Pipe Insulation

[Hopeful]

We have just had a 300 litre heat store installed, with heat input from solar thermal panels and a log burning stove with back burner. Output is hot tap water via a heat exchange and a radiator circuit.

We have gone to a lot of trouble to insulate all pipes in the house, both hot and cold, but had a specialist contractor install the log burner and heat store (solar panels had been previously installed).

During the installation of the heat store, I spotted the main cold feed in and hot feed out were about 5mm (1/4 inch) apart and asked how he was going to stop thermal bridging, then it transpired he was not going to insulate anything in the cylinder cupboard. Best I could achieve, and this was begrudgingly done, was to get him to move the hot feed away from the cold feed in, saying that if he was not going to insulate I would have to, so could he please allow me space around every pipe to do so.

So, none of the pipes in the area of the thermal store are insulated and pipes are laid in for the convenience of installation, not insulation that will now be awkward for me to do.

To me all things eco and solar should be insulated within an inch of their life and this is something I should expect from this sort of installation.

For your info, I am in the UK just north of London, so climate is not like California…

Am I wrong to think in the area of the tank, at very least the hot should be insulated, but in ideally both hot and cold ?

[J.P.M.]

We have just had a 300 litre heat store installed, with heat input from solar thermal panels and a log burning stove with back burner. Output is hot tap water via a heat exchange and a radiator circuit.

We have gone to a lot of trouble to insulate all pipes in the house, both hot and cold, but had a specialist contractor install the log burner and heat store (solar panels had been previously installed).

During the installation of the heat store, I spotted the main cold feed in and hot feed out were about 5mm (1/4 inch) apart and asked how he was going to stop thermal bridging, then it transpired he was not going to insulate anything in the cylinder cupboard. Best I could achieve, and this was begrudgingly done, was to get him to move the hot feed away from the cold feed in, saying that if he was not going to insulate I would have to, so could he please allow me space around every pipe to do so.

So, none of the pipes in the area of the thermal store are insulated and pipes are laid in for the convenience of installation, not insulation that will now be awkward for me to do.

To me all things eco and solar should be insulated within an inch of their life and this is something I should expect from this sort of installation.

For your info, I am in the UK just north of London, so climate is not like California…

Am I wrong to think in the area of the tank, at very least the hot should be insulated, but in ideally both hot and cold ?

1.) You are not wrong. But, safety first : Is there a relief valve on the solar/stove loop ? Besides trying to B.S. you, sounds like the installer was making love to the family dog on this one - that would make me wonder where else did he cheaped out.

2.) Depending on how long the uninsulated run(s) are, they may not present a terrible economic loss as much as a PITA of some unintended and uncontrolled heat gain. Unless hot/cold lines are actually touching, the heat transfer between them will be via radiation and probably of a relatively minor nature. Depending on where it is, not insulating a cold water supply may have some benefit if it is gaining heat that otherwise would be lost. Sometimes that gets tricky however. See below for one reason.

3.) Still, I agree with your pipe insulation philosophy. I have 1" Armaflex on all my solar hot water runs and at least .5" on all the hot water service in the house with most of that 1" as well, and satisfied myself of an economic life cycle analysis breakeven of 12 yrs. or less.

4.) Depending on climate/environmental conditions you may want to consider some insulation of the cold water feed lines with condensation in mind - drip damage. Obviously, the insulation in that application should be water impervious.

Cheers

[SunEagle]

I live in sunny Florida and all of the piping between the hot water storage tank and panel on my solar heating water system are insulated. The tank is rated 80 gallon and has insulation built in so no more is needed on the outside.

It seems like your installer cheated you out of the insulation as well as the access to insulate the piping yourself. A little pipe insulation is cheap and will help increase your system efficiency by not letting the heat bleed away when it gets cold.

[Hopeful]

Thanks for the info. I believe all the correct safety features are in place, thank you for checking, it is just the insulation issue that is bugging me.
From two points:

Maintaining the temperature in the heat store… You have a lagged cylinder, with a number of bare copper pipes sticking out from it, so leaking heat.

Reducing the (cold) dead leg, when you turn a hot tap on.

[organic farmer]

We have just had a 300 litre heat store installed, with heat input from solar thermal panels and a log burning stove with back burner. Output is hot tap water via a heat exchange and a radiator circuit.

We have gone to a lot of trouble to insulate all pipes in the house, both hot and cold, but had a specialist contractor install the log burner and heat store (solar panels had been previously installed).

We use a woodstove to heat our water, that circulates in a 80-gallon thermal-bank. We use that heated water to circulate through our radiant heated floors.

If your hot and cold pipes pass close to one another I would not worry about it. Consider it 'pre-heating'.



Let me explain an earlier version of our setup. I had wrapped 50 foot of 3/4 inch copper tubing around the outside of a steel drum. I spent a lot of effort getting the tubing to wrap neatly and in full contact with the drum. That drum is a part of our woodstove, it is like an expansion chamber for the burning gasses, before they lead into the stove-pipe. At the time I was experimenting with making it to do some 'secondary combustion' for me. The point of this is; with the drum at 250-400F, I was only able to get the water passing in the tubing to increase by 5- 10 degrees F. The outer curvature on the tubing making contact with the steel drum, is only a tiny point of direct contact. Heat simply did not transfer from the drum, to the tubing.

The next year, I moved the copper tubing to coil inside the steel drum. So now the hot gases leaving the fire must pass through the coils, on their way to the stove pipe. Now I get a lot of heat into the passing water. The entire circumference of the tubing is in direct contact with the hot gasses, and this makes for good heat transfer.



In my region, outdoor wood 'furnaces' are popular. These are often huge fireboxes capable of taking entire tree stumps. The fireboxes are walled-in with steel water tank. They are routinely 50 foot to 100 foot removed from the farm house. Blue and Red garden hose is used to circulate the water from the furnace to the house. These hoses are encased inside cheap commercial pipe insulation, and they are allowed to touch each other. The pipe insulation offers no more than 1 inch of foam insulation, between the hoses and the outside world. The hose-pairs, inside their pipe insulation, are laid in a trench at 4foot depth [to place them below our local frost-line]. I have asked about putting the hot and cold next to each other, but this it the industry standard procedure.



IMHO you do not have anything to worry about with the hot and the cold being near each other.

On the other hand., is there a pressure-relief?

That is a huge concern. You should know where it is. You should be prepared for the times when it 'lifts' and spews hot boiling water and steam. I keep a steel bucket under our pressure-relief, to contain all of that water.

And you need to be testing that valve at least once/year.

[Hopeful]

Thank you organic farmer

My concern is pre-cooling the hot water, not pre-heating the cold.

Your wood furnaces taking whole trunks and steel drums with heating coils is fascinating, but the difference is that being in the UK, solar panels have to work hard and the stove consumes wood that is not a free resource. You do not have energy to spare and want to make the best of all the energy you store, only using it where you intend to, limiting all the unintended loss, or at least that is my theory… No point in heating the house when you do not need to, if your priority is a hot bath.

As a matter of interest, our solar panels are about 100 foot from the house, partly running through underground (insulated) pipes.

[Hopeful]

Forgot to answer the safety question.

Ours is a pressurised system, where we have an expansion cylinder in the loft and a pressure release valve on the cylinder draining directly to the outside, however there is an open inspection port just under the pressure release valve that makes it very obvious if it is releasing. There is a test button on the valve.
The stove circuit circulates tank water with a heat sink radiator directly connected.

[Mike90250]

I've seen thin (.25" thick) self adhesive, insulative pipe tape, you can spiral or linear wrap that on the pipe and use nylon zip ties to hold it in place (I've never seen the adhesive last longer than a couple months on stuff)

[J.P.M.]

I've seen thin (.25" thick) self adhesive, insulative pipe tape, you can spiral or linear wrap that on the pipe and use nylon zip ties to hold it in place (I've never seen the adhesive last longer than a couple months on stuff)

Ditto on adhesive failure. I use similar stuff for irreg. shapes and wrap it w/ aluminum (not duct) tape - always necessary for outside application anyway. Sometimes touchup needed after 4-5 yrs.

[Naptown]

exactly how much is uninsulated and how far away from the firebox is this area?

[Hopeful]

Only the pipes within the area of the Thermal Store are un-insulated, Log burner backs onto Thermal store cupboard, so distance is minimal.

My concern is we are breaching the thermal store tank insulation with a number of bare copper pipes that are hot to the touch and so cooling unnecessarily the thermal store, also the hot water pipes are so close to cold, you cannot insulate and the hot feed to the house will suffer more than it should from a cold dead leg.

Installer has agreed to move pipes but is asking that I insulate.

My questions are to get a steer on what is reasonable to ask of my installer and what is not and I am very grateful for all the replies received so far.

[Naptown]

without pictures it is hard to say. but if next to the storage tank then yes insulate. If next to the stove combustion chamber then I would be cautious of overheating the insulation and potentially causing a fire.

[Mike90250]

I don't know more information about Pipe Insulation. What type of pipe insulation is best?

depends. Outdoors, it must be UV resistant, bird pecking resistant, squirrel resistant, and closed cell. Indoors, much more relaxed, except it must meet some toxic smoke generation standards.

[russ]

I don't know more information about Pipe Insulation. What type of pipe insulation is best?

Depends on how hot the liquid in the pipe and the surrounding (ambient) temperature will be.

[J.P.M.]

I don't know more information about Pipe Insulation. What type of pipe insulation is best?

Since you ask :
It depends on the application. Obviously, asbestos is out. For common domestic (household) hot and sometimes cold lines like A/C refrig. Closed cell foam like "Armaflex" is pretty good. Just take a deep breath when you shop it 'cause It's not cheap, but worth it. Mostly impervious to water, which is an especially good attribute for cold lines in humid locations. High service temp. - ~+220 deg. F. easy to work with. Stated insul. value is about R4 or so. Trust me on this one: After losses for breaks and around valves and other stuff, expect an effective "R" of about 2/3 of that for the overall system, maybe a bit better if you're REAL careful. If an outside app. remember - it cannot take sunlight. So, it must be wrapped. I use aluminum tape for that purpose - NOT duct tape. FYI, my experience is that alum. tape in this app. lasts about 4-5 yrs. outside and then needs rewrapping. Compress the insulation (lengthwise) about 3-4% or so when installing to cover future shrinkage. As for insulation thickness, depending on economics - fuel cost, longevity, temp. diff. and other things, I can usually make a cost effective case for 1" thk. or more. Big box doesn't carry that thickness but it's available online. Thicker than that really starts to cost more and gets difficult to work with in tight places. Also, you often wind up making your own elbows, "T"'s and 45's. Some folks disagree w/ 1" thk. and think .5" is adequate. Opinions vary. Obviously, that knocks the "R" value by about 50%. In any case, I'd avoid the cheap "frost king" type stuff from big box. Buy cheap - buy 2X or more. The amount of work required is about the same regardless of material cost. Pay your money - take your choice. Also, do not use anything combustible near a flame or any heat source above the melting or ignition temp. of any insulating material, and never cover, hide or obstruct access to any safety or regulating devices. Finally, don't put the cart before the horse and not insulate the holy grail out of any storage device (tank). That is much more cost effective and should be done before and probably more rigorously than pipe insulation endeavors. It's usually cheaper and easier too.