Heating circuit extension.

[Tristar]

I am shortly having a conservatory built onto what was an earlier extension. The radiator that will be removed, and from where the heating circuit will be extended, always has difficulty getting warm, possibly because it is furthest from the boiler, a Vaillant Thermocompact VU GB 226E. I have done all the usual flow adjustments on lockshield valves to optimise flow to this area, and the system is clean and well flushed.

Other than changing the boiler, now ten years old, what is the best way of improving the heating flow to an extension of what is an already poorly heated circuit. The pipe run to the redundant radiator is about 12 metres, nearly all 15mm, the conservatory will be a further 4 metres wide, and 6 metres long. Would it be useful, or even feasible, to fit a booster pump in the circuit?

Thanks in anticipation

 

[gas4you]

As a conservatory will require a lot of heat, then I would at least make sure this run of pipes comes off the main 22mm flow and return and if possible extend the 22mm to as near the extension as possible.

A lot of cheapo plumbers used to just T into the nearest heating pipes for an extension regardless of what size they were.

 

[Tristar]

Unfortunately it is not feasible to tap into the 22mm pipes without major disruption, and as you dont mention it I guess a booster pump is not on.

 

[gas4you]

I've never used a booster pump so I can't comment

 

[Tristar]

Thanks anyway, Dave, perhaps someone else will have had experience, the other alternative would be to put in a more powerful pump and bypass the inbuilt Vaillant pump.

 

[Balenza]

Have you shut down all the other radiators and opened the lockshield valve fully open on the troublesome radiator and if so what results did you acheive ??.
I assume it doesn't have a trv fitted.

 

[Tristar]

Yes, I've done that and it is possible to get it hot with other radiators not getting so warm. It does have a TRV, always left fully hot. It is possible with careful balancing to get the radiator hot, but always at the expense of others in the system. There are 16 radiators on the system at present, and there will be either one big or two small ones in the conservatory.

I suppose I shall have to invest in a bigger boiler.

Thanks guys.

 

[Agile]

I suppose I shall have to invest in a bigger boiler.

Thanks guys.

Oh dear!

Thats a typical DIYers illogical response!

You have been clearly told that the problem is your pipework!

Fitting any new boiler will not cure your undersized pipework.

Deal with the problem if you really want to solve it.

Tony

 

[Balenza]

Tristar wrote

Yes, I've done that and it is possible to get it hot with other radiators not getting so warm

Then its a balancing problem and not a pipework problem as some have suggested.

It does have a TRV, always left fully hot

That doesn't mean its fully open. The internals seize up regularly.

 

[gas4you]

Still could be a pipe sizing problem. When other rads turned down/off there is less heat demand from the rest of the system.

The only answer is to pipe back to 22mm and then balance properly

 

[giblets]

Have to agree with others on this one - extension pipework too small and connected to the wrong part of the system. The "plumber" who put it in should have done his job properly and upgraded the existing pipework.

You could try putting another pump in series with the boiler pump but this may cause additional noise in the system and would be very much a trial-and-error excercise.

Just as a matter of interest, what is the boiler stat set to?

 

[Tristar]

Wouldn't argue with the case for upgrading pipework, however, logistically this is completely impractical, as it would involve lifting 5 metres of upstairs flooring, removing a breakfast room wall,to gain access to vertical pipes, and digging up 4 metres of screed. It would be easier to fit a second boiler at the 'cold' end of the house, and this may prove to be the simplest answer.

The boiler stat is set to high, (not quite max). the rest of the house warms up OK, but having experimented over many years with different balancing settings, I am quite sure that the problem lies with the long run, and therefore additional pressure drop ( F/A = f rv2/2), of 15mm pipe.

My comment that I need a new boiler was based on the fact that no-one seems to think another pump in series will help, and therefore, as the Vaillant pump is integral, a new boiler with a more powerful pump could be the answer.

Tony, I would be grateful if you would refrain from unhelpful comments, they are counterproductive, as I have already accepted the argument about pipework, and have stated previously that it is impractical to upgrade them, which is why I queried the possibility of fitting a booster pump.

 

[giblets]

I don't recall saying that another pump in series would not help. What I said was that, by increasing the circulating pressure by adding another pump may cause noise problems in the rads nearer the boiler than the rad in question.

Have you considered changing the pump in the Vaillant boiler? Tt is not unknown for a pump's speed (and, therefore output) to reduce over a period of time caused by worn bearings, degrading windings, etc. This may well be a cheaper option and worth a try in the first instance. After all, the existing pump is 10 years old!

 

[Tristar]

Thanks Giblets,
Sorry, my comment was based on the fact that you were the only guy who suggested that a second pump might work, implying that no-one else has come across such a situation, and I had noted your point about possible noise issues if fitting another pump in series. My real concern with this issue is, are there likely to be other problems introduced by fitting a second pump? Which for convenience would have to be adjacent to the boiler.

It is certainly worth considering replacing the existing pump, and I will give Vaillant a ring to see if there is a more powerful replacement available.

Thanks again