Central heating dilemma

Keep_pedalling

We gas CH with a reliable 12 year old boiler, unfortunately much of the underfloor heating pipes are over 35 years old and we’re there with the original back boiler that was there when we moved in. Not only has the boiler been changed and moved there are redundant pipes running to no longer existing rads. 

I am interested in upgrading the lot, and am currently sitting on a quotation from Octopus for a heat pump system (quote includes rad changes but not renewal of all new pipe work). I thought this might be a nice project for the spring.

Unfortunately shortly after getting that quote I had to call out Domestic & General as we noticed  a significant drop off in performance when the weather turned much colder, we could not get the temp above 19 degrees and the hot water is not as hot as it should be. Upshot of the visit was that it is a sludge build up and a power flush is required  neither covered by D&G) 

Having spoken to a number of  local heating companies. They all said much same thing which is a power flush will cost several hundred pounds and there is no guarantee the problem will be solved. I am reluctant to chuck money at a system that is certainly going to be ripped out at the earliest possible opportunity. No problem if this was spring or summer but we are likely to have to survive the winter with a poorly performing system or shut it down and rely. On our supplementary heating.

This is no problem for hot water, we have an electric shower, and only use the hot tank gets is for washing and washing up. Adding a timer to the heating element means I can h heat it up between 3 & 4 am at 9p pkWh. Shutting down the CH will leave us with an electrical fire in the living room and one in the dining room, and I would need to get some oil filled heaters to take the chill off the bathroom and bedroom.

The permanent solution will be to go with the heat pump with a total re-plum and all new rads (maybe underfloor heating downstairs if affordable and practicable) or if a heat pump turns out to not be feasible in this old house, stick with a gas boiler and again all new plumbing and new rads

Either solution is going to be highly disruptive and unlikely to be started for several months, so do we  risk wasting money on something they may nor work but could save us from a chilly winter or stick it out and just pump up our electric bill and just heat the vital rooms?

FreeBear

Whack some cleaning chemicals (for example - https://www.screwfix.com/p/sentinel-x800-central-heating-system-cleaner-1ltr/704pt ), and tun the heating system for a couple of days. Stick a hosepipe on a drain down point, open the filling loop and the drain point, and fire up the boiler for an hour or so. If you have multiple drain points, move the hosepipe to those as well. Whilst this probably won't get all the sludge out, it should get you through Christmas.

If you are sticking in new radiators to go with a heat pump, new, bigger pipes would be a sensible move - I see 22mm & 28mm recommended for the flow and returns with short lengths of 15mm to the radiators. Replacing as much of the heating system as you can will cut down on the amount of sludge that will need to be dealt with when the ASHP is installed.

twopenny

Local plumber cost £125 for a power flush and my heating ran beautifully quietly after.

Keep_pedalling

twopenny said:

Local plumber cost £125 for a power flush and my heating ran beautifully quietly after.

That is very cheap for what should take around 8 hours to complete. 

ThisIsWeird

Yes, that £125 is very cheap. I guess it's a 'chemical' clean and not a P-F. Ie, add a dose of cleaner, run the system for an hour, drain down and refill. That won't shift compacted sludge in an old system.

Keep-Ped, if you are going to replace all your pipework for the new ASHP, then I can see it might be galling to have the current system P-F'd. But, if you intend to keep some or most of them, it might be worth P-Fing them now and getting the hopeful benefit right away?

Anyhoo, 'cures'. How practical are you?

You could install a Magnaclean (1) - an inline magnetic filter - on the return pipe to the boiler, add a dose of MC3, and very slowly begin to clean the bulk of the sludge from your system. Keep your eye on on t'Bay, and you'll likely get one for, I dunno, £80? And chemicals can be got cheaper on there too.

Or, what I did to sort a lesser - but still boiler-affecting - sludge problem, and that's to install a Magna as above (ie the connectors to it) but then plumb in a proper Magnacleanse (2) - a far more effective filter - first, to do the bulk of the task, and then fit the wee M'clean to keep it going. Add stronger chemicals.

Neither will remove compacted sludge overnight, at least not without you also agitating the rads to loosen what's in there, but you should begin to see some impressive sludge-collection taking place over a few weeks, and your system come back to life.

The large filter will take up some floor space, and the hoses are bulky, so you might not be happy with having it there for a few weeks if the boiler is, say, in the kitchen.

For the M'cleanse, once it's done its main task of collecting, you resell it on t'Bay for the same price, and then slot a M'clean into place to keep on working.

When you come to fit your ASHP, a proper P-F will be part of the deal.

(1) https://www.ebay.co.uk/itm/296011274359 (Will catch released sludge at a slower rate, but could still do the job over time.)

(2) https://www.ebay.co.uk/itm/155852378375 (doesn't appear to have a case, but that's not a biggie.)

(2) https://www.ebay.co.uk/itm/266477242820 (Newer, better cond, has case, but you'd need to make up 'hoses'. Normal plastic plumbing pipes could be used)

cerebus

I hope your house is very heavily insulated or you won't see much higher temps than 19 degrees on your heat pump install 

Most sludge in a system collects in the rads which stops them outputting the heat they are capable of.

If you are handy with the tools removing the rads from the walls and flushing them with a hosepipe is free and easy , plus checking the pins aren't sticking on the trv too.

There's also nothing stopping you flushing the rest of the pipework too by connecting a hosepipe to the feed and connecting the return via hosepipe to the nearest drain

Whereabouts in the UK are you, it's still quite mild here and I've yet to put the heating on 

[Deleted User]

It's not always about the outside temperature, many people have varying health conditions that make them experience the cold, in our last 2, hot, summers there are those that still need heating in their home, i visit those people and see this situation all the time.

ThisIsWeird

If you do take the rads off to flush through as Cerebus suggests, then repeatedly thump along the bottom, espec in the middle, with a soft mallet. Protect the rad surface with a cloth or similar.
You can do that too if you fit a filter. Get cleaning chemicals in there and see how much sludge you collect in a day. Then open one rad at a time fully - open the lockshield end too, but give it, say, an EXACT 5 anti-clock turns so you can return it to its starting position afterwards - and repeatedly thump that rad's bottom. 
Clean out the filter each time. The small M'clean is unlikely to catch a rad's worth on its own - not without a few cleans - so much of that sludge will now be flying around your pipes to be caught when you replace the cleaned filter.
Or, just add chemicals and let it work slowly. But this could take some time. Check how long you are supposed to leave the chemicals in.
So, if you can, fit a M'cleanse first, double-dose MC3, and open and thump one rad at a time to try and shift the majority of the sludge.

Albermarle

I hope your house is very heavily insulated or you won't see much higher temps than 19 degrees on your heat pump instal

The current problems the OP has with their CH system struggling to keep the house above 19 degrees, could be a good way to get used to what it will be like with a heat pump !

Keep_pedalling

Thanks for all the advice. I increased the flow rate on the pump this morning which has had quite a remarkable effect. I have removed and flushed out individual rads in the past and will do that to any showing cold spots now that I am getting a decent level of heat out of them. D&G won’t come out again unless I have a power flush so as I have a reasonable level of back-up until we put in a replacement system I will cancel that contract and keep my fingers crossed. 

We need to up the level of insulation and that is going to be done whatever the final fix is. The original parts of the house are solid brick, and I have a level of internal insulation on the south facing front but nothing on the side and rear original walls where we intend to install external thermal cladding. The more recent extension has insulated cavity walls. The others area to look at is the raised timber floors which I could DIY. 

Keep_pedalling

Albermarle said:

I hope your house is very heavily insulated or you won't see much higher temps than 19 degrees on your heat pump instal

The current problems the OP has with their CH system struggling to keep the house above 19 degrees, could be a good way to get used to what it will be like with a heat pump !

Good point, although we normally have it set to 20 so I am sure we can cope with it a little cooler.