2 Combi Boilers vs 1Combi and MegaFlo HE 250L

[samir_d]

Hi There,

Im looking for advice so hoping to get loads without making my head dizzy

Basically, Just had my house renovated and in the porcess of getting the New plumbing

- All New Pipes (22MM) and 15MM to rads. New Rad as well.

My Aim is to have good water pressure around the house, not sure what my water pressure actually is but i know it's good.

2 Bathrooms in the house (1 bath shower and 1 shower) and 10 rads and 2 towel warmers.

I also bought a MegaFlo HE 250L with the intention of putting it in the Cellar as I

have no where else in the house to store it.

I have a 7 year old Vaillant Boiler (Vaillant Turbox (Plus or Max) 824)

My Plumber said installing the megaflo in the cellar is not a problem but will need a

pump for the overflow.

I asked what the likelyhood of the pump breaking down - He said how long is a piece of

string (Covering his ass which is understandable)

I then asked what happens if the overflow breaks down - he said there was a high

possibilty the water would leak onto the floor of the cellar.

I then asked is it adviseable to put the megaflo in the cellar and he said not

really.

This really worried me as I didn't wan't to introduce a risk of a flood.

My plumber then recommended using my old Vaillant boiler as the a water heater for the shower and kitchen downstairs and recommended purchasing a Vaillant 837 for the Bathroom upstairs and all the rads.

My questions are:

1) Is it adviseable to put the hot water tank in the cellar?

2) How good are these pumps for the Megaflo and what will actually happen if the pump breaks down?

3) Is his solution of 2 boilers a good solution for my needs?

Any Help\Advice would be greatkly appreciated.

I have asked plumber to hold off for a a few days while i do some research.

Thanks in advance

 

[foxhole]

I would go with one boiler option, you can put an alarm on the overflow system and even connect to isolation swich, so if pump fails you get audible warning and system is shut down before overflow occurs.

 

[corgiman]

I would go with one boiler option, you can put an alarm on the overflow system and even connect to isolation swich, so if pump fails you get audible warning and system is shut down before overflow occurs.

which will be blooming rapid should the temperature relief valve blow

Still dont reckon there is a pump that can handle 90 deg plus temp at full mains pressure but I am sure we did this to death not long ago

 

[clf-gas]

Auto shut off on the PTV

flooded cellar wiould be the least of your worries.

EDIT:- Thats PRV

Jeez your quick on the keys CM

 

[corgiman]

Auto shut off on the PTV

flooded cellar wiould be the least of your worries.

cripes I missed that

 

[2face]

i would go for the worster high flow 440 condencer, ideal for multiple outlets good pressure on the hot and far less maintainable appliances in the house plus less cost to ..

 

[simond]

Before offering any advice I would want to know the standing pressure and max flow rate coming into the house.

The siting of an unvented in the cellar does have problems but the discharge is rarely full bore in a fault scenario so the quantity of water is not so bad as one would imagine. Furthermore, the temperature of the discharge would lower quite quickly as cold water is introduced.


My preference would be for the unvented if the water flow rate is sufficient; shame you can't resite it if you have room for all these combis?

 

[ChrisR]

You need very good mains indeed if you're to supply everything without constraint, but with the combi off, the unvented alone will give you more flow than another combi, for better shower/quicker bath fill.

Also a 24kW plus a 37kW combi may well mean you need a bigger gas meter, or pipes, or both.

The discharge from the unvented is something your local building control dept may be useful (or totally clueless) on. In practise you can use quite cheap devices and a little intelligence to make it safe. Sump pumps are only about £50 so you could have two!

 

[Agile]

It would be a very strange failure that discharged more than the cylinder capacity into the cellar. The main purpose of the discharge in a fault condition is to cool the cylinder. 250 li would probably be less than 200 mm deep.

Most discharges are slow drips and an audible alarm and about 15 litres of collection would usually suffice if the auto pump failed.

Interesting point for G3 professionals! The tun dish is primarily as a visual aid. Suppose this was enclosed and water tight and clear but then discharged higher up ???

I appreciate this is not covered by the regulations but nor is that rubber valve.

Tony

 

[simond]

Agile

What about frost? And the tundish is meant to be visible and audible.

 

[gas4you]

The prv discharge must have a continuous fall and terminate 100mm maximum above ground. I know we have had this topic before on here but I would never fit an unvented cylinder in a basement.

I would be thinking along the lines of a storage combi, the Vaillant Ecotec Plus 937.

If you had a 24Kw and a 37Kw then you would need a commercial gas meter. The 837 needs 4m3/hr gas and a 24kw will be around 2.5m3/hr, so this has taken you over the 6m3/hr domestic gas meter without allowing for a cooker or gas fire etc

 

[corgiman]

I have never understood the need for the tundish if the discharge is visible