Problem refilling closed CH system

neilr4

I replaced some radiators after they burst during the freeze. I didn't empty the system I just isolated the radiators and replaced with new ones, opened all the valves and turned on the mains water to refill the system but nothing happened, mains pressure is fine btw.

I opened the bleed valves on the radiator there's no water coming through the system and the pressure guage stays on zero even though the pressure regulator hasn't been adjusted. Could the expansion vessel need pumping with air? if so how much?

Billy Bunting

When you turned on the mains did you hear it filling ??

slavetothegrind

when you say pressure regulator is it one of these?

http://www.pulsardirect.ie/plumbing-supplies/productdetail.asp?ProductCatId=134&ProductSubId=5&ProductCode=COMB05

neilr4

@Billy Bunting-No I heard nothing!

@slavetothegrind-Yep that's the one!

heinbloed

@neilr4:
Connect the filling loop.

tonysea

neilr4 wrote: »

I replaced some radiators after they burst during the freeze. I didn't empty the system I just isolated the radiators and replaced with new ones, opened all the valves and turned on the mains water to refill the system but nothing happened, mains pressure is fine btw.

I opened the bleed valves on the radiator there's no water coming through the system and the pressure guage stays on zero even though the pressure regulator hasn't been adjusted. Could the expansion vessel need pumping with air? if so how much?

When u say mains, do you mean the valve located usually under the kitchen sink? If so that valve doesnt really have anythin to do with your heating. You need to establish where your system is filled from (either off the tank in attic or through a filler loop in the hot press) go to hot water cylinder you'll find two 3/4" pipes that enter the cylinder these are the flow and return to the coil in the cylinder. Look for another pipe (with a valve on it) joining one of these that looks like it might come from the attic or it could be a silver braided hose if its a filler loop. thats where the heating system is filled from.

If you still have no joy, it could be that the pipes are also burst. Which is likely if it was cold enough to burst a cast iron rad, a copper or plastic pipe wont stand a chance

Sparkpea

expansion vessel may have frozen also but its likely you are not topping up correctly, or the valves are jammed on the radiators (less likely).

Billy Bunting

Discon the filling loop and check if its passing water.

neilr4

Billy Bunting wrote: »

Discon the filling loop and check if its passing water.

That was the first thing I tried.............

Billy Bunting

When you say mains are you talking about the mains to the house ???

The system is normaly presurised at a filling loop and then turned off, if you had bursts i presume you turned off the mains to the house, turning this back on won't refill the system if its off at the filling loop.

aujopimur

If it's an auto fill valve give it a sharp whack with a spanner, that should free it.

neilr4

Mains water supply is also connected to the filling loop in order to fill/top up the system with a gate valve for ease of use..........

I've come to the conclusion that it's either the pressure regulator that's faulty or the expansion vessel either isn't pressurised or the diaphram is knackered. I will try pressurising the expansion vessel (anyone know how much pressure on air-side?)

Buford T Justice

Depends, but should be printed on the vessel.

heinbloed

Neil4r asks:

I will try pressurising the expansion vessel (anyone know how much pressure on air-side?)

It would have to be the same pressure on both sides. If -for example-the pressure of the heating side is 1 bar then the pressure of the air side would have to be 1 bar.
This means in practical installation exercise that the pressure of the heating system is known first, before pressurising the heating side. Then the air side is to pressurised to this pressure, in our example 1 bar. Then the heating side (via the mains) to 1 bar.

jeepers101

Neil it has nothing to do with the vessel. Even if the vessel was empty you should still be getting water out of the rads when bleeding. The vessel is there to cater for expansion in the system, which results from the water expanding when heating. If its empty it'll cause you pressure problems when the system is running but will not hinder you filling the system.

neilr4

jeepers101 wrote: »

Neil it has nothing to do with the vessel. Even if the vessel was empty you should still be getting water out of the rads when bleeding. The vessel is there to cater for expansion in the system, which results from the water expanding when heating. If its empty it'll cause you pressure problems when the system is running but will not hinder you filling the system.

You're right there jeepers and I agree, just needed to hear it from someone else..............the friggin thing has me demented!! Simple job that's just become a bit silly.

The building is a local social club and I'm doing this just to help out, my experience is in industrial plumbing/pipe fitting so new territory here.............

Billy Bunting

Totally agree about the pressure vessel, should still pressurise.

Non return valve on the fill loop ????

How about running a pipe and filling somewhere else ??

Buford T Justice

Can you take a pic of the loop thats not filling?

neilr4

Thanks guys for all your advice so far!!

The reason that the system wasn't filling is because the non return pressure valve was siezed, dismantled and re-assembled and problem sorted.

Another question: I set pressure in system at approx 1.2 bar and pressure in expansion vessel is similar, why would the pressure in the system be creeping up to approx 2.5bar. The mains feed into the system is closed so there is no way more water can get into the system. I opened the outlet valve and the pressure dropped fairly quickly but I'm puzzled as to why this is happening. I have repeated this procedure on a number of occasions.

sullzz

Does the pressure rise up rapidly , as in a few mins of heating turned on , if so the only reason for this is usually the expansion vessel , did you take your pressure reading of the vessel before you filled the system , try pressing in the Pump connection on the vessel and check for air, if you have no air it needs replacing and is more than likely causing your problem

jeepers101

sullzz is spot on there. If you check the pressure of the expansion vessel while you're system is full of water, you are merely checking the pressure of the system. If you did not check the pressure of the vessel before filling, you will have to isolate and drain the vessel or if this is not possible, drain the whole system and check the vessel. If there is no valve to isolate the vessel, it might be worth fitting one for next time.

As water heats up it expands. If there is no air in your vessel there is no room for the water to expand, hence the rise in pressure.

Fill the expansion vessel to around a bar (an ordinary bicycle foot pump or similar) and the heating system to around the same. You don't have to be exact about it but it shouldn't be hard to get it in the same region.