Low pressure in heating system.

PadraigL

Hi

Noticed last night that the downstairs rads were not heating. Checked for air but they were ok. The small single rads in the house were boiling. It just seems to be the bigger rads downstairs that are not heating. The bedroom rads were also heating.

The boiler was showing at 0.7bar while working and checked this morning when it was off and it was at 0.5bar. It says on the boiler that the normal operating pressure is 1 to 2.5bar.

Now there is no filling loop at the boiler but the hot press has a non return valve with s stop cock which is alway on, coming from the cold water tank in attic.

How do I pressurise the system?

Pictures attached..

Thx
P

PadraigL

So the boiler when it switches on, sounds like an airplane engine for 5 seconds.

Anyone any idea??

Thx

wiz569

That appears to be whats commonly called a "Semi sealed system" and your operating pressure looks to be fine, mine is exactly the same and works perfectly at that pressure,that stopcock and non-return valve setup is your fill loop and is permanently on,

It may be the pump thats shagged,can you check to see if you can feel any vibrations from it to suggest its actually spinning?

PadraigL

Thx wiz569.

Yea the pump seems to be running. When I pum my hand on it, I can feel vibration. The noise when starting does not seem to be coming from the pump but further up the boiler. Its like Aerlingus passsing overhead....

What's the normal way to get the pressure up above 1bar to rule that out?

thx
P

wiz569

PadraigL wrote: »

Thx wiz569.

Yea the pump seems to be running. When I pum my hand on it, I can feel vibration. The noise when starting does not seem to be coming from the pump but further up the boiler. Its like Aerlingus passsing overhead....

What's the normal way to get the pressure up above 1bar to rule that out?

thx
P

You won't unless you convert it to a fully sealed system, that pressure reading is all you will get with a semi sealed system,are the rads upstairs vented?

Is the system zoned,maybe motorised valve is stuck?

PadraigL

The system is not zoned. I have a manual valve in the hot press. When its open all rads are fed hot water. Each rad has temp control valves. When the valve is closed the copper tank is heated only.

Rads vented?? Not sure what you mean.

Thx

wiz569

PadraigL wrote: »

Rads vented?? Not sure what you mean.

Thx

As in you have vented them and there is no air trapped in them,have you tried turning off the upstairs rads to see if the downstairs ones will then heat up?

If that doesn't help might be time to call a Plumber I'm afraid

PadraigL

Sorted. A plumber friend of my father's sorted it on the phone in about 2 mins this evening.

So he got me to turn off the water from the boiler to the coil in copper tank, by closing the stopcock. This forces the heated water to my rads which worked straight away. This also confirms that the circulation pump is working ok. If this did not work he suspected the pump. The airplane sound also disappeared.

As soon as this was done he got me to open the stopcock 1 turn as he said it does not take much to heat the tank.

Also the pressure at 0.7bar is ok and based on the height of the tank from boiler.

Never seen the double rad in the sitting room so warm. We usually have the fire going and never worried too much about it and I thought it was just like that.

Thx for replies though and hopefully this may help someone else.

P

MummyBT

PadraigL wrote: »

Sorted. A plumber friend of my father's sorted it on the phone in about 2 mins this evening.

So he got me to turn off the water from the boiler to the coil in copper tank, by closing the stopcock. This forces the heated water to my rads which worked straight away. This also confirms that the circulation pump is working ok. If this did not work he suspected the pump. The airplane sound also disappeared.

As soon as this was done he got me to open the stopcock 1 turn as he said it does not take much to heat the tank.

P

Hi, was the boiler on when you did this? Presumably it was (or was just before you did it) as you’re saying shutting off stopcock forced heated water to rads? Trying to figure out what’s wrong with ours and forcing water to the rads sounds like it might be just the fix we need. We have 1 cold rad which will only heat when all others are off... how long did you have to close the stopcock for? Thx!

PadraigL

The boiler was on for me. I closed stopcock and the rads started to heat up straight away. After about 15 mins they were fully hot.
If you close stopcock before heating comes on will give same result, I am sure.

Only after all your rads are hot (30 mins or so) and have no cold spots or air then open the stopcock 1 turn to the tank coil.
I had no air as I had bled them prior to the fix as I thought that was the problem. But as far as I know my system should have no air the way it's piped.

All the rads that were not heating downstairs had warm pipes on the inlet but it just was not pumping the hot water through the rads.
Also all the small rads, in en-suite, bathroom and downstairs toilet were always warm. Hot water took the path of least resistance.

Hope this helps.