Storage Combi boilers

[Smo]

Looking to do away with the hot water storage tank in our house by getting our 1970's boiler swapped for a new combi. This will free up space for a potential en-suite (see my other post).

From what I have read, a standard combi may not provide enough HW for en-suite and main bathroom, so I have been looking at the Vaillant 937 storage combi, which apparently has HW storage built in.

My question is, are there any other 'storage' combi's on the market, or is this a unique product?

If it is the only one, can any gas safe registered fitter install it, or would I need to get someone off the vaillant list?

 

[Agile]

Any RGI can fit it.

Some who fit a ot of their boilers can get a longer warrantee period.

Be aware that after the store is depleted the 937 can only deliver its basic flow rate of about 14.3 li/min heated by 35° above the incoming temperature.

Tony

 

[Happyplumber]

Potterton 'glow worm vaillant worcester veissman all make storage combies,before you even think about going this route you need to check what your flow rate is

If you have poor flow rate then combi is total waste of time.

 

[mickyg]

check your flow rate first. If adequate I'd look at the Glowworm ultrapower sxi, excellent bit of kit and will wipe the floor with the 937 on performance as well as having a backup immersion. I believe Viessmann do the 222 as well which works the same as the Glowworm.

 

[Smo]

I've checked incoming pressure (3.0bar), but how do I check flow rate, and what does it need to be?

Is it as simple as a bucket and a stopwatch?

 

[Agile]

That will measure to open pipe flow rate.

What you need to know is the dynamic flow rate. Thats the flow rate when say 1.0 Bar is still pressent in the house pipework.

A simple guess in your case would be about 2/3 of your open pipe flow rate.

You can add together all the flow rates ( run together ) from cold tap and garden taps etc., everything supplied from the mains.

Tony

 

[Smo]

OK, tested flow rate today

kitchen tap turned on and set to leave 1.0 bar residual pressure

this gave me 28.4 L/min (10litre bucket in 21.1 secs)

will this be enough for a combi?

 

[mickyg]

nice. consiuder yourself lucky. you can pretty much have whatever you want now, system wise...