'PITCHING'

danjo-xx

Will be getting a plumber out shortly but would like to get a basic understanding of what causes 'Pitching' and how it should be remedied.

Grant Multipass 70-90 running great and think a new burner was fitted at some stage.

Ran system for an hour this evening and as there is a lot of damp problems on the roof rafters I wanted to try and trace the source of this.

I pulled the cover slightly off the expansion tank to check the temperature of the water and was met with a mini Sauna and the water was hot even the insulation over it was wilting.

The Boiler stat is still set at 85% which is recommended winter setting for this model.

The only other problem that I am aware of is that the hot water is not heating when boiler is on. Had zone valve and tank stat fitted 2yrs ago.

I checked stat is high enough, have it at 55%

Also vent pipe is dipping in below water level when it should be just hanging over.

With no hot water being heated does this make the pitching problem even more serious or less:(

Billy Bunting

Also vent pipe is dipping in below water level when it should be just hanging over.

Theres ya sauna

danjo-xx

Billy Bunting wrote: »

Theres ya sauna

I mentioned this a while ago here after getting attic insulated and someone said that it looks like it was dipped in order to hide a pitching problem.

I'm not sure if its always been dipped or just since the guys removed pipe securing bracket from wall in order to insulate pipe.

Would dipping cause syphoning and or explain why no hot water!

Billy Bunting

Difficult to be sure without seeing it but if you drop the vent into the expansion you will effectivly be piping up a rad, a rad with a 3/4 feed, and as the vent is taken off your feed to the cylinder (that is normally restricted via a balancing valve/gate valve) then your pump will find it easier to pump through your new sauna than through the cylinder, so yes, that could also be your no hot water problem.

aujopimur

Reducing the pump speed might cure the pitching, sealing or semi sealing the system or combining the cold feed and expansion would also cure the problem.

danjo-xx

Billy Bunting wrote: »

Difficult to be sure without seeing it but if you drop the vent into the expansion you will effectivly be piping up a rad, a rad with a 3/4 feed, and as the vent is taken off your feed to the cylinder (that is normally restricted via a balancing valve/gate valve) then your pump will find it easier to pump through your new sauna than through the cylinder, so yes, that could also be your no hot water problem.

Christ :mad: ...... well no prizes for guessing what I will be doing tomorrow:D

Billy Bunting

aujopimur wrote: »

Reducing the pump speed might cure the pitching, sealing or semi sealing the system or combining the cold feed and expansion would also cure the problem.

As could raising the vent out of the expansion to a suitable high :rolleyes:

Suggest you try that before altering a system that may not require it.

danjo-xx

Billy Bunting wrote: »

As could raising the vent out of the expansion to a suitable high :rolleyes:

Suggest you try that before altering a system that may not require it.

too true will start from the basic's up. As they say if it's not broken don't fix it.

danjo-xx

below is pic of exp tank vent pipe. Its a big enuf loop. How much do you suggest I keep the end from the water level. 2" or 3" .

Billy Bunting

Pic not working for me.

danjo-xx

ok for me, guess its height of loop that matters, in my case is pretty high, and end just above water level like here.

Billy Bunting

Looks like you have good hight so just remove the pipe from the water and secure it just within the tank lid, if you still have water from the vent pipe then you have a pitching problem.

danjo-xx

Removed pipe but still pitching.

aujopimur combining the cold feed and expansion would also cure the problem.

but how exactly is that done and should it be done in Hot Press or attic.

The Qualpex pipe near zone valve is the vent pipe to expansion tank in attic.

Billy Bunting

A combined feed and vent is quite acceptable if the boiler MI allow it, check your MI's first.

aujopimur

Drain the exp. tank, not the whole system to minimise any refill problems.
Cut the 1/2" as it exits the tank and tee it into the3/4" exp. keeping the 1/2" level or sloping down a little.
Don't forget to blank the 1/2" cold feed where it's been cut as it comes up from the hot press thru' the ceiling
Refill, pitching cured.
The only drawback is when refilling after a draindown as it's a bit slower to vent.

Billy Bunting

You must check the Boiler instructions, be sure your boiler has a High Limit Thermostat before combining the feed and vent.

Micky Dolenz

I'd change the vent pipe to copper. I think it's bad practice to use a plastic pipe no matter how well clipped it is. You seem to have room to take it a bit higher, even bit helps. I don't like combined feed and expansions.

Changing pump speed is a valid solution.

Ideally you need to look at the system as a whole and figure out where the pump is in relation to the vent pipe, as Billy said, water will follow the path of least resistance. Pumps can pump water through vent pipe and pull air through vent pipe so system design is important.

danjo-xx

aujopimur wrote: »

Cut the 1/2" as it exits the tank and tee it into the3/4" exp. keeping the 1/2" level or sloping down a little.

Don't forget to blank the 1/2" cold feed where it's been cut as it comes up from the hot press thru' the ceiling

Hi aujopimur thanks for you help with this. I just can't quite get a handle on this.

The object is to combine the cold feed and expansion pipes.

By 'cold' feed you mean the 1/2 pipe from the exp tank to top up the system.

If that's correct. Then

So cut this pipe in HP and insert a tee and join it to the 3/4 plex/copper vent pipe.

Then Don't forget to blank the 1/2" cold feed where it's been cut as it comes up from the hot press thru' the ceiling. I don't get this bit at all.

aujopimur

Tee in at the expansion tank in the attic.

DoneDL

I agree with Micky copper is better on the expansion pipework, if you are going to combine the F&E pipework to cure the pitching then try an air seperator at the point where you combine the two.

Micky Dolenz

And while you are at it move the gate valve on the flow to the horizontal part of the return at cylinder. It is a balancing valve that only serves to restrict expansion and as I said in another thread is illegal and dangerous.

danjo-xx

I'm not keen on combining the F+E to be honest but that's just my basic common sense approach.

What are the alternatives to doing this:

Reduce Pump Speed - Have this down to 2 now and no pitching but one or two rads are not heating.



What is the cause of pitching as I'd like to understand what 'actually' is happening!

aujopimur

The pump is pushing the flow up thru' the exp. and drawing down thru' the cold feed, thus creating a circuit in the path of least resistence.
Technically the cold feed should be connected in front of the pump on the return, very few installers do this.

Micky Dolenz

You could just seal the system. This is a sure fire way of solving the problem.

danjo-xx

aujopimur wrote: »

The pump is pushing the flow upthru' the exp. and drawing down thru' the cold feed, thus creating a circuit in the path of least resistence.
Technically the cold feed should be connected in front of the pump on the return, very few installers do this.

Would this be worth rectifying now or too costly.

You could just seal the system. This is a sure fire way of solving the problem.

How Much..... 2k+ :eek:



Combined F+E is lookin like the only kid in town at the moment:D

Micky Dolenz

I'll do it for 1K

Less then €100 in materials and under 4 hours labour.

danjo-xx

Micky Dolenz wrote: »

I'll do it for 1K

Less then €100 in materials and under 4 hours labour.

Sure wouldn't the new boiler cost that and more or can the existing boiler be adapted!

Micky Dolenz

danjo-xx wrote: »

Sure wouldn't the new boiler cost that and more or can the existing boiler be adapted!

I was kidding. It would cost nowhere near 1K, what I said after is more accurate. No boiler change needed. An expansion vessel would be swapped for expansion tank and filling loop/gauge instead of cold feed.

danjo-xx

Micky Dolenz wrote: »

I was kidding. It would cost nowhere near 1K, what I said after is more accurate. No boiler change needed. An expansion vessel would be swapped for expansion tank and filling loop/gauge instead of cold feed.

yeah I knew you were kiddin around but I didn't realise that my existing boiler could be used in a sealed system. Thats great news I might go that route.

If the filling loop is mains fed (as I think it is) would there be any prob in getting a feed to the boiler house. I have an outside tap maybe it could be taken off that.

thanks.

DoneDL

No, I would suspect that the advice will be to disconnect in the attic and install a system pressure kit in the airing cupboard.

I would also suggest insulating the pipework.

Micky Dolenz

danjo-xx wrote: »

yeah I knew you were kiddin around but I didn't realise that my existing boiler could be used in a sealed system. Thats great news I might go that route.

If the filling loop is mains fed (as I think it is) would there be any prob in getting a feed to the boiler house. I have an outside tap maybe it could be taken off that.

thanks.

Ideally you want the filling loop by boiler but you could fit it in hot press with a gauge. simply tee into mains in attic and use existing cold feed. Fit expansion vessel in hot press also on existing expansion pipe.

danjo-xx

Micky Dolenz wrote: »

Ideally you want the filling loop by boiler but you could fit it in hot press with a gauge. simply tee into mains in attic and use existing cold feed. Fit expansion vessel in hot press also on existing expansion pipe.

ooooh that is excellento, your stealing my soul now keep it coming


now!!!!! I have an old system with steel rads which wasn't looked after very much if at all by former owners, is it important that I get it flushed out properly before sealing it.it

I did have it flushed out 2yrs ago but not pressure flushed and no inhibitor was added.