Living with a combi boiler

Rosa_Damascena

NSG666 said:

Water Regs exist but are hardly ever referred or adhered to. I can't find my book but I think they stipulate that no joints should be buried in screed and also that mains fed hot and cold water pipes should be in conduit and replaceable without having to dig up a screed floor. There are plastic pipe in pipe systems which allow this although I used to make my own using a conduit from Toolstation.

ComicGeek seems to have experience of laying screed floors so might be able clarify these points.

Makes perfect sense to be able to access this easily. The screed is still days away from going down, the plumbing is far from finished and I'm sure the plan will be to comply with all the necessary regs.

SuzieSue

fezster said:

If you wanted mains pressure to multiple outlets, an unvented cylinder would have been a wiser choice. Dependent on sufficient pressure / flow rates. 

Yes, and an unvented cylinder would have given back-up hot water if the boiler failed.  But it is more expensive to install and maintain compared to a combi.  It would also have meant that the airing cupboard could not be used for storage as the unvented cylinder would have to be put in there.

fezster

NSG666 said:

Water Regs exist but are hardly ever referred or adhered to. I can't find my book but I think they stipulate that no joints should be buried in screed and also that mains fed hot and cold water pipes should be in conduit and replaceable without having to dig up a screed floor. There are plastic pipe in pipe systems which allow this although I used to make my own using a conduit from Toolstation.

IME, you'll find many joints buried in screed for hot/cold and CH pipes. However, they should always be soldered copper and always suitably protected. Pushfit and compression should not be used.

I think the regs around conduit are for the incoming mains only (though I could be wrong).

Jeepers_Creepers

Rosa, could you ask them to divert these three pipes around the perimeter (under the sink) where it avoids the UFH - that doesn't look like much of a diversion? (Tho' they'd have to be confident the additional elbows required wouldn't impact on the gas flow rate. Depending on how far away the meter is, 22mm gas pipe could be borderline for a 40kW boiler - they may need to go 28mm.)

I don't know just how significant an issue it is having them run over the UFH like that, but I have to say it certainly doesn't look like 'best practice' to me; unless they could prove to me that it's a perfectly acceptable method to use, I would personally be uncomfortable with it. The pipes would also need sleeving/running in conduit, which is another layer of thickness.

travis-powers

Don’t want to be a party pooper but shouldn’t there be a membrane between the pir and ufh?

ComicGeek

travis-powers said:

Don’t want to be a party pooper but shouldn’t there be a membrane between the pir and ufh?

The DPM should be installed underneath the insulation. The joints of the insulation board should be securely taped so that the screed doesn't run between boards and bridge the insulation. 

Gas pipework size does need to be checked as Jeepers Creepers says, as the gas flow rate for the 40kW is going to be significant - not something that can be easily corrected later if wrong!!

Hopefully a conversation tomorrow to raise these issues, and still plenty of time to resolve before the screed pour. Still easily fixable at the moment.

travis-powers

ComicGeek said:

travis-powers said:

Don’t want to be a party pooper but shouldn’t there be a membrane between the pir and ufh?

The DPM should be installed underneath the insulation. The joints of the insulation board should be securely taped so that the screed doesn't run between boards and bridge the insulation. 

Gas pipework size does need to be checked as Jeepers Creepers says, as the gas flow rate for the 40kW is going to be significant - not something that can be easily corrected later if wrong!!

Hopefully a conversation tomorrow to raise these issues, and still plenty of time to resolve before the screed pour. Still easily fixable at the moment.

I’m no expert but have prepared a lot of floors for ufh and it’s always been dpm, pir taped and than a lighter green membrane (no idea what it called) to stop the screed from eating into the pir!

ComicGeek

travis-powers said:

ComicGeek said:

travis-powers said:

Don’t want to be a party pooper but shouldn’t there be a membrane between the pir and ufh?

The DPM should be installed underneath the insulation. The joints of the insulation board should be securely taped so that the screed doesn't run between boards and bridge the insulation. 

Gas pipework size does need to be checked as Jeepers Creepers says, as the gas flow rate for the 40kW is going to be significant - not something that can be easily corrected later if wrong!!

Hopefully a conversation tomorrow to raise these issues, and still plenty of time to resolve before the screed pour. Still easily fixable at the moment.

I’m no expert but have prepared a lot of floors for ufh and it’s always been dpm, pir taped and than a lighter green membrane (no idea what it called) to stop the screed from eating into the pir!

Yes, you're absolutely right - there should be a 500 gauge polythene membrane laid over the insulation. The insulation manufacturer will normally state what steps need to be taken to protect the foil lining, but not all UFH suppliers will include this on their details - as they also don't provide it as part of their kit, it often gets forgotten.

Another_Level

Well, there been a lot of helpful comments already mentioned 

Just having a look at the photo around the mixing valve, why have soldered adaptors been used ? Some ptfe heat damage is visible and cant really see the solder flow.  Hopefully the mix valve was not subject to excessive blowlamp heat. Compression connectors are best and usefull for future maintenance.

Under floor copper pipes have already been mentioned, the above floor water pipes will need insulating. There very close together at the moment but still time to consider a plan to insulate them.Insulation helps prevent heat loss and condensation running down the pipes.

The gas pipe run needs to be checked for gas tightness and sufficient gas flow before covering up the pipe run.

All the water pipes can be pressure tested before covering up. highly recommended.

Adding a mini expansion vessel on the boiler mains water inlet may be necessary, depends on other situations.

The installer needs to ensure the showers are installed to preform as best they can, 

THe vogue gen2 is ok, not my choice but there ok and come with a long warranty.

Work in progress    Sure it will all work out Ok 

mug2007

Thanks for creating this post @Rosa_Damascena,  the contributions evaluating your boiler and ufh set up have been an interesting read, with some great points made.  

I have had condensing combi boilers fitted in my last 3 houses and for this latest house and it’s 3 bathrooms I had a system boiler fitted.  I would have loved another combi but our heating / builders didn’t recommend.  

All of our combi’s have been pretty reliable, when one broke down, we used the gym shower for a couple of days and a friends house (which had a remote control!). Admittedly in the next houses we did opt for an electric shower along with our combi after that experience.  

I would go for the handy storage cupboard.

Good luck with it all.