Where should the pressure vessel be sited

[lxbn]

My CH system was converted to a closed system. The property is on 3 floors (including the loft) and the boiler, a conventional Worcester Bosch 24cbi, is in the kitchen on the ground floor. The PV, I think 8 or 12ltr can't say exactly as the label is behind and can't be seen (supplier said that unit supplied is 12ltr but looks smaller), added when the system was converted, is in the airing cupboard on the first floor.

I've been having problems with the pressure in the CH as I have to top up every few days. I've found a small leak at a drain off valve, it's quite small but I hope it's the reason for losing pressure. Although, when the system is refilled to bring it up to 1 bar, when the system runs it climbs to between 1.5 to just over 2 bar. After the system stops and cooled it drops back sometimes to below 1 bar. If not refilled it would gradually fall to zero and shut down the boiler.

I am going to have the leak fixed and at the same time thinking of replacing the PV with a larger one, maybe 18ltr, since the heating engineer thought the vessel might be a little too small for the size of installation - and having a larger one than needed is not going to harm the system.
My question is, a) is there an optimum place to site a pressure vessel and b) which way up should it be installed - the one in place at the moment has the attachment from the CH at the top.

 

[kevplumb]

preference is on the return but it can go anywhere on the system as long as it has a permenantly open path

ie no valves etc

makes no difference which way up follow the mi's

 

[lxbn]

It looks to be on the return and no obstructions like valves in the run to the PV. OK I'm happy that the orientation of the PV is irrelevant as to turn it around looking at it I think there'd have to be some sort of platform to be built to allow for the connection.

So no problem with having a larger PV than required? - it's not a huge additional cost. Only asking because my heating engineer does not think it necessary but I would like to cover my bases while the system is drained and not have to do it again if it turns out that the system needs it.

 

[Axel]

Could fit an additional one to increase the expansion capacity - the additional one would not be as big as the replacement you are proposing, and could be sited somewhere else where there is convenient space with access to the return pipework.

 

[kevplumb]

have you checked the precharge

 

[lxbn]

By precharge I guess you mean does the PV require repressurising with a pump. This pressure problem has been around for a little while now, and about 3-4 months ago the engineer checked it and it didn't need it. I hope that's what you mean.

There is enough room where the PV is, to accommodate a larger one easily. Elsewhere I'd have a bit of a problem to keep it out of the way.

 

[Agile]

Many engineers dont check the pressure properly.

It takes about 10 min to depressurise the system, measure the air pressure and refill the system.

Many dont know ( or bother ) to recharge them properly either! It can take 10-15 minutes.

Tony

 

[lxbn]

This engineer was from Heatrae Sadia (megaflo & PV supplier). I didn't see him de-pressurise the system. He just brought along a tyre pump and tested the PV and stated that it was fine - he didn't have to use the pump. To be honest I didn't have a lot of confidence in him as he had also mis-diagnosed the cause of the problem he came to fix in the first place - a vibration in the CH system. The one who came a couple of weeks later and sorted out the problem competently (cause was malfunctioning auto by-pass valve) was also the one who suggested that the PV might be a bit small for the property (he didn't check the PV pressure). This engineer sounded competent and knowledgeable and was helpful with advice - and he fixed the problem.

My own CH engineer is a certified unvented system installer with many years experience in CH systems. He installed the megaflo and did the conversion to a closed system at the same time. I'll ask him to check again when he comes to repair the leak.

Incidently, together with the pressure problem there is another problem that my engineer is going to fix - the same auto by-pass is malfunctioning again but this time it seems to stick causing it to stay closed and the boiler shutting down due to excessive heat in the system (my engineer advised) - so it's an everyday chore to reset the boiler until my engineer replaces the valve. Although this valve was replaced only 4 months before the fault occurred, Heatrae refused to accept any responsibility for it as they say that the 2yr warranty when the original part was supplied expired about 2 weeks before I reported this fault - I just gave up.

 

[Agile]

Many engineers dont check the pressure properly.

It takes about 10 min to depressurise the system, measure the air pressure and refill the system.

Tony

You cannot properly check the EXV air pressure WITHOUT discharging ALL the pressure in the heating side. That takes a few minutes! I find it embarasing that some people in this profession are either so careless or lacking in skils.

It does rather sound to me as if the EXV may need repressurising.

It also depends on where each item is situated what pressures they are best set to. That means how high up in the house.

Tony