Only have heat to rads when I drain the return line

[Yellosub]

New here, first post. Basic issue = rads only heat when I am actively draining the rad return line to the outside of the house.

First, the lay of the land...

1800 or earlier stone built coach house. Three floors, Ground Floor, 1st Floor, Finished Attic. Open vented/Indirect system. Wood-fired back boiler Stanley 8 stove in the kitchen. Directly next to it is a Grundfos UP20 -14BX circulation pump in the return line from the rads connected to a pipe stat on the hot feed line. Ground floor has one rad in the kitchen and one rad in the living room. 1st floor has three bedrooms (two with rads), a toilet and a separate family bath with tub, shower, rad and sink/basin. Also on the first floor is the hot press with the immersion tank and above that the high cistern for the toilet and the feed and expansion cistern for the rads which are actually at attic/loft level. The finished attic has two rooms (one with a rad, the second will be getting a rad later) and the cold water secondary cistern.

The problem...

Since we moved in a year ago we've had intermittent heating on the first floor. The attic has never had a rad installed until now. And the ground floor has worked quite well. Last week we heard some humming from the Grundfos pump which I found not-so-conveniently located behind the kitchen cabinet! We began to notice the rads were cold. I thought the pump took a dump. But, figuring I had to buy a new one anyway, I removed it and disassembled it after a few short courses in plumbing from YouTube Technical Institute. The pump seems to be working fine. It spins freely and the thermostat starts and stops it running. So I reinstalled it. After installing it I thought all was well. But after about 15 minutes there was no heat again in the rads. After many more vidoes and searching forums, especially this one, and trying to bleed and balance the rads I'm stumped. The rads ONLY get warm or hot when I am actively draining the return line below the pump out to the exterior of the house. Within 15 minutes the exposed copper lines in the kitchen and the rads are all cold again. I removed and flushed the kitchen and living room rads.

Sooo, any ideas?

Some other hints...

The bathroom rad is intermittently hot even when the kitchen fire has been blazing for an hour. There is so much steam backing up through the system that I had to pipe the vent out from the F&E cistern to outside the window because it was blowing water all around the cistern cabinet above the toilet causing water the leak through the hall light fixture!!!

 

[oldbuffer]

As an initial thought, have you checked both pump valves are open. Sounds as if there is no flow unless you run the return to drain, which suggests a blockage in the return line.

 

[Yellosub]

So what I did today was a take on your advice (oldbuffer). I blew air back through the return line after draining the system. Then I picked up a new circulator pump. It's an IBO Poland brand OHI 25-60/130. I can always upgrade if I need a better pump. I had to modify the lines because the old pump was 110mm length and the new one is 130mm so at the same time I replaced all the copper lines, the inline exterior drain valve and added a pressure gauge. I wired the pump back into the pipe stat and that all works well. The system pressure is running steady at 0.5Bar. I have the pump set at switch position three hoping this would help push the water up to the attic/loft.

So now after bleeding the rads five times and balancing them about ten times I've gotten to a point where all the rooms on the ground floor and the first floor are comfortable. Primary wood heating is a pain in the rumpus. Slow to get heated up and too variable when it is hot. My sole issue now is I still can't get 1° worth of heat to the attic! Nothing at all. I have one room on the first floor that has stubs for a second rad and I pondered whether I should connect them. I doubt that would be the problem though because even if I installed a rad there I could shut off both valves and it would be the same situation as no rad and stoppered stubs. Both rooms in the attic are dead cold after nearly two hours of heating. I top filled the rad in the attic and I can't get any air to bleed. There is no pressure at all. Not even water bleeds out. I installed this rad with a thermostatic switch on the feed line.

Still stumped...

 

[oldbutnotdead]

Thermostatic switch? More detail of that, sounds like an added complication.
Steam is a concern as well, at the very least you are wasting fuel, at the worst if there is a blockage and it spreads to block both tubes from the boiler you'll have a right mess on your hands.
Thermal store is the future for solid fuel heating, its made mine very usable and controllable

 

[Yellosub]

Sorry I misspoke. I installed the attic radiator with a Regis TRV Thermostatic Radiator Valve. The instructions recommend it be installed horizontally but I normally see them all installed vertically. Could this be a problem?

Currently everything is working fine except still no attic rad heat. Since the bleed valve did nothing I removed the top plug off the attic rad and although the rad is full - no water or air poured out. If I can find my pipe snake I'm going to drain the attic rad and fish the snake down the feed and return pipes to see if there are any obstructions.

Today I measured the linear pipe length from the pump to the furthest attic rad @ 80ft/24.38m. While doing this I noticed something that I saw as a possible issue. Per my plumbing map I added some pipe diameters. I was wondering if the way the system is plumbed into the return line that expands from 1/2" into two 1" lines could be causing the problem. Could it cause a considerable pressure drop that would affect the max head height I could achieve from my new pump? The new pump is rated up to 6m head height on speed three. The vertical pumping height is 19.5ft from the top of the pump to the top of the attic rad. I've checked for inline shutoff valves between the 1st floor rad plumbing and the attic rad pipes and there are none. Should I put the pump directly into the hot feed line to the rads? It sits directly to the right of the cold return line it's attached to now.

 

[oldbutnotdead]

The TRV on the attic radiator- is the pin actually moving? Is the lockshield valve open at all?

The head required to circulate water round the system has little to do with the height of the house and much to do with the headloss (pressure drop) caused by pipe runs, elbows, bends, valves. Yes the pump has to push water uphill but in a correctly functioning system the same volume of water has to come back downhill so that bit balances (minus the headloss).
Your schematic makes me think your system may be convoluted (thus high headloss, takes forever to bleed).
The steaming is still a major concern- you really need to check that the feed and expansion pipes from the woodburner are as vertical as possible, sufficient bore (28mm) and no elbows, valves or other blockable clutter between woodburner and header tank.
Re the attic rad- how far above it is the f&e tank for the woodburner). The lack of water movement in that rad indicates either valves off somewhere or blocked (airlocked) pipes.

 

[Yellosub]

The TRV is new. Pin moves fine. I didn't put a lock shield valve on that rad but I have some new ones so I'll add one in.

I haven't had any steam issues since I replaced the pump and bled/balanced the rads.

Re Headloss - I just traced the F&E lines.


The Feed is 1" (Irish) copper line straight from the wood burner to the 3-bar safety valve (90° turn) and into the heat exchanger in the immersion tank with a Tee on the run. Above that the pipe necks down to 3/4" copper and into an elbow, then into a straight fitting changing to 3/4" pex. From there it's just a smooth sweep of 3/4" pex into the F&E tank.

The Return exits the F&E tank via 3/4" pex into an elbow then a copper shutoff valve and back into a 3/4" pex Tee on the leg. From there its a smooth sweep of 3/4" pex to changing to copper through a 3/4" copper straight fitting. At the immersion, the leg of a copper Tee heads into the heat exchanger and the run continues straight down to a copper 3-way with a drain. The 3-way heads straight back via 1" copper into the woodburner. The other side of the 3-way exit a 1/2" copper line in a smooth 180° loop back towards the pump. Prior to the pump it goes through a capped copper Tee, a copper shutoff valve, a copper elbow and the necessary copper adapters to fit to the pump.

Re The Attic Rad - I traced the whole circuit to the attic rad and there are no shutoff valves. The outlet from the F&E tank is 12" above the feed inlet at the bottom of the attic rad.

I hope that wasn't too confusing. But thanks for your input so far!

 

[oldbutnotdead]

Interesting (and worrying). Not sure about Irish building regs, I believe in England only Hep2O plastic is rated as suitable for use with uncontrolled heat sources, much less explanation required to BCO and HETAS (solid fuel installers) if the whole job is copper.
Elbows on the expansion pipe (you've called it the feed) are an invitation for airlocks- does it really dip into the water in the f & e tank or is that Paint gone mad? Or is there actually circulation from that feed pipe dipping into the f & e tank, which would explain why your attic radiator isn't working but at least acts as the thermal dump for the woodburner- hope it is a metal tank with a metal ball valve. Massive waste of energy if that is what is happening, if the system was gravity only then it wouldn't be coming into play unless the temperatures were getting overhigh but with a pump you are very likely circulating through that tank.
Likewise on the return, having a valve on the water supply to the woodburner is a big fat worry. Why would you ever isolate it for the sake of draining maybe 50 litres of cold water? And if you do happen to leave it isolated, just imagine how much fun you'll have when your water heater turns into a steam generator.
In short your heating system scares me. Was the range originally just supplying hot water and someone had the bright idea of hanging some radiators and a pump off it? I'd suggest you find someone local who is certified to work on solid fuel heating systems and get them to have a look at it- solid fuel heating can be very dangerous, the more complex it gets the more likely you are to have a catastrophic failure (involving steam) which will not be pretty and also probably not a survivable event if you happen to be in the house when it happens.

 

[Yellosub]

I'm not so sure the Irish know what Irish building regs are. Not to be disrespectful but in America all trades have to be licensed and insured. Handymen are the scary ones. And you can search a tradesman's license to see if it's current, suspended or revoked. As well as to see if they have any past or present legal actions against them. And buying a house is not "Buyer Beware" it's seller disclosure of any known problems or work done without planning permission. Everything gets inspected before the bank will sign off on a mortgage. Here the "engineer" pops in for a half hour and writes a cutesy little report that basically says "I saw things any layman could notice but there's no way I'll be held responsible if you find something later because I just look at the surface.' Kinda like a GP telling you you LOOK healthy.

The guy who remodeled this house was an Aussie bloke. Some things are quite interesting. Definitely wouldn't pass an American inspectors eye for building codes. That said I just want it safe and efficient for my family. Thankfully I'm retired so I have time to do the research, ask questions of people who are smarter than me and correct anything that is scary or sketchy.

The expansion pipe did dip into the F&E tank. In fact it was 3/4" pex pipe with a half meter length of 1" copper pipe over it to keep it under water. That was the initial symptom even before we noticed the rads were cold. When the pump started going intermittent the back boiler would steam up and puke water back into the F&E tank. Unfortunately the slip-fit copper pipe allowed the steam and water to jettison backwards out of the tank and down the wall, and of course pouring down from the hallway light fixture! For now I rerouted the pipe to a emergency drain pipe that was already installed. Now if there happens to be any steam blowback it'll vent outside rather than inside. Still not safe but it is a temp measure until I have the system figured out and fixed. Then I'll route it back above the waterline at the F&E tank. I still have no idea why they plumbed the second heat exchanger in the immersion tank to do nothing???

The F&E tank is plastic with a metal ball valve. I believe it acts as a filling loop. I may be wrong. I'm very wary of a back boiler explosion. My wife used to be a claims specialist for the second largest propane supplier in America. I've seen the photos of what explosions inside a house can do. I don't think my 600mm stone walls would survive having a gable wall disappear! I don't need a woodstove in the kitchen. I have a radiator. But I'm probably going to convert to a propane boiler as soon as I can.

So, do you see any functional issues with the pipe routing or would you venture to guess it's simply an airlock to the attic rad? Right now everything seems to be happy except for the attic rad. And I need to add one more attic rad in the other room. I figure I'll get rid of the TRV and just go with two lock shield valves like the rest of the house.

BTW, how do I add my thanks to your thanks received rating?

 

[oldbutnotdead]

I was wondering about the 2nd coil shown on the drawings- if it really is plumbed like that it doesn't make a lot of sense.
Plastic tank (unless it is fibreglass) can be v dangerous. Solid fuel systems should be designed so they can boil safely- standard plastic tanks go all floppy at about 80 degrees C, 50 litres of near boiling water through the ceiling will ruin your life. Does the water in that tank get notably warm in normal use?- it really shouldn't (in a properly designed system).

If the top of the attic rad is below the water level in the f & e tank then water should flow out of it when given the opportunity. Since it doesn't then it does suggest an airlock somewhere.

Your schematic also shows the heating pipework connected to the dhw circuit (below and to the left of the shower)- if that's real then it is rubbish and needs correcting instantly, you'll be rotting the heating system with continual fresh water and/or bathing in inhibitor (if the primary water has been treated- guessing not to be honest).

As to whether the pipework is OK, I'd say probably not- it sounds as if it has been continually added to and bodged up rather than anyone sitting back and looking at it to design it as a whole. Especially with the bits of plastic interspersed here and there..... without actually looking at the thing its hard to make a judgement on it. Does the copper work look neat and tidy or are there elbows, compression fittings, globs of solder everywhere? Do pipes run pretty much shortest distance to their associated appliance or do they meander all over the place?

With the heating, the big red flag is how long it took you to bleed the air out (and not all of it has gone, otherwise the attic rad would probably be working). If you are looking to change to propane boiler (presumably installed by someone who knows what they're doing) and the place is relatively uncluttered you might want to bite the bullet and get it completely retubed while you're at it- yes it'll add to the cost but then its done and you can move on to other things instead of spending time and effort faffing with a shoddy install.

Consider keeping the range if it is an integral part of the kitchen- it is usually possible to disconnect the wet part and leave it as a dry woodburner, gives you a good focal point and a handy heat source if you get power cuts or the propane is late (I'm assuming your place is fairly rural) plus free fuel (again if you are rural and have a chainsaw). Again I'll bang the drum for a thermal store- it'll let you have your wet woodburner and propane boiler contribute to the heating, and wet solar if you fancy it (financial payback is decades but it might be good for the soul).

Yes the caveat emptor system in England (and obviously in Ireland) does leave much to be desired- it is bizarre that you get far more consumer protection from fraud and sharp practice buying a £5 toaster than you do when buying a £500,000 house.

Wave your mouse pointer below the bottom right of each post (where it says multi quote/quote)- you should see a Thanks and Like option pop up (or more like emerge from the background gloom). Enjoy.

 

[Yellosub]

The second coil is indeed plumbed to nowhere. Not sure what they were thinking!!

50 litres of near boiling water through the ceiling will ruin your life.

Especially since it is directly over the toilet! But, since I've gotten the new pump in and the rads bled and balanced there is no more steam flowing into the F&E tank.

I don't see where the DHW and heating pipework connect?? And no, I've not added inhibitor yet. I'm still trying to understand the whole system first.

I think the plumbing looks worse in my schematic than it actually is, maybe. I don't think the PO spent a lot of time considering linear footage of piping, friction losses from connections or ease of access for maintenance. What he did do was label the pipes and their flow direction which has been immensely helpful. Overall the system is rather neatly done although a few things like the second coil really make you wonder.

I'd rather get rid of the kitchen wood burner. It looks nice but to me it's more trouble than it's worth. The estate agent gave me about ten photos from during the renovation. Behind the Stanley stove and some wallboard is the original fireplace and what looks sort of like a pizza oven above it. I'm tempted to use the flue for a propane boiler on the outside wall of the kitchen and frame out the original stone fireplaces as a feature wall. I'll look into the thermal store as well.

I'm still having trouble getting water to the attic rad. I was able to get it as high as the top of the shower on the 1st floor. The attic rad is still a few linear feet further. As far as height goes the F&E tank water level is actually only 4 inches above the top of the attic rad. I hope this is sufficient?

When I renovate the metal hay barn into a garage for my classic American trucks I'm considering using the stream on the property to run a water-powered generator for everything other than the welding circuit.

 

[Yellosub]

Hmmmm, As I said, I diverted the steam from the expansion pipe outside the house until I could get the steam backflow under control. Now I don't have the steam problem but could the fact that the expansion vent is now 8ft lower than the tank be causing the airlock to the attic rad?? Just taking a shot in the dark on this one.

 

[oldbutnotdead]

Interesting and slightly worrying. Last one first- your system is basically a gravity system so the water level within the heating system should sit at whatever level is in the F & E tank. The expansion pipe is obviously connected and live, if it wasn't you would have no hot water. If the end of it is below the water level in the F & E tank there should be water running out of it continually- that there isn't indicates a blockage or airlock. If the attic rad gets its hot feed from that pipe somewhere (which would sound consistent with the system design) then that would also figure (again, even though there is only 4" head on that rad there should be some water moving out of it with the bleed valve removed).
4" isn't really ideal- a bit more would be handy. If you do go the propane boiler route, have a think about a pressurised system (rather than gravity fed)- it'll eliminate that weak spot.

Pipes are labelled up- how nice. But is the labelling accurate? I've been led down blind alleys before when looking at marked installs (more electrical than plumbing)- only when a fault occured was it discovered that the marking was slightly slapdash and the drawings marked 'As Fitted' belonged on the shelf with Grimms Fairy Tales. Best to do a bit of verification given the oddities.

Especially with your steaming issue, I'm wondering whether that expansion pipe (which was submerged and steaming) is on the 3 bar side of the pressure relief valve next to the woodburner and the other mystery expansion pipe (coming from the apparently disconnected coil in the cylinder) is actually the real one. If your attic rad is on the 3 bar relief line that would also explain its non functioning....

BTW here's your dodgy connection

Your call on the woodburner, yes it is a hassle continually chucking wood in but if you're getting it for free it does make it worth the effort.
And good luck with the generator sketch, my cousin's partner has been talking about doing that for ages (they live in an old water mill). Depending how much fall you've got on the stream you could have wheel (over or undershot), screw, turbine....long as the stream runs all year round of course. In theory you can flog any excess power to the grid (in England you can anyway)- but that involves some regulatory hoops on the installation, does solve the problem of blending home-generated and grid-supplied power though. Doing it DIY will get you involved in a fair bit of pain arranging for safe switchover between sources and critically ensuring there is no way your generator can backfeed into the national distribution system

 

[Yellosub]

So I spent all day one multiple related projects. I lowered the attic rad by four inches. I can't raise the F&E tank. I modified the expansion pipes into the F&E tank to sit a few inches above the water line. I also added an inline shutoff valve to the F&E tank cold water supply line. I completely drained, refilled, bled and balanced the system. I'll add inhibitor when I add the other attic rad. I also retraced all the rad system feed and return lines and corrected my diagram. The only shady looking connections turned out to be my mistake. I also verified all the "labelled" lines correct for flow direction and destination. Not sure how many times I went up and down three floors but my thighs are on fire!! I attached the corrected diagram. BUT WAIT, THERE'S MORE...

I got some flow and heat to the attic rad!!!!! It wouldn't fill completely and purge off all the air or bleed some water but I did have hot water entering the radiator. Unfortunately I ran out of coal and the wood I have now is not kiln dried so temps were off a bit. I'll grab more coal tomorrow. Then I can get on to all the other projects I have on my list. I wonder if a boost pump would help the flow if it still doesn't get hot?

To oldbutnotdead: Thank you sooo much for your assistance. I couldn't have figured this out without your help.

 

[Yellosub]

Still have to go get coal. This morning I bled all the rads again and the attic rad purged all the air and then a stream of water followed. We'll see what happens when I get it up to temp with the coal.