Adding TRVs to a basic system

royan

We're in a rented farm cottage with a very basic DHW/CH system - 24h mechanical timer is the only control, no stat on tank or in rooms and no valves for circuit switching; HW temp appears to be regulated only by boiler return, and in summer we turn off the rads by their own valves. Oil-fired, sealed system with red expansion vessel in hot press (which appears to have failed, but that's another job/post). When we turn on the rads, room temperature control is, well, haphazard, as you can likely imagine. In particular upstairs always overheats when downstairs is still too cool whatever balancing act we try (and no, I don't expect the rads are properly balanced). No control if we're out. Not very efficient all round. Also HW is menacingly hot.

Can TRVs be safely/effectively added to such a system? I've read somewhere that a TRV-fitted system must have a room stat somewhere for overall control, but it seems to be fine with all rads turned off, which is all the TRVs would do, surely? Does it really need one rad left without a TRV or will the tank suffice there? I'm imagining these would be issues if the CH circuit were switched, not just in parallel with the tank.

(I'm looking for some fairly cheap/low-impact improvements for control flexibility and economy - TRVs seem to be the obvious one, I could source and fit these myself, but I can't think of any other system changes that don't involve "real" plumbing work and expense - any other thoughts?)

Sparkpea

Some people on here have said that you need a room stat but i've upgraded plenty of systems with TRVs on ALL radiators without any problems. Your system is also sealed which means you dont have to worry about oxidisation. Also if each room is controlled by a TRV then the rooms that are used less/turned down will shut off quickly and give the pump a better chance to heat the other rads. Sort of balancing itself the system although it is better balance on the lock shield valve. Also because its sealed you could set the pump to 3 if its not already. 3 would be the highest/fastest setting to help pump the heat around the rads better. I'd also suggest if you think your going to be in the house for a while then its worth putting TRVs on all the rads and one on the cylinder because its pumping hot and wasting oil. In my opinion theres no point in having TRV's on 9 out of 10 rads, or not having one on the hot tank as the boiler will still kick in. A bye-pass is also required these days. Its definately the best way to control your heat per room imo!

If you're going to be there for a while then its worth spending the money. I did the same in my last rented house and I ended up there for 3 years.

Cost wise you're maybe talking about £12 per TRV, £50 max should be ample for cylinder stat and £30 for bye-pass. Those are only rough costs. 6hrs should cover labour costs ontop of the materials.

Sparkpea

OP, if it were me i would be looking at adding a clenser(http://www.uk-plumbing.com/fernox-f3-cleanser-for-central-heating-systems-superconcentrate-p-42339.html) before you drain down and then doing a flush(draining and filling) to clean your heating system, i would add TRV's to all rads if you have a by-pass fitted or keep the bathroom one free of a TRV to keep it as a "by-pass" rad, i would add a mechanical cylinder stat (http://www.uk-plumbing.com/danfoss-randall-ravi-vmt-208-22mm-cylinder-valve-for-pumped-primaries-p-54109.html) to help reduce hot water temperature, add inhibitor after the work to prevent the build up of sludge.

Sparkpea wrote: »

Some people on here have said that you need a room stat but I've upgraded plenty of systems with TRVs on ALL radiators without any problems.

I have seen lots that have problems, it's not rocket science, the more control you have over a heating system the better you can control house temperature and fuel usage, the complaints you have for room stats are more to do with installation issues then the stat it's self, have you ever seen a properly balanced system with TRV's and a room stat, i have found it works well and there is no drama, but trying to get system controls to work properly on a unbalanced system is very difficult and leads to all the problems you have rightly identified.

On the issue of how many TRV's to use, again that's easy if there is no by-pass then a by-pass rad is required to prevent problems associated with lack of system movement, this is more noticeable on gas boilers as they are classed as low water content boilers and there is no movement in the heat exchanger.

Just before i kick my soap box in to the corner, i see two separate issues, the level of control that should be on a new installation and retro fitting system controls, for the first i would say asper chess(http://www.energysavingtrust.org.uk/Publication-Download/?p=1&pid=544) and for the second then it what ever you can afford, a bit of control is better than none. Gary.

royan

Good call re the tank TRV, I didn't know you could get those so will investigate further (I just measured the water temperature at the kitchen tap - 63°C 4h after switch-off). The bathroom is one room that I specifically want regulated, though, so I'll have to look at picking another rad or adding a bypass. I guess that should be fitted as close to the boiler as possible?

I hope to do the cleanse-and-flush too, I'm pretty sure there's no inhibitor in there after a major boiler leak earlier in the year.

Sparkpea

jeeze thats some cost for a piped in cylinder stat there!

myson are half the price
http://www.pulsardirect.co.uk/plumbing-supplies/productdetail.asp?ProductCatId=302&ProductSubId=64&ProductCode=RAV040

I also use the myson trvs and automatic byepass valve rather than a byepass rad http://www.uk-plumbing.com/myson-abv22-22mm-automatic-bypass-valve-p-1385.html

Closer to the boiler for the byepass is probably best energy efficient wise, tho it depends where the boiler is and how hard it is to get one installed at it.

In my old house where the boiler was in the garage and the pipes came across lagged but on show at high level I put my byepass in the hot press because in the winter with a new baby the heating was on 24hr and that meant there was always hot water flowing from the boiler/garage to the house/byepass so I knew I wasn't going to have any burst pipes when lots of others in my street did

royan

Sparkpea wrote: »

always hot water flowing from the boiler/garage to the house/byepass so I knew I wasn't going to have any burst pipes

Our boiler is in a metal cabinet outside the house, lagged and against two walls but I suppose still fairly exposed, so that looks like something to consider there too, thanks. More bursts are not what we need... I'm thinking also maybe a frost stat.

Edit: also, should I read anything into the fact that all these links are to UK websites / UK prices? :-/ I did look at Screwfix but seems they don't deliver here.

Sparkpea

nah I just got links from google and uk sites because im from north so can relate to costs easlier than the euro. Buy local anyway - help the recession!

royan

royan wrote: »

The bathroom is one room that I specifically want regulated, though.

The reason the bathroom is picked is barring a decent session the only room you should be naked and wet is the bathroom.

royan

gary71 wrote: »

the only room you should be naked and wet is the bathroom.

I know - but the wife gets awful migraines with ambient heat as one of the most reliable triggers, and a bathroom is, well, somewhere you can't avoid being when you really need to be there, so we want to have it pretty cool most of the time.

royan

Had a quick look for parts on adverts.ie, and via there came across this wonderful bit of quackery - Oxyvent. OK sure, keeping air out of your radiators is a good plan, but a different ("blackbody") mode of heat from your radiators? Balancing is Bad? Kirchoff's law?