TRV and condensing boilers...again

Hi All

I have got a couple of quick queries. Firstly, I have seen in this group many times that TRVs should be on all but one of the radiators. I have recently had a condensing boiler installed and the plumber put TRVs on ALL of my rads. I have been leaving the bathroom TRV at its max setting...is this ok?

Secondly, the bathroom towel rail seems to be trapping air. Each day I can release a few cm^3 from this rad. Is this normal?? The system has been in place for a couple of months now so I was expecting this to just settle down with time.

Thanks for the advice folks!

Reply to
Magpie
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Probably not ;-)

Where is your room thermostat? In that room you want to remove the head from the TRV.

Did your installer add corrosian inhibitor? It could be gases produced from corrosian by products that you are collecting rather than air.

What is happening to the system pressure over time?

Reply to
John Rumm

Hi John

There is no room thermostat connected to the system. Is this a big problem?

I *think* that he installed an inhibitor - not sure which one though. The pressure tends to drop very slightly, presumably because I am releasing the gas/air from the rad on an almost daily basis. Will this corrosion process slow up and stop or does this sound like it needs more inhib/anti-corrosive stuff in the system??

Thanks again for the advice

Reply to
Magpie

Mine did the same, and curiously it was the bathroom rad as well that trapped it...if its new plumbing it tales time for the flux to etch away at enough copper and produce the proper sludge in the system and the gases that go with it..just keep bleeding ..

Reply to
The Natural Philosopher

You only need an open rad if your boiler does not have a built in water bypass or the plumber didn't fit a seperate one. They look like a short circuit on the flow and return pipes, usually near to the boiler. Presumably the plumber either fitted one or the boiler has it built in. This is to stop the pump breaking because it has no water to pump through itself because all the rad valves have closed themselves.

A new system will vent air for about a week and then should settle down and need no further attention. My plumber over pressurised my system by a full bar and said it would be at proper 0.75 bar cold pressure in a week. I bled the rads and it reached exactly 0.75 bar in about 8 days.

Reply to
EricP

Some boilers have integrated flow switches and can have TRVs all around. What make and model of boiler?

Reply to
Doctor Drivel

We had new pipework (a number of joints) with the recent new boiler. Probably explains the bleeding I've had to do. Funnily enough, it's the bathroom rad!

Reply to
Bob Eager

I think you will find that an integral by-pass is obligatory with modern boilers. I may be wrong but I think it is in the Water Regs.

Reply to
Merryterry

It isn't.

Reply to
Doctor Drivel

Well there is supposed to be something that acts as an "interlock" i.e. some mechanism that will stop the system when the whole house is up to temperature. Otherwise the boiler will just keep running (wasting fuel) and pumping against mostly closed TRVs.

If it is a new system or has recently been refiled then you can expect a small amount of air to come out for the first few weeks as the air that is normally dissolved in the water gets removed. If you carry on getting gas at the same rate however then that could indicate a leak. Air will often accumulate in one rad - sometimes the highest in the system, or the first on the circuit. Bathroom towel rails are good for this since they tend to be tall and also hold a low water volume - so a little bit of air is noticeable.

Each time you top up the water level you will introduce more oxygenated water (more air to escape) and also dilute / use up more inhibitor (one of its purposes is to scavenge free oxygen from the water to prevent it reacting elsewhere causing corrosion)

Reply to
John Rumm

Thanks for all the good advice everyone,

The boiler (a ferroli f30b - anyone got any experience of these??)was fitted on the 1st September, though the bathroom rad was connected about

6 weeks later (after I had completed the redecorating). The bathroom rad is indeed the highest on the system. I had expected the gas/air to have stopped by now.

Sorry if this is a dumb question but I am slightly confused by the suggestion that there could be a leak causing air in the rads. If you have a pressurised system with a small hole somewhere, surely you would get leak of water from the system until the pressure equalised on both sides of the hole???

I am probably overconcerned but have had no end of problems with this plumber - I feel that I cant trust that he did a decent job. Problems have ranged between several no shows (after I had taken time off work) to gas leaks!!. I recently contacted CORGI because I hadn't received a certificate - appears that he hasn't registered the installation...

Reply to
Magpie

The f30b is not on the web site. It may be a discontinued boiler. All the range seem to have integrated auto by-pass valves. But this does not mean you can have TRVs on all rads. See the fitting instructions. Did the fitter leave them? Or ring Ferroli tech dept.

yep. If on an existing system it should have been cleaned out. I would have fitted a Magnaclean on the return to catch the debris and sludge.

Ring Ferroli and check about the TRVs and pursue Corgi as well. Did you check his Corgi card?

Reply to
Doctor Drivel

What's the pressure reading when the system is cold, and how much height is there between the pressure guage and the highest point in the heating system?

It's more complicated that that. For a big hole, what you describe is correct. For a small hole, you might see no water leaking out as it does so slower than it evaporates, but air can leak in faster. See:

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would be worth forcing out all the dissolved air by running the system at max water temperature (minimum air solubility, so max air forced out of solution) and bleeding this air out before any of it dissolves back in. Then if air reappears later, you can be pretty sure you have a leak.

Reply to
Andrew Gabriel

The f30B was on their website a couple of months ago!!! Looks like the domicompact range has superceded the f30b. The manual says that an automatic bypass must be fitted if TRV's are on all rads. I assume that this has to come before the first rad on the system??? This is just to the side of the boiler and I can see no sign of any valve...

I checked his registration on the CORGI website. If I am not happy with an installation can I get CORGI to check it and how much will that cost?

Reply to
Magpie

When cold the P is 1.5 bar. I guess there is about a 5m height difference

I will try this - though a bit nervous about doing this if there is no automatic bypass valve (see previous post)!!!

Thanks for the suggestions, much appreciated

Reply to
Magpie

It is usually set to 1 bar. See the manual for the set range.

Reply to
Doctor Drivel

It is between the flow and return at the boiler. Does the manual say a radiator must be open?

Ed Sirret may help you there. He sounds like a plumber who has gone into heating. Or someone who did short course. Corgi registered doesn't experienced.

Reply to
Doctor Drivel

It probably is a bit high for a cold system, but 5m is also a relatively high head. That alone will represent 0.5 bar of the presure the guage is reading.

Reply to
John Rumm

Norm is 0.5 to 1 bar.

Reply to
Doctor Drivel

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