Central heating pipe run length

[John]

Hi, I'm new to this group having only just found it, and I hope someone might be able to help me decide where to put a new 'system' ch boiler.

My current ch boiler is floor mounted in the kitchen and has a coventional chimney flue. The new boiler will be mounted on the other side of the wall from where the current boiler is now, in the garage. I am considering a flue through the flat roof, but if I can have longer pipe runs I could have the boiler mounted on the other side of the garage with a flue through the outside wall. This would be an advantage as it would move the flue further away from windows on the side of the house.

Is there any reason why I shouldn't extend the pipe runs to the boiler by by about 3 metres?

Thanks.

John

[Doctor Drivel]

No reason at all. Many boilers have extension flues. Some up to 60 foot.

[YAPH]

No problem at all: the limiting factors in pipe length terms with boiler placement are usually length of the flue and length versus size of the gas pipework. Assuming your CH pipes are adequately sized (22mm unless your house is a mansion) an extra 6m (total) will make very little difference.

The only other concern would be if the replacement boiler were a combi in which case the extra dead-leg of hot water pipework would be a nuisance.

One other issue with lengths of pipe in an unheated garage is frost protection. Your boiler may have built-in frost protection for itself but if there are significant lengths of pipework you will need to arrange protection for them (e.g. an air frost-stat to cut the boiler in when it gets near freezing, and a pipe-stat on the return pipe to let it cut out again when the pipes are warm).

[Steve Firth]

He wasn't asking about extension flues, you dumb bunny.

[Steve Firth]

Thank heavens, a voice of sanity. Adequate insulation on the pipe runs is also going to be worthwhile, and given the dimensions of most pipe insulation it's worth considering how the pipes are going to be fixed. Most plastic pipe clips hold the pipe too close to the wall and too close together to permit use of an adequately sized insulation.

[Doctor Drivel]

This one should be tagged.

[ARWadsworth]

Make yourself rich and design and patent some :-)

There is a market for them.

Adam

[Dave Liquorice]

I wouldn't fire the boiler for frost protection of the pipework unless it was really required. Have a stat that starts the pump and circulates the water when the temp gets down to say 5C, this will draw warm water from the house through the system to stop it freezing. OK it'll cool the house but with a well insulated pipes I doubt that the cooling will be noticeable before the house stats calls for heat anyway.

[Heliotrope Smith]

There is no problem at all. Just follow the instructions in the installation manual to extend the pipe run for your boiler.

[Doctor Drivel]

You are right. 5C? Too high. 1C. Oc is when water starts to freeze. This is assuming the boiler has integral frost protection as well. The pipe stat is to protect the pipework not the boiler. It also depends on what sort of boiler frost protection there is. The boiler may operate the pump. The boiler being uninsulated and a clear path to the cold outside air, unlike the insulated pipework, will get to freezing first, so in many cases no need for pipework protection.

[YAPH]

Knock-down blocks: the little plastic blocks with 2 holes in one side, one in the other. Cheap as chips, fit nicely under a standard plastic pipe clip to space it off about 10mm. Using one of the two holes in the 2-hole side one can also use them for spacing side-mount clips, or nail-in P clips with the nail removed and replaced by a 4mm screw.

Or you can buy some stupidly expensive standoff spacers specially designed for the pipe clips.

[YAPH]

Depends on the accuracy of your thermostat. Better set to 5C and have it come on at 0C because the stat's a bit out than set to 1C and have it sitting there happily while your pipes freeze up.

Depending on the boiler design and the state of valves in the rest of the system (think S-plan) the boiler may only warm itself up - not pipework

5 metres away.

[YAPH]

Two problems with that: if the pump's part of the boiler you can't run it separately (and legally :-)).

And you then have to have a back-up system so if you've already extracted all the heat from the pipework in the house and the house system hasn't turned the boiler on (for whatever reason) you then need to start the boiler.

Keep it simple: one system. It's not going to use /that/ much energy to keep a bit of pipework from freezing for a few nights a year.

[Dave Plowman (News)]

Not so. That process starts at 4C. And in a heating system you need to prevent it happening so 5C is a more usual trigger temperature.

[Steve Firth]

Wrong again Drivel.

[Steve Firth]

Ahbut Drivel assures us he is a heating engineer with degrees and everything, like. So he knows about these things.

[Andrew Gabriel]

Sometimes higher than that. bear in mind the frost stat itself is unlikely to be mounted in the coldest place which needs protecting, simply because an installer is unlikely to know where that is.

My Keston seems to start up the pump at somewhere under 10C, but it doesn't fire up the burner immediately. I presume it monitors the water temperature and only fires up the burner when it gets nearer zero. With the pump running, you can be sure that there aren't any areas of remote pipework which are colder that you were aware of and in danger of freezing early.

[Doctor Drivel]

That is so. Please eff off.

[Doctor Drivel]

"Water starts freezing only after its temperature has fallen to its freezing point. "

[Dave Liquorice]

Why? It's a simple control system wiring problem. What is the legal aspect, can't be CORGI as this is the OPs own boiler and doesn't touch the gas side anyway. Maybe Prat P?

Highly unlikely that you will extract all the heat from the house pipework

*and* the house as well. Remember the relatively cold water circulating through the rads in the house will pick up heat from the house. If it's cold enough for long enough for the whole fabric of the house to cool to approaching 0C you are going to have other problems...