Replacing radiators and a few questions

[will_uk]

Hi everyone, new to the forum - looks as though there are some very knowledgeable people on here so would appreciate any advice for the following.

3-bed end of terrace house, built in the late 70's. Concrete screed flooring downstairs.

Previous owners fitted a new boiler and changed the heating/hot water system over from conventional with tank to a combi system about 5 years ago.

Boiler is a Halstead Finest Gold combi type, (again, circa 5 years old)

Most of the original radiators are pretty grotty from several old DIY paintjobs and a couple are rusty on the outside. I plan to replace the radiators and fit new valves/TRVs at the same time.

I am trying to refurbish the house to a liveable standard (it's my first place). Currently empty with no flooring etc to worry about (yet!).

Firstly, most of the old radiators appear to not suit the new pipe spacing for new ones. Ie, new widths in mm - say hall radiator is 860mm wide, new sizes seem to be either 800 or 900mm etc.
What is the most acceptable method of adjusting the pipe spacing to suit the new sizes? Downstairs where the floors are screeded would it be best to cut the pipes low down and join with a new piece bent to suit or bend the pipes in situ (if possible) or is the only proper option to dig the floor up and move the pipes so that they come straight up in the required position? I assume upstairs this job should be easier as the floor can be lifted to allow re-positioning.

Secondly, when assembling the valves and connecting the pipes to the radiators, what is the best thread sealent to use - a compound (eg plumber's mait etc) or PTFE tape? The lounge/living area is now open planned and 'L' shaped. The wall thermostat is a PRT and is in fairly close proximity of two radiators in this area - can I/should I use a TRV on either of these or both or one/not the other. I appreciate in any case the principle of setting the TRV to at least as high, if not higher than the wall stat. Will one radiator in the whole house without a TRV be ok (just the towel rail)?

Thirdly, there is an extension on the back. Been built for some time and the previous owners have got two drain off points for the heating out here, with no radiators fitted. Does it sound likely that I will be able to fit a radiator to these points and then reinstate the drain offs? Obviously this isn't very detailed info here but I would appreciate any pointers

The system seemed fairly healthy when it was previously drained down, ie water from the system was pretty clean and minimal sludge. What is the best plan for refilling and/or flushing once everything is ready to be reconnected? Obviously an inhibitor would need adding but are the new radiators likely to add a lot of contamination to the boiler/pipework? Would it be a good plan of action to get as much installed and operational as possible, then get a service visit for the boiler and have the system flushed at the same time soon after (if that makes sense).

Thanks in advance for any pointers or advice. Please feel free to point out any flaws or potential problems/oversights I may have made. Money no object I would love a pro to do the whole job but funds are very tight and I'm trying to get things moving along as best I can!

Cheers,

Will

 

[Rob]

right..

Regarding different sized rads. You could use extensions and bring pipe work in to smaller rad, personallt though if done neat enough id rather extend one end outwards, the bigger rad usually covers it.

PTFE on threads and jointing paste in compression fittings.

Technically if these are connected to to flow and return pipework then yes assuming the downstairs pipe work can cope with an extra rad. System may need to be balanced to make it work.

If the system works fine and still did after you drained it down first time then its unlikely to need flushing. Although it wouldn't hurt but yes when refilling add a good quality inhibitor.

 

[will_uk]

Thanks Rob - some useful tips there, cheers.

A couple of other things that I've been thinking about. If, as an example, I was replacing the hall radiator with a 900mm instead of the original 860mm and needed the pipes to come in spacing-wise, would it be ok/a good idea to cut them low down (say an inch or two from the floor) and then fit a 15mm isolating valve to join to a suitable bent piece of pipe to fit the rad valves? I'm thinking of the isolating valve as I could get them in chrome (look nicer?) plus can work on the pipes without having to drain the system each time if needed? I'd imagine they might get a bit gummed up though over time - likely to be a problem?

By the way, can you bend chrome plated copper pipe or will the chrome be likely to flake off etc?

lastly, does anyone actually bend the pipes in this way straight from the floor - ie bend the original pipes inwards in situ an inch or two each side without joining them?

Can anyone recommend a decent 'mild?' cleanser for the system, it's not too groggy but I'm sure a slight flush would help (or is it not worth it, drained off rad water is fairly clean?)

Thanks again for any advice

Will

 

[gas4you]

Sentinel X400 and leave in for a couple of weeks.

 

[will_uk]

Thanks again,

Couple more quick Qs if I can - do radiators still need balancing if using TRVs? I presume if yes, then open them fully up whilst adjusting the lockshield. Also, assuming that the TRVs are 'reverse flow' compatible, will I still be able to balance the rads in this way (ie TRV on the return and lockshield on the flow)?

What would be the difference (if any) in doing it this way? Just trying to think where the TRVs would be in relation to room layout etc.

Many thanks guys, much appreciated

Will

 

[gas4you]

Yes , balance the rads after you have flushed them out, you can still balance using the locksheild at either end. Honeywell used to have a numbered dial on the valve body to balance with this if the trv was on the return. Don't know if they still do as I don't fit them anymore