Complete CH install advise.

[Dan1261]

Gents..

I'm after a few answers to what would be simple questions to the "experienced" around here..

I'm a novice, I don't dispute that however I've recently purchased a 1970's Dormer bungalow which hasn't had any work carried out since the day it was built. My budget is limited so looking to do as much of the work as possible..

With regards to the CH system, I think I'll be going with the Worcester Bosch 38cdi which I'll have a Gas Safe technician actually install, however I want to run all the pipework prior to the install to cut down costs etc, now what i'd like to know is....

*** - Pipework diameter from the boiler for domestic hotwater, if it's 22mm I presume it reduces down to 15mm prior to the taps.. is there and where specific to reduce it down or do I put a 22mmx22mmx15mm tee and come off that way to each HW tap and then do I cap the end of the pipe?? (2 questions in that 1)

*** - Pipework diameter from the boiler to CH (OUT) to the radiators... again if 22mm and the rads are 15mm would I just do the same set up as like I do for domestic hotwater??

*** - Pipework diameter, radiator return pipework back to the boiler??

*** - Domestic cold water.. again piping diameter from boiler around the house to the taps?

*** - Running the CH radiator pipework from downstairs to upstairs... is that just a case of tee from the outlet feed and send it up through the wall to the upstairs rads?? I presume it'd be the same for the CH return from the upstairs rads.. One pipe flowing up & one flowing back down?? Again, what diameter pipe to use.

Any and all help / advise would be much appreciated. Even if you could only answer 1 question... it's better than non.

Thanks in advance.

 

[CChris]

As an experienced DIY'er my advice, and I know you wont want to hear it, is to get somebody in who is an expert.

There are a multitude of variables to consider. Room sizes and therefor radiator sizes, distances of runs, number of radiators etc. What sort of flow rate you have and what sort of showers or baths you have will dictate piping to bathrooms. You dont want a bath taking half an hour to fill, or a rainfall shower that hasnt got enough flow. Similarly you dont want somebody flushing the toilet and scalding the person using the shower.

Im all for doing as much work myelf as possible, but Im also not a fan of doing jobs twice or having to take floors up to replace work that turns out not to be up to the job. Simple plumbing jobs of replacing pipes or adding an outside tap or even plubing in a new shower tapped off existing main runs is one thing for a DIY'er, but getting the calcs right for central heating & HW system is entirely another. If you get the pipe sizes wrong, either too large or too small, then you could be in for a world of pain in ripping the out and doing it twice, which would negate any cost saving imho.

At the very least you could see if there is a pro that would do the calcs bit for you and then at least you knnow what pipe and radiator sizes to run where. If they are prepared to do just that bit, they will most likely want you to sign to say if there are any leaks once they put water through the system its not their responsibility.

 

[John D v2.0]

For the hot water you want the smallest pipe you can as otherwise it'll taker ages for the tap to run hot. For a hand basin 10mm will do but a shower will need 15. You can run separate pipes at extra cost to avoid them affecting each other.

 

[muggles]

You've got a limited budget but you want to put an overpriced fairly average boiler in? For about £400 less you could have the excellent Intergas ECO RF 36 with a 10 year warranty - much better built and much more suited to your limited budget. Slightly less powerful on hot water but no combi will run more than one bathroom at once anyway, and that'll give you a very decent shower

 

[Doggit]

It'll be 22mm for the main flow and return under the floorboards, and then branch of to the rads in 15mm, Branch off of the flow and return in 22mm for the upstairs rads, and make sure you use pipe insulation for the flow and return circuits so that you're not heating the underfloor space. The same trick applies for the hot water pipes.

Your boiler outputs the hot water in a 15mm pipe, so this is the diameter that you'll use to the taps and bath etc. Excelent advice from Muggles, and add a combi save at the boiler to reduce the hot water flow till it's uo to temp.

Is the GSRI doing the rad calcs for you, and setting up the programmable room stat. And what are your soldering skills like. Are you doing it in copper, or plastic, and have you worked with either before.

As you haven't done this before, I'd negotiate with the installer, and get the boiler done first - which will give you a better idea of where to lay everything out, and he can help check out your skills with the initial pipework, and maybe installing one rad, as I doubt you've fitted the valves onto a rad before either.

Be realistic, and best of luck

 

[oldbuffer]

Assuming you're using a combi boiler, then:

1. Before you do ANYTHING check the pressure and flow rate of the incoming cold. Look for a minimum of 1.5 bar dynamic pressure and a flow rate of around 20lpm. Lower flow or pressure suggests a different solution.
2. Domestic Hot Water (DHW) system:
a. Keep distribution pipes to 15mm diameter, hot and cold. There should be enough pressure to give a decent flow, and there won't be as much cold in the hot line to run off before the taps run hot.
b. Run the 15mm as close to the taps as possible / convenient before converting to micro bore / flexi's.
c. Fit a decent isolation valve to each outlet (tap, WC inlet etc.)
3. Central Heating (CH) system:
a. "Backbone" of 22mm flow and 22mm return everywhere from boiler to last but one radiator.
b. Backbone includes flow and return to upstairs radiators.
c. 15mm tee'd off from backbone flow and backbone return to each radiator as close as / convenient to each radiator.
d. Don't fit isolation valves in the CH circuit, but if you must , make sure they are guaranteed for CH temperatures and full bore.
4. Do not attempt to run any gas pipe work, or to physically hang the boiler on the wall. Leave that to the qualified.

 

[Dan1261]

As an experienced DIY'er my advice, and I know you wont want to hear it, is to get somebody in who is an expert.

There are a multitude of variables to consider. Room sizes and therefor radiator sizes, distances of runs, number of radiators etc. What sort of flow rate you have and what sort of showers or baths you have will dictate piping to bathrooms. You dont want a bath taking half an hour to fill, or a rainfall shower that hasnt got enough flow. Similarly you dont want somebody flushing the toilet and scalding the person using the shower.

Im all for doing as much work myelf as possible, but Im also not a fan of doing jobs twice or having to take floors up to replace work that turns out not to be up to the job. Simple plumbing jobs of replacing pipes or adding an outside tap or even plubing in a new shower tapped off existing main runs is one thing for a DIY'er, but getting the calcs right for central heating & HW system is entirely another. If you get the pipe sizes wrong, either too large or too small, then you could be in for a world of pain in ripping the out and doing it twice, which would negate any cost saving imho.

At the very least you could see if there is a pro that would do the calcs bit for you and then at least you knnow what pipe and radiator sizes to run where. If they are prepared to do just that bit, they will most likely want you to sign to say if there are any leaks once they put water through the system its not their responsibility.

Thanks, but the reality is that I will be laying the pipe, we all need to learn sometime & when better to do it is before we move into the property and the floors etc will be up making access as easy as it's going to get.
Calcs is something i'll look into

For the hot water you want the smallest pipe you can as otherwise it'll taker ages for the tap to run hot. For a hand basin 10mm will do but a shower will need 15. You can run separate pipes at extra cost to avoid them affecting each other.

Perfect, appreciated John, thanks

You've got a limited budget but you want to put an overpriced fairly average boiler in? For about £400 less you could have the excellent Intergas ECO RF 36 with a 10 year warranty - much better built and much more suited to your limited budget. Slightly less powerful on hot water but no combi will run more than one bathroom at once anyway, and that'll give you a very decent shower

Appreciated Muggles, I'll look into the ECO RF36. Thanks for the heads up

It'll be 22mm for the main flow and return under the floorboards, and then branch of to the rads in 15mm, Branch off of the flow and return in 22mm for the upstairs rads, and make sure you use pipe insulation for the flow and return circuits so that you're not heating the underfloor space. The same trick applies for the hot water pipes.

Your boiler outputs the hot water in a 15mm pipe, so this is the diameter that you'll use to the taps and bath etc. Excelent advice from Muggles, and add a combi save at the boiler to reduce the hot water flow till it's uo to temp.

Is the GSRI doing the rad calcs for you, and setting up the programmable room stat. And what are your soldering skills like. Are you doing it in copper, or plastic, and have you worked with either before.

As you haven't done this before, I'd negotiate with the installer, and get the boiler done first - which will give you a better idea of where to lay everything out, and he can help check out your skills with the initial pipework, and maybe installing one rad, as I doubt you've fitted the valves onto a rad before either.

Be realistic, and best of luck

My soldering skills are up to scratch, but primarily will be running the pipe in plastic (JG Speedfit) obviously apart from the connections at the boiler which will be as per manufacturing instructions. Off the top of my head it's around "the 1st meter has to be copper"

As for fitting the TRV's.. aren't these simply flow controls to each rad?? Isn't it just a case of screw them into the rad and then compression fit copper pipe (15mm) through the floor to mate up with the Speedfit pipework?? Sorry for my ignorance if this isn't the case.

 

[Dan1261]

Assuming you're using a combi boiler, then:

1. Before you do ANYTHING check the pressure and flow rate of the incoming cold. Look for a minimum of 1.5 bar dynamic pressure and a flow rate of around 20lpm. Lower flow or pressure suggests a different solution.
2. Domestic Hot Water (DHW) system:
a. Keep distribution pipes to 15mm diameter, hot and cold. There should be enough pressure to give a decent flow, and there won't be as much cold in the hot line to run off before the taps run hot.
b. Run the 15mm as close to the taps as possible / convenient before converting to micro bore / flexi's.
c. Fit a decent isolation valve to each outlet (tap, WC inlet etc.)
3. Central Heating (CH) system:
a. "Backbone" of 22mm flow and 22mm return everywhere from boiler to last but one radiator.
b. Backbone includes flow and return to upstairs radiators.
c. 15mm tee'd off from backbone flow and backbone return to each radiator as close as / convenient to each radiator.
d. Don't fit isolation valves in the CH circuit, but if you must , make sure they are guaranteed for CH temperatures and full bore.
4. Do not attempt to run any gas pipe work, or to physically hang the boiler on the wall. Leave that to the qualified.

Spot on.. that's exactly what I was looking for.

I was planning on fitting inline service valves at every single tap / toilet etc

I'll be getting the incoming pressure & flow rate checked

Anything to do with the Gas side of things is not my level so will certainly be being left to the professional.

Appreciated, thanks very much

 

[bernardgreen]

Combi boilers were developed for flats and "compact" houses where there is no room to have a hot water cylinder.

Then the un-vented cylinder was developed for houses that could install a cylinder ( airing cupboard ) but did not have space for cold water storage tanks ( cisterns ) in the loft.

There is a lot to be said for cold water storage if there is space in the loft

 

[Dan1261]

Combi boilers were developed for flats and "compact" houses where there is no room to have a hot water cylinder.

Then the un-vented cylinder was developed for houses that could install a cylinder ( airing cupboard ) but did not have space for cold water storage tanks ( cisterns ) in the loft.

There is a lot to be said for cold water storage if there is space in the loft

There is no loft, it's a 1970's dormer bungalow. There is currently a tank in a relatively large cupboard, however I want to remove the tank and utilise that space for an en-suite shower room for the master bedroom.. it's big enough.

There might be room for the cistern in the apex of the roof as this is currently boarded, however it's not a large space, but then again I know it doesn't necessarily need to be a large space

 

[rob_j20]

I'm part way through doing this myself, all new system. All my radiators have arrived and i'm in the process of hanging them and running the pipework. Going to run the flow and return uncut along a wall, the boiler will be going on the other side of said wall so the installer can cut into the pipes where ever he chooses.

When sizing your radiators have a read about Delta temperatures and efficiency of a condensing boiler. Basically radiatrs are shown with a delta 50c but thats not ideal for a modern boiler. Done mine to delta 35, so i can run a lower flow temperature while putting the same heat out.

My flow rate is around 16lpm with a 2.5bar pressure. 3.5bar static.

 

[Dan1261]

I'm part way through doing this myself, all new system. All my radiators have arrived and i'm in the process of hanging them and running the pipework. Going to run the flow and return uncut along a wall, the boiler will be going on the other side of said wall so the installer can cut into the pipes where ever he chooses.

When sizing your radiators have a read about Delta temperatures and efficiency of a condensing boiler. Basically radiatrs are shown with a delta 50c but thats not ideal for a modern boiler. Done mine to delta 35, so i can run a lower flow temperature while putting the same heat out.

My flow rate is around 16lpm with a 2.5bar pressure. 3.5bar static.

How long have you spent on it so far & actually how far are you from completion??

 

[John D v2.0]

Another trick on Oversizing radiators as above is to use more than one radiator in the room, gives a more even heat. If that, if you prefer you can use 10mm pipes chased in from behind rather than on display. The only issue is the heat output wouldn't get above about 1kw per radiator and you need to switch to larger pipes once you're under the floor.

 

[rob_j20]

Doing the actual work about 2 hours so far. Only one on the wall with pipework run out of the room in 15mm waiting for the next room to be done. Didn't want to do too much over winter as the next step requires the boiler being turned off for good. Be all go in about a month when we can do without having for a month.

 

[Dan1261]

Another trick on Oversizing radiators as above is to use more than one radiator in the room, gives a more even heat. If that, if you prefer you can use 10mm pipes chased in from behind rather than on display. The only issue is the heat output wouldn't get above about 1kw per radiator and you need to switch to larger pipes once you're under the floor.

To be honest when the renovation work is complete there'll only be one large open plan living space approx 21ft x 24ft so will be fitting 2 rads in that room.. One on either side of the room, slightly offset for even distribution of the heat. This room will also have a Small modern style wall mounted gas fire if ever it's needed for those cosy nights in lol.

Bedrooms and such will fine with large full length under window rads which are currently in place however I'll get the power flushed prior to reinstalling or replaced where needed.