venting pure water

[mrcrow]

i observe when my central heating is running via the pump a flow is coming out of the vent into the header tank...it stops when i click off the pump..ps there isnt any steam so the boiler setting i presume is ok..(only set at no 1-2 on a scale of 1-5)..hot water is pretty hot at that
the tank level is fine and the ball cock is working ok..
the level never varies so the pump seems to be taking as much as its giving at this air break...
Q ..is my pump running too fast...ie too much head..or is this ok..
it doesnt bother me and the tank wont freeze..
i have attached a file for the central heating layout and the pump and radiators
i am in a bungalow so the flow is nearly all horizontal
and believe me that is how it is plumbed..and i am ok with it just now
the pump is new and quiet running
i understand the thermostatic valves shut down the rads and the pump may still run if the room stat which controls the pump keeps it running and the bathroom rad is the one with the no T valve and keeps hot all the time....thanks in anticipation
mrcrow....manchester

 

[ChrisR]

Your pump's in backwards.

It should bother you because you're introducing fresh air to the system which will corrode it very quickly.

 

[mrcrow]

Your pump's in backwards.
It should bother you because you're introducing fresh air to the system which will corrode it very quickly.

thanks chris..need to sort this out promptly

i did another diagram just to make sure i have given the correct info and
i just looked at the casing of the pump and the arrow faces the boiler lower tapping...
the boiler upper outlet goes right up the chimney space to the indirect coil...just where the riser connects with the coil is the vent pipe...
on the outlet of the coil is the makeup pipe from the bottom of the expansion tank...
then the pipework goes over the loft to two droppers to feed two circuits of radiators and return on a common pipe to the pump suction side..

where does the air come from into the system...is it from the tank?

the expansion tank level is at the full/shut ball cock postion..all the time and the flow in seems to equal any flow out

can the pump be reversed easily regarding wiring etc?
or does it need to be taken out completely and be reversed in the couplings?

thanks again

***edit...chris, i just checked the baxi service manual...and i see where the pump normally goes...mine seems to be in the 'alternative postion' pushing through the boiler from the rad return...

cheers...

 

[ChrisR]

Now I can't see why I thought the pump was backwards - unless the drg changed! Sorry!

Now it looks like all the water from the boiler which goes to the rads has to go through the HW coil first. EH?

The reason the water comes out of the vent pipe is that the pressure drop (head in metres) across the coil is more than the height between the water level in the f/e tank and the top of the vent pipe route. It would help if the loop inthe vent pipe went higher. But it seems wrong anyway.

Are you sure there aren't two flow pipes leaving the boiler? Ie one gravity for the HW and the other for the CH?

 

[mrcrow]

Now it looks like all the water from the boiler which goes to the rads has to go through the HW coil first. EH?
The reason the water comes out of the vent pipe is that the pressure drop (head in metres) across the coil is more than the height between the water level in the f/e tank and the top of the vent pipe route. It would help if the loop inthe vent pipe went higher. But it seems wrong anyway.
Are you sure there aren't two flow pipes leaving the boiler? Ie one gravity for the HW and the other for the CH?

this system was put in in 1964 and the owner was a builder...not a plumber..
why they didnt use 4 tappings on the boiler i dont know..
but there it is..my central heating water has to go through the coil...

btw your explanation now seems to make sense..ie pressure drop..thanks..thats given me some food for thought.
..its a new indirect cylinder and the connecting pipes are 28mm for gravity water and gravity/pumped ch..
i will investigate raising that pipe a bit higher...i could do it in speed fix..would that be ok...temp isnt anymore than 80 max..
could i throttle the vent pipe a bit...its only 15mm or 1/2" with an inline valve just cracked open or some restrictive pipework...to introduce some resistance?..
do you reckon the pump speed could be lowered..its at position 2...

i am investigating putting a bypass on the indirect cylinder and fitting a tank stat...there isnt one now so the hot water temp is governed always by boiler temp setting which is quite low so we dont scald ourselves..but havent figured out a way to get a electrical cable from the programmer up the chimney yet..other than surface mounted in a corner of the kitchen

perhaps at the end of the day if there is no imminent problem i can leave the vent issue till after the other mod

my plumber says a combi would be a better all round solution and tells me they cant be fitted after april this year...some change in the law doesnt allow them..???

i appreciate your help chris..and over on the rotten wood forum as well...ancient leaking boxed in toilet cistern blues..

cheers for now

mrcrow manchester

 

[doitall]

Trust me we knew how to install heating systems in 1964.

You have lost a part so look further, or trace the pipes and update your drawing.

 

[ChrisR]

Sounds like good advice. If your system really really IS exactly as you've drawn it, you'll never get satisfactory performance, it needs altering quite radically, though that may not be difficult.

 

[mrcrow]

Trust me we knew how to install heating systems in 1964.
You have lost a part so look further, or trace the pipes and update your drawing.

doitall...sorry.
chrisR many thanks again...future conversion on the front burner now...it would really help with the hot water being too hot..etc
doitall
no offence i just meant this particular person a builder in fact was the first owner of the house..and i withdraw my remark..
in my first post is the full system...and when i did the schematic i couldnt quite agree with it as well...but as you see only two boiler tappings are used and the gravity risers to the coil for hot water are boosted by the pump to do the central heating via a room stat...even though the rads have T valves...the bathroom doesnt so acts as a bypass.
ps...if the central heating is not on and just hot water...the rads will slowly get warmer due to convection...dont know if that was the original idea..
any way its easy to switch all the rads off in the warmer periods using the T valves..
the original indirect cylinder had an immerser element which i can see the old wiring for and a switch in the kitchen....but the existing one which was a replacement recently doesnt..another clue i took as the original system was immerser priority for hot water with a bonus if you ran gas central heating...the price of electricity
i will however check later again as we have had the water off and i have been re-lagging the loft pipes around the tank area and its clearer to see what's what...
thanks for your comments and suggestions
cheers
mrcrow manchester

 

[doitall]

mrcrow,

Wasn't having ago, just pointing out that you lost the bit of the system, that shows the common return, or where the central heating spits, possibly controlled with a gate, or zone valve.

 

[mrcrow]

mrcrow,
Wasn't having ago, just pointing out that you lost the bit of the system, that shows the common return, or where the central heating spits, possibly controlled with a gate, or zone valve.

cheers doitall..no probs
there are no zone valves its all gravity or pumped in the same system
mrcrow manchester