Replacing old Saunier combi with cond. combi - Use blow off?

[kirstent]

Hi,
First post but been trawling the forum for ages with interest.

We bought and renovated our house 10 years ago and got central heating system with Saunier Duval 30e combi put in. We now have to run taps at a trickle to get water hot enough for a bath although the central heating is fine.

We're about to have an extension and are planning to replace boiler with either a WB 37cdi or Vaillant 837.

The current boiler is in an airing cupboard in the middle of the first floor and is flued straight up through the loft and pitched roof. Have read your comments and views on the 2 boilers mentioned above, I've found out we can't use the existing flue system for a new boiler so will need to buy all new. My question really is about draining the condensate and a room thermostat.
Our current combi has no room thermostat, we have thermostatic valves on all the rads instead. Husband has 16th edition so could sort the wiring etc out for that or is that something a Gas safe engineer has to do? Or would it be better going the wireless route? The house will be torn apart anyway (god help me) so not too concerned about decorating/plastering etc.
Since our current combi insn't condensing we have no drain off. What we do have is a 15mm copper pipe running through the floor/walls, coming out near the back door over concrete - believe it's called a blow-off? This is just over a back patio area though, not a drain so could it be used? We could always put a gulley in there to link with rainwater drain as that's all coming up too (aagh!).

I know we should discuss this with engineer but in an effort to afford this extension we are doing a lot ourselves and we need to try and allocate budgets before we decide whether to go for a good boiler or a cheap one (we will probably sell in about 3 years) and we just need to know how much other work is needed apart from boiler swap.

I'd really appreciate any advice you can give.
Thanks in advance, Kirsten

 

[hibeealex]

If the room stat wiring is a hassel to run then go wireless they are very easy to install & can be moved to a suitable location as required ie working from home then it can be put in the office during the day.

Its not a good idea to use a copper pipe for the condensate, the condensate is acidic and will corrode the copper in no time, also the condensate comes from the boiler in 22mm and this should be the minimum size used to termination point, particularly if its going to terminate outside as the potential for freezing is high, better to come up to 32mm

 

[bengasman]

Wired controls are cheaper than wireless if you can do the wiring yourself. ANY wiring requires leccie papers, not gas.
Old "blow off" can not be used, nor can you routhe the condensate into a rainwater collection system.

 

[RusClarke10]

Under current regs, a room thermostat (interlock) needs to be fitted, this does switch the boiler off for a while stopping it cycling on and off. The Vaillant 837 is a good boiler and comes with a number of control options.

The blow off is separate to the condensate discharge, this must be run in copper to the outside, the condensate needs to be run in plastic because condensate is acidic, this needs to go to a waste whether it be a sink waste or soak away. if this is difficult you could use an condensate pump to pump the condensate away.

 

[kirstent]

Thanks so much for your replies and sorry didn't acknowledge them sooner.

OK, will look into room stat.

For condensate, think we can sort it to drain into the shower waste (the shower is next to the airing cupboard the boiler is in). It'll mean pulling out the shower tray to connect pipe into waste but we are retiling anyway so not major problem. Thankfully it's a high profile shower tray so there should be room to manouver.

Do we still need a blow-off for new boiler? I'm guessing we can use the one we've got already (or at least I hope so cos it's completely inaccessible in the house unless we pull lots of tiles and boxing out).

Also think we may go for Vokera Unica just to save a few hundred quid. This budget keeps shrinking (thanks Barclays).

Thanks again for your responses - good of you.
Kirsten