Central heating off limits for DIYer?

[Guitar_man]

With the recent cost of CH fitters charging £25 plus vat per hour, I'm tempted to have a go myself.
Is flushing, changing rads, and changing valves within the scope if the DIY enthusiast? Or is the possibility if knackering a £1000 combo boiler not worth the risk?
I'm confident with general plumbing including soldering. Any there any things I should be aware off to avoid expensive mistakes before I drain my system and replace the rads?
Cheers,
James.

 

[dcawkwell]

Yes all straightforward.

Depending on the boiler be careful that there is no air trapped in the boiler when refilling and relighting. Turn the gas off for a relight and let the boiler circulate a couple of times before letting the gas to the boiler.
The odd boiler will have an manual air vent on the top of the boiler.
Relight a boiler with trapped air at the top and it will crack/melt a heat exchanger fast there than you can say jack robinson.

I also suggest you leave it until the nice weather in the summer.
Then you don't have a problem should you run into a problem.

 

[Steelmasons]

£25 per hour????? , grab him with both feet while you can..

 

[Whitespirit66]

£25 per hour????? , grab him with both feet while you can..

Must be someone doing a foreigner. Can't be kosher, with many overheads.

 

[mogget]

Some basic DIY CH advice:

The main thing is to NEVER run the boiler without water, not even by accident!

Make sure all heating controls are electrically isolated before working on the system (check for dead).

Cut the gas as dcawkwell has said.

Make sure you know the basics of how your system is meant to work when all is working correctly.

And maybe familiarise yourself with a heatloss calculator if you need. (I've tried STARS for the first time, looks good).

Also maybe learn what delta-T means, and how the terminology can be applied (in more ways than one).

If you're just doing a small job like moving a radiator these last two may not be necessary.

 

[Guitar_man]

Can I even run the boiler without gas, the system is on a gas card, i once ran out of gas, it just flashes up f4 on the display, I'm assuming then the water is circulating in this case. If not how do I circulate it in this case. It a Veismann vitodens 100.
Not familiar with those last 2 terms, will check it out. Anyone know where the filling loop is on this?
How do I convert BTU to watts to determine if my boiler can supply the rads and the water? I'm assuming there is also heat loss due to the bare copper, is it worthwhile lagging the pipes to reduce heat loss?
Thanks!
Btw 25 plus vat was the cheapest quote!

 

[mogget]

The purpose of turning the gas off is to prevent the boiler lighting and damaging itself without water circulation while you are working on the system. It will usually throw up a fault code that may need to be reset. Once you get water circulation you can turn on the gas (I usually light at a low flow temperature for the first run after draining).

Delta-T is just a difference in temperature (in centigrade/celsius/kelvin).

it is used three common ways.

Delta-T flow and return (the most common)
Delta-T average rad temp / room temp (influences how much heat is emitted by rads)
Delta-T room temp / outside temp (influences amount of heat lost from room).

One kilowatt is 3412 btu/h.

You sound like you are going into this the right way, by being willing to learn and exercising a due degree of caution.

 

[Guitar_man]

Am i right in assuming that during water delivery all the power is diverted to the water from the heating and this doesnt need to be taken into account?

I guess i need to start googling Vitodens 100 and start learning about how to do basic boiler stuff.

How long should a typical system take to get 'Up to temperature', that is the temp is at 60-70C? It seems to take a long time on my heating system, during which the boiler will shut down, take a break, then restart, eventually hitting 70C 30-40mins later. Is this cycling normal modern condensing combi operation?

 

[D_Hailsham]

How long should a typical system take to get 'Up to temperature', that is the temp is at 60-70C? It seems to take a long time on my heating system, during which the boiler will shut down, take a break, then restart, eventually hitting 70C 30-40mins later. Is this cycling normal modern condensing combi operation?

It suggests that you boiler may be OK for hot water, which needs a high output to provide it instantly, but is over powered for the central heating.

Use Whole House Boiler Size Calculator to find your heating requirement. As you have a combi, the DHW allowance should be set to 0 (normally 2000W).

Post the result.

 

[Guitar_man]

12.98kw. I've guessed the outside dimensions.

 

[Guitar_man]

When I say the heating temp, I mean the temp of the heated water in the CH, not the DHW which takes a while to get to temperature but does get very hot after a time.
The main concern is that the CH seems to heat to say 20c, shut off, wait, heàt to 30, shut off wait, heat to 50, then 70c, at which points the rads are hot. Shouldn't it just heat until water is 70c, then keep the temp at 70c?
The CH runs are long as the heater is out back in an extension.
There is an external wifi thermostat fitted, could this be causing the modulation up to temp?
Or could that be due to the fact the rads are old and probably full of grime?

 

[RigidRaider]

One word of advice from someone who's been doing what you plan to do for quite a few years: NEVER start a DIY plumbing job on a Saturday afternoon - when you need something you'll be forced to pay B&Q prices rather than support your local proper plumbers' merchant and get competitive prices.

 

[Guitar_man]

Perhaps some useful tips might be better!
Simple job swoping a few rads out isn't it? I'll try running the CH with the gas off and see what happens.
If I could get someone for a sensible price, I'd employ someone, but as they all want to charge upwards of 240 per day, save the money, and have enough left over for beers and b and q prices!

 

[sooey]

You want a sensible price
£25 an hour plus vat is far too cheap.

 

[swbjackson]

Perhaps some useful tips might be better!
Simple job swoping a few rads out isn't it? I'll try running the CH with the gas off and see what happens.
If I could get someone for a sensible price, I'd employ someone, but as they all want to charge upwards of 240 per day, save the money, and have enough left over for beers and b and q prices!

A useful tip from me is don't come onto a site asking for advice and then alienate all the professionals by insinuating that they are over charging.

Just give it a go, what's the worst that can happen? It'll only cost you a few thousand to replace your boiler if you destroy it.