Moving from vented to unvented cylinder

mobile73

Hi, we are thinking of moving from a vented cylinder to an unvented model. The reason for this is that the pressure in our house is extremely low (not the mains pressure which is > 3 bar I believe) and this has for many years been boosted by a pump. The pump has broken down and is also extremely noisy so am looking at this as an upgrade rather than just replace the pump. I have been quoted approximately £2,800 + VAT (in London) to remove old cylinder, tank etc. and relocate unvented in loft. Does that sound reasonable? This is a G3 plumber who I have used on other jobs so trust but wanted to understand if that is around the right cost. He said would be probably a Telford or similar tank. Thanks

benson1980

Sounds reasonable. We were being quoted 3500-4000 inc VAT (in South East) for the same thing. They will presumably need to convert your heating to a sealed system as well (if so does the price include this) so worth considering a magnetic filter and potentially system clean/flush at the same time if required.

mobile73

benson1980 said:

Sounds reasonable. We were being quoted 3500-4000 inc VAT (in South East) for the same thing. They will presumably need to convert your heating to a sealed system as well (if so does the price include this) so worth considering a magnetic filter and potentially system clean/flush at the same time if required.

Thanks. He has mentioned that it may need converting to a sealed system but think that is extra on top. Still waiting for the formal quote but he has given me an indicative view

ThisIsWeird

In theory you can retain the vented 'heat-only' boiler, but worth, I think, getting a quote for converting this as well. 
No huge reason - just to lose the remaining tank in the loft, making it less susceptible to system corrosion - things like that. 
I'm assuming it can be done without replacing the boiler - just by adding an EV and gauge?

FreeBear

ThisIsWeird said: I'm assuming it can be done without replacing the boiler - just by adding an EV and gauge?

A little more nuanced than that - Will need a filling loop, an air vent placed at the highest point (on the old vent pipe perhaps), and a pressure relief valve. The system will then need a hydraulic pressure test, preferably over several days, and at twice the maximum working pressure (5-6 Bar). Some would say that 3 Bar would be enough, but if that is the rating on the relief valve, the test pressure should be higher.

A magnetic filter should be added to the return pipe on the boiler, and the system would probably benefit from a good flush. Any leaks discovered during the pressure test need to be fixed (should go without saying, but....) And all of this assumes the boiler is designed to operate in a sealed system.

As for putting the cylinder in the loft - It will be subject to colder temperatures during the winter month which will increase the heat loss. Much better to put it in the same location as the original HW tank. The small amount of heat given off will keep an airing cupboard warm, and you are not wasting the heat.

mobile73

Thanks everyone. He has confirmed the price quoted includes pressurising the existing system and the current boiler can cope with that.
In terms of magnetic filter, the boiler already has Magnaclean. Is this the same thing or something additional?

It sounds like the quote may not be as bad as it feels to me!

FreeBear

mobile73 said: In terms of magnetic filter, the boiler already has Magnaclean. Is this the same thing or something additional?

A Magnaclean is just a brand of magnetic filter. So yes, same thing.

Section62

mobile73 said:

Thanks everyone. He has confirmed the price quoted includes pressurising the existing system and the current boiler can cope with that.

Has he done anything about making sure the loft floor will cope with the weight of the hot water cylinder?  Will he need to do additional work to make sure the load is spread out over sufficient joists?

(the load from the HWC may be more than the existing cold water tank - the weight of stored water needs to be compared, not the overall size/bulk, as cold water tanks are only partially filled.)

mobile73

Section62 said:

mobile73 said:

Thanks everyone. He has confirmed the price quoted includes pressurising the existing system and the current boiler can cope with that.

Has he done anything about making sure the loft floor will cope with the weight of the hot water cylinder?  Will he need to do additional work to make sure the load is spread out over sufficient joists?

(the load from the HWC may be more than the existing cold water tank - the weight of stored water needs to be compared, not the overall size/bulk, as cold water tanks are only partially filled.)

Yes - he has said he needs to build platform / reinforce floor in loft

ThisIsWeird

Sounds ideal, Mobile - it's a guy you know and trust, it seems a decent quote, it appears to be a comprehensive install, and it should utterly transform your water supply. 
Blimey.