve.

Between the filling valve and the (cold)pressurised drinking water mains a loop is temporarily fixed, this allows for a temporary connection between the pressurised water from the mains and the central heating system.

When topping-up the pressure in the central heating system this (usually flexible) filling loop is fixed between the mains and filling valve.

After topping-up the central heating system's pressure and closing the valves again this loop is removed, flushed with clean water and stored somewhere next to the boiler to be ready for the next topping-up.

Check the boiler's manual, different makes - different parts. But the principal is the same: a filling loop must be removed to physically break the piped connection between central heating system and drinking water.

heinbloed

heinbloed wrote: »

EITHER you have a closed loop pressurised central heating system OR you have an open vented central heating system with a tank in the attic, in the tree or wherever....
Having 1 bar pressure on an open system demands a height difference of 10 meters between the tank's water surface and the pressure reading, apply logic. You can't have both systems running paralel within the same system

Heinbloed, you will find a lot of gas heating systems are fed from a tank with a check valve on the cold feed allowing for higher pressure readings for a tank fed system when heated.

OP, I would guess you have a leak on your heating system and as you thought it's the change in the incoming mains water pressure which is maintaining heating system pressure when cold. You will need to have the leak fixed so your heating system holds water, flushed if required and then a inhibitor added to keep sludge from ever causing a problem, Gary.

heinbloed

Thanks, Gary71.

You wrote:

Heinbloed, you will find a lot of gas heating systems are fed from a tank with a check valve on the cold feed allowing for higher pressure readings for a tank fed system when heated.

This is new to me, I'm not a plumber. But I think I have a bit of a connection to the laws of physics

How can a pressurised system holding 1 bar be held at this pressure when the applied pressure is less than 1 bar ?

The DHW circuit (the coper tank/storage tank) and the central heating circuit are different things, they aren't connected.

The pressure of the two could be totally different, of course.

heinbloed

heinbloed wrote: »

How can a pressurised system holding 1 bar be held at this pressure when the applied pressure is less than 1 bar ?.

it not mains fed.

I call this type of system semi-sealed, the cold feed tends to come from the main tank in the attic, so the cold reading at the boiler is the same as a normal open system, when the boiler comes on and starts to increase system pressure it closes the check valve/ non-return valve on the cold feed making the system a sealed system allowing greater system pressures, gas boilers tend to have the low pressure switch cut out to allow the boiler to fire on the lower cold pressures, Gary.

Buford T Justice

heinbloed wrote: »

Thanks, Gary71.

You wrote:


This is new to me, I'm not a plumber. But I think I have a bit of a connection to the laws of physics

How can a pressurised system holding 1 bar be held at this pressure when the applied pressure is less than 1 bar ?

The DHW circuit (the coper tank/storage tank) and the central heating circuit are different things, they aren't connected.

The pressure of the two could be totally different, of course.

I didn't get it either. An NRV fitted is one thing, but if there isn't enough head pressure to pressurise the system in the first place, how can that be?

Also, pressure increases when the heating system is on anyway, as the water expands thus increasing pressure, which would explain the higher pressure when the heat is on

Fingers McGee

Fingers McGee wrote: »

I didn't get it either. An NRV fitted is one thing, but if there isn't enough head pressure to pressurise the system in the first place, how can that be?

It's not a mains fed system so your not looking for 1bar of pressure when cold, don't confuse the requirements for a mains fed sealed system with one that is tank fed.

Buford T Justice

Now I'm confused. You're not talking about a Sealed pressurized system, and you're not talking about an open vented system.

Semi Sealed? I'm not a qualified plumber but I've not heard of that before.

If there is no expansion vessel, and there is no F&E Tank, how does one allow the water to expand safely?

Maybe I've taken you up wrong here......

Fingers McGee

Fingers McGee wrote: »

Now I'm confused. You're not talking about a Sealed pressurized system, and you're not talking about an open vented system.

Semi Sealed? I'm not a qualified plumber but I've not heard of that before.

If there is no expansion vessel, and there is no F&E Tank, how does one allow the water to expand safely?

Maybe I've taken you up wrong here......

The expansion vessel and 3 bar blow off are within the boiler as it would be with a mains fed system, a semi sealed system is very common on older installations, my only issue with them is a safety device is bypassed to allow the boiler to fire on low pressue.

heinbloed

I seem to be a bit slow, this system laid down by gary71 seems to combine various components for which there is no reason to combine them. There are lay-outs, plans of many central heating systems from a lot of manufacturers available in the www., but I couldn't find anything showing such a system.

Is there a link available to some drawings showing valve positioning, expansion vats/tanks pumps and so on of the system gary71 has told us?

G71 wrote:

Also, pressure increases when the heating system is on anyway,

Yes, but this increase is very small in a pressurised,closed system. The one I'm using is a high volume system (UFH + plumbing ST), at least 800 liters in the circuit. With a temperature increase of 20 K (from 20 C to 40 C) this shows at the manometer just a very small tick,maybe 0.02-0.1 bar increase of pressure.
Note that there is an expansion barrel included, this seems to do it's job.


Also again, the primary fuel source is of no relevance.

Quote from gary71:

you will find a lot of gas heating systems are fed from a tank

but also a frequently asked question : " I have an oil boiler and the system is loosing pressure, I have gas, pellets, ST and the same problem ...."

The laws of physics make no difference.

heinbloed

Gary71 wrote:

The expansion vessel and 3 bar blow off are within the boiler as it would be with a mains fed system,.....

There is NO mains feed system. There is a pressurised, closed loop system, gary71. Nothing else.

We can use the pressurised domestic drinking water mains to PRESSURISE the system.
But we are not allowed to FEED this system by having a permanent plumbed/piped connection between the central heating and the (drinking water) mains.

heinbloed

heinbloed wrote: »

There is NO mains feed system. There is a pressurised, closed loop system, gary71. Nothing else.

We can use the pressurised domestic drinking water mains to PRESSURISE the system.
But we are not allowed to FEED this system by having a permanent plumbed/piped connection between the central heating and the (drinking water) mains.

Your being silly, the system is fed it's water from the mains and not a tank, any qualified heating engineer understands what a mains fed system means and why a filling loop comes with two caps, if every time i said a mains fed system but don't forget we can't leave it connected to the mains so cap it, i would have no time to drink me cup of tea.

EosEnergy

Aay aay - calm down, calm down

heinbloed

heinbloed wrote: »

I seem to be a bit slow, this system laid down by gary71 seems to combine various components for which there is no reason to combine them. .

Not to you, but this design came about because installers wanted to fit boilers designed for pressurized systems and were unable to use the mains to fed the systems, so rather than use a open system they decided to have a cold feed with a non- return valve.

heinbloed wrote: »

Is there a link available to some drawings showing valve positioning, expansion vats/tanks pumps and so on of the system gary71 has told us?

Not that i know of as it isn't recognized by any gas boiler manufactures that i know, it's just a the main storage tank in the attic with the cold feed connected to it and a non-return between the tank and the heating system.

heinbloed wrote: »

Yes, but this increase is very small in a pressurised,closed system. The one I'm using is a high volume system (UFH + plumbing ST), at least 800 liters in the circuit. With a temperature increase of 20 K (from 20 C to 40 C) this shows at the manometer just a very small tick,maybe 0.02-0.1 bar increase of pressure.
Note that there is an expansion barrel included, this seems to do it's job. .

Do you base that on experience or paperwork, from my experience a semi sealed system can show greater movement on the pressure dial than a pressurized system and house holders need to be made aware so they don't think they have a pressure problem.

heinbloed wrote: »

Also again, the primary fuel source is of no relevance..

It is to me as i am a qualified gas service engineer and i can only use my findings with gas installations.

heinbloed wrote: »

but also a frequently asked question : " I have an oil boiler and the system is loosing pressure, I have gas, pellets, ST and the same problem ...."

The laws of physics make no difference.

No, but knowledge of system design does and you have a hole in your understanding of what is a common design of (gas) heating, you would need to know that a boiler designed to work at 1 bar has been adapted to work at very low system pressures and is not a fault with pressure loss. Gary

EosEnergy

EosEnergy wrote: »

Aay aay - calm down, calm down

3 hrs of Micky f****** mouse and a 3 year old who is as happy as i am grumpy, no wonder i have the hump:(.


OP, sorry for stealing your tread:o