New Boiler Installation

[burnssj]

I had a fully pumped open vented central heating system with a Glowworm 50FF conventional boiler and a separate hot water cylinder.

Due to the flue incorrectly sloping back towards the boiler (which it wasn't meant to do with this conventional boiler), rain water had run through the boiler 3 times in 4 years tripping the electrics out to the whole house. So I decided to have a new boiler fitted.

I now have a Glowworm Flexicom 24HX on the same open vented system. The only other differences being a repositioning of the pump from the airing cupboard to near the boiler and the inclusion of a central stat (I never had one before) & electronic timer/controls.

I have, and have always had, TRVs on all the rads (there are only 7 on the system).

Since the new boiler has been installed I seemed to be getting more air than I would expect in a refilled system in radiators, and coming out through the self vent in the airing cupboard.

I called the installers back and today they came and investigated and found that hot water was travelling up the cold feed because the TRVs upstairs had closed down (up to temp) thus the hot water had no where to circulate - so it look the path of least resistance and went up the cold feed.

The installer has now opened fully the gate valve hoping it might resolve the problems. Quite how air has been getting in I don't know unless the hot going up the cold feed creates air or somehow then allows air to be drawn back in? I'm not very technical (I am a female and not scared to say I don't know how these things work).

Anyway, my question is to all you plumbers/heating installers, is any idea what is causing my problems? I know the pump being moved will have disturbed the equilibrium of the whole set-up but now I'm not sure if I should be having floors up etc to see what pipes run where to remedy the problems properly. Whether the expansion pipe needs re-routing perhaps? Totally lost I am...

 

[Tibbot]

The re-location of the pump will cause your problem if the feed & vent pipes remain in the cylinder cupboard. In other words - installed by idiots who don't understand open vent neutral point.

Probably used to throwing in combis where their incompetence is less likely to show up so quickly.

 

[LUNAT]

HI

yes tibbot is right.repositioning the pump can change many things.possible faults to your problem
1.pump speed too high (try n. 2 )
2.pump fitted in the incorrect place (not followed the feed and expansion rule )
3.pump fitted wrong way
4.auto by pass not fitted so when the rads are closed water does not circulate instead it goes up the expansion tank thus in return draw air in which gets trapped in the . radiators .
best of luck.

 

[Hugh Jaleak]

Vent and cold feed should be within 150mm of each other, then the pump should be fitted after this point.

Room in which roomstat is located should not have a TRV on the rad! Ideally it should have lockshield valves both ends, set by the installer. Then as TRV's shut down as rooms hit temp, the remaining output from the boiler can be channelled through this rad until roomstat is satisfied and switches boiler off.

If the roomstat is still calling for heat and the TRV's have shut down the the output from the boiler has nowhere to go!! Sounds like the system could be pumping over. This is a serious problem, will account for the excess air and will also lead to corrosion of the system.

I would suggest you try and find someone who understands the system properly to check it over and report their findings. Either get the original installer to remedy any faults at their expense or let the new engineer sort it and send the first mob the bill!

 

[Agile]

Anyone who installs boilers is meant to be gas registered. Are you sure these people were?

A system with all TRVs is meant to have an autobypass fitted so the system water has somewhere to go if all TRVs are closed.

This fellow does not seem to even know that. That does not sound very competent. Has he completed the Benchmark Certificate?

Tony

 

[burnssj]

Yes, they are registered. I looked them up on the Gas Safe register along with their number. They came back yesterday and moved the pump back to it's original position in the airing cupboard.

So I now have boiler, open vent, cold feed, pump. Then I think it goes to the 3 way valve & then splits off for heating & hot water - something like that anyway. There is also a self venting valve and a gate valve which is open about 1 turn to allow for circulation if the TRVs shut down.

However, even though the vent comes before the cold feed, the vent gets luke warm on occasion but the cold feed pipe gets quite warm, then hot, then stone cold. Not sure how far up it's getting hot/warm. I was too knackered to climb on a chair last evening to check. I will be sending the boyfriend up in the loft tonight to check what's happening up there when it's all on & pump is circulating. But I don't appear to be getting air in (which I was when the pump was in the wrong order on the circuit) and the rads are getting hotter than they were when the pump was in it's "alternative" position. So that is an improvement at least.

The noticed the pump is on max (3) which I assume it needs to be to get the heat away from the boiler? But what do I know. I work in an office. I don't want to know anything about heating etc other than to know it is working and safe.

If water is going up in to the tank via the cold feed (& making me a radiator in the loft) then I assume I will need to get them back again as moisture in loft not good idea and clearly it's not efficient to have a semi radiator in the roof space.

 

[Agile]

Yes, they are registered.

There is also a self venting valve and a gate valve which is open about 1 turn to allow for circulation if the TRVs shut down.

I am glad they are registered but obviously not very competent if they make that basic mistake about the pump location.

The gate valve in place of an auto bypass valve is a cheap bodge which is often used by semi cowboys.

Its not approved by boiler manufacturers and the correct item should always be used on any proper quality installation.

Tony

 

[burnssj]

Did I mean gate valve? It also gets called the by-pass valve. But it's not automatic.

To be fair, the gate valve/by-pass valve in place is what's been in the property since I moved in 10 years ago. These people didn't put it in.

Now, do I send the boyfriend up in the loft before or after his tea?