Missing port valve

[TomLane]

Is it possible for a system that in my understanding should have a port valve still work if there isn't one on the system?

 

[tamz]

As in only 1 valve or no valves?
You can make anything work

 

[TomLane]

No valves at all.

Head scratcher!

 

[Whyme]

not if its fully pumped cos youd have ch and hw on together all the time. if its gravity hw and pumped ch yes.

 

[Ermintrude]

Or it's got a servo warm lever!

 

[tamz]

A lot of older systems were put in with just a pump. FEP being probably the biggest offender up this way (and they done a LOT of jobs usually a baxi wm with the pump inside the casing).
Turn the rads off in the summer is all the control they had.

You can do fully independent systems with 2 pumps instead of valves or the twin pump plan type things but its not very common to come across those.

 

[TomLane]

Okay, so I'm assuming that the missing port valve isn't hidden away somewhere & is working without it.

The problem I have is that I changed 2 rads on the system. Partially drained, topped back up via F&E.

Heating fine, but no hot water!

 

[ADM360]

Air lock? or you've moved some gunge round and blocking it?

 

[TomLane]

My thoughts were its sh1tted up!

Boiler just not firing on hot water only on programmer!

 

[tamz]

How many pipes off the boiler.
If it is gravity hw it will be airlocked.

 

[TomLane]

4 including gas.

If it was air locked would water still flow from hot tap?

 

[tamz]

Of course.

The air lock will most likely be just after the tee on the flow.
Pull the stat out on the boiler and let it boil. That will shift it.

 

[TomLane]

Not GSR so not privvy to knowing where the stat is?!

 

[tamz]

There are other more laborious ways to clear it.

 

[TomLane]

How would I go about doing in the less laborious way? ;-)

 

[Ermintrude]

Open unions on cylinder (only a smidgen and with a wet vac. If old unions you could ..... Install an aav at highest point on cylinder feeds

 

[TomLane]

Open unions on cylinder (only a smidgen and with a wet vac. If old unions you could ..... Install an aav at highest point on cylinder feeds

On hot outlet & cold inlet?

 

[tamz]

Leave the boiler. You will probably shyt yourself when it starts boiling if you've never done it before anyway.
Check the flow pipe from where the expansion tees off to the coil is dropping slightly. The air needs to run uphill to an open end to escape. Pull the pipe up a bit if it is rising to the coil and jamb something under it.
Split the nut at the coil to release any air from there. Sometimes the coil has a slight rise.
Most gravity hw systems were originally solid fuels. It didn't really matter too much if the pipe fell the wrong way as the coal would boil the water and shift it.
Once it starts working it will be fine until some other guy comes along and drains it.

 

[tamz]

On hot outlet & cold inlet?

Nothing to do with the hot water side.
It is the coil you are looking at.

 

[TomLane]

Thanks for that!

Okay, so now I've hopefully got the answer to fix it!

How & why does this happen then when draining the central heating?

What's the best way to prevent it in the future?

 

[IDCHAPPY]

Or it's got a servo warm lever!

Don't see many of them these days

 

[tamz]

It happens because you drop the water level in the system and when you refill it the air gets trapped at a high point.
Because the hot water side of the heating system is not pumped it relies on thermosyphon (pressure difference between the hot water and cooler water) so can never move it on its own.

Like this

 

[TomLane]

Thank you for taking the time to explain this. Much appreciated.

 

[Ermintrude]

Tamz hope your going to pay bum center the 4k for that tapwasher and not just dorb all over their envelopes .

 

[tamz]

I've not opened it yet. I'll save it for when i want a laff :smile: