My plumber has just replaced a failing Baxi bermuda back boiler with a new Vaillant eco 37 combi. The system now takes a painfully long time to heat the 7 radiators in my small bungalow (Hours). The pipes get hot quickly. He has put 'normal' TRVs on 6 radiators and one without a TRV. Vaillant say the pump is too strong for a single pipe system which is why it doesn't work. I now understand that I have a 37Kw boiler, this seems a lot for a 2 bed 7 rad home, could it be too powerful? What is the difference between single and two pipe TRV. Any help and comments much appreciated.[/b]
Failed boiler upgrade.
- Thread starter themechanic
- Start date
One pipe TRVS have larger bore internal waterways, because standard TRVs offer too much resistance to flow in a one pipe system. One pipe rads rely on thermo syphon for a lot of their circulation.
Danfoss do the RA-G TRV body for one pipe, to which you have to add the standard RAS TRV head.
http://www.uk-plumbing.com/danfoss-...6.html?zenid=b144434fb93a35ccb59b122099c3673e
If your plumber has used standard TRVs on one pipe, this may explain why the pipes are hot, but the rads take ages to heat. The small waterways in the standard TRVs are killing the thermo-syphon/convection effect.
You may need to get your plumber to change the valves, but including the heads, they are at least £30 each.
Just re-read your post.
Why has your plumber fitted a 37kw boiler to 7 rads in a small bungalow.
How many people live there, and how many bathrooms? Do you use lots of hot water?
This sounds like a boiler that is very over-sized. Poss a 24 or 28kw would have been ample.
Beginning to sound like your plumber hasn't covered himself in glory! Is he Gassafe regd. ?
On the positive side - you will never be short of hot water!
Why has your plumber fitted a 37kw boiler to 7 rads in a small bungalow.
How many people live there, and how many bathrooms? Do you use lots of hot water?
This sounds like a boiler that is very over-sized. Poss a 24 or 28kw would have been ample.
Beginning to sound like your plumber hasn't covered himself in glory! Is he Gassafe regd. ?
On the positive side - you will never be short of hot water!
The 37Kw boiler is in order as this allows you to have adequate supply of instant hot water. However, I would suggest that you get the heating circuit changed from the one pipe to a two pipe system if you want an efficient heating system.
How can you know this without knowing his circumstances? If he lives alone, and only has one bath, then it is over-sized.
How many people live there, and how many bathrooms? Do you use lots of hot water?
normally, two adults one bathroom No we dont use lots of hot water. Bungalow is about 11M x 9M footprint
normally, two adults one bathroom No we dont use lots of hot water. Bungalow is about 11M x 9M footprint
I should add we dont have a bath , only a shower - from the boiler -which works very well!
with the boiler set to max, it shuts down at 80C and the pipes all round the house are too hot to touch. The bathroom is the first rad and gets very hot quickly. The rest take a lot longer and never get anything like too hot to touch.
radiators are bottom fed. Is this OK on single pipe system?
radiators are bottom fed. Is this OK on single pipe system?
Yes, it made no difference
Presumably, before the new boiler, your rads heated up properly? So in that case, bottom fed works on single pipe? Changing to a sealed system should improve rad performance, not worsen it.
You can either change the TRVs, or go back to normal wheel head or lock shield valves like you had before. Obviously changing back to non-TRVs will mean that you have less control over room temps. and will upset the green brigade.
Thanks for your advice and info Witespirit66. I will fit wheelhead valves to a couple of the rads and see how it goes - a lot less grief than converting to a two pipe system. If removing the TRV's doesn't solve my problem, then I suppose I shall just have to face the two pipe installation.
Y
YELLERBELLY
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